95 S10 Starting hard/loading up at Idle

[jdailey]

I have a 95 S10 4.3 vortex with 126K on it. Recently it has been starting harder than usual( cranking longer). Once it starts, it's like it's flooded and when I let it idle it loads up and strats chugging. I have changed the plugs and it was ok for about a week, now it's back to the samething. I took it to an Advanced Auto store and they put there code reader on it and they told me it was a phase 1 O2 senser. I have talked with a dealer about it and they tell me that that may be what the truck says, but it may something happening before the O2 senser. Such as a EGR or the Fuel Injection. I can't really get a straight answer. Can anyone tell me what's going on? I am mechanically inclined and do most of my own work. But I am not up on all the electronics on these new vehicles. I liked the old plugs and points days! I am also new at this site, so any reply would be appreciated sent to [email protected]

Thanks, Jim

[Fox_Rocks]

I would think the O2 sensor would be inline....it reads how rich or lean the exhaust is and then adjust the settings accordingly. So if it's reading to lean then the computer is going to send more fuel into the motor, but meanwhile the motor is just fine where it is and now it's going to run too rich, causeing it to sputter and chug....then the O2 sensor reads this and tries to make it right, and it's just a nasty cycle. and EGR valve? maybe... but not likely..an injector? maybe...but again not too likely, you would notice a running problem through-out the whole range (idle, accel., highway, etc.) I know this sounds kinda dumb, but have you checked your timing? anyways hope some of this helped.

[jdailey]

Thanks, I kinda figured it was the 02 senser but was looking for other opinions before sending good money after bad.

[dasharue]

I have a 1995 S-15 Jimmy with the exact same problem. It takes about 10 seconds of cranking to get it to start and once it does it idles extremely rough. It also stinks of unburnt fuel when idling, gets about 13 Mpg and has a surging sensation when driving a steady 55-60 Mph. From the research that I have done, I came to the conclusion that it was the Fuel Pressure Regulator, but apparently the 95 and 96 4.3L Vortec 'W' either doesn't have one or it may be part of a combination unit under the plenum. I'm convinced I'm on the right track but could use some help determining whether or not this engine has a regulator or what does the same job as the regulator. I have already replaced the O2 sensor in the exhaust manifold and have changed the EGR valve.

[jdailey]

It turns out it was the spider assy.. It was dripping raw fuel into #4 cyl. all the time. $670.00 to repair at the dealer, but it runs great now! The spider assy. alone was over $400.

[dasharue]

My problem, which was identical to jdailey's, was fixed by replacing the Fuel Pressure Regulator on the Fuel Rail spider. I did all the work myself in about an hour and a half and the part can be found on E-Bay or at AAAParts.com for around $50.00. Here's a great article describing the problem: http://www.samscars.com/mage7.html. My Jimmy now runs perfectly!

[s15homeboy]

you guys i have a 1988 S-15 and im having the same problem you guys are having and ive already played with the distributer and i have gotten to the point that i have unpluged my PCV valve from the FI and it idles better but i also noticed hat my FI is just just dumping fuel into my enguin and it is running extremly rich. i have a good idea that it might be the o2 sencer but i was wondering if it could be another problem. I havent taken it to a mechanic yet and if i should i need to know. i need a responce soon i need this truck for work. Thanks