Hi guys
I am having issues with my 97 4wd Jimmy. When cruising at highway speed, the truck feels like it is misfiring on 1 cylinder. This is not apparent if it is getting gas but, only if I let go of the throttle to keep a steady speed. I can feel the truck jerking. It otherwise starts and idles fine. Fuel pump pressure while engine is on is steady at 56 psi and climbs to 64 psi when jerking the throttle.
Also, I have put around 2000 miles on the new engine. Using it to get to work, I average around a little over 21L/100Km or about 11 mpg. All wiring, rotor, distributor cap, pre cat O2 sensors and engine are new. And all of this is highway driving with a lite foot at between 60 to 65 mph. I think this is excessive. Any ideas what could be wrong and where to start looking?
Don

 

How have you narrowed it down to cylinder #1?

Did you also replace the injection spider?

 

Something is wrong, my 92 S-10 with the 4.3 W engine gets about 21 to 23 on the highway.

 

I haven't: One cyl.
I have not replaced the spider.
Don

 

Well, it seems like it is getting worse. The engine now stumbles at low speed while driving in town. I came back from a party yesterday night and I thought I would not make it home. This has happened a few times now and this is intermittent. It is the same feeling as if the ignition wires were leaking spark everywhere but, they are new. Where to look?
Don

 

Sounds like The same problem i have.....I didn't buy the spider, just one (poppet?) injector tube, havent installed it yet, was told it was injector one. Has anyone just replaced one tube instead of the whole spider?

 

i read your post and it sounds like you may have the same problem i was having. you should check out my thread titled Found my problem!!!!!! with author of RIFLEMAN 308, you have to go through the advanced search option to do this, it tells you about the splice pack sp423 and there are pictures i put on there showing the location and how i modified the locations of the grounds, it also sounds like you may have a leaking fuel pressure regulator and/or injector lines also, you could have both of these issues going on at the same time.

good luck