Hi there. I've been having some issues with a Jeep I just acquired and thought I would look for some feedback. If you have any ideas thanks in advance.
Jeep:
95 Jeep Cherokee, 4.0l, 5 speed transmission
Issue:
CEL code 51 (running lean), the jeep runs hotter than I would like, is harder to start than I am used to (takes longer to prime and crank), and it is getting fantastic gas mileage (somewhere in the 22-24mpg range). Other than these issues it runs quite well. There may be some loss of power, but with me having no experience of what this particular Jeep is supposed to run like it is hard to tell.
My ideas about the issue:
It seems to me that whatever is causing the Jeep to run lean would have to be on the fuel supply side (good gas mileage, running hot), otherwise the CPU would be able to try to compensate and it would be running rough and the gas mileage would be more average or lower. Perhaps I am wrong.
Things I've done so far:
I had an extra MAP sensor lying around so I changed it out. I replaced the fuel filter (just because it is never a bad idea), the fuel pump (because I don't mind having a spare), and the fuel pressure regulator. One of the O-rings on the pressure regulator was in really bad shape, so when I changed it I felt like I might have found the issue, but alas, no change in the Jeep. I have attempted to find any vacuum leaks that I can and besides the pressure regulator line (which was shot and replaced) I haven't been able to find anything leaking.
Troubleshooting:
Before I changed the pump and regulator I rented a fuel pressure test kit and found that it was running at about 29 psi at idle and 38 psi with the fuel pressure regulator vacuum hose pulled. After the engine was shut off the pressure dropped quickly and dramatically.
Well, that's about all of the information I have. The collector on the exhaust manifold is cracked, but I can't really see that causing a lean condition with the amount of back-pressure the exhaust is likely to have. Any input is greatly appreciated and should I get this issue sussed out I will try and help future posters with the same issue.
Paul
Jeep:
95 Jeep Cherokee, 4.0l, 5 speed transmission
Issue:
CEL code 51 (running lean), the jeep runs hotter than I would like, is harder to start than I am used to (takes longer to prime and crank), and it is getting fantastic gas mileage (somewhere in the 22-24mpg range). Other than these issues it runs quite well. There may be some loss of power, but with me having no experience of what this particular Jeep is supposed to run like it is hard to tell.
My ideas about the issue:
It seems to me that whatever is causing the Jeep to run lean would have to be on the fuel supply side (good gas mileage, running hot), otherwise the CPU would be able to try to compensate and it would be running rough and the gas mileage would be more average or lower. Perhaps I am wrong.
Things I've done so far:
I had an extra MAP sensor lying around so I changed it out. I replaced the fuel filter (just because it is never a bad idea), the fuel pump (because I don't mind having a spare), and the fuel pressure regulator. One of the O-rings on the pressure regulator was in really bad shape, so when I changed it I felt like I might have found the issue, but alas, no change in the Jeep. I have attempted to find any vacuum leaks that I can and besides the pressure regulator line (which was shot and replaced) I haven't been able to find anything leaking.
Troubleshooting:
Before I changed the pump and regulator I rented a fuel pressure test kit and found that it was running at about 29 psi at idle and 38 psi with the fuel pressure regulator vacuum hose pulled. After the engine was shut off the pressure dropped quickly and dramatically.
Well, that's about all of the information I have. The collector on the exhaust manifold is cracked, but I can't really see that causing a lean condition with the amount of back-pressure the exhaust is likely to have. Any input is greatly appreciated and should I get this issue sussed out I will try and help future posters with the same issue.
Paul
Adventures with code 51
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