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89 Renex Cherokee Ignoring new TPS?

Zeb Lundy

NAXJA Forum User
Location
Idaho
I have an 89 jeep Cherokee with the inline 6 and a manual transmission. It has a new crate motor that was professionally installed about 5000 miles ago. It has an erratic idle issue. It also sometimes lugs down after start up and almost dies and sometimes will die. Every time it dies it will start very strong on the next start. My local shop said it was probably the TPS because the jeep would start, drive and idle the same with the TPS plugged in or unplugged. Knowing that these Renex jeeps are known for the TPS going bad I got a new one and installed it. I set it by measuring the output and input voltages. After this it still has the idle issue and it seems to still be ignoring the TPS. Unplugging the TPS makes no difference and when I manually press down the arm on the TPS it does nothing. It seems to be ignoring the TPS data. I have read that the Renex system will learn to run without the TPS but none of the computer reset procedures I found online seem to do anything. Please Help!!!!
 
The idle air controller should also be suspect for idling problems. Cruiser54 has some good info you might look at on adjusting and testing the TPS, and some info on refreshing grounds (I suspect you might have a bad ground on the TPS sensor).

http://cruiser54.com/?p=54
http://cruiser54.com/?p=19

Bad ground at the newly painted dipstick tube stud. Or, some were left off.

Poorly indexed dizzy could be it also.
 
The idle air controller should also be suspect for idling problems. Cruiser54 has some good info you might look at on adjusting and testing the TPS, and some info on refreshing grounds (I suspect you might have a bad ground on the TPS sensor).

http://cruiser54.com/?p=54
http://cruiser54.com/?p=19


His index of really great tips is at http://cruiser54.com/. You might also look at
http://cruiser54.com/?p=47 too (that weird crimped bunch of ground wires had me wondering if someone had already hacked the wiring harness when I found it the first time)
 
Dizzy is slang or short for distributor

Oh, ok. Well I checked the TPS ground as described in the link above and it checked good. About .27 Ohm. I have an IAC valve on order and will see if that helps my idle. As for the distributor and fully re-grounding the whole system it will be a while before I will have time to do that. I am working a lot of hours just now so it my be a week or so maybe this weekend but I am not sure. I will keep you all updated. If anyone else has any ideas please let me know.
 
ummm. your condition could also be the dreaded fuel pump ballast.
Not sure if the 89 has one. but if it does.
rip it out. solder the wires together. and shoot the thing/destroy it.
 
ummm. your condition could also be the dreaded fuel pump ballast.
Not sure if the 89 has one. but if it does.
rip it out. solder the wires together. and shoot the thing/destroy it.

I already tested the ballast by bi-passing it with a piece of wire and my jeep still had the same issues. It does not seem to be a fuel pump issue as the fuel pressure checks good. But yes I think the ballast is an absurd device.
 
But yes I think the ballast is an absurd device.
it made me have one hell of a bad year. Constantly mine would not start.
in my experience so far with my 92 4.0 the tps really doesn't do anything.
I have changed it 4 times. from one that failed voltmeter test. with no change.

the idle air control valve does all the work
changed that and it cured my issue.
 
how long after start up does it "stumble"? mine will stumble a bit once it enters closed loop. i suspect its the o2 sensor for mine. might want to try unplugging it just to see how it does.

as for the tps it will run with out one installed idle should be decent. but it will almost die on a fast close of the throttle. double check that you have no broken wires in the tps wiring. your signal wire may be broken somewhere.
 
That sounds 100% like the TPS data is not getting to the ECU. You have a wiring problem!!!! Ground perhaps on the ECU side, the flat 3 pin connector.

I have an 89 jeep Cherokee with the inline 6 and a manual transmission. It has a new crate motor that was professionally installed about 5000 miles ago. It has an erratic idle issue. It also sometimes lugs down after start up and almost dies and sometimes will die. Every time it dies it will start very strong on the next start. My local shop said it was probably the TPS because the jeep would start, drive and idle the same with the TPS plugged in or unplugged. Knowing that these Renex jeeps are known for the TPS going bad I got a new one and installed it. I set it by measuring the output and input voltages. After this it still has the idle issue and it seems to still be ignoring the TPS. Unplugging the TPS makes no difference and when I manually press down the arm on the TPS it does nothing. It seems to be ignoring the TPS data. I have read that the Renex system will learn to run without the TPS but none of the computer reset procedures I found online seem to do anything. Please Help!!!!
 
.27 ohms on the ECU or TCU ground of the TPS? They are independent. The ECU side, the 3 pin side must be good or it would kill the ECU response to moving just the TPS arm. Also if the third wire with the return signal to the ECU is bad the ECU is not seeing the TPS output signal, and thus would not doing anything!!!

Oh, ok. Well I checked the TPS ground as described in the link above and it checked good. About .27 Ohm. I have an IAC valve on order and will see if that helps my idle. As for the distributor and fully re-grounding the whole system it will be a while before I will have time to do that. I am working a lot of hours just now so it my be a week or so maybe this weekend but I am not sure. I will keep you all updated. If anyone else has any ideas please let me know.
 
The fuel pump gets full battery voltage while cranking, about 11.5 volts with a good/new battery. With the engine running, and no ballast it gets too much voltage, runs the pump too hard making it noisy. It is designed to drop the voltage from about 14.7 volts to about 11.5 volts, all measured at the battery post. It extends the life of the pump.

I already tested the ballast by bi-passing it with a piece of wire and my jeep still had the same issues. It does not seem to be a fuel pump issue as the fuel pressure checks good. But yes I think the ballast is an absurd device.

Not having a TPS signal will make the engine stumble with rapid acceleration or rapid deceleration.
 
Not having a TPS signal will make the engine stumble with rapid acceleration or rapid deceleration.

The .27 I was refering to was on the ECU side. And there is no issue with it while driving. It has a lot of power no stumble on acceleration or deceleration.

Also UPDATE. The IAC valve does not seem to make a difference.
 
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