: high engine rpm at start up



smokinbob
02-05-09, 10:39 PM
The last couple of days, during cold start, I am seeing very high engine speeds for about 5 seconds, then it settles down and idles normally. I did clean the EGR and TB about 2 weeks ago. starts and idle were good then. Outside temps. have been 10-20 degrees the last few days. Thanks

Ranger
02-05-09, 11:10 PM
How high is high?

Submariner409
02-06-09, 10:24 AM
.........Hmmmmmm......Your car, cold, should start and idle at 1200 rpm for 20 - 30 seconds, drop to 900 or so for another minute, then down to normal idle - 650 or so.

N0DIH
02-07-09, 11:48 AM
I have seen engines that do this have a vacuum leak and it is just hard to control for the PCM till it warms up even a little bit.

As Ranger said, how high is high? 1000 rpm in 32F weather is expected, 1100-1200 in -10F is probably ballpark.

A bat IAT or CTS will cause them to be unusually high. A vacuum leak will also.

My 3800 L67 V6 idle table:
http://i159.photobucket.com/albums/t142/mompower/Tom/PCMTuning/3800L67Idlerpms.jpg

smokinbob
02-09-09, 01:38 PM
RPM's at initial cold start about 2,500! for about 5-7 sec.

N0DIH
02-09-09, 02:49 PM
My 80 Turbo T/A 301 V8 was spec'd at 3000 rpm cold start on the high step of the high idle cam, 2500 on next step down (I didn't allow it that high, I fixed it to my tastes...).... Love carbies!

Yours is unusually high, things I would think to look for:

1. IAC sticking in park position (open I think)
2. Vacuum leak somewhere, intake ports on the plastic intake are easy to have problems with. Our resident N* mechs can advise there, either way, not hard at all to remove and replace gasket.

Ranger
02-09-09, 06:00 PM
Yikes! That is high. Just for the hell of it, I'd pull the IAC valve and see if anything looks amiss. Then clean it up a bit. Nothing to loose.

SICKANDTWYSTED
02-15-09, 05:35 PM
on my 02 dts was at 1800 at start up and 1400 when warm, untill i replaced that iac ($200) now its at 1200 at start and 700 when warm or so. i dunno how to test the iac but mine was stuck open all the time.