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Does my TPS need replaced?


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I'm still fighting a too slow idle speed. I replaced the ISA and it does work, but it used to start at a high idle then throttle down, now I have to give it a little throttle to start. It will the idle ok til the engine get to operating temp, then it stumbles and sometimes dies when I stop at a light.

 

I tested the TPS voltage output at WOT, and it was 4.5v. The manual says 4.6 to 4.7v. I couldn't adjust it any higher.

 

Should I replace the TPS, or is 4.5v close enough? :dunno:

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You guys don't like 2.5s, do you? :(

 

I got the TPS to output 4.65v by bending the tab on it to give it a bit more travel. It starts better now, but still stumbles when warm. It will stumble for about 5 seconds when I stop, then the ISA extends enough to bring the idle up to somewhat normal.

 

Any suggestions on how to proceed?

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Thinks the 2.5 is a great engine. Reliable,efficient, dependable, economical,etc, Just don't expect V8 performance from it, Although mine has showed up a V8 now and then. Not familiar with the problems your having so unable to suggest anything, other than check all vacuum lines, fittings. Look for a vacuum leak. Give the guys a chance to respond. They don't live here 24-7. But they will help with good advice.

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I want to follow this thread, my 2.5 has a simular problem. My engine starts and runs good when cold but will have a intermittent slow idle when warm. If that engine dies when I'm going around a corner, that's scarey, it takes an incredible amount of force to turn the wheel!

 

I need to read up on how to measure and adjust my TPS switch.

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I was reviewing the 2.5L CEC System document located at jeepgarage.free.fr/own/2.5l, my 88 Comanche has an entirely different system than they show in the vacuum diagram. They also talk about a "knock sensor" located on the cylinder head? Their document is for a Cherokee, I can't imagine that the systems would be that different but maybe so.

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  • 4 weeks later...

How much longer should I wait? ;)

 

I replaced the MAT sensor. It didn't help. :(

 

Going in a different direction, the AC in my truck is an after market job. There is no AC relay, so the ECU doesn't get a signal to step up the idle speed. I can add a relay to feed it this signal, but looking at the electrical schematic, I am unsure what the signal voltage is. If I send 12v and it's supposed to be less, I suspect I will fry the ECU.

 

So, does anyone know for sure what the voltage would be? Or is this another one of my many bad ideas?

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When the truck is first started it runs in an open loop mode until it warms up getting preset info from the ecu, then runs in closed loop mode getting its info from the sensors. Have you tried cleaning the IAC and throttle body. I would test the O2 sensor also. Not familiar with the 2.5 so just giving some ideas

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I don't think the 2.5 has an IAC. The TB has been cleaned and recleaned. I'm not sure how to test the O2 sensor, other than it runs the same with it disconnected. The O2 sensor has 3 wires, while the ones I see online are only 1 wire.

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Thanks, I'll look into that.

 

Another question: Are the MAT and CTS the same? I noticed the wire connector ends are reversed. I was thinking of trying the new MAT sensor in place of the CTS. I can change the connector end if the sensors are the same.

 

EDIT: never mind, they are different. :(

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