Hey guys... 2 weeks ago, I started getting a high RPM stutter at around 5,000 rpm that would also make the car take longer to accelerate shift to 3rd gear (it's an A4). It got progressively worse, with stuttering occuring lower in the RPM range (still over 4000 RPM though) and also became evident on 1-2 shifts.

Stuttering never occured when I revved the car in idle though. Driving normally (no WOT blasts) the car runs great.... and idle is fine.

I replaced the coil and coil wire, checked the plug wires (MSD 8.5mm OVC are less than a year old) and also cleaned the fuel system, replaced the fuel filter and fuel pressure seems ok. And the problem persisted.

After driving for a week with no WOT blasts... I tested the car out again.... and the stutter was gone. The car drove as well as always and revved freely. It seemed like the car fixed itself!

Then 2 days ago, it came back. I was pi$$ed as we had our Toronto F-body drag day the following day. Nevertheless, I took it to the track with the stutter.

First 2 runs the car stuttered on 1-2 and 2-3 shifts and I hit 14.1x times. 3rd and 4th passes, it got better and only stuttered on 2-3 shifts hitting 13.7x times. Then the stutter went away completely and I hit 13.5x times. The car was running really strong at the end (actually breaking out in the bracket races).... and I can't figure it out.

I was debating whether it was the Opti... but does anyone have any clue of what type of problem could "fix itself" over time and also get worse at others?

PS. I was also getting up to 10 degrees of knock a while before this problem was happening. This occured intermittently as well... but odly enough... stopped happening in the last 2 runs of the day, as well as on the street later. Not sure if it is related.


Thanks everyone for reading this long post.... and thank you in advance to all who could offer me any suggestions.

 

TTT For those who may have not seen the thread.

 

this may sound really stupid on my part but sounds like something is loose/not connected right? Like a plug, or plug wire, or the coil wire? Maybe that knock thing IS related to something. Your studdering just might be that knock retarding timing and it not actually being a studder but just a big drop in timing, my car kinda felt like that till the LT4KM. I dont know really but maybe some things you should double check. Just a side note, I stopped using that fuel injector cleaner in a can crap since my SES light would pop on everytime i used that stuff (it was NOT a coincidence or God is telling me something then).

 

Sounds to me like a possible valvetrain problem

Did u check over Lifters, Pushrods, Valvesprings?

I had a similar problem. Maybe u bent a pushrod or cracked a valvespring.

 

Thanks for the reply ChickenScreamer... I was thinking something was loose, but I've checked all my wires several times. The coil wire and coil were even replaced. With respect to cleaning the fuel lines and injectors, I actually took it to a shop and ran it on their professional machine for an hour.

That sounds like something to consider Wheelman. However, I haven't heard any excess drivetrain noise and with an Automatic, I haven't missed any shifts that would cause my hardened pushrods (95's came with hardened rods) to bend. Furthermore, I'm not sure any of these drivetrain components would self correct, as the car is running strong right now... for the time being anyways. That's the thing that's making this problem hard to diagnose.... it doesn't happen all the time.


Thanks for the ideas guys...I'll check them all out... so keep'em coming.

 

my car has been doing the same thing for 4 or 5 months now. I can't figure out what it is. I changed the opti-spark, plugs, wires, coil, coil wire, etc., etc. and it still does it. Good luck, post on here if you find out what's wrong, I'd like to know....