Mongo

After a new O2 sensor to put the car back on closed loop, it still won't run well. When in open loop mode, the car runs fine at operating temperature. As soon as I plug the O2 sensor back in and do the battery reset thing, once the LH adapts, the car's idle drops below 600 slowly and then stalls out. There is a significance in temperature when this happens as it ONLY happens when the car's temperature is at 1/2 & below 3/4 on the gauge. Cold starts and warm-up are completely fine until it hits that range.

I took another ohm reading on the temp II itself when the car was at 1/2 and showed a range of 250-253 on both pins to EZK and LH from the sensor. I grounded the lead to the ohmmeter on the body though as I couldn't get the negative reader under the temp sensor. There is a presence of dried coolant build up on the hex of the sensor and below it. I am wondering if this would cause a possible shorting issue that may tell the LH to go full rich.

I still have '87 chips in this new LH and the EZK is '87 of course so no spanner/hammer will diagnose this car easy for me. Still going nuts here and still need some help. Exorcism has not been ruled out either..

Mongo

Talked to one of the great ones... there may be a possibility my new LH can be read through a diagnostic tool. Does anyone in the Bay Area have a Spanner/Hammer to hook up to the rectangular plug on my car. I don't want to bother Bill Ball for one down in Alamo if there is someone closer to San Rafael with one.

6mil928

That youtube clip is fantastic. Oh yea the car. My 81 runs better with no O2 as well.

Lizard928

This begs the obvious question. Has the O2 sensor been replaced with a factory new part, a universal, or replaced at all?

The sign of dried coolant around the sensor will not cause any issues so dont worry about that.

6mil928

Colin does it make a difference if it is universal or OEM? I guess it might be more important on the newer cars.

dprantl

It doesn't make any difference, but it does open up new potential failure points depending on how the generic O2 sensor was put in place.

Dan
'91 928GT S/C 475hp/460lb.ft

Lizard928

Bingo! We have a winner.

And right now, it is trying to eliminate all of the possible failure points.

Mongo

Is the consensus that because I put in a new Bosch universal O2 sensor that it's still the failing point?

I can somewhat agree with that as breaking wires may cause potential issues later on as opposed to just getting a brand new O2. The previous sensor was a universal also. I have run universals on virtually all of my cars with no issues on any. I have also relocated the spliced in harness in the CE panel area as opposed to under the car now where it's more susceptible to water exposure.

Mongo

For the heck of it, I'm going to swap in my old Temp II and see what happens. I know that sensor was functioning before replacing it as preventative maintenance. Just have this gut feeling something may be wrong with the Temp II even if it is 'new.' I feel like all the problems started since I installed it about 8 months ago.

6mil928

Keep us posted.

Mongo

Will do. Got my fingers crossed hoping to God it's a defective Temp II causing this whole damned thing.

michaelathome

I have said it before, it is your throttle positioning switch. It is likely rotated in the wrong orientation so you fail to get the "click" you need for idle. I had the same problem. If you passed emissions your LH is most likely working fine, if however can only compensate for so many factors. The TPS is just that, like a like a 3 way light switch, idle + driving + wide open throttle. If the TPS is rotated too far in one direction or the other you may loose idle or you may loose WOT. There may be some cable adjustments that you can do at the firewall where the cables pass thru it OR at the throttle assembly but I am guessing that you will need to just pull your intake and fix it under the plenum.

Michael.

P.S. Just did it, car idols fine now.

michaelathome

[QUOTE=Mongo;7130692]Hey Michael,

"I can clearly hear the audible click when opening up the throttle via the linkage on top of the engine." [/QUOTE=Mongo;7130692]

Can you hear it click thru all three modes, idle, normal and WOT? Actually now knowing that mine idles fine BUT I can't hear a click I would ask you to look at that as labor intensive as it is. After testing several S4 and later cars at Frenzy year before last, most that had done intake refreshes couldn't get into WOT. They all had TPS that were all alligned incorrectly. I was the one of the few that could actually get into WOT but had a bad idle and would stall. I would say that of the maybe 10 tested, 5 or 6 couldn't reach WOT, 3 or 4 were correct and I was the only idle issue but had WOT. Sucks but there is a reason that the TPS has oval fittings. It needs to be adjusted right in order to work correctly.

That said there are probubly a few S4's out there that can't catch us if WOT isn't working when the rest is working well.

It really sounds like you have adjusted/replaced everything as best you could BUT if you overlooked the angle of adjustment on the TPS your problem could be that simple.

Michael

Mongo

If I don't have the issue with the O2 disconnected, than how can it be related to TPS? Open loop the car runs like a million bucks. Idle and WOT switch is still included in open loop mode.


If I can't get closed loop to work on this car I'm going to ROW non-cat coding and a CO/Idle Potentiometer. This is getting ridiculous after about $2,500 in parts.

Bill51sdr

GET OR BORROW A SPANNER/HAMMER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!