i have a 1992 blazer with a 4.3 vortec. the engine runs fine when its cold but as soon as it gets up to normal opperating temperature it idles rough and studders. i have checked and cleaned E.G.R valve didnt make a difference. bought a new one, didnt help either. i think it might be a sensor like the o2 or the I.A.C. i havnt checked those yet. i was told that the problem could be a gummed up throttle body. any help or suggustions would be appreciated thanks for your help

 

Mine had the same problem, It was the Ho2. It would be in open loop intil it warmed up and when it went to closed loop it started surging and idling like !@#$. check to o2

 

srry did you say h02? or did you mean the 02 sensor. i'll have to check that anyway. thanks for your help.

 

hO2 = heated O2 sensor

Also, you can pull and clean the IAC (2 T-20 or T-25 torx screws). Just clean the pintle at the end, then use a little motor oil to lube the o-ring before you reinstall. Cleaning the throttle body is easy - just loosen the clamp on the air intake hose where it meets the engine and remove it. Clean the plate that you see - both sides - and the housing around it to make sure it seals completely when closed.

I'd do those first since they don't actually cost you anything except time. If you don't see any improvement, then I'd check the more costly stuff.

 

my 1992 blazer has the 4.3 cpi. it starts perfectly and idles fine right until it warms up. than the idle starts acting up, (truck idle is surging) this problem only use to occur when the truck was under a load like towing my boat. people have told me it's the O2 sensor, E.G.R valve or MAP sensor... by any chance could it be the coil? the O2 sensor was changed 4 years ago. and the problem didn't seem to go. any help would be greatly appreciated.

 

You had this same problem 4 years ago and replacing the O2 sensor did not help?

This sounds like a problem that occurs once the ECU comes off the idle enrichment mode (or goes into closed loop operation) which would lead me to the O2 sensor.

Seeing as how the fuel systems on the CPI motors are known to have problems, have you tested the fuel pressure? If not, I would start there. Please report the results and we will work from there.

*Moving to 1st Gen Tech* - The Tech Article (DIY) section is for Tech Articles only, not for technical questions.

 

yea, while it was in for a emissions test they told us it needed a new o2 sensor.whether they actually changed it or just charged us for one i don't know. i never usually have work done on it by someone else, i do the work my self. are there any other sensors that activate when the truck is at normal operating temperature?

 

Well... All of them are used by the ECU...

How is the performance (other than idle) once the truck is up to operating temperature?

Have you checked the base timing? HINT: you will have to disconnect the timing wire (brown if I remember correctly) located on the inside of the truck on the right side of the transmission tunnel. Pull back the carpet near the firewall and you should find it.

 

performance is greatly affected by the issue. but im now starting to think it's the catalytic converter. if it's clogged exuast gases are going to have trouble leaving thus buggering up the e.g.r valve with carbon; if i pound the gas it'll clear the carbon from the E.G.R and the truck will run fine again for 5 minutes until carbon gets back into the egr. do think thats the issue?

 

*Merging threads* - I thought this problem sounded familiar.
You may want to consider changing the O2 sensor if it was changed 4 years ago. How could such a problem exist for 4 years without repairs being made??

Please do not PM for tech help. If your post has gone a day or two without response, bump it...