My 92 Blazer (4.3) has started hesitating,, It used to get better as the engine got warm.. but lately it has gotton worse feels like I was running out of gas.. I checked my fuel pressure and it seemed of,, check the fuel filter and that was fine too...
any ideas??? before i drop my gas tank and check the fuel pump??

 

Fuel filter, tune up, timing adjustment, bad gas, cracked vacuum hose, disconnected vacuum hose, clogged EGR, bad PCV and Clogged air filter would be the first places Id look. Mine did the same, I replaced ALL the vacuum lines and it stopped. But I also did a tune up and fuel filter not to long before the hoses.

 

Thanks for the advise, I pulled my EGR,, and its very clean,and appears to be working ok,,,I then replaced my air filter (it was very dirty) no help there, check all of my vacuum lines and a few were cracking but still held ,, but I replaced them anyhow. Ran engine and was fine during the first few mins of idling,, then I road tested it and within a mile or less it started to hesitate and tried to stall as I gave it throttle,,, pulled back home,, and it would not idle, unless I kept on the throttle,,,,it kept surging for about 2 mins then smoothed out,, but when I tried to rev it,, it would hesitate for a sec and then rev up,,,,I unplugged (what I think is) the MAF....(sits on the firewall about the center, with a four prong plug,,,no vacuum lines,,,,) and the engine did not die,,, It should have died if right???
would love to hear anyone's thoughts on this shade tree mechanics diagnostic???
Thanks ahead of time for any help or advise on this...., [/align]

 

my 98 does basiclly the same thing. the problem gradually got worse as time goes on , or atleast in my case it didi have a post goin right now trying to solve the problem , but all fingers are poiting at fuel pump.

 

You did not disconnect the MAF (it is located inlinebetween the aircleaner and the Throttle Body if you have CMFI). That might have been a relay for headlights or something else???

According to my little amount of research available to me it could be that you need to have your O2S checked (Long Term Fuel Trim should count above 108) if not then you need to look either at the connectors or wiring if that is fine then the O2 sensor itself. But to do this check you will have to pull the hose off the Evaportative Purge port on the back of the intake on the passenger side...

 

That's right,,, the MAF has 2 vacuum lines on it and another smaller wire harness (maybe 2 or 3 prongs) and come to think of it I replaced that,,, with the o-2 sensor about a year and a half ago
Maybe what I pulled off was a TPS (throttle pos sensor)?? It looks just like map sensor,,,
I know that it is related to the engine control, because when I disconnected it.. it triggered my "service engine light" and being that this is an OBD-1 system, I know that this warning light has nothing to do with a routine service or a reminder to change oil,,, because when I plugged it back in,,,and cycled the ECM, (some call it a ECU,,,) the light turned off..
I was thinking maybe my cat is getting clogged,,, but I still get fairly good pressure coming off my exhaust,,, just by feeling it with my hand,,,,...I'm still pondering what module it was that I have unplugged,,, because with it unplugged my idle is doing ok,,, not great but it doesn't try and die and doesn't have the big hesitation when I give it gas,,,,,

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ok here is what I have disconnected, (picture,, and a diagnostic flow chart) I don't know why,,, when I disconnected it..... that it idled better and did not die,,, I hope that this means something???,,,any thoughts on this?? [/align]

[IMG]local://upfiles/5632/08CA0DEF1A5F4509B752D135F7D5C0DA.jpg[/IMG]

[IMG]local://upfiles/5632/17904ED4450D4320B5E2DCF684DC9C4B.gif[/IMG]

[IMG]local://upfiles/5632/99E3B697B01A4762903DC5AA303B2130.jpg[/IMG]

[IMG]local://upfiles/5632/555EFF2119824347AD5CEACC0E06805B.gif[/IMG]

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Its called a ESC


*EDIT: swartlkk* - Combined consecutive posts. Please use the EDIT feature to add any additional information to your post if another member has yet to reply.

 

ESC would be the Electronic Spark Control module this might be the module that is causing the bad idle.

 

Thanks again for all the advise,,, I thought that I figured it out,,, but this morning on my way to work (with the ESC unplugged still) it started doing the same thing,,, hesitating, stalling out and having a hard time getting past speeds of 25 mph... then all of a sunned it stopped and it ran perfect...I'm thinking fuel pump now???????any thoughts on that?
Thanks again for allow me to pick your brain
Jim[/align]

 

Jim, you did not dissconnect the MAF. The MAF has NO vacuums lines to it, and the connector has more than 3 wires. Plus your engine DOES NOT use a MAF. It uses a MAP sensor for the load input to the ECM. The only thing I can think of that you disconnected would be a solenoid that contols fuel vapos for the evap system. That would not effect drivability at all. Now I see you pulled the trouble tree for code 43. What made you go to that tree? Did you have a code 43? You have not mentioned a SES light, or codes yet. What you need to do to check you fuel pressure is have a fuel pressure gauge on the truck while the problem is happening, and watch what the pressure is. If it drops below spec then replace the pump. Good Luck, Korey.

 

No codes no check engine light (after I plugged back in my ESC)..
Yesterday it finally gave out all the way, died on the road after it started the surging hesitating thing, I am confident now that it is my fuel pump, going to replace it now, will post the outcome.