PDA

View Full Version : Very Strange Problem.



dannslc
08-23-2007, 01:51 PM
I have been having boost issues with my car for quite some time now and recently got sick of it so I took it in.
Shop said I have no boost leaks or vac leaks, no codes, and am spiking at 18 psi and coming down to about 14-15. Vac is at about 20. I have the apr 91 chip. Still running bad. It is an 01 btw.
The car is still feeling under powered and doggy under acceration. I went for a ride with the tech and he felt the same thing. The car is smooth but slow. It seems like a stock 1.8t, maybe even slower. The shop can't really find anything else wrong with the car.
My maf was changed a coulpe months ago.

What else could possibly be causing this? Any help would be great. I am going nuts with this problem.

Poopie
08-23-2007, 03:42 PM
do you have any timing logs?

Daft
08-23-2007, 05:33 PM
Yeah, logs of measuring blocks 003, 020 and 115 would be a good start. The ideal log would be a couple 3rd gear pulls to get a picture of the engine's performance under WOT.

I wonder if the N75 is faulty. Typically you'd get some sort of error code relating to N75 duty cycle.

Instead of further speculation, just try and get some logs.

sixfiveoh
08-23-2007, 05:39 PM
If he had a faulty N75, would he be boosting 18psi?

dannslc
08-23-2007, 05:56 PM
The tech logged the car on the test drive and said everything looked ok. I was starting to think the n75 might be bad, but I would think it would throw a code though.

quattro16
08-23-2007, 07:24 PM
N75 Dont usually throw codes all the time. And they do cause it to be doggy. Change it out and it should fix it.

dannslc
08-23-2007, 07:29 PM
Alright I will definently try that.
With a bad n75 why is the boost and everything operating correctly.

dannslc
08-24-2007, 07:54 PM
My shop is saying that couldn't possibly be the n75. Whats next?
The only thing I can come up with is the timing. We are going to log it again next week.

capea4
08-24-2007, 09:00 PM
hows the exhaust? Could it be collapsed baffles in the exhaust? Maybe a half melted cat?

jaybquick@JHM
08-24-2007, 11:18 PM
My shop is saying that couldn't possibly be the n75.

Correct.




hows the exhaust? Could it be collapsed baffles in the exhaust? Maybe a half melted cat?


I was leaning towards plugged exhaust as well. It is very common to see plugged cats.just unbolt the exhaust at the turbo and run it real quick with a spacer keeping it separated. That is what I do.

audiFUEGO
08-25-2007, 08:54 AM
i had a very similar problem and im still dealing with it. The car would spike high boost but it just wouldnt more fast at all...


i took the cat out and installed a test pipe. But i dont know if its fixed cause im still in safe mode until i install that stupid map sensor on my fmic...

NOMIND
10-29-2009, 06:21 AM
Hey guys does anyone know if a plugged cat would limit my boost to 5-6 psi? I have been though every part of the turbo system I can including swapping out the n75, 710, MAF, and even the turbo. I also pressurized the system with a smoke machine and fixed any tiny leak I could find but cannot get it back to max boost. I do not have any codes or cel. Would'nt a plugged cat trigger a CEL or fault codes?

jaybquick@JHM
12-22-2009, 09:12 AM
Hey guys does anyone know if a plugged cat would limit my boost to 5-6 psi? I have been though every part of the turbo system I can including swapping out the n75, 710, MAF, and even the turbo. I also pressurized the system with a smoke machine and fixed any tiny leak I could find but cannot get it back to max boost. I do not have any codes or cel. Would'nt a plugged cat trigger a CEL or fault codes?

yes a plugged cat can cause this and no it won't necessarily set a CEL.

Zaraeleus
12-23-2009, 01:57 PM
Intermittent Diverter release?

Dynamite
12-23-2009, 02:10 PM
to check for a plugged cat/muffler let the car warm up to operating temp then in neutral/park record the intake mani vacuum it should be about 20 inch Hg then rev to 2000rpm and back off suddenly to idle and record the vac again, do this 4 times or so on the 4th time if the vacuum is more than 1 inch Hg higher than at idle the 1st time there could be something plugging the exhaust. its by no means full proof but its free and quick to do