Hi guys,

I've done a lot of reading to see if I could find a solution prior to posting this message. I have a '94 S10 Blazer CPI with 220K miles on it. Recent things done to it were, New spider with regulator, nut kit, intake manifold gaskets, spark plugs, rotors. No fuel leaks in intake plenum and fuel pressure is holding at a steady 60psi and when key off for a few seconds would hold 55psi. Car runs fine before. EGR was changed two years ago and I cleaned it again, still the same.

Problem is I haven't driven it for a month and when I went to start it, I need to step on the gas pedal to start it and the idle speed would surge up and down, up and down continously looking to shut itself off. Seems like a vacuum leak but I checked all the hoses and it seems fine. If i put it in reverse, it dies. I could drive it but it would stall when I come to a stop light unless i keep my foot on the gas pedal. When I'm driving it, the surges does not happen at all, it happens only in park gear. Do you guys have any suggestions on this problem? I did notice the throttle cable is a tad too loose but don't think it is adjustable. Could that be causing my idle problem?

I tested the TPS and the readings look ok. Can the Idle air control valve be causing this problem? I didn't see where this valve was when I looked near the throttle. Any advice is appreciated and thanks for the attention --Barry

 

When i bought my dad his 92' it ran sorta like this. to find out the egr was stuck open by a piece of carbon. Pop off the egr and clean it with some brake cleaner and your wifes favorite toothbrush. You can get a gasket with a screen to prevent this from happening again.


edit : oh yea,pop off the idle air control and blast some brake cleaner on that too. they usually just get dirty.

 

The pressure has to hold up to 55 psi for 10 mins nothing let. If it dont you have a leak somewhere. Any thing lower then 55 psi means there is a problem in the fuel system.

 

hello,

checked the fuel pressure again and its good running and when i turn the car off. i also replaced the egr, throttle position sensor and idle air control valve. problem is still the same. Now I can't even step on the gas to start the car. after numerous attempt, i waited a few hours and it started (without needed to step on the gas) with the same symptoms i mentioned on the thread before. It surges up and down and will shut itself off if i put it into gear.

i'm beginning to wonder if it's the ignition coil or control module but then it'll start after a few hours but surges up and down. older posts mentioned it could be the alternation but I'm getting 14V at the battery consistently even during the surges and battery is new. i'll try to replace ignition stuff and report back. thanks for the attention.

cpi, regulator, line kit, rotors, plugs, cap are all new. i might just junk it if all else fail.

 

k,are you checking the pressure with a actual gauge? These cpis are VERY sensitive to pressure. lack a few psi off and you wont never get it right. If its not priming to 60 at key on,replace the pump with a ac delco ONLY. if it primes to say 57,dont say "oh that should be good enough? its not. These engines need that extra few psi to run efficiently.

 

Follow this for the proper way to diagnose the fuel system.
96+ Fuel System Diagnosis - Blazer Forum - Chevy Blazer Forums

 

I used a fuel guage from my friend to do the measurements. It was within spec but I'll do it again I guess. When it runs the oil pressure guage needle goes up and down following the surge. I'll do more troubleshooting before I replace the pump. thanks for the advice.

 

When I replaced my regulator it would to this, also ran really rich. But my fuel pressure was at 90 psi becasue my regulator wasn't adjusted right. Have you tried reseting the computer? I know it made a difference when i adjusted timing, maybe it will for replacing the spider. Same procedure as clearing codes.

 

I had the very same issue. I replaced fuel pump, ignition coil, Spark control module, injectors and everything. still the same damn problem. We finally figured it out when we took a timing light to it, and saw the timing mark jumping around erratically up and down, it never stayed in one spot! Anyhow, turns out, the problem was a broken harmonic balancer. Turns out to be a common problem with the Blazers. The rubber used in the balancer can break and wreak havoc on the engine as the ECM tries to adjust timing.