yj help

[kingaircj]

I have an 88 yj with 2.5 ax5 231. When the engine is cool it runs perfect. As it warms up it runs like crap. You have to "feather" the gas to keep the engine running, and if you are good you can be driving down the road. Less then 5 miles an hour at best.

Here a small list of whats been done the last serveral years:
Frame was replaced. Old was rusted.
Head was replaced. crack old one
TPS was replaced
Crank senser replaced
New coil, wire, plugs, cap, rotor
Fuel pressure regulater overhauled
Replaced vac hoses, removed metal tubing
Pluged egr tube at the manifold. Tube was to rusted.
MAP senser tested good.

Please help

 

[SteelHeadz]

Prior to the List of all the parts that was replaced, did it run like crap as well?

 

[kingaircj]

Only had it for a couple days before start the frame off resto. But as far as I can reminber yes it ran fine.

 

[SteelHeadz]

Does it smell like raw fuel coming out of the tail pipe like it's running rich when it's warmed up?

 

[kingaircj]

Not really, I am with you on a fuel issue, however you have to almost floor it to keep running. If you can get the RPM past 3000 it runs better, but still not as good as a cold engine.

 

[kingaircj]

to get past 3000 rpm you have to go though a surging battle around 2500 rpm.

 

[SteelHeadz]

could be starving for fuel? whats the fuel pressure like?, you've mentioned about Overhauling the fuel pressure regulator. i personally have never heard of this. it usually get's replaced if it was faulty. also, what happens when you remove the plug on the EGR tube after warm up?

 

[kingaircj]

Fuel pressure is 15.2 (15.0 is what the book said) Kit from autoparts store comes with springs, and gaskets.

As for the EGR the manifold was welded closed. Tube is still open just about 1/2 from where it would have been (rust).

 

[SteelHeadz]

could it be that a pair of vac. lines got switched?

 

[kingaircj]

I check that. maybe.

 

[SteelHeadz]

Sorry for all the questions. since you mentioned that it ran fine prior to the restoration indicates that you probablly created the issue. it's just a matter of re-checking all that you have gone through. although there is still a possibility that a component is failing and just so happen to occur after the restoration. either way, you need to do the process of elimination of what's not the problem.

 

[Bounty__Hunter]

Could be a bad catalytic converter. The catalyst expands as it heats up, choking the engine gradually until it no longer runs. Then it will run fine if allowed to cool.

 

[kingaircj]

Sorry for the long pause in the thread. Ok took off the exhaust. Ran sluggish after warming up still. Replaced MAP and ran sluggish warm. Replaced the temp sensor (last thing to replace) still ran bad. To recap runs great cold (70 - 80 mph) when temp warms up >160 unable to go 5 - 10 mph. You have to floor it the let off to go.

 

[SteelHeadz]

Sorry for the long pause in the thread. Ok took off the exhaust. Ran sluggish after warming up still. Replaced MAP and ran sluggish warm. Replaced the temp sensor (last thing to replace) still ran bad. To recap runs great cold (70 - 80 mph) when temp warms up >160 unable to go 5 - 10 mph. You have to floor it the let off to go.

I would take Bounty_Hunters advice, Replace the Catalytic Converter..

 

[kingaircj]

I undid the exhaust to see if the tail pipe was pressuring up, and the jeep did not run better. It should have ran better if it was the CC right?

If I do anything to the CC is bypassing. (OK has no emissions)

 

[Bounty__Hunter]

If you disconnected the exhaust ahead of the catalytic converter and it still ran bad, then that rules out the catalytic converter.

Have you replaced the injector?

 

[kingaircj]

overhaud it the injecter. After reading some other thread thinking maybe timming?

 

[BaconYJ]

My 89 2.5L YJ did the same thing in Moab couple years ago. Turned out to be a failing fuel pump in the gas tank. It would run great while cool and for a little bit after that then it was a chore to get the rpm's over 3k. After i took the pump out it was slightly deformed as if it would heat up and expand not allowing the parts to move/slide within it correctly. The Jeep would almost act like it is vapor locked but pulling the gas cap off fuel would gush out and be very hot.

Just my 2cents

Bacon

 

[buckaroo kid]

Have you checked the carb to make sure that its not choking its. My 89 did that and it was that I had a wire for my elec choke broke. So when it was cold it would run but when it warmed up it won't run. I would check there first and then move to the fuel filters and then the fuel pump.

 

[buckaroo kid]

If it was the timming it would run like crap all the time not just when it warms up.