Engine idles perfectly but misfires with any gas
Junior Member
Joined: Nov 2018
Posts: 492
From: Grayson KY
Update: I was slow putting the upper intake back together because I didn't want to get water in there and it's been rainy in Western Washington. Pro tip: tighten the fuel lines all the way when putting the intake back together, seeing gas pour onto your exhaust pipes is a little scary. I got everything together and ran it with the EGR unplugged, the exhaust smelled like old car exhaust but the Blazer was not improved.
Back to square 1
I'm going to check fuel pressure again because at this point I think I'm losing my mind and it has to be suspect. The injectors seemed fine as I'd expect since they're the updated ones. Going a little insane trying to figure this out
Back to square 1
I'm going to check fuel pressure again because at this point I think I'm losing my mind and it has to be suspect. The injectors seemed fine as I'd expect since they're the updated ones. Going a little insane trying to figure this out
I forgot to mention but yes, I replaced the MAF sensor and I used a whole can of throttle body cleaner doing the throttle body and intake when I had it apart
Junior Member
Joined: Nov 2018
Posts: 492
From: Grayson KY
New Member
Joined: Sep 2017
Posts: 5
From: Alberta
I sure hope you're able to find the problem. This was happening to me a few years back when I was first working on my Jimmy. I have the engine out now and am rebuilding it so I know it's fine mechanically. Have you done a compression test yet? When I pulled the motor I found cylinder 1 had low compression (about 73psi), the minimum is 100psi and should be within 70% of the max compression reading. I think the max was 140 something. I reconditioned the valves with some valve grinding compound and am going to replace the timing chain, it has a little slack, not a lot though even with over 300,000km. I pray this fixes it. If not, I only have the O2 sensors and PCU to test. I have replaced everything else (spider, crank sensor, distributor, plugs, wires, coil, ignition module thing.)
Senior Member
Joined: Oct 2019
Posts: 699
From: West-Central Florida
this thread is a touch old but
2 things, Replaced the upper intake gaskets?
No leaks from the lower intake gaskets? Air and/or coolant?
Check fuel pump voltage at connector and then at frame, when the pump prime is being ran. on my Rig the ignition switch was the catchall for this issue.
2 things, Replaced the upper intake gaskets?
No leaks from the lower intake gaskets? Air and/or coolant?
Check fuel pump voltage at connector and then at frame, when the pump prime is being ran. on my Rig the ignition switch was the catchall for this issue.
Starting Member
Joined: Mar 2020
Posts: 107
something else to check, put a fuel pressure gauge on it.. make sure you get 60psi when you turn the key on, and that it holds 60psi once the pump turns off. if it bleeds down fast enough to notice it, there's a a good chance your CPI unit is leaking internally.
also something I've noticed no one has touched on.. might be a good time to do a leak-down test on all 6 cylinders. .it could be something like a sticky valve causing the issue.
also something I've noticed no one has touched on.. might be a good time to do a leak-down test on all 6 cylinders. .it could be something like a sticky valve causing the issue.
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