94 blazer 4.3 runs rough

i have a 94 blazer that runs rough. idle surges. when you pull the plugs they show signs of overheating such as lean fuel mixture. i have put to fuel pumps in and replaced all ignition components. suspecting o2 sensor or cpi unit. cpi unit usually makes it rich not lean though. o2 sensor shows good with my scanner. any suggestions?

Reply to
gmtech
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EGR valve stuck open by piece of carbon ?? Any DTC codes ??

Reply to
Reed

checked egr valve and decarbonized engine. no codes

Reply to
gmtech

What are the fuel trims?

Reply to
aarcuda69062

If its a VIN "W" and has never had a CPI injector you might as well get one. Ive gone though 2 in 130K miles. The last one had a good size leak in the pressure side plastic hose making it hard to start when sitting shortly after shutdown and it idled rough. I have seen the egr get a piece of carbon stuck under it, you should check that too. I think I have gotten an EGR code when it happened though ,but you never know..... And like aarcuda said check the block learn. IIRC gm's "official" way of checking the injector is a high block learn and/or integrater.

Reply to
ShoeSalesman

Did you check all your vacuum lines? I had similar problems with my 94 last year. I found a vacuum line behind the carb had hardened and had a hairline crack( it wasn't easily visible till I took the line off. Replaced the line and solved the problem.

R> i have a 94 blazer that runs rough. idle surges. when you pull the

Reply to
ronlin79

fuel trim was like 117 i have it wrote down out in the shop. will have to make sure. have checked vacuum lines so far didnt find anything. i think i will go ahead and put a cpi unit in it and replace o2 sensor and see what happens.

r> Did you check all your vacuum lines? I had similar problems with my 94

Reply to
gmtech

117 means that the computer is subtracting fuel in response to a rich condition.

Leaking injector poppets, leaking fuel pressure regulator, leaking internal lines (nut kit) or an evap problem would be the first things to check.

Reply to
aarcuda69062

Yep, at your mileage go for it. It will run like a new truck too :) I think I paid about $250 for the injector unit last time but I got it at the dealer too.

Reply to
ShoeSalesman

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