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

[rjSupra]

Hi guys, thanks for the assistance!

I have a battery charger with a 50 amp starting setting, to start the car with the battery in it from your garage A.C. This worked pretty good with a bad battery before on the car, before I bought a new (cheap) battery. Autolite Silver series $67 with core on sale direct internet. Probably not a great battery, but I was not sure at that point I could keep the car (had that unsolved mega coolant problem that grounded it for 2 months at the time, and had thought if the steel line under the headers was toast I'd probably sell the car as is with disclosures).

So, I am guessing I should be getting enough juice. I am separated from the car's location for another day, hopefully when I get back it will warm up a bit and I can re-try. The car sat about 24 hrs overnight in fact (not same day), in biting cold since it had last been driven 30 miles / 45 minutes. So far, the alternator has been keeping the battery charged. The car has sat for 7+ days in bad cold before and fired right up as always.

I have not done the spark plugs. They looked, well used, but not terrible. No real oil that I can recall, although it's possible one was wet a little bit. Mostly I remember normal carbon deposits (at the time no plug gapper tool, so could not check the gaps). Have not done the wires, no idea when they were done last, although visually they look ok (i've seen a lot worse).

Any thoughts what that wisp of smoke behind the motor, close to the firewall could have been? And the slight plastic-y burning smell? That happened the last time I tried to start her, with a paper clip jumping either the engine error code check terminals, or the fuel pump 12v bypass I can't quite remember which one I had it in.

It sounds like the 02 sensor can't be at fault for all these issues, so I appreciate knowing that now. Don't really know what they do aside from I gather measuring oxygen levels in exhaust to send setting info to the car for fuel rich / lean levels etc... I do have a multi meter so next step would be to test a few of the components that way. It was just too cold and dark the other day to deal with it.

Thanks again.

[cre]

Originally Posted by rjSupra

Any thoughts what that wisp of smoke behind the motor, close to the firewall could have been? And the slight plastic-y burning smell? That happened the last time I tried to start her, with a paper clip jumping either the engine error code check terminals, or the fuel pump 12v bypass I can't quite remember which one I had it in.

Sure.... the wire harness. Start there. Check to see if you can hear fuel moving through the fuel rail with B+ and FP jumped... check if B+ has a constant 12v.

Originally Posted by rjSupra

It sounds like the 02 sensor can't be at fault for all these issues, so I appreciate knowing that now. Don't really know what they do aside from I gather measuring oxygen levels in exhaust to send setting info to the car for fuel rich / lean levels etc.

A bad O2 sensor may be good enough to cause a slightly bad reading.... Usually when they go though they're so far out of range that the ECU disregards the sensor altogether.

[rjSupra]

Originally Posted by cre

Sure.... the wire harness. Start there. Check to see if you can hear fuel moving through the fuel rail with B+ and FP jumped... check if B+ has a constant 12v.

Yeah, thanks, already jumped this and verified that I can hear fuel moving through the fuel rail. That part is good.

Originally Posted by cre

A bad O2 sensor may be good enough to cause a slightly bad reading.... Usually when they go though they're so far out of range that the ECU disregards the sensor altogether.

My current weak hope is that the super cold made it too hard to start, which I know doesn't really mean anything or make sense. I am pretty sure I've started her that cold before. I'm going to have to look into this ignitor thing too.

[rjSupra]

Ok, this is good, but weird. The car started on the 2nd try today.
It seemed like it was not actually running, but I let off on the starter ignition key and it chugged on it's own slowly and then ran. It idled normal.

It was probably 17 degrees that other night. A car guy I talked to tonight said it was probably the 02 sensor is shot, and the car is only in one mode - like an 'emergency' type of mode, b/c the sensor can't detect when it's running too rich and to cut back etc etc...

Does this all seem to make sense? He said if it was the ignition coils it would not run period, and it was running like it always does (not super strong and crappy fuel mileage) tonight. So maybe I just pop in a new 02 sensor and that could be the end of that?

Thanks!

[cre]

How can I say this simply?


No.

[rjSupra]

Hey Cre:

Thanks for jumping in again. To clarify, did you mean that the 02 sensor won't prohibit the ECU from detecting proper levels in the exhaust to set, uh things it does like fuel mixture, air etc etc... (therefore crap mpg and maybe cranky starting in the cold perhaps with the 'wrong' settings for fuel / air)
or did you mean 'No' to the thought that if the coils were shot it wouldn't run at all.
This guy was not a Supra expert, but works on cars before as a mechanic and does know the Supra somewhat (like that it's an inline 6 3.0 liter etc...)
Perhaps he does not know there were 3 ignition coils in this car. He also did not seem to know what an igniter is in it. But he did state a shot 02 sensor that is triggering OBD means the correct levels can't be achieved for all engine temps, and this would account for not running great, perhaps bad starting cold etc...

Thanks again!

[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.

[straight6power]

Can the 7mge ingnition system b put on a 7mgte...

[cre]

The distributor/points system? It may be manageable, definitely not possible the other way around but controlling it and pulling the three separate ignition signals into one may prove to be more effort than it's worth.