Idle problems

[lee0123567]

I have an 87 with a fuel injected 350. When it's idling the RPM's go up and down by a few hundred every couple seconds and sometimes it goes so low it stalls out. What could be causing this problem?

 

[89Suburban]

Getting a check engine light at all?

 

[lee0123567]

Yeah, it's off and on

 

[89Suburban]

Did you try to pull the codes?

Here is the list of codes:

http://www.gmsquarebody.com/forum/showthread.php?t=6844

 

[Jims86]

Vacuum leak is first that comes to mind, but like 89s said, always check and clear/ fix codes first...gives you a clean sheet to work with.

 

[89Suburban]

I got a really detailed manual from Retro on diagnosing these codes. I just started looking at it today. I got to find a way to get it posted on here. Jim I got to email this to ya later.

 

[Jims86]

I got a really detailed manual from Retro on diagnosing these codes. I just started looking at it today. I got to find a way to get it posted on here. Jim I got to email this to ya later.

Kool!
I usually do a continuity check on the offending circuit of the wiring harness from the comonent plug to the ECM plug before replacing sensors.

 

[89Suburban]

Kool!
I usually do a continuity check on the offending circuit of the wiring harness from the comonent plug to the ECM plug before replacing sensors.

Let me know if it came through

 

[Jims86]

Got it...Thanks!

 

[89Suburban]

Got it...Thanks!

Scroll down to the Code 32 section, great read there. I really would like to get that whole thing posted up here for the whole file.

 

[sticman]

Sounds like the IAC is still functioning
Surging TBI very rare that the obd1 computer will set a code
For me i would start with
1 Dirty IAC / IAC passage in the throttle body. helps with control of idle
2 Vacuum leak, Computer needs a good vacuum signal to the sensor
then maybe
3 fluctuating fuel pressure
4 leaking injectors
Too hot of a cam

 

[lee0123567]

None of the places around here can read something this old, ffaaacccckkkkk

 

[HotRodPC]

None of the places around here can read something this old, ffaaacccckkkkk

That's true. You can't read OBD 1 codes with an OBD 2 code reader. Most everything before 96 is OBD 1. (Not Everything, MOST Everything). You can read your own codes using a paper clip in the ALDL and counting your CEL flashes. No special tools needed.

 

[lee0123567]

I've noticed it does it just when the truck is warmed up. When it's cold it idles around 1000ish and it's fine. But when it's warm it goes down to 600 and idles out or does the pulsing thing where it goes up and down.

 

[anubisani]

fixed my high idle problem today turns out pcv was missing, funny thing when i put in the pcv the truck began acting erratic even tried to shut off, engine light came on , then the ecm made the adjustments and it started running great after that