Serious idle problem
 

94 S10 4.3l cpi runs good until it warms up, then all he** breaks loose. Bearly will idle, surging, popping, give it gas and it smooths right out.

I've been dealing with other issues for a while now. It wouldn't start, when it was cold, as a result of low fuel pressure, installed a new OEM pump, and it starts like a champ now!

Replaced a leaky FPR, tested the TPS and MAP with the old multimeter and replaced them, checked timing, replaced plugs, oil pressure sender, fuel filter, checked timing. I've spent untold hours looking for vacum leaks, replaced vacum hoses and air filter.

I've wrenched on non-fuel injected vehicles for a lot of years, but I just can't seem to solve this one.

RE: Serious idle problem
 

I have and still have the same problem, try cleaning the EGR

RE: Serious idle problem
 

Thanks, for the tip, already tried that one.

RE: Serious idle problem
 

Any codes? Do you have a scan tool available? IF so, watch what the O2 sensor starts doing as the engine warms up. I suspect it is "sticking", and running the egine lean.

RE: Serious idle problem
 

No codes. Good tip on the O2 sensor, thanks for the reply.

RE: Serious idle problem
 

Replaced O2 sensor, old one had black sooty deposit(running rich?). It will still idle along fine, then start to drop Rpms, almost stall, exhaust pop, then either catch or stall completely. I am at my wits end on this one, anyone have a similar problem?

RE: Serious idle problem
 

HAve the same issue, looking for answer too. usually stalls on idle. Disconnecting tan/white wire under passenger carpet gets me home, barely.

RE: Serious idle problem
 

you seem to have quite alot of toolsdouble check that fuel pressure in regards to bleed off. When cold that 4.3 would demand more fuel where when warm.....I have no doubt that pressure is right there at key on(60ish probably)but when you key off-that's what I'd want to see. My thought is the GM 'nut unit' that attaches to your FPR-or something else in the plenum. Just a free guess. JP:(