Hey guys, well, whenever I start the car, warm or cold, the RPM's bounce up and down for at least a minute or two solid. Then she smoothes out. Car seems to drive fine with plenty of power and no hesitation once shes a lil warmed up. Any ideas?

Also i got a SES light today for the first time. I will scan and see what comes up! Thanks fellas!

Will

 

mines the same, has done it ever since i put the lt1 cam in.....i figure it's something to do with my ignition.....mine pops too though while the tach bounces, then will idle/run perfectly after...

 

i get the same thing, i think the check engine light is a code 32 and the rpm fluctuation is caused by the EGR valve

 

i think my egr is disconnected, but i get no engine code trouble....which is what is wierd

 

I know on mine, at least I'm pretty sure, it has something to do with warming up and the 02 sensor not reading accurate until warmed up, going with a 3 wire 02 sensor supposedly fixes this.

mike/1449

 

thats what a friend of mine told me, that since the intake runners are so long that im having cold start issues, the fuel is getting injected into the intake, the vapor is hitting the cold runners, recondensing, then not combusting all the way and coming out the exhaust and burning...but i can drive my car for 20 minutes, turn it off, then 2 minutes later restart and it will pop and bounce like crazy for a little, and some mornings it can be ice cold and it'll start perfectly, and other days it will give me hell, overall warm weather has helped a little, but it still does it

 

Exactly, I can totally relate to the popping and all that. Its almost like a carburated motor. I start mine in the morning, and she will stay at a faster idle until the temp is reached. It will not kick down manually. Weird, I am new to the EFI game, so every little thing is getting me asking questions. The car is stock, with the only mod being the elec fan runs all the time. I will do some messin around this weekend and see what I can see. The cap and rotor are new, but plugs, wires, ign module (such a thing? on L98's? I'm used to my HEI 86) Anyways, time to trouble shoot! Thanks guys

Will

 

I don't buy that cold start horse crap, but I do buy that the o2 sensor is not warm enough to produce an arcurate signal so the car jumps around trying to make it rich/lean until it warms up and gives a good signal, this is coming from cartek in jersey who are actually pretty god with fuel injection, even tho I will NEVER take a car to them again due to their tendency to rip people off.

 

why can i drive my car for 20 minutes, turn it off, restart it 2 minute later and it still does that, but some mornings it will start perfectly....do the planents have to have a certain alignment for it to consistently not backfire?

 

Mine does this everytime i start the car. regardless. Im with Stealth.....

Will

 

Well mine's weird, maybe my O2 sensor is just starting to go but EVER since the cam swap it's done never, never before. 9 out of 10 times the 1st start of the day it does it. I could drive the car 20 miles, put it in park, it would idle like a watch at 600RPM. I could turn the motor off, then INSTANTLY restart it, and it would go nuts, backfiring and the tach would bounce. I would wait a minute, the rpms would even out, hold at like 1200, and slowly drop to 600 and it would run perfect, idle perfect, drive perfect. I could turn the engine off and restart it instantly and it would do it again. Then again some days it will not do it on the first start, it would not do it the 2nd start, then out of nowhere do it the 3rd start. I would believe it was a sensor if it always did it like yours, the inconsistency is what bothers me. The motor also has trouble reving when it backfires and bounces. If I floor it while the tack is bouncing the car struggles to rev, and the whole car shakes like made, but once it even out it revs like a dream.

 

When it's cold the o2 sensor isn't being used so the problem is in the fuel system or the EGR being stuck.

 

Take the TB off and clean it up completely. That includes the IAC and the manifold the IAC screws into. Clean it with brake cleaner and reassemble. Then set the base idle and TPS in that order.

 

funny you guys are disscussing this. My car is doing the excact opposite and im getting frustrated cause i really need this car to stay runny deopendable for a few more months. When i start my car in the morning..it idles and runs as decent as its going to get, till it gets to about 150 degrees, then it sporactly fluctuates rpms from 2000 to almost stalling out. Its a stock 305 tpi with a few free mods and a hypertech chip,but it ran great for awhile with the chip. Also im in florida and would like to run my ac without it getting 230-240 degrees, anything to do about that? The timing is 6 over..good plugs and wires..new tps sensor. Im really getting frustrated...any help would be great...Thanks..

 

i know i dont have an Iroc (hopefully one day), but i do have a 95z. i put an aftermarket cam in over the winter and ever since its been doing the exact same thing (fluctuating at startup). only for about a minute or 2. havent really looked into what it might be, but the thread caught my attention cause i had done a search about this topic and didnt come up with anything. some good ideas on here, hmmm.....