Another A3 low power - limp mode thread

Hey folks,
Hopefully you can give me a few pointers here. Here is my situation.

• 1997 A3 175,000 miles
• running good but saw that the intake needed cleaning (preventative maintenance)
• cleaned the intake (this is my second cleaning since owning the car)
• car ran really nice for about a week and then I went into limp mode.
• VAG-COM 5.04d - said I had the 575 intermittent different pressures etc.
• When the car ran good I could hear a low toned whistle when you accelerate quickly.
• I seem to be getting more exhaust gases up under the hood and into the hvac system
• Took off the turbo/intercooler hoses and inspected for splits/problems etc. - none found
• Replaced the N75 valve - still went into limp mode
• Put a pry bar on the waste gate actuator and it seems to have lot of spring pressure but it would move

Question 1: I have a Pierburg MAF but I don't understand the procedure for checking this (also read the FAQ)? Need pointers with the VAG-COM program.

Question 2: How do you test the wastegate valve to see if it is moving?

Question 3: Boost gauge - Where does this hook up and what info will it tell me?

Any recommendations are appreciated.
Steve

1) Chances are excellent that the MAF is fine. You can test it with VCDS and doing a run while logging group 3 in engine section.

2) Wastegate takes pressure to open. You can rig a bicycle pump with gauge and a nipple adapter to test the wastegate. Whatever you do, lubricate the linkage with a good synthetic spray. Superlube, Triflow, etc.

3) Boost gauge tees off the line from the upper intercooler pipe and the ECU.

Now replace ALL your boost lines, including the one inside the ECU. I like silicone, and have a post in the How-to section above telling you what you need and where to get it.

Or you could drive down and see me. I have the hose hanging on the wall.

limp mode

I had intermittent limp mode problems and did most everything, but it wasnt cured till I put some deoxit on the maf contacts, now no more limp mode. might not work for you but it is cheap to do.

Finally had a chance to look at the car again. I hooked up an air line to the wastegate valve diapham (blue line) and the wastegate operated cleanly and held in place as long as the air pressure was on (no leakage in the diapham)

I did a MAF test. Here are the results. What do you guys think?

Also I it seems that I have an exhaust leak up under the hood? Depending on where the leak is, could this make a differentiation in pressures in the turbo system? If so, would I replace the manifold and turbo gaskets? I have been under the car while the engine is running and could not identify where the leak was located.
I apologize for the novice questions. All my wrenching has been done on gas motors.

This chart shows the car running ok and then it hit the wall (limp mode) . Before it hits limp mode I can hear a low toned whistle of a lot of air moving with the accelerator floored.



Here is a chart after I cleared the codes.

MAF is suspicious. Drive down. I have a new one on the shelf, and we could put it in and see if it cures the problem. No charge.

Paramedick,
Sent you a PM.

I have a 97 Passat that similarly goes into limp mode @ high speeds ( ~73-78 mph in high gear ) from cruise control use when I get boost above ~12-15 psig actual for more than a few seconds . Above that speed range ( 80 & up ) it seems to be ok . This happens mainly while going up steep grades where power is required to keep speed with the cc set . I can feather the throttle to keep it from happening but with the cc on it almost always happens in this speed range on a grade of steepness and above .

It also occurs in lower gears while pushing up steep grades @ speed . Been dealing with this issue for years but haven't had a clue what was causing it . The boost numbers really don't seem that high to me .

When I got the car 10+ years ago I couldn't make it go into limp mode . Now it can be a real pain to drive at speed across mountains in the west and the hills in the mid-west . Eastern MO on I-70 with the hills can be a real pain at speed with it being thrown into limp mode by CC use .

I've checked all the hoses , replaced them all over the years . I haven't replaced the one in the ECU but the ECU & intake were replaced a few years back under the TV recall . I have a boost gauge & use a SG-II to watch pressure and I do like a hawk .

Like I said I could hold far higher boost #'s without ever going into limp mode until a few years back . I could hold 20+ psig actual for a period of time before without limp mode before .

Does that sound like the MAF contact issue ?? Or could the hose inside the ECU cause this ?? N75 ?? Intake is clean so I'm sure that isn't the issue . I've been trying to figure this one out for a while ...........

Any ideas ??????????

With the help of Paramedick (THANKS!) I have a course of action. First of all I have a leaky downpipe and have a pretty good hunch that the catalyst may be clogged. My MAF sensor is a bit iffy. I was watching the MAF numbers on my way home last night and saw several times that when 850 was requested 580 was the actual flow at 2800 - 3200 rpm but was already in limp mode.

This week I plan on having the downpipe and cat fixed. I'll check the numbers afterwards and see how it does.

RotaryKid - have you checked your catalyst?

Update

I believe I finally have my A3 low power issue fixed.

1.) Catalyst was clogged! I gave the cat an "enema". My friend mig welded a new tail section to the catalyst and I reinstalled an empty catalyst. I also salvaged the internal contents and sold it for $45 at my local recycle center.

2.) Exhaust leak - the downpipe was intact. My exhaust leak was from the flexpipe (cracked) that goes from the exhaust manifold to the EGR cooler. The part cost $133 dollars - Ouch!!!

3.)In the process of fixing - I gouged the coolant hose that goes from cylinder head to the EGR cooler - another VW specialty part.......$$

4.) I replaced the passenger and driver door switch that controls the courtesy light - the door switches were shorting out. I think this also fixed my alarm issues.

I'M BACK ON THE ROAD!!!!

steve b said:

I believe I finally have my A3 low power issue fixed.

1.) Catalyst was clogged! I gave the cat an "enema". My friend mig welded a new tail section to the catalyst and I reinstalled an empty catalyst. I also salvaged the internal contents and sold it for $45 at my local recycle center.

2.) Exhaust leak - the downpipe was intact. My exhaust leak was from the flexpipe (cracked) that goes from the exhaust manifold to the EGR cooler. The part cost $133 dollars - Ouch!!!

3.)In the process of fixing - I gouged the coolant hose that goes from cylinder head to the EGR cooler - another VW specialty part.......$$

4.) I replaced the passenger and driver door switch that controls the courtesy light - the door switches were shorting out. I think this also fixed my alarm issues.

I'M BACK ON THE ROAD!!!!

Click to expand...

Please tell me more about the $45 recycled internals of the cat. Is it Platinum and how much was in there by weight? I believe I have an original cat and want to have a peek in there.

I really don't have any information about the material. I know that it was a "honeycomb" type of material, gray in color. There must have been a few pounds of the stuff and it took a bit of work to get it all out without damaging the shell of the catalyst. I used some long rods, long chisels and a hammer.
The person running the recycling center just said "it's the good stuff" so I am assuming it was platinum. They also take your personal information to make sure your not on the police list for stolen goods. There has been a lot of catalyst stealing in our neck of the woods. Last year I think they were going as high as $65 for a whole cat when the prices of metal were up.
I believe most of the recycling centers will take the whole catalyst if you don't want to do the hard work but I needed the shell to refit back into the exhaust.
Wish I could be of more help.

What did the honeycomb look like? Was it clogged? fallen to pieces? How much performance was gained after gutting compared to pre-limp mode? Good job and glad the problems is fixed!

Honeycomb looks like honeycomb - not sure how else to describe it. Think of several hundred tiny tubes that run longitudinally along the catalyst.

It seemed that it was clogged by about 40% around the outer edges. It seemed to happen about a week after cleaning the intake manifold. Possibly the extra flow of air through the exhaust knocked some crap loose and plugged it up.

The honeycomb material was all intact - nothing falling apart.

Originally I thought the MAF sensor might be bad. I took a test after cleaning the cat and the numbers look much better than before. The car does not go into limp mode. I have not checked the milage yet. Definitely tell the car breaths better.