Completed multiple mods and have a weird idle problem...

[tmoneyballin]

I have a built 98 cobra, 5 speed, forged internals, heads and intake already installed naturally aspirated and functioning properly prior to the below modifications.

I recently added 4:30 gears, Aluminum Driveshaft, Cold Air Intake, took the upper and lower intake manifolds off to clean the IMRC's and also replaced the IMRC module that is bolted to the bottom of the lower intake manifold. THE CAR RUNS SICK NOW - WILL STOMP VETTE'S ALL DAY LONG BUT....These mods were all done at the same time and the car wasn't driven for 2 weeks...

Whenever I put the car in neutral it revs up to exactly 2,000 rpms(as if I were giving it gas to keep it there like I was going to launch it - just trying to give you guys a picture) it will stay exactly at 2,000 rpms for about a second, give or take, and then rev down to normal idle which is 900-1000 rpms like an engine would normally rev down from 2,000 rpms to idle. I can also be sitting at idle, we'll call it 900rpms and put the clutch in and it will rev up to 2,000 rpms and do the same thing.

I am wondering if you guys have any suggestions of what is causing this - I mean "technically" it gives me a little more edge off the line - essentially the car helps launch itself if I may(burning more gas obviously) - but I am more concerned if it's something that needs to be fixed, or is it as simple as unplugging my battery(again) and seeing if that will clear it up - my mustang friends are at a loss for what would cause this...We originally unplugged the battery multiple times to get the idle to correctly be at 900 rpms after the computer reset itself.

Bottom line is the car is running AWESOME - I beat a supercharged cobra last night that wanted to mess around - if that says anything...but the ONE problem is this stupid idle thing. I am not sure if its complicated to fix it or if I just need to unplug the battery and see if it will fix itself....

THANKS FOR THE ADVICE!!!

 

[squares98]

Your 98 cobra with stock heads, cams, spanks on Vettes and S/C cobras?


It's might be your TPS. Have you checked the wires connecting to it. A bad connection will sometimes cause that.

 

[tmoneyballin]

It could be that man, I haven't checked that personally(my friend did most of the hands on engine stuff, I just helped). If it is, do I need to be careful driving the car until it is addressed - meaning no trying to spank that new vette I am going to pass tonight at 9:30 where he always tries to F%$# with me?

My car has over $10,000 into it - I loosely implied that when I said "built" - heads, intake, gear, and WAY too much more to list. The poor guy in the 03 cobra asked what I had done to it and I said just exhaust and wanted to know if he'd run it for fun...He knew what was up after he saw my tail lights.... My brother also refuses to race me now that I have done all that to my car because my old setup could beat his 2000 vette already, never mind the 65 hp I just added to the car with various "goodies" oh and the 430 gear - that will help too. I went for the higher gear because I have a lower compression(my request when the car was built, so I can one day supercharge it) and therefore a 430 gear feels more like what a 410 should feel like with stock compression.

Thanks again for the advice and like I said do I need to drive the car gently until I address this problem?

 

[squares98]

I have a similar isue with my car. Every few months the idle will hang. I know that if I go and give the wires going into the tps a little wiggle the idle settles down. I try to push the wires more into the connector on the tps.

Yep those n/a 4'vs with all the trimmings really scream. Congrats.

 

[tmoneyballin]

So potentially when we were putting that cold air kit on we could have messed with it but wiggling stuff around...? The thing is the base line idle of 900rpms is accurate, I am just puzzled about the hesitation to want it to bump back up to 2,000 hold for a second and then return to regular idle.

Also, do you think I should baby the car until this type of problem is corrected or am I only messing with wasting more gas...in other words can I try and run the new vette tonight or should I hold off???

Thanks Bro

 

[steveb24]

ive noticed that anytime i mess with the tune.. even if its raising the idle or the messing with timing.. it always does that. usually takes a good hour of pcm reset and a few days to get normal again.