Boonedocks
Michigan
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Joined: 06/23/2006
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This is my third season with an 89 Southwind. No misfiring in the first season, but in the second season, misfiring started under certain conditions. If I drove for at least an hour and then sat for around half an hour, upon resuming the engine would misfire. Or, after around 3 hours of driving with shorter stops, the misfiring would start. Sometimes is was just 1, 2 or 3 misses, but at others it would be some serious on and off misfiring. Frequently it would be very quickly after restarting back out, but at other times it might take 15 minutes or so before it would start. It showed up far more so pulling any kind of grade. On rare occasions, backfire can be heard.
The remedy was to rest, sometimes by the side of the road for at least an hour and use a box fan to help the cooling down process. I became convinced it might be vapor lock so had mechanic consider an extra electric fuel pump. Come to find out, there is an electric pump in the tank of this model and it wasn’t working so he pulled tank and replaced it with both of us assuming problem would be solved, but no it appeared again on the first trip out. Yesterday, he replaced the coil, remembering that another customer had similar symptoms with a coil problem, but on my test drive, the misfiring appeared again (following an hour drive and a 30-minute rest, it then appeared about 20 minutes later into the drive).
We both are about out of ideas. Heat soak seems to be the cause of the problem. Upon setting sufficiently long with all that heat rising off that hot engine causes an intermittent failure to something. But to what? Distributor cap?
It is so unnerving when you are misfiring down the road and especially pulling hills and having to sit by the side of the road.
Any suggestions appreciated!
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scbullis
Travis AFB CA
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Joined: 03/30/2007
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Just a thought, but have you replaced the ignition wires? They do degrade over time, especially in a high temp environment, and will cause misfires. Also, your thought on the distributor cap might not be too far off.
Had a 92 TBI 454. Didn't have a full misfire, but ran rough and erratic when it warmed up. New wires and cap fixed it.
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1995brave
San Antonio, TX
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Joined: 01/24/2006
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Also check the filters on the frame rail and in the carb. Another thing to check is the distributor for play, a worn distributor can cause the failure.
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bill h
el segundo
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Joined: 08/02/2001
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Your mechanic done good by going after the coil. That is often the culprit. Especially non-Delco coils.
Agree on plug wires being a good place to start. Replacing them is good PM, anyway.
The module in the distributor is also heat-sensitive. If a previous mechanic replaced it with a non-Delco unit or did not use the silicone heat sink compound, trouble is likely.
Another possibility is a wire that has broken conductor and works until heat softens the insulation, allowing it to sag and open the gap in the conductor. This can be tested by visual inspection, substitution or by pulling on warm wires and judging their feel. A non-solid feel when pulled will tell you. You can also watch the needle on an analog meter while you jiggle and massage wires. Also check wiring and connections inside the distributor.
A push-on connector can be not quite tight enough, and expand a little with heat. check the positive connection on the distributor first.
Bill and Susan
84 Barth 30 tag powered by ht502/Thorley, Gear Vendors OD
Siamese Calvin and Airedale Hobbes
4WD Toyota toad
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Mike Hohnstein
Germantown, Wi
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Joined: 01/04/2004
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Sounds like HEI distributor woes. I always carry a complete replacement, including rotor, cap and wires. There is a reason for that.
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Boonedocks
Michigan
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Joined: 06/23/2006
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Am appreciating all these good thoughts. I did replace the spark plug wires during this saga and that didn't solve it; misfired exactly the same before and after. Will definitely be trying some distributor-related things based on this help.
Any other thoughts, please keep them coming to try to help me out. DW getting even more uptight over this than me who is driving it.
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wdbates
Oak Hills, ca
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Joined: 07/22/2003
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We had many a bad Ing module that would go bad when hot and start missing. There is also another problem I discovered on new plug wires is that if you didnt use factory wire holders and guides and made the mistake of tapeing or wraping 2 or more plug wires togeather when hot they would start fireing togeather thus creating a backfire under load (high kv demand) when hot!.. And the one that took me several hours to find was a bad diode trio in the ALT and discovered that the misfire would go away when I took the hot lead off the ALT..
Geneva & Warren
04 34m expedition
300 ISB cummins/6speed
Oak hills CA
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WGLASSJR
NORTH CAROLINA
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Joined: 07/28/2007
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Yoy can buy a brand new dist on ebay for $100.00 or close.It could possibly be a camshaft but the systems your discribing dont sound like cam.Be sure you dont have dirt or water in the carb.But sounds like dist to me
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Poltax
UT
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Joined: 01/30/2003
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Here is another suggestion. It might be the bushings in the distributor. If they get worn enough you can start to get a missfire. I had this happen one time to me with a Ford Torino. It would run great then all of the sudden it would start to missfire and then be ok. Sometimes it would kill the engine like it was out of fuel. Then after the motor sat for a half hour or so it would be ok again. It drove me nuts till we figured out it was the distributor.
We dont race on Elvis's Birthday.
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Jim83Itasca
La Quinta Calif
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Joined: 09/16/2003
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Bill & Mike.......Right on.
The heat sink compound is extremely important, The modules seem to heat soak and break down after driving for 1 hour plus.....
Either a "Chebby AC Delco" or a napa 4090 module are the prefered replacments in that order.......
Another aid for the heat problem is to use a "Brass button" in the cap instead of the "Carbon" button which with the increased electrical resistance creats more heat.....
Jim
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