Troubleshooting 4.7 WJ Power Loss
09-04-2017, 11:14 AM
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Troubleshooting 4.7 WJ Power Loss
Hi Guys-
The other day, my Jeep suddenly lost power on the freeway. It was a very warm day (around 100°), and the AC was running. The temp gauge was high, like 235°, but stable. (It normally runs perfectly well at 208° if I'm not using the AC, even on a hot day). I was moving at about 75 MPH when I felt the engine lose power and it started pinging like a machine gun. I got over to the side of the road and let it sit for an hour. I checked the fluids and everything was clean- no water in the oil, no burnt ATF, etc.
After a while, I tried starting it again. It would start, but pinged loudly and wouldn't stay running long enough to build any power. It sounded and felt like the timing was WAY off, like it wanted to run but just couldn't get the spark and compression to meet up.
I got it home, and it's been sitting for several days. I tried to start it today, but same thing- wants to run but quits quickly. I would like it to be something as simple as a bad camshaft sensor, but I'm thinking it could be that I threw a timing chain.
Has anyone had a similar experience? Any thoughts on how I should proceed? Thanks.
The other day, my Jeep suddenly lost power on the freeway. It was a very warm day (around 100°), and the AC was running. The temp gauge was high, like 235°, but stable. (It normally runs perfectly well at 208° if I'm not using the AC, even on a hot day). I was moving at about 75 MPH when I felt the engine lose power and it started pinging like a machine gun. I got over to the side of the road and let it sit for an hour. I checked the fluids and everything was clean- no water in the oil, no burnt ATF, etc.
After a while, I tried starting it again. It would start, but pinged loudly and wouldn't stay running long enough to build any power. It sounded and felt like the timing was WAY off, like it wanted to run but just couldn't get the spark and compression to meet up.
I got it home, and it's been sitting for several days. I tried to start it today, but same thing- wants to run but quits quickly. I would like it to be something as simple as a bad camshaft sensor, but I'm thinking it could be that I threw a timing chain.
Has anyone had a similar experience? Any thoughts on how I should proceed? Thanks.
09-09-2017, 08:38 PM
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Update
I finally got time to look at it today, and to make a longer story shorter, I found the #7 exhaust rocker loose under the cam when the valve is closed. It was still in position, but I could twist it and pull it out. I'm guessing that if I pull the head, I'm going to find a dropped valve seat or at worst, a bent valve. It wasn't really making any mechanical noise, so I'm hoping the valve is OK. So probably time for some head work.
09-10-2017, 11:12 PM
#4
Old fart with a wrench
If the valve spring is still at normal height with the rocker loose, it may be a collapsed/stuck hydraulic anchor.
09-10-2017, 11:25 PM
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No such luck. The springs (I found one on each bank) are sitting lower than normal when in the fully closed position. The top of the motor has been disassembled, tomorrow night will be exhaust manifolds.
09-11-2017, 06:33 AM
#6
Old fart with a wrench
Well.....That truly sucks! From what I've seen, the front (water pump, front covers, and chains) are a nightmare.
