Analyize This! (Very wierd info on my Cobra)

[akatherazor4]

About 2 month's ago my car suddenly developed a surging at idle issue along with the rpm's hanging up. Myself and others have looked at the car extensively with no results of how to resolve this issue so far. At this point the IAC, VSS, and MAF have been checked and tested, a new computer has recently been put in the car with no result, and almost every other possible thing you can think of has been checked or played with. At this time the problem still occurs and fixing it remains a mystery.

Fast forward to yesterday where I took the time to change the oil, swap out the fuel filter, put in some new plugs and clean the K&N filter. None of this affected my issues but general maintenence was out of the way. When I pulled the plugs I noticed that all of them where white on the tips meaning I have a serious lean condition going on. Now I'm running the same exact tune that reports a 12:1 A/F ration on the dyno no less.

Moving to today, I decided to run a compression test on my car and re-check the new plugs. The car seemed to feel a little weak along with shooting a little smoke out of the left tailpipe on startup. I and others figured the bottom end was on it's way out the door. Not a good feeling when you become aware of this matter. Anyway I pulled the plugs and sure enough they are showing a lean condition. The tips are as white as a ghost. I proceed to do the compression test only to find that it's between 200-210psi on all 8 cylinders!

This is turning out to be by far the wierdest car I have ever owned. The idle surging and rpm hangups are still here, the plugs show a serious lean condition while the dyno says different and no detonation has ever occured either. To top it off the motor is strong as hell after a years worth of Vortech abuse at over 14psi! Is this thing posessed or what?:shrug:

Razor.

 

[03DOHC]

Sounds like a vacuum leak.

 

[akatherazor4]

Originally posted by 03DOHC
Sounds like a vacuum leak.

I wish it was that simple bro. No vacume leak to speak of on this, It was the first thing checked.

Razor.:beer:

 

[SS killer]

sounds like a headache. hope your motor is not shot.

 

[akatherazor4]

Originally posted by svtcobra01
sounds like a headache. hope your motor is not shot.

Well according to the compression test, It can't get any stronger! It's just the combination of everything that doesn't make sense.:shrug:

Razor.

 

[03CobraBro]

I'd say vacuum leak as well... That sounds similar to the symptons my dads 5.0 is having (which he's going to be getting fixed soon.)

Maybe its a bad EGR sensor? I'v also heard of that contributing to idle problems.

 

[wolves]

Can't help, but waiting patiently if anyone has any other ideas. I have the same problem. Had a new IAC put in by the dealer, the VSS and MAF checked, no problems there. Very annoying idle surge and rpm's hang when I get off the highway or after a hard run, stays near 3K then it comes down eventually.

 

[akatherazor4]

Originally posted by wolves
Can't help, but waiting patiently if anyone has any other ideas. I have the same problem. Had a new IAC put in by the dealer, the VSS and MAF checked, no problems there. Very annoying idle surge and rpm's hang when I get off the highway or after a hard run, stays near 3K then it comes down eventually.

Yup same thing here man. What in the world could cause this is beyond me at this point. There's got to be somebody, somewhere that knows what causes this.

Razor.:beer:

 

[01cobrakid]

i had the same problem right after the new tune. Drove it right back to the shop, disconnected the battery for 5 mins hooked it back up and all is good!!!!!!!

Mike

 

[Joe Lynch]

Razor--I haven't had exactly the same problem, but I have had something similar. On mine, it was the chip edge connector. I disconnected the battery, removed the computer and cleaned the edge connector, and then put the chip back in, and the idle was stable again.

Since you have changed the computer, this may not fix yours. In that case, I would temporarily block off the EGR valve and see if that helps. It would affect the engine just like a vacuum leak. Also, check the PCV valve and make sure it isn't sticking.

Those are all easy checks and MAYbe you will find something. But my bet is that you will have to put an Autotap on it and see what the computer is really seeing and doing. That would be the next step if you can't find some simple mechanical problem.

Hope you find it.

Joe

 

[BlueStripe]

PCV valve? That took care of some funny idles in my car.

 

[99Cobra Supercharged]

Small sudjestion, Very carefully check your ducting. On one of my tunes, Paxton found a pin hole in one of my pastic ducting. Caused havoc.

 

[THE FLASH]

How about reflashing the computer? I was talking to a guy with an 01 cobra who had a rpm surging problem and he said they reflashed the computer?

JC

 

[akatherazor4]

Originally posted by Joe Lynch
Razor--I haven't had exactly the same problem, but I have had something similar. On mine, it was the chip edge connector. I disconnected the battery, removed the computer and cleaned the edge connector, and then put the chip back in, and the idle was stable again.

Since you have changed the computer, this may not fix yours. In that case, I would temporarily block off the EGR valve and see if that helps. It would affect the engine just like a vacuum leak. Also, check the PCV valve and make sure it isn't sticking.

Those are all easy checks and MAYbe you will find something. But my bet is that you will have to put an Autotap on it and see what the computer is really seeing and doing. That would be the next step if you can't find some simple mechanical problem.

Hope you find it.

Joe

Thanks for the reply Joe. The edge connector on the computer has been cleaned (new one) so that's not it. I'll check the EGR valve and the PVC to see what's happening. I'll let ya know.

Razor.:beer:

 

[akatherazor4]

Originally posted by 99CobraSupercharged
Small sudjestion, Very carefully check your ducting. On one of my tunes, Paxton found a pin hole in one of my pastic ducting. Caused havoc.

Well we have checked extensively for a vacume leak and nothing was found. I've had one before and it also made my boost gauge fluctuate as well. That helped to track down the leak. Boost gauges are good for more then just reading boost.

Razor.:beer:

 

[akatherazor4]

Originally posted by JC'S01COBRA
How about reflashing the computer? I was talking to a guy with an 01 cobra who had a rpm surging problem and he said they reflashed the computer?

JC

Just put a new computer in the car altogeather. This problem occurs both with the chip in the computer and with the computer by itself.

Razor.

 

[WHITESNAKEVERT]

Maybe the O2 sensor is sending a rich condition signal to the computer and it is doing it's best to lean you out?? Happened to me but they found it immediately once on the computer. It was running warm and lighting the check engine light oo.

 

[SnakeyHorse]

That sounds like the car doing an idle relearn. I would further investigate the chip and computer. Most likely the comp, since you said it does it with out the chip. Also, how long have you had the chip and the problem. If the problem doesn't show up on the dyno, that would indicate a part throtle problem, most likely not addressed in the burn on your chip, but maybe something got messed up.

 

[akatherazor4]

Originally posted by SnakeyHorse
That sounds like the car doing an idle relearn. I would further investigate the chip and computer. Most likely the comp, since you said it does it with out the chip. Also, how long have you had the chip and the problem. If the problem doesn't show up on the dyno, that would indicate a part throtle problem, most likely not addressed in the burn on your chip, but maybe something got messed up.

The chip has been in the car for about a year now. The computer was just replaced about a week ago and solved nothing pertaining to my problem. There's probably a honda civic stuck in my tailpipe or something.:lol:

Razor.:beer:

 

[VenomousSVT]

I am having my idle hang up at like 1100 too....not sure what is causing the problem. I have looked everywhere for vaccum leaks and nothing. It takes after getting stopped like 25 seconds to drop down below 1000.