1994 Chevy Blazer idle rough and then shutt's off

roger_1105 · Posted at Wed Nov 19, 2008 9:02 am

Engine Performance problem
1994 Chevy Blazer V8 Four Wheel Drive Manual 203000 miles

Hi! i have a 1994 FULL SIZE CHEVY BLAZER 5.7/350 and 2 weeks ago i startered in the morning for work with no problem, warm it up and drive it. after 3 mins of driving the truck started to idle rough so i step on the gas and went back to normal for another minute and then once again the fail. the truck finally shutted off, i took a look at the engine for some lose wire or anything weird. Everything appear to be fine so i started again and it runs fine but when it warmed up the problem was back. i tough it was the ignition module so i replaced bud the fail still there. i just did the entire tune up 2 months ago. i went to a garage and they could not find the problem because the truck it was rinning fine. two weeks later (today) the problem is back the same thing idle rough but just did it for 5 mins and went back to normal. i drove it back home an did not have any problem. Do you think it should be a problem like the egr, egr solenoid or iac valve?. thanks.

pear69 · Posted at Wed Nov 19, 2008 9:38 am

The problem you describe could be 1 million different things. First, I am assuming that this problem rears it ugly head when the engine is up to operating temperature. Your comuter goes through a series of checks as the engine warms up. These tests take 3 to 5 minutes. The computer relies on different sensors to adjust fuel delivery and things like that. Sensors like the ones you describe usually - but not always - sent a trouble code that triggers the check engine light. Is this light on when the problem occurs?
Just changing sensors without testing them will lead you down the wrong path and cost you excessive money. Autozone or a place like that can and will test many sensors free of charge.
The two sensors that can be tested but are just better to replace are the Engine Coolant Temperature Sensor (ECT) and the Intake Air Temperature Sensor (IAT). The test proceedures are very time consuming and are not worth the effort. But they rarely fail so change them as a last step.
Did this problem happen after the tune up? If so, what brand parts did you use for the tune up? Is the check engine light on? If so, what are the trouble codes? Autozone will scan the computer for free and tell you the codes.