Transmission or engine or?

BigClay

BigClay

Knower of useless ZJ things
Joined
Sep 24, 2008
Location
Winston-Salem
In my 98 TJ with 4.0 and AX15 with 200k, when in 3rd gear, and and trying to grab 4th, if I step on it some more the engine bogs down and the RPMs drop. It also feels like I have to wind it out a lot more to get to the next gear. Going up a hill at 45, I almost have to go down to 2nd to be able to keep speed. I have 4.10 duffs and haven't had this problem before. Is the transmission about to go or is it the motor?
 
Sounds like it's time for a tune up. Do you know how old the plugs and wires are? How about fuel filter?
 
That is a good point, I am not sure how old either are, I have only had the jeep a year and only put about 1k miles on it.
 
TPS is known to be problematic on the 97-97 4.0s but yes check ur tune up first.
 
John, you mean 97-99 maybe? This is a 98.
 
^^^I think that's where I'm at with my Tacoma. I noticed it was losing power and would bog when I floored it at interstate speed. Plugs and wires helped eliminate the bog, but I still feel like I'm down on power.
 
The engine noise also seems to be louder when accelerating, a clogged cat could help explain that too.
 
Did the problem come on suddenly or slowly over some time?
 
rodney eppes said:
Check that tune up, & if that don't help, think about the Cat converter.
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Easy test to see if it is a clogged converter. Loosen the exhaust bolts from the manifold to tailpipe, you don't have to take them all the way out just enough to let exhaust pass through before the cat. Test drive and if it doesn't bog down you have a clogged cat!
 
dackers said:
Easy test to see if it is a clogged converter. Loosen the exhaust bolts from the manifold to tailpipe, you don't have to take them all the way out just enough to let exhaust pass through before the cat. Test drive and if it doesn't bog down you have a clogged cat!
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Cool trick.

drkelly said:
Did the problem come on suddenly or slowly over some time?
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I didn't drive it much over the winter so this spring I noticed the first time I took it out.
 
two threads in a row i get to mention this....

engines are air pumps, if they arent running right, check the input and the output.
check your air box.
check your exhaust pipes for crimps.

if it cant move air, it cant make power.


if all that checks out start looking at fuel delivery and ignition.
 
BigClay said:
John, you mean 97-99 maybe? This is a 98.
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sorry yes i meant 97-98 are more problematic with the TPS than any other year XJs for some reason...at least in all my years of dealing with them weekly, those years always give more issues with TPS and stupid map sensor more than the Renix sometimes lol. had any luck yet
 
Took it by an exhaust shop and the muffler and cat are good (cat looks almost new). I will change the plugs and wires tonight.

Any other thoughts?
 
Just did new plugs and wires and it does idle better but the problem still exists.

I can barely maintain 40mph in 3rd to 4th on a slight inline, a big hill and I have grab 2nd to even maintain 35mph. What is going on?
 
Do you have a simple scanner? You can hook it up and drive around and watch parameter response. To see if something is responding funny.

If not, PM me and you can borrow mine.
 
hey, check your coil and see if it's cracked right by the 2 bolts...and do you know how to check the TPS voltage at idel and WOT...pretty simple and will tell you a lot. under a load, the coil or cam sensor would be a culprit but as stated before, the TPS is always problematic on those year models for some reason..too bad your not closer, have tons of sensors laying around u could test out. Check for 5.0v on the middle wire to your TPS and should lower as you approach WOT: (someone correct me if its the other way around. .8v throttle closed and should rise towards 5.0 at WOT and fluctuate in between). it's one or the other, my brain is fubbing on me right now, sorry.
 
could your fuel pump be going bad? mine was going out in my f350 and was doing that, I thought it was the tranny. it finally died on me. just a thought? :beer:
 
I'd have to check fuel pressure and also for a clogged cat. Easy way to test cat is to see I'd the inlet is substantially hotter than the outlet. That is a dead giveaway to a restriction.
 
If you have had ethanol sitting in it for a year with only 1k miles, fuel filter is/was clogged and your fuel pump is weak/clogged. Is the fuel pump external to the tank on an XJ? If so and it is hot then there is a restriction somewhere in the lines. Can you check fuel pressure at the rail on a 4.0?
 
Thanks for all the ideas guys. Local place tested the fuel pressure and it was really low. The fuel filter is in the tank, so they are looking at the filter and the pump as we speak. Hopefully this will solve my problem.

Thanks again
 
Success!!!

So after the fuel pump was replaced it was a little better, and between that and the new plugs/wires, it fires up much faster. It still wasn't right, so I took it to a different exhaust shop and they tested both cats and both were completely clogged. What it looks like happened was someone at some point used a BFH to help clearance the second cat (which appears to be only a few years old) and damaged the internals which clogged it up, which meant more heat going into the first cat, causing it to fail.

I never knew how much power the jeep actually had haha
 
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