97 TJ runs horrible if at all - JeepForum.com
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post #1 of 25 Old 06-21-2019, 08:43 PM Thread Starter
ReconRabbit
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97 TJ runs horrible if at all

Vehicle: 1997 TJ, 2.5 manual
I bought the Jeep dirt cheap as a project. Previous owner said he had the motor overheat so the motor was rebuilt 5000 miles ago. It got hot again, he had it checked and they said there was antifreeze in the exhaust. He gave up and sold it.
When I brought it home, it did start and idle, but I didn't run it much for fear of hurting the engine.

I pulled the head, it was warped so I had it surfaced. Put it all back together with Mopar gaskets and followed the assembly sequence in the factory shop manual.

Changed the oil, replaced the water pump as preventative maintenance, new belt, new radiator hoses, new plugs and wires.

With it all back together, if it does happen to start, it barely idles. It's rough and choppy and even with the accelerator floored it won't rev over 1000 rpm. Every once in a while, it'll start, idle fine, rev great, then fall into the horrible death shake idle with no power.

I've got a scanner and the only time the check engine light has come on it read faulty tps. I replaced that, no change. No more codes, and no codes on the internal key diagnostics other than the normal 12 and 55.

Help!


If your Jeeps not leaking it's out of fluids.
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post #2 of 25 Old 06-21-2019, 08:47 PM Thread Starter
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I forgot, I did pull the throttle body off, remove all the sensors, clean the iac and the throttle body itself. Reinstalled with a new gasket. No change.

If your Jeeps not leaking it's out of fluids.
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post #3 of 25 Old 06-22-2019, 07:46 AM
jtec
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BASICS,
spark at plugs,
fuel pressure. PSI
injector pulse.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 25 Old 06-22-2019, 12:40 PM Thread Starter
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That's not basics. I don't have a test port on the rail and so I'd have to buy a $55 adapter to test fuel pressure.

Coil puts out good spark, I have spark at cylinders.

I have now tested: CPS, TPS, engine temp sensor, intake air temperature and they check out ok.

Distributor is on correct firing order.

Had a friend who is a GM tech stop out, he traced wiring to no ground coming out of the pcm for the TPS and the manifold temp sensor. I grounded those to bypass the pcm problem, still no better.

If your Jeeps not leaking it's out of fluids.
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post #5 of 25 Old 06-22-2019, 01:01 PM
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Sometimes a faulty sensor ground issue is caused by a short in the clockspring -- try removing your horn relay to see if the Jeep will start and run normally.

2000 TJ SE
2005 LJ Rubicon
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post #6 of 25 Old 06-22-2019, 02:07 PM Thread Starter
ReconRabbit
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No dice, but thanks for the tip.

If your Jeeps not leaking it's out of fluids.
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post #7 of 25 Old 06-22-2019, 02:26 PM
jtec
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please tell what basics are if not spark and fuel?

With NO schraider valve to attach gauge try spraying carb cleaner into TB as someone tries to start - did it try to fire or run on the spray?

Did you friend from GM get a scanner on the system - check for codes?

is your SRS light on?
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When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #8 of 25 Old 06-22-2019, 02:43 PM Thread Starter
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I have a scanner, I'm getting no codes.

Spray at the throttle body has no effect on the engine. It will start and crappy idle most of the time. But you can't do anything to get the rpms up. Or it to idle normally.

When it's cranking and won't start, it sounds like the timing is off, it's popping and backfiring.

What troubles me the most is that a couple times it has started, idled normally, and revved up fine. But that's probably 1 time in 20. And when it runs good, it falls back into the rough idle with no acceleration.

And I'm not a new jf member, I just couldn't remember my login password from my cj days. Now that I am an owner again, I'll be hanging around this forum.

If your Jeeps not leaking it's out of fluids.
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post #9 of 25 Old 06-22-2019, 04:44 PM
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Quote:
Originally Posted by nzirbel View Post
Spray at the throttle body has no effect on the engine.
This makes me think the problem is likely more on the ignition end of the spectrum, but the recent head work has a nagging thought in the back of my mind that compression may be an issue somehow. That aside, a few questions come to mind:
  • When you say you're getting spark at the cylinders, did you check each individual plug while cranking?
  • Have you tried pulling one plug wire off the distributor at a time at idle to see if the idle quality changes?
  • Is the center rotor carbon contact present on the inside of the cap?
  • Are the contacts in the cap and on the rotor clean and shiny?
  • Is your scanner capable of displaying live data, and if so, what readings are you getting for the MAP, TPS, and coolant temp sensor at idle?
  • Have you tried running the engine with the upstream o2 sensor disconnected?
  • Have you tried checking for exhaust restrictions?
  • Have you done a compression check?

2000 TJ SE
2005 LJ Rubicon
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post #10 of 25 Old 06-22-2019, 04:50 PM
Boojo35
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You need good spark, good fuel delivery, proper timing, good compression, no air restrictions intake or exhaust, and good fuel quality to make an engine have a hope of running correctly. With new technology you may have other things that can mess with it.

If it pops and backfires I would suspect timing, moisture in the distributor cap, incorrect firing order, plug wires arcing, etc. Some valve train issues can cause similar issues also but maybe some thing as simple as a bad cap and rotor could be your issue.

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #11 of 25 Old 06-22-2019, 05:33 PM Thread Starter
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So to complicate it even more: I'm leaning towards ignition. So I went through the procedure to check the camshaft sensor in the distributor. It checked out fine. Just for fun I hit the key when I was done and it started up and ran fine. The idle was a little high, but it sounded good and revved great. I looked at the gauge cluster and it said check gauges, and no gauge was working.

Ok, I turned it off and restarted it to try and pick the gauges up. Back to rough idle and no acceleration. I'm definitely ready to kill it with fire!!!!

If your Jeeps not leaking it's out of fluids.
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post #12 of 25 Old 06-23-2019, 09:00 PM Thread Starter
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Today's update: I hit the key and it started right up. Idle was good, revved up no problems. Next, a warning beep, the check gauges light comes on, and all the dash gauges died.

Thought I'd let it run and warm up. Couple minutes later, a sputter and it died. Now it won't restart, I've got nothing.

I'm pretty sure I'm down to a faulty pcm unless someone has any other advice.

If your Jeeps not leaking it's out of fluids.
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post #13 of 25 Old 06-23-2019, 09:17 PM
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Unplug the black PCM connector, check to see if you're getting 12.6v to pin 22 (RD/WT) and pin 2 (RD/LG) at the harness connector with the ignition switched on. Make sure you have good continuity to ground at pins 31 and 32 (BK/TN) of the harness connector.

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post #14 of 25 Old 06-23-2019, 11:43 PM
Jimwfl
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Unplug the upstream O2 sensor... Then check Ignition switch. My 97 always stutter at start and new O2 fixed. Lost gauges & start up because of corrosion in Ignition switch. 2 separate things at 2 separate times... Good luck & I hope you figure it out!
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post #15 of 25 Old 06-24-2019, 05:42 PM Thread Starter
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Quote:
Originally Posted by mukluk View Post
Unplug the black PCM connector, check to see if you're getting 12.6v to pin 22 (RD/WT) and pin 2 (RD/LG) at the harness connector with the ignition switched on. Make sure you have good continuity to ground at pins 31 and 32 (BK/TN) of the harness connector.
I've got 12v at the first 2 pins. I didn't have ground on pin 31, my GM tech traced the wires, checked continuity, and said it's most likely the pcm. He advised that I could just ground the sensors that pin 31 feeds and try it with no guarantee. I grounded them and it's back feeding ground into the pcm if that makes sense.

It did start and run good like that after a bunch of messing around, but then it just coughed and died After it died yesterday, I've now got no spark. It'll crank like crazy with no fire.

If your Jeeps not leaking it's out of fluids.
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