Hello there, have been looking forums for more than a month, but no luck.

I have Audi A4 (95) 1.8, it lost its power under full throttle plus sometimes fires from air intake.

What has been done:
[ol][*]Oil changed;[*]oil filter changed;[*]fuel filter changed;[*]air filter changed;[*]air intake, near throttle cleaned from oil;[*]changed that whole "thingy" that generates sparks (sorry, don't know english term); spark plugs;[*]changed mass air flow intake meter;[*]stationary diagnostics;[*]fuel pressure check.[/ol]What was found:
[ol][*]Electronics and all meters ok;[*]fuel pressure ok;[*]there seemed to be something fishy with sparks in 4th cylinder (showed a bit smaller current, than the rest). I was offered to chenge that "thingy"- nothing;[*]mass air flow meter was also fishy- same thing after changing it;[*]no vaccum leak;[*]normal fuel mixture;[*]lambda seems not to be working.[/ol]I'm taking her Monday for checking of lambda, timing, cat etc., however maybe you have some suggestions before spending another bunch of cash on deeper diagnostics?

By the way, when all of these problems started I've tried taking out air filter- it helped, but putting it back resulted in the same problems- then a week later I've tried it again- this time it didn't fix the problem like first try- I guess it gets worse.

Please if you have some ideas, share, as I'm tired driving my wifes RAV4 and miss my car. And try to be as clear as possible, as I don't know all technical terms in english.

 

i don't understand what you mean by fires from the intake. are you saying you see fire coming out of the intake? you also said you took the air filter out and ran the car? that's not good buddy. you have to get your fault codes read and then post them. as far as the thing that creates spark, are you talking about the part that you have to take out with a 16mm ratchet and extension or the thing you see on top of that?

 

Nono, you've got me wrong. I haven't tried to drive with no air filter inside (just reving up in garage- it was enough to start firing).

I don;t know how do you call it (firing). I guess its misfire- no flames, just a GOOD blasting sound and force enough to give a good shake for intake box. It does not happen all the time, just during extreme acceleration at lower rpm's. But the feeling that someone is holding the car from behind is always, until I don't rev up to at least 3-4000 rpms.

Thats the problem- there are not a single error code (except lambda, but this already was 2 years ago while I bought the car). Its a bit strange, as fuel consumption all this time was normal (factory statement +1l/100km.

I don't know if there's a connection here, but I was getting to repair my brakes and on my way there I missed a huge hole in parking lot and got a really awful hit to the bottom. Could a broken cat particles jam up exhaust and cause this thing? They've tested emission and they are normal.

Car doesn't like high loads (full acceleration, going uphill in higher gear). When its reved up then everythings OK.

BY saying "thingy" I meant that box (relays) that outputs four plugs you connect to spark plugs. Hope this explanation is a bit more "digestive" .

 

it could be that cat. hit it with your hand a bit. if it's misfiring, you'll see the check engine light flashing. you might have a stored code. it doesn't hurt to clear it.

 

You mean the ICM, ignition control module.

 

Thanx CrazyHawk.

Codes were cleared several times during 2 years, but this lambda error always came back after about 1000km.

Engine light never showed up.

If I shake cat what should I try to hear or see?

 

Ok. Finally fixed, so I thought it might be helpful some somebody.

I checked regarding spark plug change as somehow I thought it was suspicious. It appears that they didn't even change those as they seemed to be OK... well they weren't...

Changed spark plugs and my oh my how life has changed... Thanks to oil and filter, air filter, fuel filter, spark rellays and spark plugs changed, car is consuming fuel even less than manual says (1.8 engine).

Just keep in mind to start changing spark plugs and checking ordinary things before you get dirty in vaccum leaks, electronic problems and other expensive diagnosis business...