mistaake
Real Name: Michael
Hi y'all, hoping for some help on my 97 Suburban I just picked up for really cheap. It has about 210k miles. I'd consider the misfire a "hard miss" in that it's very obvious, the vehicle shakes noticeably at idle and generally doesn't run great. That said, I was able to drive it a short distance home and it was able to achieve 80mph no problem (albeit with flashing engine light the whole time)...
Previous owner replaced plugs, wires, distributor, cap, and rotor in an effort to resolve the issue with no luck.
What I have done so far:
1. Checked with scantool to be sure CMP retard is set correctly (it is)
2. Checked to be sure all plug wires are hooked up in the right order and go to the right cylinder (all good here)
3. Pulled the plug on cyl8, looks like they used Bosch Iridium (ew), plug had strong fuel odor. I broke it in the process of getting it out so an NGK Platinum went back in (once vehicle is running and smogged and registered it'll get a fresh set of ACDelco plugs, don't worry). Also while I was messing with plugs I used an inline spark tester and spark was present.
4. Compression test on cyl8 showed 180psi. I didn't check any others because the compression tester broke. Oops.
5. used a cheap borescope I had floating around to look inside cyl8. Didn't work very well, i could see only part of the piston, but the part I saw didn't have a hole in it or something.
6. Removed valve cover, started engine, everything looked fine - all the things went up and down with engine running. You know what I mean.
7. Reassembled everything. Symptoms persist.
So, uh, what's next? I'd say it's a bad injector but there was a ton of fuel on the plug and it smells really bad like raw gas when running so I don't think it's a fuel delivery issue?
If it matters, the engine seems to sound fine, no abnormal noises. Oil looks really dark and nasty. Also, it does seem to use a little coolant.
If I had to pick what was next I'd get a working compression tester, have a helper, and do a proper compression test (pull all plugs out) and compare the numbers. If that is good then I would do new fuel injection spider... But that's expensive and a lot of work if that's not the problem.
Previous owner replaced plugs, wires, distributor, cap, and rotor in an effort to resolve the issue with no luck.
What I have done so far:
1. Checked with scantool to be sure CMP retard is set correctly (it is)
2. Checked to be sure all plug wires are hooked up in the right order and go to the right cylinder (all good here)
3. Pulled the plug on cyl8, looks like they used Bosch Iridium (ew), plug had strong fuel odor. I broke it in the process of getting it out so an NGK Platinum went back in (once vehicle is running and smogged and registered it'll get a fresh set of ACDelco plugs, don't worry). Also while I was messing with plugs I used an inline spark tester and spark was present.
4. Compression test on cyl8 showed 180psi. I didn't check any others because the compression tester broke. Oops.
5. used a cheap borescope I had floating around to look inside cyl8. Didn't work very well, i could see only part of the piston, but the part I saw didn't have a hole in it or something.
6. Removed valve cover, started engine, everything looked fine - all the things went up and down with engine running. You know what I mean.
7. Reassembled everything. Symptoms persist.
So, uh, what's next? I'd say it's a bad injector but there was a ton of fuel on the plug and it smells really bad like raw gas when running so I don't think it's a fuel delivery issue?
If it matters, the engine seems to sound fine, no abnormal noises. Oil looks really dark and nasty. Also, it does seem to use a little coolant.
If I had to pick what was next I'd get a working compression tester, have a helper, and do a proper compression test (pull all plugs out) and compare the numbers. If that is good then I would do new fuel injection spider... But that's expensive and a lot of work if that's not the problem.
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