Insane temp problem...FOUND & FIXED!
 

I can feel my hair growing back by the minute! For those who've been reading about my saga, you know I've stopped at nothing short of an engine teardown. I did pull it out though and did everything I could think of to resolve it. Well, short answer is that when I bought my car, the o2 sensor was disconnected and the light was beaming. I reset the light and decided to replaced the sensor. Went to Checker Auto and bought the Bosch one for my car...or so I was told. Bastards gave me the wrong one! Talked with my neighbor friend and asked him if it was possible that the wrong sensor could do this. He said "yep" so I disconnected it and had my friend richen my mixture a bit to compensate. Drove it today in mid-80 weather, jumping on the pedal through town and it never topped 215. The o2 sensor had been on my mind for weeks and I kick myself for not pulling it sooner. Now, I'm just going to drive her :D

Congrats. Good job!!!!

Great news!!! You must feel sooo good right now! So, did you pull the O2 all together or did you replace it with the correct one. I am tempted to pull mine and see if it runs better/faster. Thoughts?

I didnt pull it, I just unplugged it. Some places need it for emissions. Also, if you do disconnect it, it's been recommended on this board to set the CO to 3.5% (I believe).

Dont keep telling me I need a BIGGER cooler!

That's bizarre! From what I've understood, the sensor is more of a 'fine tune', and only has ANY effect if mixture is correct in the first place. Otherwise, the system will be in open or closed loop all of the time(?) Your car was simply running extremely lean all of this time, had you ever checked the mixture through all of this?

At any rate, glad that you found it! There is mixed opinon around here, but I say put the right sensor in and set it right. It's a great system when working properly. Happy driving! :cool:

UTKarmann_Ghia

Congradulation, I follow your saga and happy to learn that you finally found the cause of your over heating.

So the cause was a too lean condition due to a faulty 02 sensor?

Yeah!!!
I'm glad the Porsche gods saw it fit to place an expert mech so close to you :)

Whelp, that would be my guess that it mustve been running very lean. I did have it checked out by the local wrench, but whenever he set it my engine would lean surge at idle. He said it was good, but obviously not. I too was under the impression that the o2 sensor could not have been a serious issue, but I drove around for the better part of an hour today and she was STUCK at 215. Another couple of hot days and I'll claim victory. I still dont believe it, so I'm being a bit skeptical, but man I've run the snot outa her and she's stayin cooooool :D

Here's to all the guys who gave me good, heck any, advice! http://www.pelicanparts.com/support/smileys/wat6.gif

Matt,
Glad that you finally solved the dreaded temp. issue !
What % did you set the co, 3.50% ? How is the car running & starting now that it is set richer?

-Chris

Whaa hoo!!!! I've been following this from you first post and I'm glad to see you got it resolved.

I have been following your posts and am glad you finally seem to have it sorted out!

Man, I've been driving like a crazy man the past couple of days. What a relief to not have to worry about my temps. No more driving like grandma for me!

Type911, I'm not sure what the co is set to right now. Had my neighbor adjust it and we didnt have a gauge to verify it. It was set to 1.5% before (o2 disconnected) and we turned the allen about 10 minutes in the richen direction. Smog here is not that stringent, but I'd like to set it at 3.5% when I get a chance. My guess is that she's at least 3% but that's just a guess. She idles great (no more lean surging either) and has always started and run well.

Oh! My friend also mentioned that I wasn't getting full throttle either. I adjusted the throttle linkage too and it feels like I've got about an inch more pedal now.

Hmmm, glad to hear you fixed your issue. I may be wrong but i believe most of the SC's on the board have disconnected the o2 sensor anyhow.

That's true, it seems that the disconnection of the o2 sensor for the SCs is common place. But I have not yet heard of them causing this kindof problem! Believe me, that sucker is NEVER getting hooked up again!

I find it difficult to believe that the wrong O2 sensor could cause this problem. AFIK, they all produce the same output.
-Chris

I agree with Chris, the majority of O2 sensors are heated or unheated, there are very few with a different output voltage. My guess is your closed loop control system does not work and you are running too lean with the O2 sensor connected. I think you might be premature in blaming Checker Auto.

You can easily measure the O2 sensor voltage output to verify its operation...

Wonderful that you found the problem, I hope.

I'd be interested in the CHT & EGT that would cause that hot issue

Possibly that switch on the throttle that disengages the closed loop system under conditions of wide open throttle might not be working.

Matt,

Glad to hear of your progress!

Sounds like the OXS control module is malfunctioning. I doubt if a generic O2 sensor could cause the overheating ... unless miswired! If a low-impedance load was placed on the O2 sensor ... it was probably damaged or destroyed. Even the load of a conventional analog VOM can burn out the O2 sensor! That is why a DMM with greater thean 10-megOhm input impedance is always specified for testing O2 sensors.

<b>It also sounds like your mechanic that took some mixture readings [OK or inconclusive, as I recall] either misread or misinterpreted the results!!!</b>

Your goal of 3.5% CO is probably a reasonable goal.

Seems true though - disconnecting the O2 sensor typically makes your car run richer, which as a result, cooler. I know when I disconnect mine, my oil temps are at least 15 degrees cooler.

Well Warren, I know they checked the mixture at idle, but that's it. And what you say makes sense as the sensor should not make enough of a difference to make a car run sooo lean that it becomes thermonuclear! It's a single-wire o2 sensor, so you really cant miswire this one.

The good news is that I ran it over 250 once and for just a few minutes. Other times it just got to 250 before I finished my drive or just pulled over. I HOPE I did not cause any damage to my engine. I may just get a leakdown test run on it just to make sure. But man, have I missed really running her! She's running just great :D

Steve, I thought that on DME cars, (3.2s), the sensor has to be hooked up to run(?). :cool:

Hey Denis SmileWavy - Motronics doesn't need to have an O2 sensor hooked up in order to run, as evidenced by the European spec and ROW versions which don't come equipped with one. However, the U.S. versions with a cat are equipped so to keep the mixtures at stoichiometric or the car can run rich and overwork the cat, also to keep emissions compliant. However I don't have a cat, and in doing some testing on some chips I am working on, I decided to unplug the O2 sensor just to see what the effects were. My car did run cooler by 10-15 degrees, and with the same chip that a lot of the guys here are running and are already reporting a great change in power and throttle response, I got what appeared to be another dramatic level in throttle response and pull than I already had - leaping like a screaming banshee. My fuel mileage has probably went down the toilet doing this though. This is not with my MAF sensor, but with the factory Bosch air flow sensor and a cone filter. I don't know if its my imagination or what, so all you guys running my chips on a non-catted car, unplug your O2 sensor and tell me if you notice anything.

Just replaced the O2 sensor on my 86 and fuel economy went way up.

Ok, I've run the car for a month (or more) with no overheating problems. Took it for a long drive in the mountains with 80 degree temps and it stayed between 210-220 degrees with the fan disconnected. So it appears that the gremlin is gone :D

Steve, you mentioned 10-15 degrees cooler for the disconnect, but I was looking at 50-60 degrees temp increase. I do not know what's causing the increase specifically, but disconnecting it fixed my problem. It would have to be either the Bosch generic o2 sensor (I'm assuming that it's generic) or the circuit/computer itself. Either way I'm driving the poop outa her :D

This seems reasonable.

I failed smog twice for NOX. High combustion temperatures. I also had a serious detonation problem, even when I poored in Octane booster!

After replacing the O2 sensor and richening up the mixture to 3%, I passed smog (barely, my CO went from below average to the upper limit), but my NOX dropped to acceptable limits.

I also have no detonation, even if I just run straight 91 octane with no booster.

The CIS mixture test at idle would not identify an O2 sensor problem, since the sensor is disconencted to get a proper mixture reading.

Kurt B, high temps, high NOx and detonation problems are all related to a lean mixture.

NOx forms when there are high combustion temps and excess air. Nitrogen does not burn readily, so in normal combustion, the fuel consumes most of the O2, and the temps are not high enough to generate NOx.