Hesitation/Miss at constant throttle...

[CajunKenny]

I have checked for codes and there are none. I have checked for vac leaks and haven't found any. New plugs gapped at .030. Set of used plug wires that ohm'd out good when installed two months ago.

At idle the miss/hesitation is somewhat evident. At a constant 3k rpm in neutral, it's more evident. At a constant 3k rpm while driving is even more evident, and of course under boost is REALLY evident. Lots of 'evidents' there...

The knowns and the clues:

Clutch starting to slip under heavy load.
A burning rubber type smell after coming to a stop (could be clutch related).
U-Joints are properly aligned.
While in boost, the boost fluctuates 1 to 3 pounds.

While in boost, I wouldn't describe it as a miss or a slip really. It's like it gets bits of more power rather losing power. If that makes sense...

This thread here almost describes my problem exactly!
http://www.mkiiitech.com/forum/showthread.php?t=884

Sorry for the novel!

 

[jdemara]

Start of a BHG?

 

[CajunKenny]

I suppose anything is possible; but, I not likely since I just repaired one of those about 4k miles ago.

I'll try to get a long overdue compression and leak down test done tomorrow.

 

[johnathan1]

I used to have this problem...turned out to be the wiring to the CPS. I removed the connector and soldered the CPS wires to the engine harness, and my engine became silky smooth again. Could also be bad plugs. I switched out my stock Denso plugs (was running just fine) and put in a new set of NGK's, and it ran terribly. Put the originals back in, and have been running them ever since. Just a few things to think about.

 

[CajunKenny]

Yeah, thanks!

I just installed a CPS that passed inspections according to the TSRM; but, it could definitely be wiring. That is a common problem. I'll look into that and I also have a set of iridiums I could temporarily put in to see if that changes anything.

 

[rayall01]

Don't overlook the coilpack, and wires. I had and idle stumble after my rebuild, so I replaced my coilpack and wires, and problem solved.

 

[CajunKenny]

That's a good idea too. I have several spares.

 

[mattsplat72]

Hey Kenny is the ground wire on the coil pack tight?

 

[rayall01]

Hey Kenny is the ground wire on the coil pack tight?

Another good idea, but when it happened to my stepson, it ran fine, but made an awful ticking noise.

 

[mattsplat72]

I was thinking that if he was getting on it the torque might shift the weight of the packs and they might be arcing off of the head. Worth a shot. My money is on a loose wire that is getting shifted around with the motor.

 

[zambini]

i have also heard of small misfire problems caused by the ground wire in the ignitor. theres a tutorial for modding it and making it better around here somewhere..

 

[CajunKenny]

Great suggestions everyone. Keep em coming!

I didn't get a chance to work on the car today. Hopefully tomorrow...

 

[CajunKenny]

Ok. I only had time to switch out coil packs. It does seem to edle a hair better so we'll give that a dance tomorrow and see what she does.

Earlier today I was able to log a couple of runs using the maft pro. This is new to me; but, my afr's didn't seem very stable. It oscillated except on decel. The spikes I saw seemed to correlate to what I'm feeling with the car.

Can any of you maft pro veterans tell me if your afr data streams are flat while at a constant speed or do they oscillate up and down? I didn't measure it; but, my eyeball tells me its oscillating at around 400hz.

 

[zambini]

damn thats interesting..

 

[thedave925]

400 is huge. There is supposed to be some ocillation of course, like 20-40hz. Codes? Maybe a solder joint is working loose in the harness, they don't last very long if you don't shrink wrap them.
Sounds like an afm issue...
Have you
-Recently unpowered the ECU so its still learning?
-Checked for codes?
-Tried resetting your WBO2?

What was the last thing you messed with before this happened?

 

[CajunKenny]

It was something that just developed and now that I've recently installed 550's and a Maft Pro, it's more evident. More evident because of more power of course.

I soldered each clip on and shrink wrapped the solder joints. I do this type of stuff for a living so I don't question my work there at all.

I just installed one of my spare coil packs so I'll see if there any changes with that. I have a spare AFM. I'll try that too.

I have not recently reset the ECU.
There are no codes.
I have the AEM UEGO WB. Is there a reset for that one? I'll have to go dig out my instructions on that...

 

[thedave925]

There's only so many things that have that effect on the engine.
AFM
CPS
TPS
ISC
incorrect vsv routing?
Fuel pump resistor?

I suggested afm from my own experiences with my maft install, running afc mode and going to speed/density. I got some wire mixed up so it did that to me at idle, up and down really bad. Like the ecu was switching between listening to the voltage from the maft and afm simutaneously. Thats the point where i eliminated the afm and went full speed density.
I'm running the innovative lc-1 WB and they provide a reset (user installed momentary interupt switch in the ground or something) to wire in, i'm not sure about the UEGO.

 

[CajunKenny]

I hear ya. I am going to switch to speed density in the near future. I was hesitant to do that until I tracked this problem down. I didn't want to risk compounding problems.

As you described with your AFM situation, someone else suggested that I just go ahead and convert to Speed Density and that may solve my problem.

Until I can narrow things down, it's a guessing game. I got a lot of good suggestions thus far so I'll employ them over the weekend and what concludes.

 

[mk3mitch]

I have a similar problem right now, my car misses a whole lot at idle. Ran the codes yesterday, and its saying the TPS, Gonna change it tomorrow. Was also thinking coil pack, as I have no vacuum leaks, new plugs, and new wires, BUT, When the car is cold, the first few minutes, it idles smooth, then when it warms up it misses. So I was thinking it can't be the coil pack, or could it? Any info greatly appeciated.

 

[CajunKenny]

Ok. Today the problem persists with the second coil pack. It even got worse. It got bad enough that the cel flashed a couple of times so I was hoping to find some trouble codes when I got home and I DID!!!!!! Woo Hoo!!!!!

Now I have a direction to go. I got codes 24 and 34.

I'll be trying my spare afm to see if that clears up 34.

I'm thinking 24 is because of the maft pro. Can any of you maft guys chime in on that?

Thanks everyone!!