98 Cherokee Classic

I have 232K on my beloved GC Limited. Recently, only under heavy load, it started running rough. The check engine light would flash and then it would go back to normal. I did a scan and the code P0301 came up, misfire on cylinder one. I had all the plugs and the coil pack on cylinder one replaced. No change. I can drive it carefully without issue, until such time as I have to accelerate quickly, then the issue returns. I can easily "reset" it by putting the truck in neutral and turning it of and on.

I brought it to a mechanic and he asked when I last replaced the timing chain(s). I am no mechanic, but I found it odd that he said chains, plural. Is there more than on timing chain? He also said that the issue is due to the camshaft and crankshaft not being synced. He said I needed to have the timing chain(s) replaced and new cam phasers installed. This is way over my head from a repair perspective and I am not sure I even understand the situation well enough to evaluate what to do. The truck has no rust, good tires and brakes, and no other (known) issues but I feel like a repair of this magnitude might be more than the truck is worth.

I already looked at trading it in on slightly newer, lower miles truck and was only offered $1,500, without disclosing any issues. Could someone with some working knowledge of these engines provide me with an opinion as to whether it is time to move on or seriously consider a repair.

Thanks in advance.

98 Cherokee Classic

Did as much research on this as I could, just trying to determine if repairing my engine is a viable option. Talked to mechanic again and the timing chain vs. chains thing was a misunderstanding on my part. He does maintain that my issue is a timing issue. The info I could find on line suggested the timing chain would outlast the motor in most cases. The timing chain is not broken, I am driving the vehicle every day. So if it is timing issue, would that mean the timing chain is either stretched to the point that it will break soon, or it has jumped a tooth on the timing gear? What worries me is If I proceed with the mechanic's reccomedation, replace the timing chain and cam phasers, and it turns out it was something else I will be back to square one. I'd welcome any comments or advice. Thanks.

BlueRidgeMark

Find another mechanic. You almost certainly don't have a timing problem.

You most likely have a minor issue that needs a bit of troubleshooting. You are a loooong way from needing to replace it.

Might be a fuel supply problem. You can rent a fuel pressure gauge from most auto parts stores, for free. Check Autozone and Advance. They both 'rent' tools. The deal is that you buy it for full price, use it, and return it for full refund. This way they don't have to chase people for tools that have not been returned.

Some vehicles have a fuel filter in the tank as part of the fuel pump. Others have an external filter as well. If you have an external filter, try replacing it. They're cheap.

You might also have a clogged cat.

BTW, I'm not familiar with the 5.7, but a V8 should have two timing chains if it's an overhead cam engine.

98 Cherokee Classic

Thanks BRM for the advice. I am going to take your advice and find someone else. The mechanic is a good guy, and I don't believe he is trying to deliberately mislead me, but maybe he is just not good with these engines. Funny you mentioned clogged cat becuase with my limited knowledge and experience, that is what I felt the symptons I have been experiencing pointed towards. The same mechanic I mentioned said I was off base and the cat converter was fine. How do test a cat? I have an OBD scanner, would it throw a code?

I understand what you are saying regarding trouble shooting. And I am realize you are giving me a place to start with the fuel filter, but the only time the misfire occurs, is when I accelerate quickly. Runs perfectly all other times. If it was a fuel pump or filter, wouldn't it happen more frequently?

BlueRidgeMark

Two things:

1. A plugged cat might throw a code, might not. There is a pressure test that can be done, but it requires a special tool. Ask your mechanic why he thinks the cat is good.
2. When you stomp on the gas pedal, you create a sudden requirement for more fuel. A clogged filter may not allow enough flow for that requirement, but could allow enough fuel to run at a steady state. Worth checking, anyway.

If your timing were off, it would run badly all the time.

98 Cherokee Classic

BlueRidgeMark, thanks for following up. I was referred, by a friend, to a different mechanic. I am going to take it to him on Wednesday morning and just tell him the symptoms, not any of the previous mechanic's diagnosis or my own "guesses". I will let them trouble shoot it as you mentioned. Hopefully, they can at least determine the issue. Thanks again for your reply and your help. I will provide an update regarding what they say.

98 Cherokee Classic

Follow up. I guess my Jeep is done. Mechanic said it was either a lifter or a camshaft. $709 to diagnose which. ~= $2000 if lifter or $4500 if camshaft, the $709 would go towards the repair if I chose to proceed. That is too rich for my blood.

BlueRidgeMark

Those prices are way out of line. You can replace the engine for that.

98 Cherokee Classic

I agree with you. I actually had them quote what a new engine would cost. $7500 installed. I am in Chicago and everything is priced sky high and the garages are so busy around here you have to make an appointment well in advance. But still. I will say that they took the time to do a full inspection. In addition to the engine issues, not surprisingly my front suspension need some major attention. There is also coolant leak I was unaware of from the water pump and possibly the timing cover, etc., etc... As much as I like the Jeep, I don't think it would be worth investing in all the repairs needed. I'll dump it and will find something else. I am an XJ man at heart but they are so hard to come by around here. Everything is soooooooooo rusty from the salt.

Thanks again BlueRidgeMark.

4.3L XJ

I am curious. What tests did the mechanic perform to say it is a lifter or cam shaft. Sounds a little suspicious to me

98 Cherokee Classic

Just a computer test. The code is P0301, misfire on cylinder 1. I already replaced all the plugs and the coil pack on cylinder 1. It runs perfectly under 2K RPM but misfires consistently above that. They said that was their best diagnosis without tearing it down. They wanted $709 to do that, which would allow them to determine the actual problem. The $709 would go towards the repair if chose to proceed.

4.3L XJ

Well, the one thing not mentioned here is a possible injector problem. I would suggest clearing the code, swapping #1 with another injector and see if that cylinder generates a misfire.. One other thing is how long since you have changed the O2 sensors. If they are getting worn out, then it could become lean and be borderline for running properly

98 Cherokee Classic

Regarding O2 sensors, they have been changed, can't remember exactly when, but relatively recently. That is a good idea with the injector. Thanks for the suggestions. I will see if i can get the inector swap done this weekend and see if what happens.

98 Cherokee Classic

It took me a little longer to try this than i would have liked, but it was not the injector. In addtion, while milking it around, driving like a granny, I started getting tranismission solenoid codes and the truck would randomly shift into 4th gear and be stuck there until I shut it off and restarted it. With all of this, I dumped it. Found a 2004 WJ "Columbia Edition". Never heard of one or seen one. Seems like a Laredo with a sun-roof and nicer interior. Thanks to all who replied for taking the time. Wish me luck...