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Old 12-18-2008, 05:59 PM   #1
Join Date: Dec 2008
Posts: 6
Exclamation 4.0L spluttering/stalling/bucking- no codes? TPS?

Hey guys, I've just bought a TJ Wrangler 2001 4.0L manual, and sometimes it drives fine, and other times when cruising along at 60km/h (37mph) in 4th, it lacks pickup and spluttler a little before accelerating.

Also, it has cut out a few times while driving and I've had to pull over to the side of the road. It bucks badly quite often when going up steep hills as well. Today coming up a steep hill I had to rev it right out and keep slipping the clutch to get it to go up at all.

I've brought it to the service centre, and they cleaned the throttle body and injectors, as well as ran the codes (at a cost of $350 AUD all up). It showed no codes whatsoever, so they couldn't fix the problem.

They suggested it might be the throttle position sensor, but they weren't sure. Is it possible for the TPS to malfunction and not show a code? Since it's going to cost me $350 AUD for a TPS I'd rather not replace it if I don't need to.

Thanks heaps

Note: Live in Australia - no Aus option when I registered thats why it says Cali!

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Old 12-19-2008, 08:07 AM   #2
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Location: Poconos
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IMO - Take the least expensive option for now and fill up somewhere else for a couple of tanks. Throw in a can of injector cleaner on the next tank and re-evaluate your problem.

I had a similar experience when I filled up at one of the local stations here and I believe I got a lot of water in the tank.

Welcome to WF mate!


It ain't no fun unless you get some of it on you.
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Old 12-19-2008, 02:24 PM   #3
Join Date: Nov 2008
Location: athens, ga
Posts: 14
similar problem

hey, i have a tps problem as well, except in a 4 cylinder.

mine does have the Check engine light on and codes to TPS. I replaced the TPS(only $30 usd) myself (fairly easy, once you find it) but the problem still existed. I talked to my family's favorite mechanic today, and i think that the wiring in and out of the TPS is jacked up. I bought the jeep used, and there is all sorts of tape on the wires. so tomorrow i will be handing the jeep to the pros and hoping that fixes it. I will let you know.

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Old 12-19-2008, 07:00 PM   #4
Join Date: Dec 2008
Posts: 6
Injectors cleaned. Throttle body cleaned. TPS checked off the car - ranges from .23ish to 5.5ish. All seems to be fine but still splutters.

Any ideas?
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Old 12-19-2008, 07:29 PM   #5
Join Date: Oct 2008
Location: Butler Ohio
Posts: 19
Bucking could be fuel so run a pressure check under a load.

Crankshaft position sensor is a possibility.

Keep in mind that the PCM does not monitor these circuits so all problems will not trigger the MIL.
Fuel pressure (although a rich or lean condition might)
Secondary ignition
Engine compression
Plugged exhaust (cat)
Injector mechanical malfunctions
Throttle body air flow (plugged air cleaner,etc.)

Some basic testing and troubleshooting should be in order. OBD II is a wonderful tool but mechanics who live by it should also know internal combustion engine basics.
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Old 12-20-2008, 08:16 AM   #6
Join Date: Dec 2008
Posts: 6
Ok thanks, I'll have to check these out

Fuel pressure (although a rich or lean condition might) - I'll need to test it.
Secondary ignition - How do I test?
Engine compression - Should be fine - 90,000kms (56000 miles).
Plugged exhaust (cat) - emissions aren't an issue so I can drill it out.
Injector mechanical malfunctions - Injectors tested and cleaned
Throttle body air flow (plugged air cleaner,etc.) - All checked and fine.

Strangely, the problem is intermittent, occuring say 15% of the time, which leads me to believe it isn't a blocked cat. and probably more ignition based. May be a fuel pump problem also, I'll have to check out the FSM on how to test it.

Does anyone know where to find a copy online? I can't seem to find one.

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Old 12-25-2008, 04:41 AM   #7
Join Date: Dec 2008
Posts: 6
Okay people. Replaced plugs, and sprayed all my sensors with WD40 spray.
Car ran great for quite a while, then started to buck and splutter again, but only for a short time.

So I've ruled out the plugs having issues,
And it seems spraying the sensors has had an effect and intermittently fixed the problem.

The throttle is really touchy, and as soon as I press it, it hesitates for a split second, then takes off. Could this be the TPS even though it doesn't pull a code?

And it lacks low down power. Below 1500rpm it doesn't sound fantastic, and doesn't have a lot of pickup. Is this normal? As I've never driven another jeep.

Thanks and Merry Christmas
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Old 12-25-2008, 10:02 PM   #8
Join Date: Nov 2008
Location: athens, ga
Posts: 14

hey, I just got my jeep back from the shop. I had thought my problem was tps, but it turned out to be pcm. unfortunately i just had the shop do it (too detailed for me) so it was expensive, but the tj is running beautifully. it is idling really steady, and is not sputtering or bucking at all during acceleration. only problem is i found out my airbag doesn't work through this process, and now that has to be replaced.

hope that you figure it out soon... merry Christmas!

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Old 12-29-2008, 12:19 AM   #9
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Location: Garfield, NJ
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Possible vacuum leak? I had that happen something similar to my car and ended up changing the intake manifold gasket.
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Old 12-29-2008, 05:09 AM   #10
Join Date: Dec 2008
Posts: 6
Ok. Another update!

Went for a drive today, got home and the car's idle was rough and poor, and there was a rattling noise that was quite loud and only present when the clutch was out? Odd.

I sprayed the crank angle sensor, tps, ECU, as well as another sensor on top of the throttle body and no change (sprayed with WD40/water dispersant). I then hit the CAS again with spray, and the cars revs jumped up to 1000rpm, then it started to idle perfectly. No rattle noise.

Any ideas on whether this was the CAS playing up, and spraying it fixed it, or another sensor I sprayed?

As it pulls no codes, I'm leaning toward the CAS, as it doesn't usually display a code when it malfunctions.

Any help would be really appreciated!!
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Old 01-01-2009, 05:44 PM   #11
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Location: Garfield, NJ
Posts: 249
It puzzles me that a sensor such as the Crank Angle Sensor would give you problems and not give you a Check Engine Light. Are you sure is not a vacuum leak or a craked exhaut manifold?
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Old 01-05-2009, 02:02 AM   #12
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Apparantly the Crank Sensor doesn't pull a code
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Old 01-05-2009, 03:20 AM   #13
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Wipe off the residue of WD-40. It "moves" moisture (and dirt,) but it also attracts it. Use a GOOD electrical cleaner that's designed for electrical terminals. They don't leave a residue. Radio Shack, electrical/electronics supply houses have it.

(Take a freshly ground shiny piece of steel, coat it heavily with WD-40 - leave it on wet grass overnight - next morning it's badly rusted - UNDERNEATH all the WD-40.)

CPS can set a code, but it's rare. When it loses sync, it fails too fast for the PCM to read it.

Have a good look at the CPS connector at the wiring harness - open it - CLEAN it with that GOOD electrical cleaner, then close and open it a couple of times. Often it's just a poor connection.

It's no wonder the country is falling apart - stupidity abounds!
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