Sonama Highrider gas in oil

[email protected] · July 13, 2018

I recently purchased a 94 Sonoma Highrider. Had a bad miss and didn't want to hold a steady rpm. Would idle fine but when giving gas would lose rpms when hold steady on peddle. After doing a complete tune up decided to take the truck for a drive. Made it a couple miles and the truck died. Would crank but wouldn't start and could smell fuel bad. After getting truck home and going over it found gas in the oil. What would cause it and where do I start?

HoosierZ · July 13, 2018

The 4.3 in the S10/ Sonoma has what I believe is called Sequential Port Injection. It uses a single injector and an octopus of tubes connecting between the injector and the 6 individual intake ports. The tubes are plastic and they deteriorate over time and crack. I would check the tubes as leak in them would cause the symptoms you described.

Supreme Pizza · July 13, 2018

I don't have much experience with that specific vehicle, but I have heard that they have problems with the fuel injection "Spider".

If your injection systems is supplying too much fuel\ -, it would run poorly, stall, and could leak fuel into the cylinders. The fuel would bypass the pistons and wind up in the oil.

Little Red Jimmy · May 5, 2019

I had gas in my oil. Changed spider assembly. #2 injector wasn’t working. Changed oil and filter, plugs, etc. Still have random misfire code. P0300.

Too soon to see if there will be fuel in my oil again.

Was told that also when truck sits, as mine did, gas can leak into cylinders too.

Gotta do another fuel pressure test since the work I’ve done and see if it’s still an issue as I had a decrease in pressure when reaching higher rpm’s and an increase when idling. From what I’ve read in the Haynes manual, that’s backwards. ?

Ive been troubleshooting random misfire code for 6 months now. $$

My 2003 GMC Sonoma 4.3l runs great revved up past 1500 rpm’s but misfires, backfires, hesitates, stumbles, chug-chug, smelly catalytic converter egg smell, engine shakes, etc. Not fun.

Have you scanned it for codes??