CLK 200 kompressor strange injector problem
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Audi S4 -99
Ok, since i had no problems previously when i ran it with maf unplugged, i decided to test that again.
So it seems with maf unplugged it works again with no problems and i can see very steady afr of about 12-11:1 at wot with 5bar of fuel pressure. With maf plugged in i get 17-18:1 afr at wot, but the reading is much more erratic..
Can i still have a bad maf, even though i just replaced the part??
I think i need to run at boost without maf connected to verify this, but i cannot get boost without it since ecu drops boost when maf disconnected..
What could i do to get boost with maf disconnected, any suggestions?
So it seems with maf unplugged it works again with no problems and i can see very steady afr of about 12-11:1 at wot with 5bar of fuel pressure. With maf plugged in i get 17-18:1 afr at wot, but the reading is much more erratic..
Can i still have a bad maf, even though i just replaced the part??
I think i need to run at boost without maf connected to verify this, but i cannot get boost without it since ecu drops boost when maf disconnected..
What could i do to get boost with maf disconnected, any suggestions?
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Audi S4 -99
Ok, after some more testing i think i have narrowed the issue down to the MAF. Here is what i did, i pulled the compressor magnetic clutch connector just to keep the engine from going on boost just so i could see differences better when running with/without maf connected.
Also, i had my other scan tool connected to see the maf output voltages on a graph form.
So, i started with maf disconnected and saw afr on my wideband go from 14- dropping as i floor it, like it should.
Then i connected the maf and watch the afr go to about 16:1 after flooring it on 2500 rpm and see it constantly on 16:1 until at 3500 rpm i see afr jolt to about 10:1. So this clearly confirms the symptoms i had before at this rev range.
So i do another run with maf connected, this time observing the scan tool for maf volts graph/rpm graph. After 2500 rpm i see a clear drop in the maf volts that jumps up at around 3500 rpm.
On these runs the jerking did not happen, i assume because of no boost/engine not so lean at 2500-3500rpm.
So i'm pretty convinced now that i need a new maf, i can only assume that the one i just replaced with was also bad since it was a junker part..
But before i replace i want to ask where is the engine breather on these engines that can clog/cause fouling of maf? I want to make sure i do not foul the new maf once i replace it..
Also, i had my other scan tool connected to see the maf output voltages on a graph form.
So, i started with maf disconnected and saw afr on my wideband go from 14- dropping as i floor it, like it should.
Then i connected the maf and watch the afr go to about 16:1 after flooring it on 2500 rpm and see it constantly on 16:1 until at 3500 rpm i see afr jolt to about 10:1. So this clearly confirms the symptoms i had before at this rev range.
So i do another run with maf connected, this time observing the scan tool for maf volts graph/rpm graph. After 2500 rpm i see a clear drop in the maf volts that jumps up at around 3500 rpm.
On these runs the jerking did not happen, i assume because of no boost/engine not so lean at 2500-3500rpm.
So i'm pretty convinced now that i need a new maf, i can only assume that the one i just replaced with was also bad since it was a junker part..
But before i replace i want to ask where is the engine breather on these engines that can clog/cause fouling of maf? I want to make sure i do not foul the new maf once i replace it..
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Audi S4 -99
I had simliar problem and found the MAF sensor was very oily and when I accelerated hard, it would make the car bog down and I could only accelerate slowly. This then made me look into the cause of the oil and thanks to the forum discovered 2 blocked breather nozzels on the fuel intake, once cleared no more oil contamination and sharp acceleration.
I want to take a look if they are blocked in mine..
Thread Starter
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Audi S4 -99
Thread Starter
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Joined: Oct 2013
Posts: 37
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Audi S4 -99
Update, finally got around to check the breather nozzles.
Pulled the intake, other one of the hoses going to the breathers snapped right off, second one was surprisingly good. I suspect someone replaced the other one in the past.. Anyways i replaced the bad hose with some general fuel/oil rubber hose.
Nozzles were both completely plugged up. I used some iron wire to open them up, i noticed it was best to push from top->down that way it was easier to do, even though the front nozzle is a bit harder to get to, because of the machined ridges on the head.
I noticed break cleaner is good stuff to get the black stuff off from the intake.
I put everything back together and decided to not replace the MAF just yet, but wait for couple of days of driving to clear any possible oil residue left in the intake/air hoses..
Pulled the intake, other one of the hoses going to the breathers snapped right off, second one was surprisingly good. I suspect someone replaced the other one in the past.. Anyways i replaced the bad hose with some general fuel/oil rubber hose.
Nozzles were both completely plugged up. I used some iron wire to open them up, i noticed it was best to push from top->down that way it was easier to do, even though the front nozzle is a bit harder to get to, because of the machined ridges on the head.
I noticed break cleaner is good stuff to get the black stuff off from the intake.
I put everything back together and decided to not replace the MAF just yet, but wait for couple of days of driving to clear any possible oil residue left in the intake/air hoses..
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Audi S4 -99
Ok, one final update. 
I put in the new MAF and now the car finally works like it should!
Runs very smooth now through the whole rev range.
I even noticed that slight jerkiness while running cold was gone..
Pretty awesome after dealing with this problem for about a year altogether..
So thanks again to A1EK for pointing this out and everyone else also.
So the used Bosch MAF was faulty to begin with! Kind of wish i had bought a new one right away. This new one is a Pierburg one, it's a slightly cheaper alternative to the Bosch original one. 95 eur compared to 127 eur, where i bought it from..
But i guess i can use the extra MAF body for MAF relocation project i had planned..
I put in the new MAF and now the car finally works like it should!
Runs very smooth now through the whole rev range.
I even noticed that slight jerkiness while running cold was gone..
Pretty awesome after dealing with this problem for about a year altogether..
So thanks again to A1EK for pointing this out and everyone else also.
So the used Bosch MAF was faulty to begin with! Kind of wish i had bought a new one right away. This new one is a Pierburg one, it's a slightly cheaper alternative to the Bosch original one. 95 eur compared to 127 eur, where i bought it from..
But i guess i can use the extra MAF body for MAF relocation project i had planned..
Last edited by Vilpo; Jun 28, 2015 at 07:24 PM.
