ok i am baffled. i have no codes. my 98 blazer 4.3 runs perfect a majority of the time but randomly, by randomly i mean every month or two, it will lose power missfire and reak of gas out of the tailpipe.the only code it will show is a misfire.this last time it fouled a plug and has a dead cylinder now. the weird thing it will run perfect after turnig it of and letting it sit for a little bit.I dont klnow if its the pump or regulator or injectors or what. i am ready to pull my hair out on this problem. anybody have an idea of the cause.

 

So which is it, a 95 or a 98?

 

crap sorry dont know what i was thinking. its a 98. once again its running perfect now. the only thing that i can think of is maybe a faulty fuel pump,maybe getting hot or bad connection idk. but its been hard to start in the mornings when leaving out to work so i am wondering if im making enough pressure. i tried reading up on the injection system..do these have poppet valves ? if so how much pressure is needed to enable them? what should my fuel pressure be? i am going to get a guage today and check it. if it looks good then i am once again back to being baffled.

 

If it is randomly screwing up, I would look into an electrical problem. This does not necessarily mean fuel pump as a loose or corroded ground wire to the PCM can cause all sorts of problems as well. Are there any other conditions that you find trigger the problem? Raining? Hot? Driving down a certain road?

But the next time that you experience this problem, have a fuel pressure tester on hand to hook up to the test port. It is located behind the throttle body slightly towards the driver side of the motor. For nothing else, this may help you eliminate the fuel system as a cause.

As far as the fuel injection system goes, you have the SCFI injection system. This system has a central injector pack which houses six individual electronic injectors and the fuel pressure regulator. The six injectors feed pressure actuated poppet nozzles through nylon tubes. These nozzles are located down in the intake port directly before the cylinder head. The SCFI injection system requires 55-60psi to properly start and should not drop below 52psi during operation. I have posted the book fuel system diagnosis in the DIY section, but I do not believe that you will need to go through that at this point.

 

ok thansk for the advice,i will just have to keep a fuel pressure guage with me..it could be another month or two before it happens again. And no, it doesnt seem to make a difference if its hot cold or wet outside.I have been on a 1800 mile trip out of state twice with out any problems .So i guess i will just hope to catch it when its messing up with a guage and will check any grounds i can find. one thing it did do on my way home yesterday was when i just got off the highway and came to a stop it was running fine.then i left the light took a turn and all the sudden had a straight miss like a bad plug. but when idling it ran smooth but as soon as the throttle was pressed it missed. so i chugged home and turned it off. about hour later i started it and had the straight miss in idle as well.i figured it was a gas fouled plug.so i was planning on changing the plugs this weekend but today it was hard to start and then idled and ran perfect. damn gremlins..

 

ok heres an update.i changed th plugs yesterday andput in some high dollarfuel system cleaner withnot much luck.ichecked the fuel pressure when running normal. stays around 55psi idleing. it has started to be an everyday thing now with it running like crap and missing.i checked the pressure when its running like crap and it is still above 50 around 55 like it should.it reaks of gas when its missing so i really figured it would had a drop in pressure if maybe if an injector was malfunctioning but still no luck on the culprit..I also noticed when it has been sitting for long periods of time its hard to start. so i checked the pressure this morning and before starting would only get to high 40's.and when cranking on it the pressure slowly drops.Isnt the pump supposed to run while cranking? cuz i think it is not running when cranking. but after a few tries it starts and pressure jumps to 55. and if i turn it off and the pump delay is on it goes up to 60 like i figured it should.so anyways this is the degrading update. any ideas?this thing is killing me in gas with all ready horrid gas prices. any chance this might be the dreaded high dollar fuel injector spider acting up? i dont really know how a bad injector would act.

 

I am actually wondering if something is not affecting the power supply to the fuel pump when you are having this problem. 40psi is not enough to properly operate the poppet nozzles.

Have you tried looking at the fuel pressure after you turn the key off? It should drop a bit, but hold steady after the initial drop. If it continues to bleed down to nothing, then there is a leak in the system somewhere.

 

well the weird thing is i have noticed that randomly the pressure does drop after the key is off but not all the time..majority of the time it holds at 60psi. other times it will fall about 3psi a second. the only thing i could think of would maybe be a injector leaking? or would the poppet valves keep this from happening?

 

well another negative update...it is now gotten so bad that it will barely keep up with traffic with it floored. i did notice this morning that i could feel it surging and getting power in pulses then went straight to no power...its barely even drivable when it does this.its gone from a very random problem to multiple times a day..and is getting harder to start in the mornings. i noticed i could barely hear the fuel pump come on but after about 5 minutes or so of cranking and stopping sranking and stopping it finally started and when it was to that point, the pump was much louder. So either something is sticking open and no putting much pressure on the pump or a bad connection...but still doesnt make sense the way it feels only sometimes..anytime i had a pump go out before it was out. going to do the wiggle test while running on any part of the harness i can get my hand on ...after that i am stumped

*Combining Consecutive Posts*

HOLY CRAP I FOUND IT!!!!!!!!!you would never guess the culprit..somehow there is fuel pressure in the connector on top of the intake where the harness plugs in to the injector spider. the pressure behind the connector actually pushed a few of the wire/pins straight out of the connector. i started wiggling the harness starting there while running and it would either almost die or would rev up and smooth out. so i opened the connector cover and low and behold the pins with the little seals had been pushed out of the connector and when i jiggled them they started spewing fuel out. now i am hopefully sure fuel should not be there and am thinking either something is cracked inside or maybe the regulator is leaking. i have never been into a motor with the under intake injector spider.if any body has any advise on the cause or maybe even a repair

 

HOLY CRAP I FOUND IT!!!!!!!!!you would never guess the culprit..somehow there is fuel pressure in the connector on top of the intake where the harness plugs in to the injector spider. the pressure behind the connector actually pushed a few of the wire/pins straight out of the connector. i started wiggling the harness starting there while running and it would either almost die or would rev up and smooth out. so i opened the connector cover and low and behold the pins with the little seals had been pushed out of the connector and when i jiggled them they started spewing fuel out. now i am hopefully sure fuel should not be there and am thinking either something is cracked inside or maybe the regulator is leaking. i have never been into a motor with the under intake injector spider.if any body has any advise on the cause or maybe even a repair