97 TJ 2.5 idles fine and revs fine till I try to drive

M

Mcilvain85

New Member
Joined
Oct 16, 2020
Messages
9
Location
Ohio
It’s a 97 2.5l 5 speed. Been sitting a long while and just recently got it going with new parts.
Clutch
Alternator
Battery
Plugs and wires
Cap and rotor
Fuel tank
Starter

Problem is that it will start and idle just fine, most times It will rev out without any hesitation sitting in neutral. But as soon as I put it in gear and try to drive it, it wants to die with any throttle input. Occasionally it does this before putting it in gear but not often. No CEL at any point, had it on a scan tool but didn’t show any codes. Also cleaned the throttle body. Haven’t seen any wiring issues or vacuum leaks so far. Not real sure where to go from here, trying to avoid just throwing new sensors at it.
 
I'd throw a code reader on it that can read live data and keep an eye on your TPS values (Should scale the percentage up as throttle input increases). It kind of sounds like it's getting starved for fuel under load? I'd check the fuel pressure as well. Is it hard to start? I'm not too familiar with diagnosing these as I just recently picked mine up as well, but, sticking with the basics goes for every vehicle.
 
Working on the scan tool, it’s a snap on ethos, just trying to find the correct key to do it, it’s somewhere. I’m going to have to pick up a pressure tester for the fuel system. Wouldn’t say hard to start really, starts usually one the first attempt, If not it’s the second and that’s only with cranking for 3-5 seconds, so I wouldn’t really say hard to start.
 
So did some testing, fuel pressure is steady at 41 psi through the rpm range. It showed a code for the tps, tested it and it was fine, and readings from all other sensors appeared good. Seems to start cutting out anywhere above idle once it’s up to temp. Any ideas?
 
Cps was functioning fine, had a live readout of all the sensors, had a code for one of the o2’s, but the live read outs for it didn’t appear out of the ordinary, can’t remember which, but the downstream is non existent and hadn’t been there for a long while.
 
Dont buy/swap pcm for 1000$ atleast thats what i would do if i lived in usa. It doesnt worth it, i would just buy beatup suzuki sidekick or if you really love jeep swap brainless mercedes om diesel or kubota.
 
Just went out to try it with the o2 unplugged and never got the chance, it was stone cold and immediately started cutting out with any throttle. Did same with the o2 unplugged
 
Then its coil rail. Check your coil rail without multimeter, check spark plug gaps, i dont know about 2.5 gap but its very important
 
Any news? Can you try this test, give throttle lesser than 1000rps maybe even lesser than 800-500rpms and look at tach needle. Will i go down to almost zero and go up again?
 
Tach operates fine, checked the coil and it was just slightly over on ohms, replaced the tps and nothin changed
 
As an easy no cost step have you checked the IAC, they can get pretty dirty and sitting it may have gummed up.
 
I just reread the first post and see you cleaned the throttle body did you remove the IAC to clean it?
 
also the torque converter may be the issue, Lucas transmission fix worked miracles on my old transmission for around $20 and it Made a difference almost right away.
 
It’s a manual trans, didn’t remove the iac to clean it, just sprayed it will cleaner at idle. As soon as I thought I had it pegged as only at operating temps, the next day it did the same while cold. I have an upstream o2 on the way as well as a new coil. Also a throttle body gasket so I can pull it for a good cleaning. Gonna roll the dice on the downstream o2, I don’t have a cat and don’t much feel like paying for one
 
Is your crankshart pos. Sensor authentic mopar? Even if its working properly sometimes it gets a little bit place change you can loosen the bolt and readjust it.
 
Update, did a compression test test and cylinder 1 is at 90 psi and cylinders 2 and 3 are at 130 psi. Gonna be getting a simple rebuild soon.
 
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