Problem solved: Wiring harness was bad, now cats are bad

[ShadetreeSHOguy]

Not sure...
FWIW, the carb cleaner method does not always work. You will probably have to pull the intake completly apart and re-seal it, thats what I had to do when I couldn't find mine.

But before you do that.. I suppose you could check the wiring harness for the O2 sensor by test for continuity on each wire (unplug EEC-red lead @pin black lead @ O2 connector).

Yeah, ive heard the same thing about carb cleaners. My suggestion is maybe getting a propane torch and not light the flame and just run the gas around the intake, finer mist so it wont splatter anywhere and you can pinpoint it better.

 

[n8rsk8r]

For a while now I've been getting a 136 code. O2 sensor right? I changed out the sensor with a new Bosch one from vatozone, reset the computer, CEL came back on, guess which code? So I change plugs and wires to Motorcraft and Taylor, reset the computer...CEL back on, code uno tres seis. I hear a tick tick tick from the rear exhaust, so I think "cool, I'll just get this fixed"...take it to the exhaust shop, he re-welds a few places, no more tick tick tick. Reset the computer...CEL come back on...136. Faulty O2? Changed that this morning with a known good one. Reset the computer, code 136. Checked for vacuum leaks: none, no exhaust leaks heard. So, no vac leaks, exhaust leaks, good o2s, MAF was changed recently with a known good one. What would cause a lean code on one bank? Idle is fine, power seems to be there, but this keeps coming on after about 10 minutes of driving. Yup, I can shut off the car, turn it back on, and then drive...after 10 minutes CEL comes on. I'm at a loss here. HELP!!!

KOER code 136 HEGO [HO2S-2] sensor circuit indicates system always lean.

How long until you received the code AFTER installing new O2? was in immediately after? Did you in fact have a NEW O2? If you replaced it and it took a while for it to come back on, maybe a couple cyl. are burning a ton of oil. How is your oil consumption? The only real reason for this code besides faulty wiring harness would be that the O2 is getting contaminated. But you are infact running LEAN not rich. Meaning the O2 is not being able to produce the voltage it would normally put out to produce a normal condition.

If it was immediately after you plugged in the new O2, then I would lean toward your wiring harness. Let me know, I can type up the thorough check procedure if you want. Or even scan a page outta a book on EEC-IV's.

EDIT: I forgot to agree with Phoenix above and that it could be your MAF also. When they get messed up, dirty whatever, they will help to throw the O2 codes as well.

 

[SeanMc]

KOER code 136 HEGO [HO2S-2] sensor circuit indicates system always lean.

How long until you received the code AFTER installing new O2? was in immediately after? Did you in fact have a NEW O2? If you replaced it and it took a while for it to come back on, maybe a couple cyl. are burning a ton of oil. How is your oil consumption? The only real reason for this code besides faulty wiring harness would be that the O2 is getting contaminated. But you are infact running LEAN not rich. Meaning the O2 is not being able to produce the voltage it would normally put out to produce a normal condition.

If it was immediately after you plugged in the new O2, then I would lean toward your wiring harness. Let me know, I can type up the thorough check procedure if you want. Or even scan a page outta a book on EEC-IV's.

EDIT: I forgot to agree with Phoenix above and that it could be your MAF also. When they get messed up, dirty whatever, they will help to throw the O2 codes as well.

It was about 10 minutes after I plugged in the known working O2. I drove for a good 1.5 hours, stopped at an ATM, after I started the car back up, there was no CEL light. The car couldn't have cooled down in the 2 minutes I was at the ATM. So, whatcha think?
The person who asked about oil consumption...after 2600 miles since my last oil change, it's barely just under the full mark.

 

[sho'd]

i had the same problem, but it ended up being on of my conectors i umpluged on the wiring harness while replacing my transsmission, my tps also stopped working, i unplugged it, sprayed brake cleaner at it, dielectric greased the conectors and plugged them in and no problems since, i will post a pic of what conector it was, you never know, could be that simple.

 

[SeanMc]

i had the same problem, but it ended up being on of my conectors i umpluged on the wiring harness while replacing my transsmission, my tps also stopped working, i unplugged it, sprayed brake cleaner at it, dielectric greased the conectors and plugged them in and no problems since, i will post a pic of what conector it was, you never know, could be that simple.

Thanks.

 

[firstgen89sho]

check the grounds for the HEGO's as I have run into that before, the check engine light would come on and stay on after about 5 mins of driving, and would go out, then come back on again, I traced it down to either power or ground of the HEGO heater circut, found out that the ground wire, that grounds in the valley of the engine, was not making a proper ground, moved the ground around and never had any more problems with the check engine light.

 

[SeanMc]

check the grounds for the HEGO's as I have run into that before, the check engine light would come on and stay on after about 5 mins of driving, and would go out, then come back on again, I traced it down to either power or ground of the HEGO heater circut, found out that the ground wire, that grounds in the valley of the engine, was not making a proper ground, moved the ground around and never had any more problems with the check engine light.

That makes sense. Did you have to pull the fuel rails to get to it?

 

[ohfosho]

136 (R) Oxygen sensor not switching/system lean Left or Front HO2S - Fuel control- as per sho phoenix project

you are changing the front/left, O2 sensor?
just want to make sure... usually you should change both at the same time...the other is usually close to as bad. and you should replace them with new ones, not used.

 

[SeanMc]

136 (R) Oxygen sensor not switching/system lean Left or Front HO2S - Fuel control- as per sho phoenix project

you are changing the front/left, O2 sensor?
just want to make sure... usually you should change both at the same time...the other is usually close to as bad. and you should replace them with new ones, not used.

I replaced a new one with one with maybe 20 miles on it.

 

[RAYJAY]

getting the same problem my codes on my 1993 3.2 atx are

172 (R,M) Oxygen sensor not switching - system is or was lean - Single, Right or Rear HO2S - Fuel control

173 (R,M) Oxygen sensor not switching - system is or was rich - Single, Right orr Rear HO2S - Fuel control

which sensor is this ? by radiator or by fire wall ?//

getting light 15 to 20 min of driving will flash on and off while running car runs great if light was not on could nor even tell there was a problem

Jeff

did replace both with new 02 sensors

I also changed my computer to a d4u1 could this be a problem

 

[SeanMc]

Reset everything, and you should be ok. I found my problem though, the couplers I got are to short. I did the propane thing, and 4 out of 6 would make the idle change.

 

[SeanMc]

changed out the couplers, reset the computer, did the propane thing..no change in idle, CEL came back on, code 136 again. Ordered some injectors from 1993MTXSHO and I'm going to get them cleaned and flowbalanced. Maybe one is clogged? I don't know, running out of ideas.

 

[SeanMc]

Ok, I'm back :wave:

I finally got a TwEECer, hooked it up, and it shows that the front O2 is reading at max of .07 volts, while the other is reading .7-.9v. Could this be a connection issue?

 

[SeanMc]

We most likely found the problem...wiring. Thanks guys for all your help and suggestions. Josh and Slo SHO may end up being right here.

 

[SeanMc]

Used an ohm meter from the main PCM connector to the o2 connectors, and the injectors, and everything checked out a-ok (very low resistance .001-0). I do have a new symptom: sub par accelleration after 10 minutes of driving, and fuel cutting out going uphill and some turns when the tank is at 1/4 or less. After a little bit of sub par accelleration, it seems the CEL comes on giving a 136 code. When the car is first fired up, for 10 minutes, there is plenty of power, but you can feel it start to bog down, and then *bam* CEL giving me a 136. Is this a fuel pump issue?

 

[SASHO91]

This is a shot out into left field, but what the ****...
Maybe the wiring harness is "messed up" (pinched. etc) somewhere... While the car is cold, the signal flows freely through the said wire, but once the engine bay starts to get hot, it could start to increase the resistance in the wire.
Have you tried the pin-out/ohm check with the car hot, Sean?

 

[SeanMc]

This is a shot out into left field, but what the ****...
Maybe the wiring harness is "messed up" (pinched. etc) somewhere... While the car is cold, the signal flows freely through the said wire, but once the engine bay starts to get hot, it could start to increase the resistance in the wire.
Have you tried the pin-out/ohm check with the car hot, Sean?

When I did this, I had just come back from running an errand. So it was warm.

 

[SASHO91]

So, have you tried it with the car cool?

 

[SeanMc]

So, have you tried it with the car cool?

When the car is cool, everything works beautifully. Symptoms only show after about 10 minutes of driving.

 

[SASHO91]

I meant, do the resistance check with the car cool to see if you get a different reading as opposed to the hot reading.