tobykinkle

My 97 A4 is acting up....Sometimes it will act like it has no power and shutters (normally from a stop and go, but has done it just driving. The tach jumps between 500 and 2000 when it happens.) If I give it gas, it acts like it wants to die. If I put it in nuetral and rev the engine, then drop it back into gear, it solves the problem. I hooked up a fuel press guage to it to see if it was a fuel problem. The guage stayed the same when it hesitates and when it runs normal...No code comes on...My mechanic thinks it could be coil packs, but it doesnt happen all the time. Car can be warm or cold, and it will still do it.....Any help would be appreciated

Lago Blue

So perhaps it's not a fuel thing. That would leave air and spark.

Please tell us more about your car: auto or manual?

Have you done the telephone cord mod?

Have you done the EGR mod?

Are there any stored codes even though no CEL has been lit?

Is your MAF sensor really clean?

What vacuum do you pull at warm idle, and if possible when it is acting-up?

When it is mis-behaving can you pull the plug wires one by one to see if they still all cause the engine to stumble further?

tobykinkle

Please tell us more about your car: auto or manual? AUTOHave you done the telephone cord mod? What????I dont think I messed with it

Have you done the EGR mod? No, what is it?

Are there any stored codes even though no CEL has been lit? Not that I know of
Is your MAF sensor really clean? Have a cool air intake system and clean the MAF every time I change the oil (5 to 6K)
What vacuum do you pull at warm idle, and if possible when it is acting-up? No idea, but if I am at a stop light and accelerate, or am turning slowly then accelerate, it happens. Not all the time though.
When it is mis-behaving can you pull the plug wires one by one to see if they still all cause the engine to stumble further? I cant, because it only happens when I am driving. The spark plugs look fine and are newish (15K miles) and the wires seem fine.

The car does it when its cold, or warm. I am jjust afraid if I dont figure it out, its gonna stall at an intersection and WHAM!!!

Lago Blue

<u>Auto.</u> Your car has an auto tranny, something I know nothing about what effects that might have on your engine. It may have some influence, I have no knowledge of how it might or not.

<u>Are there any stored codes even though no CEL has been lit?</u> You need to know. Read how at 12v.org. Then check for them. Write them down. Clear them. See if they return.

<u>Is your MAF sensor really clean?</u> Does your "cool air intake system" include a filter that has oil on it? If it does, ditch it for the OEM stuff.

<u>What vacuum do you pull at warm idle, and if possible when it is acting-up?</u> Don't get an idea, get a vacuum gauge.

Sir, you appear to have managed to check the fuel pressure while it was "acting-up", "The guage stayed the same when it hesitates and when it runs normal...". How did you do that? If you can check the fuel pressure at all, you can do these other things. "the wires seem fine" Did you mind-meld them, or meter them?

<u>The telephone cord mod.</u> Search for it on this forum. Do it to your car.

<u>The EGR mod.</u> Search for it on this forum. Do it to your car.

Do be afraid, but do these things to start eliminating possible causes.

An alternative to doing these basic diagnostic/house-keeing items is to just start replacing parts randomly, or pay someone else to. That might work.

tobykinkle

My car has had the intake on it for almost 3years,and have never had this problem. Yes, it is an oiled filter, but when I clean and oil it, i let it drain for about 3 hours before reinstalling in my car. I also clean the MAF every time. As far as the wires, yes, my mechanic and I metered them (inline light...hook it to he end of the wire and then to the sparkplug.) For the fuel pressure, the mechanic hooked up his fuel pressure guage and taped it to the outside of the windshield (looked like **** for 3 days, but it eliminated the fuel as the culprit. IIRC it was around 55 psi)

I dont like throwing money into my car by replacing parts that I dont need, thats why I posted this question. I will look for the telephone wire mod and egr mod later on the forum.

I do remember seeing a code come on about a year ago for something EGR(OBDII scanned) but it went away after about 2 days. It could still be there, but my scanner doesnt pick it up, and I dont have a VAG-COM.

Lago Blue

Just curious, please describe any possible advantage of an air filter that has bigger holes in it than the OEM one, takes 3 hours to change, and poses a long term health risk to your MAF Sensor.

In that same vein, what good does said K&N filter/cool air intake do for your otherwise stock car that the OEM filter and OEM factory filter-box with it's original cold air intake; does not?

Re: "The tach jumps between 500 and 2000 when it happens."

ISV:

https://www.audiworld.com/forums/sho...&highlight=air

ISV detailed cleaning:

http://forums.quattroworld.com/12vv6/msgs/414.phtml

Does your intake still include the OEM black plastic "Noise Damper" that connects to the throttle body? If so, and you have not ever replaced the OEM rubber seal between these two; you may need to do that; and do the said telephone cord mod.

Something else to check - Noise Damper attachment:

https://www.audiworld.com/forums/sho...php?p=22447395

Beyond the above, it may be your EGR System, Evap Cannister Purge Valve or other simple vacuum leak. The vacuum gauge is another one that you can run while driving the car.

I totally agree, don't change parts you don't need to, just check the ones you've already got, use a little logic, common sense, and the simple and cheap periodic maintence suggested in the above posts will do in most cases.

Because your issue is just drive-ability, and <i>not</i> that your car has quit altogether, there is a fairly good chance that your issue may be one of a simple lack of required maintenance entirely fixable by you; and not one where a single expensive defective part requires replacement to cure. That is what my suggestions are trying to point you toward.

Hope this helps.

rs4tech

the tach jumping around is the dead giveaway of what the problem is...the coil packs. they will always fail and give you 2 dead cylinders, which is why the tach jumps around...I do agree with lago blue though and you need to go through and try to take care of other known problems and fix them before they become major headaches...

tobykinkle

It just happened again, and this time the engine light cameon. I ran an OBDII scanner and picked up two codes:

P0401- Insufficient EGR flow
P0159- O2 Sensor (Bank 2, Sensor 2)

Looks like I have some stuff to figure out this weekend. Going to replace the O2 sensor and test the EGR this weekend. Might do the telephone cord mod while my car is down. I really dont want to replace the coil pack ($$$) so Im gonna see if this solves the problem, and if not, anyone have a cheap coil pack LOL......Thanks all.

rs4tech

autohausaz.com...$135 shipped to your door for a coil pack. the egr flow problem is more than likely a clogged up egr port in the intake manifold. also try to draw vacuum on the valve itself i have occasionally seen the diaphram in the valve tear, but it is not extreemly common

Lago Blue

but first remember that the O2 sensor can be metered and it's performance observed, prior to its' just being yanked, as it being identified via a CEL may just be a symptom, not a cause.

If you do the cheap stuff first, and clear the code, it may not return.

Forum search reveals such articles as:

https://www.audiworld.com/forums/sho...&highlight=EGR

follow the links back for EGR functionality explanation, system diagrams, example diagnosis and fixing; EGR mod; & more...

RS4tech might be right about the coils, and it reminded me that the degradation of the wires <i>to</i> the coils (under the Intake Manifold) is another known issue and although prevention is still cheaper, this is a less expensive fix.