Car runs fine for first 8 to 10 miles, then starts to miss at lower rpm. You know when you're slowing down and don't want to downshift, the car should be able to "lug" just a little - well it just won't do it. If I downshift so that the rpm's go up - it'll run fine. I've replaced the plugs, rotor, cap, wires, swapped the Coil, AMM, ECU with parts from a parts car - it is an automatic so I can't swap the ICU I don't think. It feels like the timing is "jumping" drastically or something like that - really doesn't feel like fuel is cutting off. I've held on to the fuel pump relays while the miss is occurring and they don't seem to be clicking off and on. I have the correct number ICU on the way to check that out - that's about the only thing left. Another theory, could the Hall Sensor give this kind of trouble? I figured it would either be good or bad - not in between/intermittent. Help!

updates: got the replacement ICU, swapped it out and car wouldn't even start! The number was different, but I was assured by the parts man that it would work. Punt.....I had another distributor from an 1985+ car........put that in and the car started with the replacement ICU - then quit when I moved the ICU and connector a little...hmmmm...began to suspect a faulty connection at the ICU, started dinking around with a scratch awl to tension the female connector pins and cut a ditch in my hand when the awl slipped out of the pin hole..ouch....quit that as I probably now had replaced the "bite" for when I reassemble. I immediately went back to the original distributor and looked it over. After close inspection, I don't see any reason why it would be causing the problem - like I said before - it's usually either good or bad, not subject to a post warm up problem. I'll continue to systematically work through it post what finally fixes it!

Those ICU connector pins (and sleeves?) are reported to be troublesome once the connector is unplugged. Also, the ICU for the MT is different from the AT version:

1346105 = Manual
1317295 = Auto

I don't know what effect swapping in the wrong one would have.

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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

After doing some research here, evidence seems to pint to the alternator. I'm going to have it bench tested down the street to see if it's at fault.

I'm having the exact same problem on my 82 (manually tranny) and I've performed the same fixes as sjones except for the AMM and Coil. Problem persists. Would advancing the timing from 0 to 12 degrees help? I replaced the timing belt last fall, maybe its jumped a tooth?

"Would advancing the timing from 0 to 12 degrees help? "
Yes. You aren't supposed to be running at 0 degrees. Performance will suffer though emissions tend to be better.
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1980 245 Canadian B21A with SU carb and M46 trans in Brampton, Ont.

The repair manuals all state to line up the timing marks, that would leave it at 0' degrees, any thoughts?

The distributor sets the timing of the spark. There is a hash mark on the dist. rim which will line up with the rotor at 0'.

After lining the belt-timing marks up and intalling belt cover, check the timing with a timing light/gun. Loosen the distributor and turn to adjust (advance) timing using the marks on the plastic timing belt cover by the crank pulley as guide.
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1980 245 Canadian B21A with SU carb and M46 trans in Brampton, Ont.

It's possible the car has a bad knock sensor or the wire to it has broken off or crumbled. It's also possible I guess that it REALLY IS knocking badly, and retarding the timing significantly because of it.

Possibly better gas will help it. 93 octane or better.

Good luck!
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Rob Bareiss, New London CT ::: Roterande Fläkt Och Drivremmar!

I unhooked the knock sensor already - no change. I figured the ECU would just keep the timing "constan" with it unhooked and I would notice a change because the problem would either go away or be constant regardless of RPM or temperature.

Try replacing the 25-blade fuse under the hood.

I can't see how this could be RPM related.........temperature possibly from slight heating due to current flow....but highly unlikely. Usually a fuse and/or connection are either good or bad....but I have seen some strange stuff! I'll try it tonight. Thanks!

While you're at it, look at the fuse 12 contacts for weak tension and/or corrosion.

I believe that a marginal electrical connection anywhere can react to vibration and temperature. At fuse 12, such a reaction might affect the Fuel relay and ECU.
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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Coolant sensor could be faulty, this can make the ECU think the engine is still cold and keep the mixture rich which will cause performance problems. There are 2 sensors, one for the guage and one feeding the ECU.
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David Hunter

I have checked the FI coolant sensor per the Bentley manual and it tests within the specs for cold and warm conditions. But - the reason I first tested it is another nagging issue that's been going on for years. When I first start the car, it will die unless you pat the accelerator and keep it revved up a little.....so naturally I went to that sensor first because its' main job is to provide rich mixture on start up. Maybe I messed up my first test. I'll check it again tonight! Thanks!