99 Blazer, inconsistent problem. Loss of power and engine shaking but at times its perfectly fine. I replaced cap, rotor, plugs, wires, and cleaned the MAF sensor, which helped but now maybe 50/50 bad/good. Fuel pump, spider injector, fuel filter the problem? Mechanic who did the plugs isn't sure and even went to a dealer and they said "couldn't get the problem to occur".

Also do most of you replace the fuel pump before it goes bad? I'm at 173k. Wasn't sure what % can get by without an issue.

Any suggestions?

Thanks!

 

i dont know how often it occurs by saying its an inconsistent problem. Once a week? Once a month? Every couple months? Knowing a number would help.

what you are describing sounds like an inherited problem with these blazers. Have you cleaned your EGR. Yes i know it sounds wierd, i thought it did too. But these 4.3's are notorious for having pieces of carbon build up in your intake manifold and then they will break off and get stuck in your egr and it wont seal properly. This causes air to get into the engine during combustion and causes a lean condition. My 95 has done it multiple times. It runs awful. Sounds like it is about to stall out.

If you are near a highway when it starts to do it, drive onto it and it will usually clear out but sometimes it doesnt. You may have to take your upper intake plenum off and clean out the egr port. That is where all the big pieces of carbon build up.

Good Luck!

 

The coil on my 96 was shorting. Look for evidence of arcing around the frame of the coil. Of course, it could be anything else too I'd also pull off the EGR if your car has one and clean it very well. I've had the symptoms you describe from that too.

 

Is the money light on, if so what codes you got?

 

No I dont , I always check fuel pressure and if everything is good I dont replace it.

 

If it only acts up when warmed up it could be the coolant temperature sensor. If the VCM thinks the engine is cooler than it is the VCM will richen the fuel up too much causing rough running.
The best way to find your problem is with a good scanner (not a cheap code reader) that can display all the PID's. Your answer will be there.