Tommy928

I have an 87' automatic. Today when I started her up it was running very rough so I took it around the block a couple of times to see if it would clear itself up. The engine was losing power as I drove so I pulled back on to my driveway and saw that smoke was emitting from the hood. The smoke was coming from the backside of the engine with a strong burn smell. There may be a little smoke around the catalytic converters also. I also smelled gas when I started her up. The car was idling at around 750rpm and dropped to around 200rpm when I put it in gear but didn't die but no power.

Any ideas of whats wrong? Clogged converters? Bad oxygen sensor? Flexplate?

Tommy

Donald

Tommy-
How long has it been since last run? And are you or SO missing a cat? Did the smoke start immediately or after getting to op. temp, did it continue or dissipate after a short time?
Check this thread if you suspect the other cat (conv.):
<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=14&t=001346" target="_blank">http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=14&t=001346</a>

Donald

Tommy928

Donald,

Thank you for the reply. I drive the car a couple of times a week. The smoke started after the car was warmed. The smoke is light gray and smelled like burned insulation than rubber or oil. It has stock cats. When I saw smoke I tuned off the engine immediately. Smoke continued for 10 minutes until it cooled.

Tommy

Mike Schmidt

Check to see if you're getting spark to both cylinder banks. If one cylinder bank isn't getting spark due to a bad coil or something, the car will still run. It will be down on power though. Fuel will continue to go through those cylinders that aren't firing, and will cause the cats to get extremely hot. Hot enough to actually start the car on fire if it's continued to be driven in that condition.

Tommy928

Mike,

Thanks for the idea. It sure sound like a logical explaination to my problem. I will check it out tomorrow.

Tommy

Tommy928

Well, the car would not even start today. I could hear the fuel going in and the engine would run for half a second then died. So I am guessing the problem is the ignition control units "exciter" in front of the radiator? What exactly does the "exciter" do anyway?

Tommy

WallyP

First thing to check would be the relays.

1) Check the backup l;amps and make sure that they work. If so,
2) Swap relay XXII (backup lamps) with relay XX. If this solves the problem, buy a new relay. If not,
3) Swap the removed relay (now presumed good) with relay XXV (LH Jetronic). If that cures the problem, buy a new realy. If not,swap the removed relay with relay XVI (EZK ignition). It will look different, but will be functionally interchangeable.

If none of this helps, let us know.

Tommy928

Wally,

Tried all of them - didn't work.

Donald

Have you checked the vacuum lines?
Donald

jpitman

I thought it was well known that most electrical devices operate on smoke. Once the smoke escapes, they stop working, and unless you are quick enough to catch ALL the smoke and push it back in, it will never work again.

Sorry, couldnt resist.

Smoke anywhere in a car is really scary.
jp

WallyP

There are several devices that can be used to check for spark on a plug wire. If you have, or can borrow, an inductive-pickup timing light, that is probably the easiest. If not, check at an auto parts store for an inexpensive tool that can tell you whether or not there is spark present without disconnecting the plug wire. You do NOT want one that fits into the plug wire and requires you to disconnect the wire.

BE CAREFUL!! The ignition system on the 928 can seriously hurt you!

Using the tester, check for spark on each of the plug wires. If you are missing spark on four wires, the most common problem is a bad coil wire. Other possibilities include a bad coil, a bad connection, a bad rotor or cap, etc. Be certain to carefully check the appropriate coil wire for corrosion on the ends and for arcing to ground

Tommy928

Wally,

The spark plugs, wires, caps, and rotors are all new installed 1000 miles ago. So I assumed they are all okay but I will try the timing light suggestion.

How do I check if the coils are bad? What resistant number should I be looking for?

Thanks,
Tommy

WallyP

You can take your choice of statements:
"I know that they are good because I just installed them."
"Anytime you have a problem after you work on it, look again at what you did."

Best way to check the coils are by checking the output with the timing light. The coil wires probably cause more problems than anything else in the area.

Tommy928

I just wanted to update everyone that I've finally got the car fixed. It turned out that both coils were bad. I put new coils in and the car started up immediately. It runs much better than before I had the problem. The coil on my 944 (same coil as 928) also went bad a few year ago. Seems like a good idea to change the coils after 80K miles or so.

By the way I measured the resistance of the primary and secondary of the bad coils. The primary was okay at 0.5 ohm. The secondary was off by 500 ohms at 4500 ohms (they should be 5K to 7.2K).

Thanks to all who advised me on the problem.

Tommy