Need some help as I’m lost as to what’s the next diagnostic step. 1994 4.0. Supposedly rebuilt by PO about 20k miles ago. I’ve owned about a year. Over this time I’ve replaced valve cover gaskets, fluids, plugs, FPR, cleaned up vacuum lines so no leaks, new header and downpipe, o2 sensor, alternator, flushed coolant. Many other non engine things as well. has a “whistle” part throttle, having done the exhaust and throttle body gaskets assumed it was from k&n intake PO installed.
For quite a while now it was running rich, just replaced FPR with the correct one. Amazing how so many listings have a 3.5 bar FPR versus the 2.7 bar. Also been having smoke from exhaust. Exhaust I’m not losing coolant. Did a compression test have lowest of 140 on cylinder 4 other all 160. Don’t have the tools to do a leak down test.
Plugs all looked good on inspection.
I’m not quite sure what to do next. I figured I would find low compression on one cylinder probably a valve seat or a burnt valve. Worst case rings. However, I have good compression.
I burned through a quart of oil roughly every 500 miles have tried thicker oils Rotella 15 W 40 is what I regularly run have tried additives as well that “stop smoke”. Idles fairly good does have an aftermarket camshaft in it. I’m unsure of the exact model of the camshaft is the previous owner did not provide the cam card. I adjusted the throttle body screw and I idle it around 900 rpm.
I’m at a loss as to what to do. I can’t really go thicker on oil. I don’t think I have an issue with my rings given good compression. I don’t have any obvious leaks of oil but yet I’m not foulibg out an O2 sensor.
Sorry for the long post, but if anyone has any ideas on what to check next, I am shooting in the dark
For quite a while now it was running rich, just replaced FPR with the correct one. Amazing how so many listings have a 3.5 bar FPR versus the 2.7 bar. Also been having smoke from exhaust. Exhaust I’m not losing coolant. Did a compression test have lowest of 140 on cylinder 4 other all 160. Don’t have the tools to do a leak down test.
Plugs all looked good on inspection.
I’m not quite sure what to do next. I figured I would find low compression on one cylinder probably a valve seat or a burnt valve. Worst case rings. However, I have good compression.
I burned through a quart of oil roughly every 500 miles have tried thicker oils Rotella 15 W 40 is what I regularly run have tried additives as well that “stop smoke”. Idles fairly good does have an aftermarket camshaft in it. I’m unsure of the exact model of the camshaft is the previous owner did not provide the cam card. I adjusted the throttle body screw and I idle it around 900 rpm.
I’m at a loss as to what to do. I can’t really go thicker on oil. I don’t think I have an issue with my rings given good compression. I don’t have any obvious leaks of oil but yet I’m not foulibg out an O2 sensor.
Sorry for the long post, but if anyone has any ideas on what to check next, I am shooting in the dark