2001 Jimmy 4x4 4.3L misfire after replacing lower intake gsket
enrico1750
03-31-2008, 11:32 AM
After replacing the lower intake manifold gasket along with the plenum gasket and valve body gasket along with the distributor cap and rotor because they were pretty well worn and the spark plugs because of the mileage on the vehicle, currently 85k, I now have a misfire in cylinders #5 and #6. In addition, I replaced the various vacuum lines to the engine and the 4wd. Some of them were so dry that they disintegrated with just a touch. Actually, it's a 'no fuel' situation in these cylinders.
I pulled the plugs for #5 and #6 and they're dry. The other plugs look normal, i.e. a little dark after only running till the thermostat opened. I swapped the plugs in cylinders #5 and #6 with those in cylinders #1 and # 4 to see if the problem would travel with the plugs. No change. The problem stayed with #5 and #6. I then checked the various vacuum lines to make sure that they were plugged in. No problems here. I pulled the electrical connector for the cpi in case any of the pins had been bent on re-assembly. No problem there either.
Where can I find a diagnostic procedure for the cpi? I've searched the web and haven't found it yet. I'm curious if there's something in the cpi unit that would not supply fuel to those 2 cylinders. It would be awfully coincidental if those particular injectors had suddenly developed a problem. Whether or not I find a diagnostic procedure I'll also check the intake for any fuel leaks. If I can't get a clear view with the intake valve body removed then I'll pull the plenum.
Am I overlooking something? Any ideas or suggestions would be appreciated. From looking through the forum I'm sure that I'll convert the system over to mfi if I find that there's anything wrong with the cpi.
Thanks.
I pulled the plugs for #5 and #6 and they're dry. The other plugs look normal, i.e. a little dark after only running till the thermostat opened. I swapped the plugs in cylinders #5 and #6 with those in cylinders #1 and # 4 to see if the problem would travel with the plugs. No change. The problem stayed with #5 and #6. I then checked the various vacuum lines to make sure that they were plugged in. No problems here. I pulled the electrical connector for the cpi in case any of the pins had been bent on re-assembly. No problem there either.
Where can I find a diagnostic procedure for the cpi? I've searched the web and haven't found it yet. I'm curious if there's something in the cpi unit that would not supply fuel to those 2 cylinders. It would be awfully coincidental if those particular injectors had suddenly developed a problem. Whether or not I find a diagnostic procedure I'll also check the intake for any fuel leaks. If I can't get a clear view with the intake valve body removed then I'll pull the plenum.
Am I overlooking something? Any ideas or suggestions would be appreciated. From looking through the forum I'm sure that I'll convert the system over to mfi if I find that there's anything wrong with the cpi.
Thanks.
old_master
03-31-2008, 02:42 PM
You've done several things, any one of them could cause the rough running.
What brand of parts did you use?
Check plug wire location on the distributor cap: passenger side, front of vehicle to rear are cyls 2, 4, and 6. Driver side front to rear are cyls 3, 1, and 5.
Check the power brake booster vacuum line. The booster draws vacuum from both 5 & 6. If the line is leaking, both cylinders will run lean.
What brand of parts did you use?
Check plug wire location on the distributor cap: passenger side, front of vehicle to rear are cyls 2, 4, and 6. Driver side front to rear are cyls 3, 1, and 5.
Check the power brake booster vacuum line. The booster draws vacuum from both 5 & 6. If the line is leaking, both cylinders will run lean.
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