ALH weird serious engine problem

tgray

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I have a 2001 ALH TDI with about 300,000 miles on it. It seemed to be running fine starting fine until I took it out on the road and found it had no power. I found the turbo vanes were stuck so I repaired that issue. Then the car would not rev past 3,000 sputtering and missing and smoking clouds of white smoke.
I tried different MAF sensors but the same result. When I unhooked the EGR vacuum the revs and power came back but when it is throttled to about 3,000 and back repeatedly and quickly, the engine will suddenly start making weird howling sputtering sounds in the intake like the turbo is doing something strange and the engine will start chugging and missing very bad. Sometimes the miss is so bad the engine will die if I let the throttle off. The engine puts out clouds of white smoke. When I go to restart the engine it sounds like the valves are all open with no compression. Within about 10 seconds the engine will always start and idle smooth again with no problems. I can repeat this issue over and over but does seem to get better when it is warm.
Has anyone experience such a problem? My one guess it sounds like the valves are sticking and messing with the turbo flows. But I am stumped, if the valves were sticking why it would not act up under full throttle or idle. It only acts up when I keep punching the throttle back and forth. The other thought was it was the injection pump going out.
The other weird part is I can't seem to find a way to hook up the EGR. If I do connect the vacuum tube it doesn't like to rev past 3,000 again and has no power.
Just for the record, I never really had this car on the road but bought it with some body damage so I don't know much about its history other than it was being driven before the accident.
Any ideas to verify what is wrong before I tear the engine down and find nothing wrong but a bad injection pump?
 

tgray

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The timing belt was said to be replaced by the previous owner. After inspecting it I find it was new recently and found the marks where he just lined things up and put a new one in. After a quick check yesterday it was lined up right for his paint marks (with injection pump pin pushed in the line up hole) and tight, but I didn't have a chance to verify the cam was set correctly from the proper set slot in back. When I get a chance I will pull the valve cover and take a look under that for a quick visual inspection. Valve lifter problems would make sense if the reving up and down would somehow cause them to pump up higher than they should and open up the valves. It also would make sense the more I think about it as the condition is so repeatable and consistent - like the oil bleeds off the lifters and all is normal again.
My other thought was perhaps the original timing belt messed up but the valves were only bent enough to make them stick a little. But the sticking only allows the lifters to compensate with some over adjustment and then loosing compression temporarily.
 

wonneber

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The timing belt was said to be replaced by the previous owner. After inspecting it I find it was new recently and found the marks where he just lined things up and put a new one in.
I would wonder if everything was changed, not just the belt to save $$$
Did you get paperwork showing what was replaced or just verbal?

If in doubt I would replace everything and not worry about catastrophic failure down the road.

Rich W.
 

jettawreck

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Paint marks (the "mark and pray" method) typically shows someone who wasn't versed in TDI repair has been at work and it may well be a new belt slapped in after a previous "event". Proper locking tools (or some such suitable items) should be used to verify proper crank/cam/IP timing upon finding such signs.
I would remove the valve cover for a good inspection and then a proper complete TB replacement.
 

Tdijarhead

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My first tdi, the 2000, someone had just replaced the timing belt and put the tensioner on wrong so that by the time I had driven it home the misaligned belt had lost a 1/4 inch of material from the inside where it had rubbed.

Buying a tdi with a "fresh timing belt change" means nothing unless you know the previous owner is tdi literate and trust him.

With the "mark and pray" evidence, if this were mine I would not only do a complete tb job with new belt, rollers, water pump and tensioner, but I would also pull the head to inspect the valves. There is a good possibility someone broke a belt and then just slapped a new belt on and sold the car. In which case in about 10,000 or so miles one of the valves will break off and drop into the cylinder.

Finding evidence ,paint marks, of a mark and pray job is not comforting. It means someone didn't know what they were doing. I have paint marks on my 2000, no I didn't put them there.
 

tryin2vw

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With the "mark and pray" evidence, if this were mine I would not only do a complete tb job with new belt, rollers, water pump and tensioner, but I would also pull the head to inspect the valves. There is a good possibility someone broke a belt and then just slapped a new belt on and sold the car. In which case in about 10,000 or so miles one of the valves will break off and drop into the cylinder.

Finding evidence ,paint marks, of a mark and pray job is not comforting. It means someone didn't know what they were doing. I have paint marks on my 2000, no I didn't put them there.
I found this out the hard way.
 

oilhammer

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There are just too many to list....
You need to redo the timing belt properly, that much is certain.

However, from your description it sounds like you may have a bad oil pump. More specific, the pressure regulating valve in the pump is stuck and forcing full potential pressure on the system, which overpumps the hydraulic lifters, causing them to hang open and cause a loss of compression.

It gets better when it is warm because the oil will be thinner. In some cases I have seen it where you can start the engine up cold, and so long as it stays at just idle speed for a while it will be driveable. But if you try to increase the RPMs at all while cold it will push the lifters over the edge.

You can verify this with an oil pressure gauge at the sensor, but be careful as I have seen VAG engines peg 150 psi gauges in seconds when that oil pump sticks. :eek:
 

tgray

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Thanks so much for your responses and helpful ideas. I agree - I had another car that had a "new" belt and found the tensioner spring hold tab was all mangled and messed up and turned backwards. It was a disaster waiting to happen. It is probably best, if you buy a car and don't know the history, just pull it in the shop and put a new belt in it or do some serious checking.
I am curious about oilhammer's idea and it is an easy check. I will get a gauge on as soon as I can and post the results and thanks for the warning reminder. Hydraulic pressure bursting a low pressure gauge can be very dangerous. I think I have one that goes at least to 500 psi and stay away from it while reading it.
This car was hit in the front and busted the oil filter housing where the pressure regulator is. I put in a different one I had laying around off another engine I had from a short block core - perhaps something got stuck up a bleed off port that I missed when I cleaned it up. Without a proper diagnosis like that I could end up tearing the whole engine apart and find nothing wrong with the head, valves or the pistons.
 

tgray

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I was reading the post again more carefully by oil hammer and realized he was talking about the regulator being in the oil pump itself. I was thinking it was located in the filter housing. In any case I need to first find what the gauge says.
 

oilhammer

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There are just too many to list....
The one in the oil filter housing is for the oil filter/cooler. The pump itself has a regulating valve in a small cylindrical bore in the casting capped off by a steel plug.

There is a piston and a spring inside that bore in the pump, and it allows excess pressure to bypass right there at the pump and drain right back into the oil sump. The relief pressure is 12 bar, meaning it should never allow more than that, which is pretty high all by itself. That is about 175 psi maximum. So when that valve sticks, the actual pressure on a cold engine when the oil is thickest can go extremely high. So high you'd actually need an ATF pressure gauge to accurately read it, but if it immediately pegs a 150 psi gauge it is probably a safe bet to say it is stuck.

I suppose you could try and take the pump apart, but getting that steel plug out without damaging it in such a way that you could press it back in place and feel confident it would stay secure could be a challenge. New oil pumps are not terribly expensive, and not difficult to replace.
 

tgray

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I just put a gauge on the engine and it was looking like it was running between the 40-80 psi range at a quick glance - the guage went to 475 psi so the lower range was not too accurate. Nothing to indicate that it is too high. I was just sitting in the car pumping the throttle and watching the gauge. When the chugging and missing started up there was no change in the needle. Sometimes the missing and chugging is way worse than other days I have tried it. One thought was perhaps chunks of gunk is falling off from the intake and messing things up for a little while and then it all goes back to normal. Today it actually didn't run to bad for me most of the time and would consistently rev up to 4500 and then back to a smooth idle.
 

benhart16

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My first thought is the EGR. Is it still hooked up? I'd unhook the valves just as a diagnostic check, because my jetta behaved in a similar manner, so my fix was to unhook everything and flash an EGRless tune. Not that I wouldn't redo the timing belt because a TB failure is a stupid reason to trash an engine, it seems unlikely to me that if it was working fine for a while after it was installed and all the marks still line up that the timing belt is the root cause. The reasons a diesel will run rough and blow white smoke at a given RPM is either something is going on with the pump, or its starving for air. I'd also check actual timing with Vagcom just to make sure the timing adjuster in the pump hasn't gone bad.
 
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tgray

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Thanks for the info on the location of the oil pressure relief valve. The other weird part to me is that it runs so bad always when I hook up the egr valve to the vacuum hose. I have tried messing with the settings in the ECU but it didn't change anything behavior. The actual and desired settings move around, don't always match and don't make a lot of sense if I remember right. I have taken the EGR off and inspected it, cleaned it and tested it with vacuum and looks like it behaves just fine. I even took the control solenoid apart and that all looked good as well but perhaps it is not. I just was wondering if the intake valves would be causing this behavior as well. Shouldn't this engine be able to handle a wide open egr valve at full throttle? This engine will not rev past 3,000 with the EGR hooked up.
I have run out of time with my shop so I am going to have to put this project on hold for a while until I can get a few other pressing things done. So when I do get back to it I will continue my investigations and post the findings which sounds like tearing into the head/valves
 

benhart16

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I'd unhook the vacuum hoses from both the EGR valve and the intake butterfly valve and see what happens (assuming you haven't done this already).
 

tgray

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The timing was checked, holds steady and is spot on. At first I thought it was something in the injection pump but then when it free wheels on restarting after it starts chugging and dies shows to me there is clearly a compression loss.
 

benhart16

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Ah, I meant to say check the actual injection timing with vagcom when the engine is running, and compare the actual vs expected. The tune maps can call for a 10-15 degree advance of injection timing depending on input and operating conditions. This should rule out any issues with injection timing. If you are confident there are compression issues, then it looks like removing the head is in your future.
 

tgray

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Actually I didn't think of that. Good idea to see what happens or changes.
 

tgray

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Actually I didn't think of that. Good idea to see what happens or changes. Referring to pulling off the anti-shudder valve vacuum.
 

UhOh

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I would definitely look to make sure your ASV isn't sticking: the description of it sometimes turning over really easy sounds like a stuck ASV.

Could also look to unplug your MAF. It's amazing how bad MAFs can make things really screwed up.
 

oilhammer

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There are just too many to list....
The EGR is normally duty cycled to match the requested flow via monitoring the MAF signal. The EGR will normally be OPEN at idle on the ALH, unless it idles for a couple minutes then the ECU will command it closed. Rev the engine a bit, and it will go back to being duty cycled open.

It is a very simple system. Vacuum feeds from the source (mechanical vacuum pump) and is the same source that feeds the vacuum controller for the turbocharger and the anti shudder valve. The engine will run OK with the EGR disabled, if you like, for testing purposes to rule it out, but generally the EGR in any sort of failure mode will not cause the engine to run poorly, it simply won't work.

Good hint given about checking the anti shudder valve for not functioning correctly. It should remain open all the time, only closing for a second when the engine shuts off, then opening again right away. The solenoid for that is self venting, to atmosphere, underneath that little "hat" on the end of it. Vacuum source feeds in the far end nipple (towards the driver's side of the engine when viewed as the solenoid is mounted in the bracket on the intake). The other nipple goes to the vacuum actuator that works the valve itself.

Again, you could disable that whole thing and the engine should still run just fine.
 

tgray

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No change in the problem with ASV unhooked, EGR unhooked and I have had the MAF unplugged and plugged into 2 other MAF's with no change. The only thing that changes the problem that I can tell, is the temperature of the engine. Sometimes it actually seems to disappear. The only thing that makes it go weird is a constant pumping the throttle from idle to 4,000 RPMS. Then it goes into a chugging symptom. Sometimes it sounds like one cylinder and sometimes it is so bad it just dies. Then if I crank it right away it sounds like no compression. If I let it sit it starts back up smooths out to normal when I hold a steady 1500 RPM. My vote is its sounding more like sticky lifters. When I get a chance I will pull of the cam/valve cover and see what it looks like underneath. Perhaps this is a separate problem but it still doesn't make any sense of why the EGR will basically pull all power out of the engine when it is hooked up and only rev to about 3,000. It is so bad that I can hardly make it up my drive way hill. When it is unhooked the engine pulls smooth and hard and will spin the wheels on the same hill. That is why it seems to me the engine is sound on the piston and ring level. And, there are no codes thrown. Perhaps I should give it a drive down the road and see if I can get one to throw under driving conditions.
 

tgray

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Here it is a few months later I decided after the weather turned to take another look. Now the car runs great down the road. It has full normal power all the way with no issues and everything hooked up. The only thing I did over the winter was run the car several times at long idle periods and rev the engine a little. My guess is the valves or lifters were sticking and loosened up or perhaps sticking injectors. Thanks for all your input.
 

tgray

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Now on to my next project - a tdi conversion into a real nice GLI VR6 Jetta.
 

wonneber

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Back to when you did have the problem, was it below freezing? (Mid Oct)
The last few cold days (within the last 2 weeks) I had a loss of power while the motor was cold for up to 30 minutes then suddenly back to normal.
I'm wondering if its a bit of moisture freezing in a vacuum line or valve.
Did you check how much vacuum you had at the time?
The nipple on the vacuum pump is known to be loose, mine is.
Also the line to the brake booster is known to crack.

Rich W.
 

tgray

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No, this problem was after the car sat for a long time when I was working on things and was in the hot of the summer. The vacuum was good. I know it was good as when I hooked up the egr valve it pulled it on full and ran horrible when I put it under a load. It really seemed like something was sticking in the valves and the more it ran the better it would run.
 

tgray

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I finally got a chance to get back to the project and the engine is still running bad again like it was in the beginning. I decided to change the oil pump as it is an easy swap and the engine has a lot of miles anyway. There is no change after the new oil pump. Punching the throttle over and over while running the rpms up to about 3-4000 and the car looses compression and dies. It has to be the valves or valve lifters sticking but I am not sure how to figure out which one. Maybe if I pull the valve cover off I can push down on the valves and see if they feel sticky. Whatever it is the problem is mainly on 3 of the 4 cylinders as it will sometimes keep running on one. I keep wondering if I would just run it on the road with some sort of additive in the oil for a while things would loosen up. Otherwise it sounds like a head needs to come off.
 

jettawreck

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I'm sticking with my opinion/suggestion in post #5, or something similar. Bad lifters, worn/damaged cam, etc.
Given the fact that there were paint marks on the TB/components and no good documentation on past history I wouldn't rule out a past "event", which as far as I've read, (which I haven't followed the intermediate details) has not been investigated or ruled out.
Pull the valve cover.
 

UhOh

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If this were a cam/lifter issue I'd think that it wouldn't sort itself out. This has all the feel of it being an electrical issue. Temperature changes can also affect electrical function.

This needs to be hooked up to VCDS: I"m surprised this hasn't been mentioned- has there even been a check for codes? I'd bet that this ends up being an IP wiring issue. (could it be a thermo Tee issue?)
 
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