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TPS or CPS or something else???

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Old 06-25-2010 | 11:07 AM
  #1  
csmart30's Avatar
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Joined: Dec 2009
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From: Provo, UT
Year: 1993
Model: Cherokee
Engine: 4.0 straight 6
Question TPS or CPS or something else???

I have a 93 country. First off after i've been driving around, seems to be no matter how long, and turn it off if it sits for more than 20-30 minutes but less than 2 hours I have a hard time starting ( I know the time frame seems weird but that's usually what it is) and have to have the gas pedal to the floor to start, but it doesn't flood. I can hear the fuel pump prime, and when I check the rail I have a good amount of fuel. So my thought was CPS.

Secondly only recently while I'm driving I hit "dead spots" where the jeep dies down for a second but then comes right back to life, usually. So I also thought maybe TPS 3 days ago I hit a dead spot while turning at a stop light and It just died on me. While trying to start back up had previously said starting problem.

So whatcha think? I've checked all the connections, cleaned them with CRC electric cleaner and was tempted to throw some Di-electric grease on them but didn't. All I have in my bank account are some moths, but I start work on monday so in 2 weeks i'll really be able to get whatever i need to fix it, but temporarily am broke.
Old 06-25-2010 | 11:11 AM
  #2  
davida's Avatar
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Joined: May 2009
Posts: 296
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From: Wy & OK
Year: 83 CJ7 & '96 XJ & '97 XJ
Model: Cherokee
Engine: 258ci, 4.0 & 4.0
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First I'd check for a trouble code, even if your check engine light isn't on.
Old 06-25-2010 | 02:28 PM
  #3  
Eli Lilly's Avatar
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From: South Florida, USA
Year: 1995
Model: Cherokee
Engine: 4.0
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Although it can be a few different things, I had this happen on mine and it was a POS coolant temperature sensor that died after 2 months and started reporting 600K ohms. It's an easy sensor to test, just unplug it and see if the problem goes away. Other items to check are TPS, IAC, MAP, and possibly CPS. I wouldn't start at the CPS, though. But my symptom was identical to yours, wouldn't start unless floored. The PCM was picking up a "it's zero degrees outside" signal from the CTS and it was enrichening the fuel mixture like crazy, so opening the butterfly was the only thing that let enough air in.

-E

Last edited by Eli Lilly; 06-25-2010 at 02:31 PM.
Old 06-25-2010 | 03:05 PM
  #4  
Bustedback's Avatar
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Joined: Feb 2010
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From: Oroville, CA
Year: 1995
Model: Grand Cherokee
Engine: 4.0 with all of the noise and clatter
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A CTS (coolant temp sensor) could cause a problem if it is telling the PCM it is really cold outside, you would have some black smoke coming out of the tail pipe because it is dumping more fuel than the engine needs. If you had a scan tool that could read real time data, you could check the TPS voltage and see if there is a dead spot at a certain position. You can do it with a DVOM too, but I don't remember how at the moment.
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