car suddenly wont start - never ran great anyway, esp. cold, now cranks, but won't st

[cre]

The car will run fine with a bad O2 sensor. Once the signal get out of range the ECU just ignores it. When running cold you would see no difference at all as it is as the ECU doesn't use the O2 sensor until the engine is close to normal operating temp. This is the case with almost ALL EFI equipped cars from the mid 90's and earlier. I've already covered this once... Unplug it, there should be very little difference. Your mechanic is either used to vehicles from the 60's or only new "plug it in and that neato machine will tell you what to replace" models.

Coil packs will cause intermittent misfires and if there's a break in the circuit they'll usually be fine when the engine is warm but falter when cold as the conduits shrink and the gap widens.

Have you checked the timing (both mechanical and ignition)? Have you inspected the timing belt? Have you diagnosed the transmission codes yet?


EDIT: There is VERY little which will put the ECU into "limp mode"... the only one that's really common is a code 52 or heavy knock detection.

[rjSupra]

Thanks for the explanations Cre. Before getting this car I have to admit I really did not know what an Oxy sensor was, what it looked like, and what it did - in any car let alone this one. Sorry for the newb-ness.
I did pull my CPS to repair the coolant problem before and very carefully set it back in correctly aligned the way it was supposed to be (TSRM) with the crank at TDC both visually on the pulley. So that part of the ignition is in spec.
(in also ran identically to how it ran before I pulled it out).
I have not gone any further than finding the two transmission code problems so far. Have not been around the car for several days and have not put the volt meter to different parts / wiring yet.
My car is not having knock problems, nor is it mis - firing. Although today for the first time after starting it and it was idling fine for 2-3 minutes, it did stumble heavily once during idle and then ran normal after that. (like the motor sounded like it was bogging down and like it would almost stop running for a few seconds and then went back to normal idling about 600 rpms like nothing had happened).

You might be right about the mechanic guy - could be either one of those types you suggested.

[cre]

The sensors used in modern vehicles provide a LOT more information about the fuel mixture and are accurate under a much wider range of conditions; They're known as "wideband" sensors and they do serve as a diagnostic tool.

Older types of oxygen sensors (aka "Lambda" sensors) are only capable of detecting a very specific mixture; get outside of that range and it provides essentially zero data. They're useless except as a trim sensor to adjust for that 1% that the mixture may be off... Your mileage may suffer from a bad one, but it's not going to stop running.

[rjSupra]

Car stranded me after work one day and refused to start in relatively cold weather (30 F?) Would not start at all no matter what I did. If my car is cold I usually blip the throttle a little bit and back it off to start it. I've noticed if it doesn't start the first try I am usually screwed and it won't start at all. Especially if I can't start on 2 tried, I'm really in trouble.
Oh, the batt is good, the motor cranks and cranks and almost starts when it's bad and then won't run.
Jumped it the next day and it started on try #2. If the car is warm, it can start with no throttle. Down to 13.2 MPG, and running really poorly. Worse than before and harder to start. I have so little power up inclines. Even with the turbo at +6 on the gauge I can accelerate up big hills but not much. Without a lot of boost, I loose speed and crawl up them. Climbed a very steep but less than quarter mile hill and my car temp went up really high - about 80% of the gauge last night as I was going super slow up it.

To set and check ignition timing, I just borrowed a friend's timing gun and followed the TSRM online and my Haynes Celica 86 and on models manual and I had no light at all coming from the gun with the thing all connected right and the car warm and running with the T - E terminals connected. Dunno if the gun is broken or I am doing it wrong. (Sunpro timing gun with red lead onto batt +, blk lead onto batt - or grounded to alt bracket and I got no light). Other end onto #6 spark wire - cleaned and solid contact on the inductive clamp, then on #1 spark wire, then on #4 and #5 with a bad connection on #5, no light from anything.

And, I checked and all my engine error codes are cleared after starting the car about 8 times and running it 3 times a total of about 40 miles. So far the O2 sensor error is not back, nor the Igniter / Ignition coil error code.
I also found I have a spare ignitor that came from a donor car, it looks visually a little better than the igniter in my car - should I switch that out in case?

[El_supracabra]

If i were you i would start Ohm'ing sensors

pick up coils
http://www.cygnusx1.net/Supra/Librar....aspx?S=IG&P=9
http://www.cygnusx1.net/Supra/Librar...aspx?S=IG&P=12

plug wires
[2 pages NEXT]

check igniter
http://www.cygnusx1.net/Supra/Librar...aspx?S=IG&P=15

check CPS
http://www.cygnusx1.net/Supra/Librar...aspx?S=IG&P=16

just check everything on this page. lol
http://www.cygnusx1.net/Supra/Librar....aspx?S=FI&P=1

something else you may def want to take a peek at....
http://www.cygnusx1.net/Supra/Librar...spx?S=FI&P=124

[rjSupra]

Thanks El Supracabra, I like the forum name!

Thanks for the links. That's next on my battery of tests to run on this troublesome car.

I pulled the CPS before, inspected it, it looks good. Replaced stupid seal that was leaking a lot while there so my motor is a lot cleaner now. I set the CPS in the correct way per TSRM.

EDIT: I GUESS I JUST DIDN'T KNOW HOW TO SET UP THE GUN. My friend told me I did it wrong, so I will try that again the right way tomorrow night. (oops).

But my car is weak as a kitten and seems to be getting worse. Before it always started reliably, at least before it got really cold in the winter. And I need to really press the accelerator to move the car and I still don't keep up with normal traffic unless I hammer it and am boosting on the Turbo a lot.

[rjSupra]

Ok, so I hooked up the timing gun right this time.
The timing (w/ TE1 and e1 jumped) was reading 15 degrees. I dialed it back lower and it almost immediately bogged down and sounded like crap near 10 (the idle speed dropped significantly and was barely chugging).

I bumped it up to 18 degrees BTDC and it sounded way better. But my idle jumped up from 600-650 rpm to about 1000 rpm... hmmm....

So I turned car off to see if car would re-set the idle itself and it did (at 18 now). So then I decided to try to dial it slowly about the 11 degree mark (and see if the idle would re-program itself) which it did and I have the idle stabilized at 600 - 640 RPM.

I also clamped the pickup on #1, #3, and #5 spark leads. I was trying to use this as a quick test to see if I was even getting any electric up from each ignition coil, and I was getting the light coming on all three. So I am sort of guessing that I probably don't have a toasted ignition coil, or a bad igniter. The plug wires all look pretty solid, they are Sumitomo from 2002. But keep in mind this car was without inspection sticker since 2005, so it was almost rarely driven for many years down a private road only with little mileage on the wires.

When I throttled the gas, I was getting, uh, not full on exhaust backfires, but a deeper and quieter popping after abruptly letting off the throttle from 1000 to 2000 rpms (it was not a loud tail pop / snap, sounded more mellow and deeper up the exhaust sort of). This happened before and after I set the ignition to 15 (at start), 18 or so as where to my ear the car seemed to run smoothest, and then to 11 where I settled on setting the ignition.

My friend was saying that on his old Buick ('67 Skylark), he advanced his spark to 18-20 degrees to make it run smooth - or it ran quite poorly where it was specified to run. He later discovered a significant vacuum leak many months or years even later, and then could set it back to spec. He was suggesting I could have a vacuum leak perhaps. Anyone think that is the case here?

Thanks!