CEL light on can not retrieve codes, runs good in KOER

[markopolo]

So here is what I have going on. I have a 94 3.0 5speed 4x4. When I start it, it will fire right up run good and then die or sometimes try to die. Then upon restarting it will idle down to around 500rpm and run rough, almost like its cammed. Take it for a drive and it will run halfway decent. When its under a load it will bog down then take off similar to turbo lag. The weird part is when I try to retrieve codes I cant get any out of it. I have a jumper between the eec connector and the test lead. When I have the jumper in place it doesn't do the surging under a load. It runs great actually. It also idles high (1200-1500rpm) when the jumper is in place. I would leave the jumper in all the time but its a pain to start when at temp. It dies or tries to die several times before it levels out.

I was just wondering if anybody out there has heard/seen of this....

 

[RonD]

I would disconnect the negative battery terminal for 5 minutes then reconnect it, this will reset the computer and CEL.

See how long it takes to come back on.

I would check the ECT sensor with an OHM meter.
The ECT sensor is a TWO wire sensor that tells the computer the engine temp, so it is the "choke" for a fuel injected engine.
reads like you are running with no "choke", low idle and rough running when cold.
Look here for the test numbers you should get:
http://oldfuelinjection.com/?p=28

There will be a ONE wire sensor/sender near the ECT, it is for the dash board temp gauge.

 

[markopolo]

I have tried the battery reset. I ohmed the ect and didnt get any sort of resistance. I feel that I have more than 1 problem going on here. Ill replace the ect this weekend.

 

[markopolo]

I would disconnect the negative battery terminal for 5 minutes then reconnect it, this will reset the computer and CEL.

See how long it takes to come back on.

I would check the ECT sensor with an OHM meter.
The ECT sensor is a TWO wire sensor that tells the computer the engine temp, so it is the "choke" for a fuel injected engine.
reads like you are running with no "choke", low idle and rough running when cold.
Look here for the test numbers you should get:
http://oldfuelinjection.com/?p=28

There will be a ONE wire sensor/sender near the ECT, it is for the dash board temp gauge.

Thank you for the site!!
A couple of new devolopments:
1. I am an idiot and had my ohm meter on the wrong setting. The ECT reads fine
2. On the website you gave me I found a way to retrieve codes that I had not tried. I tried that and was able to pull 4 codes

118, 123, 113, & 539

118, 123, and 113 all are sensor circuits about 4.6v for the ECT, TPS, and ACT

So I'm now thinking i have a VREF issue.... or something of the sort

 

[markopolo]

So I did some wire tracing this morning and came across some 'pecker tracks'
When I bought the truck you could start it with out pushing the clutch in. Come to find out the SIGRTN wire was in with the clutch switch. Some one had tied it directly to the wire going to the ECM along with bypassing the start circuit portion of the switch.

I undid the SIGRTN wire and unplugged the neg batt cable for about 10min.
I started the truck and all of my previous symtoms had passed but now it just would die when I hit the gas. Unplug the TPS and runs like a charm.

Tested the TPS and max voltage at WOT is 1.8v.


I hope all of this helps someone....

 

[Rearanger]

Good troubleshoot.

 

[markopolo]

So to continue this saga...

After a while if running with the TPS unplugged I decided to break down spend the $45 and buy a new one.

After breaking the old one to get it off, I installed the new one and no change in symptoms. Thinking I had bad new part, I checked voltage again came up with the same result. This led me back to my 118, 123, and 113 codes. So in tracing the SIGRTN wire down again (which is almost literally goes everywhere) I decided I was going to ground it and see what happens.

After a temporary ground was setup I started the truck with no problems and it drove like it should!

I setup a permanent ground and have been driving it like that for a while now with no problems what so ever.

Idk what problem I'm masking with that but I'm sure it will rear it's ugly head at some point when I least expect it.


Sent from my iPhone using Tapatalk