95 gmc jimmy rough idle, hard starts, and rich fuel smell. Like stated above my 4.3l vortec has been progressively having a harder time starting and running in the past few months. this truck has 263k miles on her so yes she’s old, but i’ve tried to do my maintenance and keep it running as long as i can i’m just not looking to dump money into a sh**box and see if i can find a semi diagnosis before i even start digging around in the engine. I’ve already done the cheap stuff like disconnect cat ( could be the fuel smell ), checked plugs which were pretty black but weren’t damaged and i cleaned all 6 plugs, checked map, cleaned egr and throttle body but to pretty much no avail. i would add that at idle it kind of sounds like it has a misfire but i haven’t seen the cel come on in a few months. also seems to drink gas. where should i start guys?

 

95 is the transition year for ODB from I to 1.5 to II which can make scanning for codes a challenge. Do you have a compatible code reader? Any codes?

Were the plugs all black or only some cylinders?


George

 

thanks a lot for responding george. yes, i’m aware that 95 is the transition year between one 1 and 2 and to be honest i’ve tried using obd 2 and no codes came up. are there any hardware stores that have 1.5 readers? i hear they get expensive but it would be nice to read live data and see what’s going on. when i checked the plugs they all looked similar with the amount of carbon, there is one spark plug i didn’t check which is located behind the steering column and is a major PIA. i might upload a video if i can of it running to help explain this “misfire” sound and another strange metallic sound when i cut the engine and can’t figure out what it is, this sound also occurs when i rev over 2500 rpm and let off the throttle. not sure if related. Thanks a lot, jack

 

https://youtube.com/shorts/FrCQrpSxl...KT-zjK9H3kXn4z

https://youtube.com/shorts/lQjkDsu0q...UsddmEK33jXXc1

https://youtube.com/shorts/CvcZmqqYU...cNj87Mgx3hTOkU

 

I believe that Actron CP9145 and CP9150 can read ODB 1.5. There are used ones on ebay for around $150

George

 

On a 92 I once had I had the fuel line break under the intake plenum. It caused the O2 to be fouled along with poor running of the engine.

The carbon on your plugs could be because of unmetered fuel getting into the cylinders.

 

Since all the plugs are fouled evenly Its probably either an O2 sensor, leak in the plenum or high fuel pressure from a blocked return line. Codes may help if you get a reader.

George

 

As Christine & George have stated, I would look into the fuel supply components internal to the intake plenum. Specifically the FPR & the 'nut kit' (fuel lines inside the plenum). A fuel pressure test should give a good indicator as to whether you have a leak. The Fuel pressure regulator on Blazer 4.3L CPI W engine tech article runs through some alternate troubleshooting steps by removing the manifold tuning valve from the top of the upper intake plenum and having a look inside. In your case, if you have excessive fuel pressure leak down and because you have stated that all of the plugs are fouled, it is likely that you are leaking from both the FPR and the 'nut kit'. These components separately tend to result in different sides of the engine becoming fuel fouled as a result of how the intake is designed.

If you plan on removing the upper plenum, I would have the FPR, 'nut kit' and a new gasket on hand to get it done. Both of these are very common issues with the CPI engines.

 

okay guys so i did some research on the fuel leaks with the FPR and nut kit and decided to see if i could catch a video by putting a camera into the plenum and seeing if i could see the leak but instead i heard this.. sounds like a vacuum or something not sure but no way it’s normal right? ideas?

link: https://streamable.com/m0iozh