• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

Bad startup when cold....

sco77

sco77

New member
Ever since I got my engine together and running I can't figure out what is causing cold starts to be so bad, on cold start (under 100-120F coolant I would say) it will lope between 2000 and 500 rpm, sometimes even stall now that it's cold out.. It will do this for about 30 seconds, unless you touch the gas then it will correct itself faster. EVERY sensor is new, and I even tried swapping in another MAF and IAC. Got a completely different computer tune and it didn't change at all. There is ABSOLUTELY no vacuum leaks, unless its at the LIM (I don't see how).

Maybe unrelated but it also vibrates very rough around 1500rpm. Looking at scans I see no misfiring or any sensor values out of the ordinary. Could a dying battery cause this? I do know one of the cells in the battery is failed/failing (no starting problems but low 11.x voltage).
 


whats it charging at? if it cranks then fires up then the battery shows over 12 volts it should run ok.

kinda sounds like a vac leak, try carb cleaner sprayed at the vac lines and base of the blower trick yet?
 


Most times after a cam, you'll get that surging start up. DH has mentioned bumping timing in the idle to smooth it out.
 
i have the same mods and the same issue. Cold start sometimes will lope a little bit, I think that it's the N* IAC valve trying to maintain a good AFR during the start phase. You can try to take it out and clean it and see if it helps response. I think the N* acts just a little bit richer on startup.

I know in the PCM there is a IAC step value, I don't know what the optimum value should be for the N* versus a stock throttle body.

Another option is to drill a small (1/16" - 3/32") hole in the TB plate to let just a little bit more air.
 


I could never figure it out no matter what I tried via tune or anything so I just said to hell with it and have gotten used to it...
 
You must log in or register to reply here.
Back
Top