another Renix idle thread (lots of searching first, i promise)

This weekend I spent about a day fixing the wiring on my 87 waggy. Alot of the wires in the relay center were melted, and one of the relay sockets was pretty fried. Some jackass tried to fix it with wire nuts, butt splices, tape, and even some black RTV. So I cut out all of the bad stuff and soldered in new wire with solder butt splices, then heat shrinked everything. Replaced the fried relay socket, and 2 of the relays. Then I added some new 1/0 battery cables. I also replaced my crank sensor in an attempt to fix a stalling problem, which worked beautifully. The ol girl was running better than ever!! I should have left well enough alone, but my MAP sensor connector and my IAT connector had broken clips, and since they are both weatherpack connectors I grabbed some new ones from work and replaced them. Just pulled the pins out and replaced the housing, sounds simple, yes? As soon as I changed the connectors the jeep started but idles extremely rough. Sounded like a top fuel dragster idling it was so rich. Then it came out of it and idled fine for about 10 seconds, then dropped again. Now it just goes back and forth, rough for about 10 seconds then fine for about 10 seconds. When it's rough it won't rev up, just backfires and sputters. I turned the idle up to about 1000 and it will idle but something is wrong. I looked at the FSM and the wires in both plugs are in the correct locations, so what could it be?

probabl;y knocked the vacuum tube to the MAP sensor off of the throttle body.

Ecomike said:

probabl;y knocked the vacuum tube to the MAP sensor off of the throttle body.

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x2.

This happened to me. Turns out I knocked the little rubber plug out of the TB somehow.

That was my first thought also, checked and double checked. it is hooked up and not cracked anywhere.

When you replaced the connectors, are you sure that there is a solid connection between them and the wiring?

Are the O2 sensor wires OK? Mine hit the manifold once, and over heated and melted wires in 2 locations.

Sounds like you got to MAP sensor wires criss crossed. Check them for reversed polarity, with a meter, never mind the wire colors.

You did that with the engine off right? Not sure if it's OK on a Jeep, but I blew up the MAP/MAT sensor on a Nissan (pretty sure it's a combined unit on Nissans...) once by disconnecting and reconnecting it with the engine running. Kinda sucked.

kastein said:

You did that with the engine off right? Not sure if it's OK on a Jeep, but I blew up the MAP/MAT sensor on a Nissan (pretty sure it's a combined unit on Nissans...) once by disconnecting and reconnecting it with the engine running. Kinda sucked.

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That is not a problem with renix. I have connected several of my Renix sensors backwards (by mistake, weatherpacks were damaged, and alignment plastic was broken) , and connected and disconnected them hot with no problem.

I tested all connections with my multimeter and everything checks out fine. I followed the test procedures in the manual with a vacuum pump and voltmeter and the MAP sensor checked out. The IAT checked out as well, now I am at a loss. Somebody has to have had this problem before and fixed it!

Everything tested fine through the connectors that you replaced?

yes, everything tested fine. MAP is steady 5 volts in and 1.69 out at idle, no dead spots. IAT is within range, I forget the reading i got but it was in range.

Still sounds like one set of wires on the IAC or MAT were reversed. I had the same problem when I reversed the TPS and O2 sensor wires on 2 different occasions.

There are no reversed wires. I have checked and re checked them all. I am beginning to think this is a seperate issue that just appeared miraculously (sp?) when I changed them, or maybe I screwed up the ECU somehow. The hunt continues....................

Curtis, I'm at a loss. That's such a bizarre problem.

Have you checked all your vacuum lines?

Curtis_H said:

There are no reversed wires. I have checked and re checked them all. I am beginning to think this is a seperate issue that just appeared miraculously (sp?) when I changed them, or maybe I screwed up the ECU somehow. The hunt continues....................

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You might try checking the signals to the ECU, at the ECU, live. It might be more revealing, especially if there is more wiring harness damage hidden deeper in the harness.

Also, try disconnecting the O2 sensor. Start it up and let it run. IF the problem goes away, it is the O2 sensor or wiring or O2 sensor heater relay....

If that does not work, do the same with the TPS sensor only. Disconnect it, and see if the hunting stops. IF it does, then reconnect it and test the TPS signal to the ECU live for a variable signal.

You did clean, and replace the block and frame grounds right? Did you check the ECU and MAP sensor grounds (power off) with an ohm meter, between the sensor ground wire at the sensor and the battery negative post? IT should be less than one ohm, even when wiggling wires.

I had to run new sensor grounds on my TPS, from my TPS straight to the battery.

Thats a good suggestion to check the signal live at the ECU. I will do that this weekend. I did not check the TPS ground for resistance but I did check the MAP, it was 10.5 ohms. If it should be less than 1 then that may be my problem. I will do some more testing and report back, thanks for all your help!!

Oh and yes, i cleaned/replaced all my grounds . new - batt cable and new ring terminals on block, one new ground strap, and new ring terminals behind washer res.

My ground for my TPS went bad and has caused really bad idling. I ran a ground straight to the battery.

Curtis_H said:

Oh and yes, i cleaned/replaced all my grounds . new - batt cable and new ring terminals on block, one new ground strap, and new ring terminals behind washer res.

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I did the same thing, but still had bad, poor grounds on both sides of my TPS. Never found the source, just ran new grounds from the sensor to the battery. Your MAP ground is way too high.