Intermittant Mystery

My '81 244 is experiencing such an odd mix of intermittant problems I am not sure where to look for a culprit. My idle has been a little iffy for about 2 months, usually acting like it might stall after I started it cold, but getting better after warming up. Then the alternator stopped charging and all my dash lights were off, but after cleaning and reconnecting some wires it was basically fixed, but sometimes the dash lights still wouldn't light up upon first starting the car, but if I turned it off and restarted it they almost always came on, if not the first then the second restart. I decided it was in good shape after driving it problem-free for a week; I put some liquid electrical tape on some badly-insulated wires at the firewall harness then didn't drive it over the weekend. Monday morning I get it, no dash lights but I expect that, I start it and it can't idle at all, just surges then completely stalls. Try again two or three times, no matter if I give it gas or not, the engine is revving wildly then completely stalling out. I try it again the next day after some rain clears up, same deal, except after restarting it the third time or so it barely manages to stay on and eventually it starts to steady out, but then dies. Then today, the third day since the problem first occured, I hop in, all the dash lights come on, I start it up and it's right back to how it used to be when I drove it for a week straight, the idle is a little iffy but basically fine. I thought when the idle was a complete wreck that it must be a vacuum line, but now I'm not so sure since it's so intermittant. The only thing I can think is that it must be electrical, perhaps the main engine harness? I just can't imagine what else could cause such an array of strange problems that appear and disappear so suddenly without my touching a thing. This car is my daily, and I'm a schoolteacher, so I really have to try to get on the right track, at very least so I can point the mechanic in the right direction if I can't do it myself.
Thanks everyone.

There are probably a couple of things going on here. Very common for the engine wiring harness to decay and cause strange intermittent issues. Your description of repairing the wires tells me you have frayed corroded wiring that needs to be replaced. There is an important ground wire on the case of the alternator that goes to the bracket on the engine. The alternator won't charge without that ground being in good condition. There is also a ground from the valve cover to the rear firewall. Make sure that is also in good shape with a clean tight connection.

What engine is in your car? You could have a kjetronic injected engine or have one of the very early efi engines. Knowing what you engine we are dealing with would help guide me to more suggestions.

dl242gt said:

There are probably a couple of things going on here. Very common for the engine wiring harness to decay and cause strange intermittent issues. Your description of repairing the wires tells me you have frayed corroded wiring that needs to be replaced. There is an important ground wire on the case of the alternator that goes to the bracket on the engine. The alternator won't charge without that ground being in good condition. There is also a ground from the valve cover to the rear firewall. Make sure that is also in good shape with a clean tight connection.

What engine is in your car? You could have a kjetronic injected engine or have one of the very early efi engines. Knowing what you engine we are dealing with would help guide me to more suggestions.

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That alternator ground had broken clean off earlier, so I put a new eye on it and then cleaned the connection on the engine bracket. One thing worth noting on that front, whenever I ground the battery warning light wire to the alternator case the lights all work, so perhaps the alternator is just in the stages of failing? Still seems odd to me. As for my engine, what's the easiest way for me to determine that? VIN? I've got the 2.1l with the m46, but I'm not sure if that would indicate anything. VIN is YV1AX4541B1657559. One other thing that might tell you, my car has the old style 2-pole auxiliary air valve, not an idle air control valve. Let me know if any other info would be of use.

Does your engine have black teflon fuel lines going into the cylinder head? It would be one for each injector. Or is it a fuel rail with four electric injectors? The 45 in the vin only tells me it's some type of B21F. Most of the 81 cars are kjet injected.

The bosch style alternator has diodes that provide the internal connection to the warning light. I've had those diodes fail and cause a no charge since the warning light didn't work. I'd suggest also checking the brushes and make sure they aren't worn out. Your car may be updated to an internal regulator which is held on with two screws. Or there will be three wires coming out of the brush holder held with the two screws. The wires run to the voltage regulator mounted on the inner right fender. That is if your charging system is original.

dl242gt said:

Does your engine have black teflon fuel lines going into the cylinder head? It would be one for each injector. Or is it a fuel rail with four electric injectors? The 45 in the vin only tells me it's some type of B21F. Most of the 81 cars are kjet injected.

The bosch style alternator has diodes that provide the internal connection to the warning light. I've had those diodes fail and cause a no charge since the warning light didn't work. I'd suggest also checking the brushes and make sure they aren't worn out. Your car may be updated to an internal regulator which is held on with two screws. Or there will be three wires coming out of the brush holder held with the two screws. The wires run to the voltage regulator mounted on the inner right fender. That is if your charging system is original.

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I think it's the first one, but I'm not certain, here's a pair of photos that may make it obvious:





As for the alternator, it has been upgraded with an internal voltage regulator, and I checked the brushes and they didn't look worn down to me, certainly not in comparison to a couple of videos I looked up of obviously worn down brushes. The car only has around 120,000 miles on it, so they couldn't have been in there for that many miles. Maybe I'll check those diodes. Are there any diagrams of those alternators or are they basically all similar enough I could research basic alternator repair and figure it out? Thanks for your answers so far.

That's a kjetronic injected engine. One of the alternator repair kits that have the diode packs would take care of any bad diodes. Don't know how easy they are to get now. Ebay used to have rebuild kits and there is a break down of the alternator in Haynes manuals. At 120k miles it might be time for some longer term type repairs like injector seals, cleaning/servicing the pcv box. Fuel filter is good to keep up with on kjet engines. They like clean fuel. I'd suggest checking out the ozvolvo web site archives for the green book repair manuals. They explain very well how the fuel injection system works and how to test it.

dl242gt said:

That's a kjetronic injected engine. One of the alternator repair kits that have the diode packs would take care of any bad diodes. Don't know how easy they are to get now. Ebay used to have rebuild kits and there is a break down of the alternator in Haynes manuals. At 120k miles it might be time for some longer term type repairs like injector seals, cleaning/servicing the pcv box. Fuel filter is good to keep up with on kjet engines. They like clean fuel. I'd suggest checking out the ozvolvo web site archives for the green book repair manuals. They explain very well how the fuel injection system works and how to test it.

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Great thanks. So you think it''s a fuel injector problem in all likelihood. I do know the fuel filter was recently cleaned. I'll look for a diode kit aswell. Maybe some servicing to the various bits you mentioned will help the issue. I'm still puzzled why I had such a drastic change for a few days only for it to return to it's former functionality, but maybe its the wiring as you said earlier. Guess it's time to make a checklist and start working down it.

I was suggesting that the seals around each fuel injector may need to be replaced. They cause a vacuum leak. If you really want to work on the alternator then look for a kit but alternators are usually easy to get for the auto parts stores.

Another suggestion is to clean or replace the fuses. They get corroded and can cause strange intermittent problems like you are experiencing. I would suggest buying the copper and brass versions not the pot metal ones. They sell the copper and brass fuses on ebay and amazon.