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Replaced TPS - Idle now WORSE!

P

peuglow

NAXJA Forum User
Location
MA
Replaced TPS - Idle now much worse

Hey guys

New to this forum, but not new to Jeeps. I'm limited in my knowledge on this stuff, but I was hoping for some tips.

1996 XJ inline 6 4.0 liter automatic. 250k on the engine, but she was running without issue.

I was having some issues with sputtering while driving. Engine wouldn't stall, but would cut out the power down to 500/1000 RPMs. This happened with a cold engine, a warm engine, back roads and on the highway. Also, no CEL was thrown.

I replaced the dist cap, rotor, wires. Plugs looked OK. Cut in a new catalytic converter and muffler. Still had the issue.

Then last night I replaced the TPS. Went to start her up, now the idle is really rough, all over the place, and she throws up a CEL. The TPS is a new part from Advance Auto.

Any ideas what the issue is? She sounds like she's sucking in a LOT of air since I changed the TPS.

Any help would be greatly appreciated.
 
Last edited:
Pull the iac valve out and gently clean it. Just be sure not to push or pull the plunger. Then use a q-tip and some cleaner to clean the tb passages.
 
Thanks, will do.

I'm just curious, if I haven't touched anything else when changing the TPS, why would the idle be so much worse. It's all over the place.
 
That's a puzzler, perhaps you got a crappy sensor. I don't trust any electronics from advanced. I'd try stickin the old one back in, it's easy enough to swap.
 
That's a good call. I was thinking of doing that. Hope it's a bunk sensor. Maybe I can find an OEM one at the junkyard and see if that does the trick. Thanks man, and I'll let everyone know how it turns out.
 
I've had the same problems with my '96. When the original TPS failed, I bought a new Standard brand piece. Was actually worse. I went to the junkyard and loaded up on previously-loved units, and tried them one by one to find the one that was the happiest. It's been in there about a year and a half, and it's still behaving. Cross-reference the part number, and see which vehicles are likely donors. Right off the top of my head, '91 through most '96 XJ and possibly 4.0 ZJ are good bet. '96 Classic models mostly use '97 wiring, including plugs, and the TPS plug is one that changed for '97.
 
Did you end up 'resetting' the battery after you put the new TPS in? I was reading you can disconnect the battery and essential reset the comp so it can 'relearn' for the new sensor.
 
Yes, I did follow the procedures to reset the computer. Curiously, though, my problems started after I had the recall 'reflash' service performed a few years ago. The recall was to reflash the computer, and check the catalytic converter. The car didn't feel the same afterward, the TPS problems started a few months later, and now the cat is rattling, the ceramic honeycomb is cracked and broken. It even threw a code a while ago, something like ineffective catalyst. I asked the dealer what was involved in the reflash, and of course they didn't know. I've scoured the junkyards for un-flashed '96 computers, and curiously they're all gone. Plenty of '95s (OBDI) and '97s (different animal, as far as I can tell).
 
What was the point of the recall? Just out of curiousity.

I'm going to try resetting the computer tonight and see if that helps. My buddy has a JY TPS that I will try out if that fails and I can accredit it to a faulty part from Advance. I'm hoping this works, because I've been without the Jeep since Halloween, and sharing my wife's Accord isn't ideal by any stretch.

I actually have a new(er) catalytic on there now because my mechanic thought it was a plugged pipe to blame for my sputtering issue. So after doing the dist cap, wires, rotor, cat/muffler, we have moved onto the TPS.
 
The point of the recall was to re-flash the computer and check the cat. How or why, I don't have a clue. Neither did the dealer. If you look into it, let us know!
 
bimmerjeeper said:
Rule #1 of the forums is not to buy non-OEM sensors.
TPS from dealer is like $70.
Click to expand...

I have 5 Renix Jeeps now and I have never bought a single OEM dealer part.

But I am getting more and selective about where I buy parts, and the brands I buy!!!!! 2 years ago 95% of what I used was from Azone (with few problems), now 80% is Rockauto (but you need to be selective of the brand and shipping issues, weight), and 10%/10% Azone / Oreily's, and a little AAuto. I recently started buying Murray brand parts, also Standard brand, when they were listed as made in Israel or Italy, versus China!!! And Azone has slashed their warranties lately!!!!!
 
A TPS can be easily checked with an analog meter to see if it's good. I have a Duracrap TPS which has been perfect, while my aftermarket CTS was off by 30 degrees, and the oil pressure sensor didn't mate well with the factory plug, resulting it erratic gauge operation. I wound up re-using old OEM sensors for those two. Aftermarket sensors are hit-or-miss in my experience, but it's easy to check the TPS with a cheap meter.
 
Ok, so I reset the computer last night, let her run for a few minutes. The idle was slightly better. Idled just under 1000 RPM for the most part, once in a while would jump, and even come down to where it seemed like it would stall out.

It was dark, so I noticed some of the plug wires I just replaced (Before doing the TPS I did the dist cap, rotor, and wires) are arcing through the insulation. I can also see some arcing down near (underneath?) the cap. I will crank the cap down tighter tonight and replace all the wires again with higher quality wires. I used the Xact brand, and I'm thinking they are garbage.

Any opinions on MSD or Autolite wires? There's a huge difference in the price between the two, and money is tight. I may even go to AZone to get some Bosch wires. I used them a long time ago and they were good.
 
Good find! Many times wires will arc intermittently, making diagnosis difficult. Don't waste time, get the good wires. Fix 'em up, let us know how it works out.
 
Make sure you have the rotor all the way down on the shaft, locked in place. Also check that you don't have 2 wires crisscrossed!!!! And make sure the cap is on straight.

If you still get arcing consider that the timing chain may have jumped? I use the good wires at Azone myself. I think they are Bosch now, use to be Duralast?

Also check the engine block ground!!!!
 
Thanks Mike. I will go through and ensure the cap/rotor etc are tight. Wire order should be good, triple checked w/ Haynes manual when doing the wires. I drove her for a good hour before I had this issue (sputtering, power dropping way down) again. Not sure if the insulation in the wires is faulty, or user error. Either way, I'm returning these cheap Advance "Xact" plug wires and buying Bosche from Azone, which I've used in the past and were great.

Grounds looked OK, though I didn't give too thorough of a check. Will go through her tonight with a fine-toothed comb and hopefully it will yield my DD back, since I haven't had one since Halloween.
 
Arcing plug wires is sure a huge clue. But based on your reports here, if new plug wires don't solve it, and it gets hard to start, start thinking CPS next, in case you have 2 problems, LOL.:D
 
Hahah yes, that was my next step. Hopefully it doesn't come to that, the plug wires solve the issue, and I get my DD back!
 
Testing the TPS....Does anyone have a detailed step-by-step write-up of how to test the TPS? Where it's located, what prong you put the red probe to, what prong you touch the black probe to, if the car is running or off, what the meter should read, etc. Just saying "Bro, it's easy" doesn't make it easy.
 
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