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Old 03-05-2009, 13:33   #1 (permalink)
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HELP! '92 Thunderbird 3.8L SC

Hi all, and thanks for looking here. I NEED HELP!

I have a '92 Thunderbird 3.8L SC. It won't start.

The other day, I cranked and cranked and cranked, and it turned over and spat and coughed and wanted to go...

and then it cranked and cranked and it spat and coughed and wanted to go...

After about 10 minutes of intermittent cranking I FINALLY got it to start, but it wouldn't idle. I had to keep the RPM's above 1200 for it to stay running. Below 1200 RPMs it would begin to stall.

For the first 5 minutes it sounded like it was missing a little bit, but after that it smoothed out and ran well. I kept it at 1200 RPMs for about 15 more minutes. I goosed the throttle a couple of times, bringing it up to 5000 RPMs and it DIDN'T backfire or bog down. It sounded really good.

BUT... when I went to drive it, it stalled on me because it didn't want to idle. I was able to start it back up with about 5 seconds of cranking, and it sounded similar to the cranking and coughing from before. I think it started quickly because the engine was nice and warm.

THEN... it stalled out again because I tried idling it. This time, the starter had burned out and I had to put it away for the night.

SO... after changing the starter it is going back to the crank crank crank cough cough crank crank crank and I haven't been able to get it started for 2days now.

HERE's what I've done in the last 2 days to try to fix the problem:

Changed all the spark plugs and verified that all plugs are getting nice blue spark
Changed the coil pack (One of the cylinders wasn't getting spark, now it is)
Emptied the fuel tank (In case there was bad fuel)
Changed the fuel filter
Installed 10 gallons of new premium fuel with Gumout injector cleaner (which hasn't been able to take effect because it won't even start now)
Checked the fuel pressure at the schrader valve (found it to be 40 psi which is in spec)

I have not used an OBD1 code scanner yet... I'm trying to figure out if that is the next step.

What are your thoughts?

Considering the engine ran well once I got it above 1200 RPM, I really don't think it's a spark or timing issue. I don't think it would run that well if it were either of these.

Also, I don't think its a plugged catalytic converter because, again, I was able to goose it without it bogging down, popping, or backfiring.

I have good fuel pressure, but I don't know the condition of the injectors...
If the injector screens are clogged or if the injectors are spraying correctly, could this cause problems on startup? If the problem is with the injectors on startup, would it run so well at 1200 RPM and fail to idle well?

Basically, what is the most likely culprit for non-starting, poor idling, and then running well after the engine RPMs are up?

I really appreciate it if you made it this far and would greatly appreciate your responses. I hope I've expressed my problem clearly. I'll be in touch.

Thanks.

PS Just a further note, I pulled 2 of the driver's side spark plugs and smelled them to make sure they are getting fuel and they came out looking black. They are not fouled, but they do have a black residue on them. It does not look like oil, it looks like carbon with gas on it. It could be oil, I really can't tell. It doesn't seem tacky enough to be oil. Like I said, carbon with gas on it. Maybe I'll go do a compression test. But would it run so well at higher RPM's if there were bad compression? I will go do a compression check on these cylinders and post my results.
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Old 03-05-2009, 19:16   #2 (permalink)
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Re: HELP! '92 Thunderbird 3.8L SC

You should check the MAF, TPS and O2 sensors. All three of those could cause that. Or the combination.
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Old 03-05-2009, 22:05   #3 (permalink)
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Re: HELP! '92 Thunderbird 3.8L SC

I checked the TPS and it had .8 Volts, which is in spec.
I checked the coolant temp sensor and it showed about 60 ohms, which is where it should be at 50 degrees farenheit.
I checked that the O2 sensor is connected, but have no way of telling if it's working. That shouldn't have anything to do with startup anyways.
I DID NOT check the MAF. I need to read up on that to see what the specs are.
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Old 03-05-2009, 22:17   #4 (permalink)
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Re: HELP! '92 Thunderbird 3.8L SC

Correction. There is a way to check the O2 sensor: by measuring the resistance at room temperature (70 degrees.) It should be 6 ohms. I will check this tomorrow.
I will also check the MAF, but it only has specs for when the engine is running, so I don't know how far this will get me. It's supposed to be about .6 Volts at idle, so I'm suspecting .5 Volts when the engines off????? I don't know.
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Old 03-05-2009, 22:19   #5 (permalink)
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Re: HELP! '92 Thunderbird 3.8L SC

PS to all who are reading... I will be checking the camshaft sensor synchronizer tomorrow as well.
Also...
I found a timing groove on the pulley behind the harmonic balancer. Is that groove supposed to be at the 12 'o clock position when cylinder number one is at top dead center?
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Old 03-07-2009, 13:05   #6 (permalink)
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Re: HELP! '92 Thunderbird 3.8L SC

The cam.P.S will not do that. You can disconnect it and the motor will run on " limp " mode. The grove in the balancer can be in two different positions. One for the hand held timing light and one for the magnetic pick up on a scope. A bad spark modual will do as described. You are describing a flooded engine. If your plugs are black they are fouled.
What is your rail pressure before you start the engine ? Does your engine oil smell of gas ? Also check for a vacumm leak. a ruptured pressure regulator diaphram will flood the
engine. I've seen lots. you HAVE to put the engine on a " real time " scan tool. The
$50.00 code reader will tell you squat. Oh yah, a bad E.C.M. will also cause this. A proper
scan tool will tell you if this is the case. It could be as simple as full 12 volts not getting to the coil pack during the crank cycle. Bottom line. Send it to a qualified tech. 02 sensor will not cause this.
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Old 03-07-2009, 16:53   #7 (permalink)
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Re: HELP! '92 Thunderbird 3.8L SC

dido, you need to have it on a real time scanner.
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Old 03-07-2009, 16:56   #8 (permalink)
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Re: HELP! '92 Thunderbird 3.8L SC

Just wondering, have you or some one else messed with the distributor? If so it might be way out of time. Also, have you tried unhooking just the (-) battery terminal for about 10mins while leaving the (+) hooked up? (when the car is off)
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Old 03-07-2009, 17:49   #9 (permalink)
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Re: HELP! '92 Thunderbird 3.8L SC

have u checked your idle air control valve? thats what mine was.
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Old 03-09-2009, 17:51   #10 (permalink)
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Re: HELP! '92 Thunderbird 3.8L SC

Hello again to all, and thanks for the responses.

In response to your responses:

Instead of using an OBD1 tester, I did a self test by going to the EEC test port, jumping two of the terminals, and using a test light connected to the positive battery terminal so that the test light "blinked" codes at me.

This resulted in a few trivial codes popping up, like "transmission fluid not up to temp" but nothing helpful.

I have had the battery disconnected and reconnected many times for minutes and sometimes hours as I've tinkered around with the engine, and this has produced no noticable changes.

Now that I look at your exact suggestion, I have never left "just the positive" connected. It is either both or none.

I'm not sure why leaving just the positive connected would do anything... I'll try and in the meantime maybe you can tell me what that does.

There is no distributor, but there is an adjustment where the distributor would be. Now I can't think of the name. I think it talks to the ignition control module. I was reading about it on "www.chiltonlibrary.com"

Chilton's describes how to adjust this timing... I need to go back and look so I can tell you exactly what adjustment I'm talking about. It's not the timing chain... again, I think it talks to the ignition control module and it's where the distributor would normally be.

You're correct, the camshaft sensor will just put the engine into "limp" mode. I disconnected it and it actually started for a couple seconds, but was very weak and sick sounding. It sounded really bad, as if the timing were still off, then it stalled.

Yes, the engine is definitely flooded because I'm getting carbon buildup on brand new plugs. Yes the oil smells like gas because I flooded it by cranking it so much and the gas slipped past the rings. I'm afraid its going to blow up, so I'll be changing the oil before I proceed.

The pressure at the rail was 40 psi, which is in spec as far as I understand.

Ruptured pressure regulator huh? I ruled that out considering I have good fuel pressure, but maybe I have too much.

It is a fact, I AM GETTING LOTS OF FUEL TO ALL CYLINDERS AND IT DEFINITELY IS FLOODING.

Gentlemen, at this point I'm thinking one of three things:

A bad computer
A bad ignition control module
The timing is off

I'm leaning toward the timing is off because as I mentioned, the engine ran when I actually had it started and up to 1200 RPM. I feel like it would not have run as well at higher RPMs if the computer or ignition control module were bad. However, I think it could run OK with the timing being slightly off at higher RPMs because the computer could compensate for that and plus the engine is up to temp?????? (This is a big MAYBE)

OK, I will keep you updated on what's going on. Sorry I haven't been on here in a couple of days. I'll be in touch.

And by the way, I acknowledge that you mentioned a "real time scanner" I just didn't think there was such a thing for a 1992. I thought it was too old to really "tell on itself" like the OBD2's...
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