blown 87

That is a very good way of stating this.

ErnestSw

I don't like the diagnosis from a logical point of view.

docmirror

Jim, the ICBM is connected and fully funtional.

Ernie, I'm all ears, let me know what I can do to satisfy. The car is running good after a few gallons of gas were run through it. Difference was noted five minutes after changing fuel.

Roger.

I have your hammer. If you ever want to see it again, put 500,000 UK sterling in unmarked bills, in a used large Dairy Queen bag. take the bag to corner of Martin Luther King, and Malcolm X blvd in lower Dallas. Drop it in the third blue dumpster from the corner. Go into Papa Louie's accross the street and ask for 'Big Mo'. Tell him "I hate fried chicken" then bark once like a dog.

If you contact the police; the hammer dies. If you doublecross us; the hammer dies. If you don't pay; the hammer dies. OH, and we want Brandy set free too!!

worf928

Very interesting conclusion. I used to get bad gas all the time in Boston. But, that was 10+ years ago.

I wonder if the cold TX temperatures and our first winter with 10% cornholio gasoline has anything to do with this?

Any petroleum engineers around?

Mike Frye

Doc,

Going out on a limb here, and maybe overstepping my bounds, but didn't you recently have a thread about your son using it to go back and forth to school. Could you have gotten sugar (or whatever) in the tank?

docmirror

Mike no prob, thanks for the insight. that is a possibility. I keep the tank filler locked, but it could be taken out I guess. We were concerned about the car getting keyed, so tank problem is also possible. He's also been spending a lot of after hours at school too. Dark parking lot, no one around, it could happen.

ROG100

I have friends in the tip of Italy - be afraid, very afraid!

macreel

Roger.. aahhh, mia amici sciciliano guarda mea.

Hey, what kind of (winter formula) gas-a-hol
you guys got down there ??


G'luck all.

ErnestSw

Give me a logical connection between bad gas and the temp sensors' delta and I'll accept your explanation. I think it's more likely that something got fixed or fixed itself that caused the delta in the first place. It's the delta that's the whole point here and that indicates the risk of 928 fricasee.

Bill Ball

Presumably the bad gas affected one of the test cylinders more than the other leading to a temp difference of more than 150 degrees.

docmirror

The delta of the voltage on the sensors is measured by the ICM circuit. It has one, and only one function. If the delta is too high (or the resistance is wrong) a latch gets set in the module and the appropriate relay side is de-energized. Also, the LED on the module is lit, and the car runs on 4 cylinders because the + voltage supply to the four injectors is cut. It is the minus side of the injector circuit that is pulsed by the EZK in response to the various sensor inputs from MAF, TPS, block temp sensor, O2, etc.

The delta of the two temp sensors has no effect on the control of the timing or delay of the ignition, and has no effect on the pulse sent to the injectors. It is what we call a 'discrete' circuit who's only function, as Jim has spoke of, to keep the car from catching fire should there be a regular misfire on one bank of the engine.

The 'limp home' mode is reset on key-off, and the cycle starts again. In my case, I believe the circuit was doing exactly what it was designed to do. When a misfire becomes regular enough to cause a loss of heat, the current will flow in one direction due to the RTDs being at different resistance. When that happens, the voltage rises to a critical value of about 2.5millivolts, and the latch is set, turning on the LED for that group, and removing power from the associated integrated relay, which pulls the +12V from terminal 4 and 1 of the injectors for those four injectors.

The embedded relays can be seen on sheet 10, grid H/J 81. The output of the relay passes through a molex connector on pins 2 and 5, and goes down to the injector multiconnector. No +12V, no injector pulse, no extra fuel in teh exhaust and less chance of fire.

I agree with Bill, this should not be jumpered by a casual observer of the system(like me). I jumpered mine long enough to get from my house to roger's house, and check the resistance when hot. Once we validated that the resistance cicuit was working as planned, the ICM was re-conected, and we searched elsewhere. The fact that we didn't get a limp home is due to not running the car long enough to get a regular misfire.

docmirror

Roger; Don't make me send you a 'chip' to prove I'm capable of it! Bwahahahhahahahaha.

ErnestSw

You're missing the whole point. Bad gas will not create ANY delta, but will affect all cyllinders equally.

chaadster

FWIW, I've experienced stumbling and low power from low octane fuel in my Audi A6. Maybe Doc's son didn't realize the car needs Premium fuel, and put in the inexpensive stuff?

ErnestSw

So? What's that got to do with the problem as diagnosed?