Ok I am coming back again hoping for some help. My car has been at a transmission shop for the past week, going from what I was hoping to be just a TC replacment to a complete rebuild due to the condition of the trans. He is stating that part of the reason the trans went bad was the underboost code. They are stating that it needs To be remedied ASAP, so what else should I look for? Can a bad camshaft cause the code? Mine seems to be OK, with barely detectable wear on the lobes and lifters. Could a mistake while doing the BSM have anything to do with it (previous owner with questionable mechanical skills)? I am just looking for any other suggestions, so I don't ruin my fresh (and expensive) transmission.
Code P0299 "turbo underboost" Resolution Repository
- Thread starter SUNRG
- Start date
racer4
Member
I just got done yesterday diagnosing a limp mode problem. This guy had his failed T/C replaced a couple of months ago, long before any underboost p0299 codes.
I started by pressure testing the entire boost system by using an adapter made from a 1 1/2" fernco rubber pipe connector and some pipe fittings. I thought this should be done first as I just changed the timing belt a few weeks ago and wasn't sure if the intercooler crossover pipe seals failed or blew apart. Connections were hard to get apart when I put the bumper into the service position. I pumped up the system and used soapy water to check all connections and the intercooler end tanks. All was good.
I then decided to check the turbo actuator system. The turbo vanes are controlled through the N75 valve, which is basically a solenoid valve. Closed when no voltage is present, open with 12v. When the valve is open, it allows vacuum to pull the turbo vane actuator in, increasing boost. The valve can be tested by trying to pull vacuum though the port labeled "vac". It should hold vacuum and not leak down. You can test the electrical side as well by applying voltage to the valve (negative is the rounded side of the plug, positive is the flat side). It should click and open the path from "vac" to "out". When voltage is removed, the valve should close again. The port labeled "atm" (to airbox) lets the valve vent air quickly when it is cycling. I read on here somewhere that you can use VCDS in basic settings to make the computer cycle the N75 and induce boost. Channel 11 is the number. Click the button at the top and the engine revs to about 1400 and cycles the N75 open and closed causing boost which can be heard and operates the actuator which can be seen. Failed N75 did none of these during the test. Test doesn't indicate pass or fail either, it just operates the system.
Note: do not used compressed air to blow out the N75. There is a thin rubber diaphragm which could be damaged. Brake cleaner did nothing to help this valve either, I tried. In fact it made the valve stick worse. Curiosity got the better of me so I cut the valve apart. There was a white powdery substance on the internal metal shaft causing it to stick. Cleaning it off didn't help either. This valve seems like it could be very finicky in its operation, and would be the first item I would check in the future. Especially with intermittent problems. Smooth turbo vane actuator movement should also be checked, as well as MAF signals.
As a precaution, all vacuum line was replaced with thick wall silicone. Don't bother with the thin walled Chinese crap they sometimes sell at parts stores that says suitable for turbo systems. It's not. It collapses on moderate bends.
As another precaution, the EGR was removed and the gunk cleaned out using seafoam spray.
Car has a rocketchip stage 2 and runs like a bat out of hell now. Hope this helps.
I started by pressure testing the entire boost system by using an adapter made from a 1 1/2" fernco rubber pipe connector and some pipe fittings. I thought this should be done first as I just changed the timing belt a few weeks ago and wasn't sure if the intercooler crossover pipe seals failed or blew apart. Connections were hard to get apart when I put the bumper into the service position. I pumped up the system and used soapy water to check all connections and the intercooler end tanks. All was good.
I then decided to check the turbo actuator system. The turbo vanes are controlled through the N75 valve, which is basically a solenoid valve. Closed when no voltage is present, open with 12v. When the valve is open, it allows vacuum to pull the turbo vane actuator in, increasing boost. The valve can be tested by trying to pull vacuum though the port labeled "vac". It should hold vacuum and not leak down. You can test the electrical side as well by applying voltage to the valve (negative is the rounded side of the plug, positive is the flat side). It should click and open the path from "vac" to "out". When voltage is removed, the valve should close again. The port labeled "atm" (to airbox) lets the valve vent air quickly when it is cycling. I read on here somewhere that you can use VCDS in basic settings to make the computer cycle the N75 and induce boost. Channel 11 is the number. Click the button at the top and the engine revs to about 1400 and cycles the N75 open and closed causing boost which can be heard and operates the actuator which can be seen. Failed N75 did none of these during the test. Test doesn't indicate pass or fail either, it just operates the system.
Note: do not used compressed air to blow out the N75. There is a thin rubber diaphragm which could be damaged. Brake cleaner did nothing to help this valve either, I tried. In fact it made the valve stick worse. Curiosity got the better of me so I cut the valve apart. There was a white powdery substance on the internal metal shaft causing it to stick. Cleaning it off didn't help either. This valve seems like it could be very finicky in its operation, and would be the first item I would check in the future. Especially with intermittent problems. Smooth turbo vane actuator movement should also be checked, as well as MAF signals.
As a precaution, all vacuum line was replaced with thick wall silicone. Don't bother with the thin walled Chinese crap they sometimes sell at parts stores that says suitable for turbo systems. It's not. It collapses on moderate bends.
As another precaution, the EGR was removed and the gunk cleaned out using seafoam spray.
Car has a rocketchip stage 2 and runs like a bat out of hell now. Hope this helps.
Turbospool
Veteran Member
Just in case you are not aware...... your Transmission also has a TCM under the passenger seat that should it become compromised by moisture with definitely affect your transmission. Check under your passenger seat for dampness. Otherwise you may replace your TC. or even your transmission, and still have problems. Just giving you a heads up , my friend.
When they pulled the transmission it was beat, clutches we jammed into the drum, splines on the stater wer stripping and the filter was full of metal.
On another note I have given up and took the car to another shop with some TDI experience to try and figure out the limp mode issue. I literally checked and double checked every potential cause listed on the myturbodiesel write up as well as in this thread.
On another note I have given up and took the car to another shop with some TDI experience to try and figure out the limp mode issue. I literally checked and double checked every potential cause listed on the myturbodiesel write up as well as in this thread.
I fought this 0299 business for a couple weeks. Also had the MAF cel. Finally put 10 pound of air right past the air box.Found a split in the air charge hose right before the EGR. The 90 degree piece. Fixed it for now with RV goop and a narrow screw type hose clamp. Cleaned it good first with brake cleaner. Runs like a champ now. Anyone made a silicone hose for this application?
nissansentra
Active member
Underboost with p0299
Hello,
My symptoms seemsto be underboost all the time only after the car heats up. In the mornigns its fine and will pull hard in 2nd gear then after driving for 2 min or so it doesnt pull at all. Also, my cruise doesnt work, is that related to that n75 valve? With these symptoms what do u guys think is the problem?
Thanks,
Jordan
Hello,
My symptoms seemsto be underboost all the time only after the car heats up. In the mornigns its fine and will pull hard in 2nd gear then after driving for 2 min or so it doesnt pull at all. Also, my cruise doesnt work, is that related to that n75 valve? With these symptoms what do u guys think is the problem?
Thanks,
Jordan
Sounds like you are getting limp mode, any CEL? Read here and get to work: http://www.myturbodiesel.com/1000q/multi/limp-mode-TDI-fix.htm
flashmayo
Veteran Member
Underboost P0299 1556 Issue and Resolution
There are a lot of threads indicating problems with underboost, but not many with resolutions.
Mine is a 03 Jetta. The symptoms were the classic underboost symptoms. I couldn't get the engine to spool up to 4K rpms in 3rd gear. It would go into limp mode and at times throw a code. The symptoms got worse just after Matt-98AHU did my 2nd timing belt at about 189K, which threw another element into the troubleshooting process. I assumed that this was just coincidental from the start. I still believe that.
So to track this down I did the following:
Checked the vacuum system-
25" Hg at the vacuum pump. This is perfect.
about 20" Hg at the actuator. This is plenty.
All original hoses were replaced 50 K miles earlier.
Checked the VNT actuator-
Pull 25" of vacuum on the vnt actuator and it holds that vacuum. VNT operational. Good
Connected the vacuum tester to the VNT actuator, it moves smoothly through it's whole range. Starts moving at 4" and hits the stop at 18" Hg. That's right at spec. Good
Check operation of the N75.
Watch the actuator move when someone starts the car. Good.
Matt used his VCDS to exercise the actuator. Good.
Replaced Fuel Filter.
Replaced Air filter.
Swapped the MAF with a known good one.
Check for boost leaks-
Build a boost leak tester. Photos here https://plus.google.com/u/0/photos/1...93054411129757
Basically this is isolating the boost path, which is between the output of the turbo and the EGR. So disconnect the rubber hose at the turbo and plug it, remove the end of the rubber hose at the EGR, push air into this end using a compressor. You have to make plugs from PVC and the air
injector of PVC and a compressor fitting. The boost reaches 30 - 35 psi so it has to be able to hold this much pressure from the compressor.
I had no leaks in the boost path. It held until the upper fitting blew off at 40 psi. Good.
Finally bought a VCDS, which I was hesitant to do. This didn't tell me
anything I didn't know already, but it does give a common language with
which to communicate with on line resources.
The group 11 log told me that I was underboosting until limp mode kicked
in.
Removed the EGR to check to see if it was getting stuck open by gunk in
the valve seat. Cleaned the minute amount of gunk out of the valve.
EGR functional. Good.
So at this point there should not be any underboost, but there is. The only things left are turbo and exhaust system. I talked to 3 TDI mechanics who all said that they had never replaced a catalytic converter and never seen one clogged up.
On sage advise from a seasoned TDI mechanic, I tested the exhaust system by loosening the 3 flange bolts holding the downpipe to the exhaust manifold.
Bingo. No more limp mode, no codes, and the car runs faster than I've ever seen it run. I can accelerate on hills in 5th gear, where before it would go into limp mode on a level roadway. I expect that performance will be reduced a little when I put a new cat on it, but am 99% sure that I have found the problem.
So in summary, check the vacuum lines and vnt and vane movement first, look for oil splatters indicating a cracked hose. Don't rule out a clogged cat. It's easier to check than removing the turbo or even the EGR.
Thanks go to Matt-98AHU (Matt), oldpoopie (Justin), runonbeer (Robby), and fixumhausrich (Rich) for answering my pleas for guidance.
Good Luck,
John
There are a lot of threads indicating problems with underboost, but not many with resolutions.
Mine is a 03 Jetta. The symptoms were the classic underboost symptoms. I couldn't get the engine to spool up to 4K rpms in 3rd gear. It would go into limp mode and at times throw a code. The symptoms got worse just after Matt-98AHU did my 2nd timing belt at about 189K, which threw another element into the troubleshooting process. I assumed that this was just coincidental from the start. I still believe that.
So to track this down I did the following:
Checked the vacuum system-
25" Hg at the vacuum pump. This is perfect.
about 20" Hg at the actuator. This is plenty.
All original hoses were replaced 50 K miles earlier.
Checked the VNT actuator-
Pull 25" of vacuum on the vnt actuator and it holds that vacuum. VNT operational. Good
Connected the vacuum tester to the VNT actuator, it moves smoothly through it's whole range. Starts moving at 4" and hits the stop at 18" Hg. That's right at spec. Good
Check operation of the N75.
Watch the actuator move when someone starts the car. Good.
Matt used his VCDS to exercise the actuator. Good.
Replaced Fuel Filter.
Replaced Air filter.
Swapped the MAF with a known good one.
Check for boost leaks-
Build a boost leak tester. Photos here https://plus.google.com/u/0/photos/1...93054411129757
Basically this is isolating the boost path, which is between the output of the turbo and the EGR. So disconnect the rubber hose at the turbo and plug it, remove the end of the rubber hose at the EGR, push air into this end using a compressor. You have to make plugs from PVC and the air
injector of PVC and a compressor fitting. The boost reaches 30 - 35 psi so it has to be able to hold this much pressure from the compressor.
I had no leaks in the boost path. It held until the upper fitting blew off at 40 psi. Good.
Finally bought a VCDS, which I was hesitant to do. This didn't tell me
anything I didn't know already, but it does give a common language with
which to communicate with on line resources.
The group 11 log told me that I was underboosting until limp mode kicked
in.
Removed the EGR to check to see if it was getting stuck open by gunk in
the valve seat. Cleaned the minute amount of gunk out of the valve.
EGR functional. Good.
So at this point there should not be any underboost, but there is. The only things left are turbo and exhaust system. I talked to 3 TDI mechanics who all said that they had never replaced a catalytic converter and never seen one clogged up.
On sage advise from a seasoned TDI mechanic, I tested the exhaust system by loosening the 3 flange bolts holding the downpipe to the exhaust manifold.
Bingo. No more limp mode, no codes, and the car runs faster than I've ever seen it run. I can accelerate on hills in 5th gear, where before it would go into limp mode on a level roadway. I expect that performance will be reduced a little when I put a new cat on it, but am 99% sure that I have found the problem.
So in summary, check the vacuum lines and vnt and vane movement first, look for oil splatters indicating a cracked hose. Don't rule out a clogged cat. It's easier to check than removing the turbo or even the EGR.
Thanks go to Matt-98AHU (Matt), oldpoopie (Justin), runonbeer (Robby), and fixumhausrich (Rich) for answering my pleas for guidance.
Good Luck,
John
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Just adding my 2 cents on this 'P0299' code.
I recently replaced my head, turbo, and nearly all of the hoses and lines connected to those parts. The work was done by a local shop and twice during that process I picked up the car, drove it and got the 'no power'. Each time I took it back they found or broke something else that then needed to be replaced. 1st was a rocker assembly, 2nd was a single injector. 2 months later (read yesterday) it happened again. This time I checked here and used VAGCOM to scan for codes and got P0299. After reading all of your really helpful posts I checked under my hood and found the recirculation/re-breather tube was barely connected on the end where it connects into the air intake. After all of the work, they didn't replace the compression clamp. I easily pushed it back on, it kind of snapped into position. I reset the code and also changed my Transmission code to 0001134 for 'Sports Mode'. I didn't have a hose clamp handy but I took it for a test drive and it responded well. The shifting was much calmer and smoother and the code has not yet returned. I still need to put a clamp on that tube, but for now it's not generating an error.
BTW - I did contact Midas and asked about the cost of a catalytic converter replacement and they told me there wasn't one listed for my vehicle. Can anyone shed light on this?
Thanks for all the great posts!
Charlie
I recently replaced my head, turbo, and nearly all of the hoses and lines connected to those parts. The work was done by a local shop and twice during that process I picked up the car, drove it and got the 'no power'. Each time I took it back they found or broke something else that then needed to be replaced. 1st was a rocker assembly, 2nd was a single injector. 2 months later (read yesterday) it happened again. This time I checked here and used VAGCOM to scan for codes and got P0299. After reading all of your really helpful posts I checked under my hood and found the recirculation/re-breather tube was barely connected on the end where it connects into the air intake. After all of the work, they didn't replace the compression clamp. I easily pushed it back on, it kind of snapped into position. I reset the code and also changed my Transmission code to 0001134 for 'Sports Mode'. I didn't have a hose clamp handy but I took it for a test drive and it responded well. The shifting was much calmer and smoother and the code has not yet returned. I still need to put a clamp on that tube, but for now it's not generating an error.
BTW - I did contact Midas and asked about the cost of a catalytic converter replacement and they told me there wasn't one listed for my vehicle. Can anyone shed light on this?
Thanks for all the great posts!
Charlie
On my 2003 jetta I keep getting the 299 error code but no apparent turbo problems. Replaced some vacuum lines and n75 valve but same thing happens. Could til be the n18 valve? Any ideas?
TheGrove
TDIClub Enthusiast, Veteran Member
- Joined
- May 17, 2006
- Location
- S Central PA (Breezewood)
- TDI
- 2012 Passat SEL Premium Opera Red - Dieselgate Fix, KermaTDI Tune, 2004 Passat GLS Northern Green-RIP
Carnarob, I thought I would mention you are in the Passat forum, not the Jetta forum. There are many similarities but they are different cars and engines.
blueracer84074
New member
Black Jetta
Hello I am new to this forum and was wondering if I could get a little advise, I recently purchased a 2006 jetta tdi because there known to be fuel misors but now it is having some issues. First thing the cel came on and gave me po101 so I put a new maf on it with no improvement then replaced the fuel filter and had it serviced and still no improvement now I took it to a local shop and they say the turbo is oily and the intercooler is oily too it gave them p0101,p0299 positive current control circuit open. There is a big power loss and no boost should I get a replacement turbo?
Hello I am new to this forum and was wondering if I could get a little advise, I recently purchased a 2006 jetta tdi because there known to be fuel misors but now it is having some issues. First thing the cel came on and gave me po101 so I put a new maf on it with no improvement then replaced the fuel filter and had it serviced and still no improvement now I took it to a local shop and they say the turbo is oily and the intercooler is oily too it gave them p0101,p0299 positive current control circuit open. There is a big power loss and no boost should I get a replacement turbo?
blueracer84074, I thought I would let you know that you are posting into the Passat forum. While they do share some similarities, the Passat and Jetta use different engines.
truman
Top Post Dawg
I have had occasional limp mode when driving up a moderate incline at 70mph for better than a year. Has happened about 1/mo but more often recently. P0299 emissions code happens infrequently.
I cleaned the egr valve and replaced a short piece of vacuum line at the check valve and vacuum line from N75 to turbo. The short piece at the check valve was suspect- connection was rather loose.
Fingers crossed, no limp the past 3 days.
It "may" be my imagination, but it sure seems like the turbo spools a lot faster. So far so good.
7/22/14 UPDATE
Limp mode at the usual spot on the way to work this morning, so there is still another issue. My trusty guru KCTDI will delve into it further.
At the top of the list will be tandem pump nipple and charge pressure pipe and other vacuum lines as well.
I will say it is running better.
I cleaned the egr valve and replaced a short piece of vacuum line at the check valve and vacuum line from N75 to turbo. The short piece at the check valve was suspect- connection was rather loose.
Fingers crossed, no limp the past 3 days.
It "may" be my imagination, but it sure seems like the turbo spools a lot faster. So far so good.
7/22/14 UPDATE
Limp mode at the usual spot on the way to work this morning, so there is still another issue. My trusty guru KCTDI will delve into it further.
At the top of the list will be tandem pump nipple and charge pressure pipe and other vacuum lines as well.
I will say it is running better.
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Fasteddie10
Veteran Member
- Joined
- Jun 23, 2011
- Location
- Illinois
- TDI
- 2004 Jetta Wagon TDI, 2-2005 Passat Wagon TDIs, 2-2004 Passat Wagon TDIs
Cleaned out my N75 with one shot of contact cleaner
I had a 200 mBar delta between my desired MAP and my actual MAP while warm and going down a flat road. When the engine was cold the delta increased and if it gets greater than 400 mBar then it goes into the limp mode, limits the output torque to 150 NM. I cleaned out my N75 with one shot of contact cleaner down the tubing from the air cleaner. The desired and actual MAP graph lines are on top of each other now! No more P0299, no limp mode.
I had a 200 mBar delta between my desired MAP and my actual MAP while warm and going down a flat road. When the engine was cold the delta increased and if it gets greater than 400 mBar then it goes into the limp mode, limits the output torque to 150 NM. I cleaned out my N75 with one shot of contact cleaner down the tubing from the air cleaner. The desired and actual MAP graph lines are on top of each other now! No more P0299, no limp mode.
Whiteboy84
Well-known member
Anyone know what would cause a very loud whine from the turbo, limp mode, and a P0299 code. Checked N75, checked actuator, checked all vacuum lines for leaks.
Sent from my SCH-I605 using Tapatalk
Sent from my SCH-I605 using Tapatalk
released81101
Member
limp mode
I recently had a new used 85,000 mile motor and a new used turbo installed in my 06 vw jetta TDI. The reason they were installed is because previous went bad. Turbo went into limp mode and I was told it was bad, then the timing belt broke. Mechanic said the piston dropped and caused the motor to be bad. It had 256,000 miles on it.
Now that my newer parts are installed my car is back in limped mode. My mechanic says I need to break this newer motor in and the more I do all that bad build up that caused the previous limp mode will blow out.
So my question is this true? Or is there something I can do to fix this?
The car is super face on straight runs but on hills it barely does 20 mph.
I recently had a new used 85,000 mile motor and a new used turbo installed in my 06 vw jetta TDI. The reason they were installed is because previous went bad. Turbo went into limp mode and I was told it was bad, then the timing belt broke. Mechanic said the piston dropped and caused the motor to be bad. It had 256,000 miles on it.
Now that my newer parts are installed my car is back in limped mode. My mechanic says I need to break this newer motor in and the more I do all that bad build up that caused the previous limp mode will blow out.
So my question is this true? Or is there something I can do to fix this?
The car is super face on straight runs but on hills it barely does 20 mph.
Limp mode doesn't wear in. If there is carbon in the VNT actuator vanes/pivots, no amount of driving will clean it out. The turbo needs to be removed and the pivots and actuator ring cleaned.
... If that is your problem. Easiest way to check is to take a vacuum pump and try to activate the VNT actuator manually - it should start to move around 3-4" vacuum and opn fully around 18".
In my case the lock nut on the actuator rod came loose (I share the blame in this, as I had the actuator off to free it up a couple weeks prior and must not have tightened it fully). With the nut backed off, the knurled adjuster nut moved down the rod, effectively making the rod too long. It would only start to move around 18" - far too late.
Adjusted it shorter and tested to make sure that the actuator starts to move at 3-4" vacuum, and all is well now.
... If that is your problem. Easiest way to check is to take a vacuum pump and try to activate the VNT actuator manually - it should start to move around 3-4" vacuum and opn fully around 18".
In my case the lock nut on the actuator rod came loose (I share the blame in this, as I had the actuator off to free it up a couple weeks prior and must not have tightened it fully). With the nut backed off, the knurled adjuster nut moved down the rod, effectively making the rod too long. It would only start to move around 18" - far too late.
Adjusted it shorter and tested to make sure that the actuator starts to move at 3-4" vacuum, and all is well now.
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released81101
Member
where can i get a vacuum pump for this? if this is the case does The turbo needs to be removed and the pivots and actuator ring cleaned? Its only been on for about a week.
Pep boys sell them, same with autozone. The best one I found however (in the US) is at harbor frieght - $20, and got the job done.
If the ring/vanes are stuck with carbon, the only thing that will fix it for any length of time is removal, disassembly and cleaning.
If the ring/vanes are stuck with carbon, the only thing that will fix it for any length of time is removal, disassembly and cleaning.
Whiteboy84
Well-known member
I had to P0299, limp mode, engine fault workshop message, flashing glow plug light, no boost and a whine that sounded like a siren coming from my turbo on my 2009 Jetta TDI. The turbo had failed and the impeller was hitting the housing causing metal shavings to go into the exhaust and egr. Total cost of repair $2,875.00. Using guru in Birmingham, al at Hutchinson Volkswagen.
truman
Top Post Dawg
Charge pressure hose replaced by KCTDI- it had a 1" split. Seems to run a little smoother now and exhaust at WOT is now a gray haze rather than black. FE may be up slightly also. Hopefully, no more limp mode.
I had a couple of limps in the past week. 2 days ago, I put a reinforcing hose like BIODZL suggested in a previous post. It also made the connection to the VNT nipple tighter. I used a 2" piece of fuel hose over the end of the vacuum hose- real snug fit. I looked around for any signs of soot leakage from the other charge tubes- non evident. Since making this last mod, I haven't had another limp, but it's early. Long road trip tomorrow, so we'll see what happens.
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truman
Top Post Dawg
I think this appears to be a valid point. I did a similar mod with a 2" piece of fuel hose which fits tightly over the end of the vacuum line connection to the VNT actuator. The overlay hose also tightens the connection of the vacuum hose to the actuator nipple. I had 2 limps last week on my daily commute, and non since doing this mod. We just made a trip from MO to Aspen and not a single limp incident so far. I will report back with further results.I have been having the same problem for months. Last weekend I replaced the hose between the N75 and the turbo and decided to provide some strain relief at the turbo actuator. Basically I cut a 3-inch piece of transmission oil hose with an inside diameter just slightly larger than the outside diameter of the vacuum hose. I slid the tranny cooler hose over the end of the vacuum hose, firmly attached the vacuum hose to the turbo actuator, then slid the tranny hose down toward the turbo actuator. Looks nice, eh?
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My car would go into limp mode primarily when driving at low loads at the point at which I would slowly start to accelerate. Often this would happen in the morning as mentioned by other posters. The best (worst) example was driving West on I-80 down a hill, and just as the road leveled out while I was still coasting, and as I started to press on the go pedal, poof! No oomph to get over the next hill as several semi-trucks are crawling up my tail!
After a week of driving, no more limp mode!
Why would this work? First, the extreme bend that the hose has to endure has always bothered me. Just seemed like a problem waiting to happen. I figure that since the vacuum is highest when the boost is at zero, this is when the hose is most likely to collapse under the strain of the vacuum. Any small bend or kink in the hose is going to make it more probable to pinch off the vacuum "flow." When the ECU tells the N75 to give more boost (less vacuum) the hose is pinched off and under vacuum. Eventually the hose will open up, but the ECU is too impatient and acts to protect the engine and throws it into limp mode.
Biodezl
Veteran Member
For the record, this mod reduced limp mode occurrence, but eventually limp mode returned for other reasons. Currently I am limp-free for months with stock programming after adding sealant goop to the boost hose connections. If I install the RC+1 ECU, limp modes are generally more frequent and are rampant when using Biodiesel B100 and the RC+1 ECU. In fact, limp mode is certain if the RC+1 ECU is installed and I use anything over B50 in the first tank of fuel. The ECU needs to complete its emissions checks and one of those checks fails if the first 50-100 miles are with anything but mostly ULSD dino fuel.
Also, I think the many causes of poor boost control cause long-term degradation of the turbo/VNT actuator. I noticed that after long drives (soot burned away) the turbo boost is more responsive, but after weeks of driving only on city streets, the boost becomes progressively more sluggish. Poor boost control is both a symptom of soot buildup, but can also be a cause of soot if the fuel/air ratio isn't right. So, as important as any particular fix is fixing it quickly to prevent soot buildup and eventual turbo damage.
auntulna
Veteran Member
I'm just one point of data, but my recent experience of low, low power after a head gasket replacement led to disassembly of the turbo and resetting by Franko6, and double checking all vacuum and pressure hoses plus new O-rings, new N75, checking vacuum readings and boost pressure. New fuel filter, air filter, cabin filter!
The turbo didn't have any buildup in it and the actuator worked like it was supposed to. It was only after installing new injectors that the car got its full power with RC2, and it runs great. No limps since then, and pushing it hard.
Injectors as the problem hasn't really been mentioned for PDs, but Frank thinks they will show up with less than normal function as time goes on. Research continues. I wish it was a lot more practical to swap them for test runs, cuz you just won't know if they're still delivering 100%.
The turbo didn't have any buildup in it and the actuator worked like it was supposed to. It was only after installing new injectors that the car got its full power with RC2, and it runs great. No limps since then, and pushing it hard.
Injectors as the problem hasn't really been mentioned for PDs, but Frank thinks they will show up with less than normal function as time goes on. Research continues. I wish it was a lot more practical to swap them for test runs, cuz you just won't know if they're still delivering 100%.
truman
Top Post Dawg
Just returned from our trip to Aspen- not 1 single limp on the entire trip. So for the moment, I'm feeling good about the situation.
could this also happen for my MIV 2003 ALH, when I reinstalled the hose I just slid it back on maybe this is where the whistle is coming from? any ideas ?
Bosserdet
Well-known member
tyrone shoelaces
Well-known member
Anyone ever have any issues with the sensor/valve for the crankcase vent back into the intake? Was pressure testing CAC system for leaks and found the 90deg hose at the intake split, changed that and then found the MAP sensor leaking through the sensor body, fixed and and test drove the car and the sensor cam apart but before I noticed that I went to pressurize the system again and oil came blowing out the dipstick tube because for whatever reason pressure started going through that sensor where the crankcase pressure dumps back int o the turbo intake pipe.