Help me diagnosis - Rough idle, momentary drops in power on small throttle input -3.2

**tspesh** · 08-12-2016 09:35 AM

I bought this car with 98,000 on it, it currently has 156,000 on it. I keep the oil full and changed though it does have a leak in the timing cover gasket and I just replaced the valve cover gaskets which took care of a pretty gnarly leak there. That leak got oil into the spark plug chambers. When I did that job I replaced all plugs and coils. What prompted that job was that cylinder #2 was misfiring and upon checking the plug I noticed that the coils were also drenched in oil and a little carbed up (not all of them but I found the coils cheap enough to just swap them all).

I was hoping this would help address the issue I have with the car but it really didn't seem to. It did fix the mis-fire.

So here are the symptoms:

When it's very hot outside and the car has not been running a while, the engine will drop revs when idling or even when moving with a very low throttle input. It's a standard, so it's most pronounced when in 1st and trying to slowly (think: creeping through a parking lot).

I also see this at highway speeds though. When you're actually moving it's more subtle but the car lurches because the engine will drop power briefly and repeatedly.

When I open the door there is an audible electric noise, it sounds like a motor trying to do something but it's not a healthy noise, it sounds like it's struggling. This made me think that it was maybe the fuel pump but 1.) the Audi dealership tested it and said it's fin and 2.) i'm not sure the fuel pump is activated by just opening the door. What is that noise?

I'm seriously wondering if the throttle body is just dying? Is that completely asinine?

Any help is good help.

**MacFady** · 08-12-2016 09:56 AM

Yes, it's asinine. First address what you know is wrong, by the sounds of it you haven't addressed whats going on behind the timing cover. Confirm through reading other threads with a more detailed explanation of what effect normal operation of the torque converter can have on your RPMS (may find more in the B6 section) and confirm that this is not what you are experiencing. Also, note that it is normal for your car to idle above 1000RPM for the first 30-60 seconds upon starting and then closer to 800 RPMS afterward. When "...the car lurches because the engine will drop power briefly and repeatedly" are you getting a flashing check engine light, that would indicate a misfire and sounds like you've had issues with your plugs, coil packs etc.

Maybe record the "electronic" sound you are hearing. Is it only when the vehicle is running? Does it start and stop with you opening and closing the door? Where is the sound coming from ie: front, back, left, right, under the rear seat etc.

**pezgoon** · 08-12-2016 10:39 AM

Originally Posted by MacFady

Yes, it's asinine. First address what you know is wrong, by the sounds of it you haven't addressed whats going on behind the timing cover. Confirm through reading other threads with a more detailed explanation of what effect normal operation of the torque converter can have on your RPMS (may find more in the B6 section) and confirm that this is not what you are experiencing. Also, note that it is normal for your car to idle above 1000RPM for the first 30-60 seconds upon starting and then closer to 800 RPMS afterward. When "...the car lurches because the engine will drop power briefly and repeatedly" are you getting a flashing check engine light, that would indicate a misfire and sounds like you've had issues with your plugs, coil packs etc.

Maybe record the "electronic" sound you are hearing. Is it only when the vehicle is running? Does it start and stop with you opening and closing the door? Where is the sound coming from ie: front, back, left, right, under the rear seat etc.

He said its a manual...

tspesh, yes the fuel pump primes when you open the door. I think it does it when you unlock the door as well, also does it when you turn the key to the on position, so you can turn it to the on position and listen to it and deem how healthy you think it is.

Whens the last time the fuel filter was changed? It's supposed to be done every 30k and if its never been done there's a good chance your in tank pump *could* be on its way out.

Try timing how long it takes for the pump to prime, I'm starting to see signs that the longer it takes to prime, points to how well its working

And if you Throttle body was on its way out the car would know, these things can pretty much diagnose themselves

And by rough idle, do you mean that you can physically feel the car shaking? Or more so rpm wise. If its physical and you've never replaced your motor mounts then I'd point more to those than the engine.

Any codes since the misfires?

You have checked/been replacing your cam follower correct?

**tspesh** · 08-12-2016 02:13 PM

Firstly thanks for the replies. Next, I feel like a bad parent so I'll do my best to answer this stuff honestly.

1. The electric noise has to be the fuel pump then. I didn't realize opening the door would wake that thing up. I'll try and get a recording of it.

2. Bad Father Moment: I'm not sure the filter has ever been done under my ownership.

3. I'm not sure how to measure that, if the sound I'm hearing is in fact the fuel pump then I'm not sure how long it takes to prime is relevant because the noise is one of electric death. Instead of a small whine like you'd expect from a fuel pump it's more like a clickity clackity stutter. Think how a bad starter sounds as the servo is clicking, except much quieter. Thing is, the car starts beautifully every-time.

4. Re: throttle body -- fair enough

5. Rough idle...i'll grab a video of it. It's a drop in revs/power, momentarily. The high-rev upon start and then dropping down to 800...that much I've seen over the years to realize it's normal. This is not that. It's not a matter of the car shaking or anything like that so the motor-mount angle probably isn't what we're talking. It's more like the car want's to stall, but the revs never drop low enough for that to happen. And again, when it's doing it...it makes for a pretty "not smooth" drive.

The weird thing to all of this is that it isn't consistent. I just drove across town and conditions were perfect to replicate it: It hadn't been running for a while (last night), it's hot out, and it's been baking in the sun. Ordinarily this is when it would be the most severe, but today it ran fine.

**pezgoon** · 08-12-2016 02:33 PM

Originally Posted by tspesh

Firstly thanks for the replies. Next, I feel like a bad parent so I'll do my best to answer this stuff honestly.

1. The electric noise has to be the fuel pump then. I didn't realize opening the door would wake that thing up. I'll try and get a recording of it.

2. Bad Father Moment: I'm not sure the filter has ever been done under my ownership.

3. I'm not sure how to measure that, if the sound I'm hearing is in fact the fuel pump then I'm not sure how long it takes to prime is relevant because the noise is one of electric death. Instead of a small whine like you'd expect from a fuel pump it's more like a clickity clackity stutter. Think how a bad starter sounds as the servo is clicking, except much quieter. Thing is, the car starts beautifully every-time.

4. Re: throttle body -- fair enough

5. Rough idle...i'll grab a video of it. It's a drop in revs/power, momentarily. The high-rev upon start and then dropping down to 800...that much I've seen over the years to realize it's normal. This is not that. It's not a matter of the car shaking or anything like that so the motor-mount angle probably isn't what we're talking. It's more like the car want's to stall, but the revs never drop low enough for that to happen. And again, when it's doing it...it makes for a pretty "not smooth" drive.

The weird thing to all of this is that it isn't consistent. I just drove across town and conditions were perfect to replicate it: It hadn't been running for a while (last night), it's hot out, and it's been baking in the sun. Ordinarily this is when it would be the most severe, but today it ran fine.

Awesome response thanks for reading it all makes it much easier

One last thing, cam follower, whens it been replaced? If it hasn't... not good... It could be worn through which would mean the intake cam is worn along with the HPFP which could give similar symptoms and its not cheap to deal with

When the fuel pump is priming, its a sort of whirr sound. I meant timing it by counting (one second two seconds etc.) I only ask as my A4 has 40k and my mothers has 140k so I have a comparison, shes getting low fuel pressure codes intermittently and has a weird stumble when it starts sometimes (intermittently) does the acceleration thing etc. Her fuel pump runs for about 5 seconds every time, mine runs for a half second every time no matter how long its sat. I believe its her fuel pump causing the issues (or camshaft but with the way the pump is priming we are starting to point to that) as we've already replaced her HPFP and the low pressure sensor and it didn't help. BUT her cam follower was not worn through nor ever has been, thats why I suggest checking it if you never have and maaaybe be prepared to find ugly things (not guaranteed but very possible)

No check engine codes besides the misfires correct?

Also if you had those oil leaks like that, have you replaced the PCV? normally when you get the oil leaks from the valve cover it means the PCV is bad and is blowing out the seals. I'm not positive but I've heard it can create some weird issues which the turbo building up pressure in the crank case and causing odd things to happen (and blowing out every seal in the engine)

As a last thing that I just thought of/recalled. These cars have BAD carbon build up issues because of it being a direct injection engine (no gas washes over the intake valves so all the oil from the pcv builds up on it) I would suggest reading up on it (in the tech section or just search) but thinking about your symptoms, if you have no CEL, I'm thinking your due for a carbon cleaning. The intake manifold has to be pulled off, and the intake valves are either soaked in a chemical and scrubbed which can be done at home (takes hours and hours) or you pay an indy/dealer to do a walnut blast which is about 300-600$ and is done in a couple hours.

The carbon eventually builds up enough causing issues with the intake valves closing properly causing rough idle and stutter at low rpm's.

I'm not sure how mechanical you are in dealing with cars as that would also help in suggestions of you to pull things off or find a good mechanic etc

I would read up on A. Cam follower, B. PCV, C. Carbon buildup. (and do the fuel filter) and try to get us a video of the noises your referring to, its very hard to diagnose without seeing the car lol

Ps, the fuel pump IS pretty loud even in good shape, shouldn't be clicking though

PSS Sorry its so long lol

**pezgoon** · 08-12-2016 03:45 PM

Also, just as an after thought, the ac was off during all this testing right?

And is the 3.2 in the title your engine? If so you'd have better luck I'm the s4 rs4 forums than here, this is for the four cylinders

**tspesh** · 08-24-2016 08:57 AM

Appreciate your followup. I've been out of town a bit thus the lack of response.