91 LeBaron misfire

The car is a 1991 Chrysler LeBaron GTC with the Mitsubishi 3.0 V6. It has developed an intermittent misfire that starts at either idle or at speed. The check engine light comes on, but the misfire often clears before we can get the car to a shop, and then the light clears when the car is turned off.

We’ve had the car for about a year and a half and hadn’t caught up on all the maintenance yet. I changed the spark plugs and air filter, plus PCV valve. The breather filters were completely gunked up and were changed, and I cleaned out the breather tubes. Spark plugs No. 1 and 3 were fouled, but all of them had lots of ash.

The engine still misfired after that.

Simply getting the car booked into a shop that handles 1991 codes is difficult as the car is needed for work. I managed to get the CEL blink codes, and they are, with Haynes Manual translations:

12 - Number of key-ons since last fault or since faults were erased

26 - INJ 1 peak current not reached

OR INJ 2 peak current not reached

OR INJ 3 peak current not reached

- the description talks about high resistance in the related injector bank

27 - Injector 1 control circuit

OR INJ 1 control circuit

OR INJ 2 control circuit

OR INJ 3 control circuit

OR INJ 4 control circuit

- the description talks about the respective injector output driver not responding properly to the control signal

We’ve tried mixing in some fuel injector cleaner with a tankful of gas, that hasn’t done it yet.

So, any ideas?

Go here http://www.allpar.com/fix/80s-codes.html and read the notes at bottom that pertains to code 26. Its possible its just the injector wire connector needing cleaned with some electric connector cleaner.

I’ll have to try that. I take it we’re talking about the connectors at each injector, plus, I guess, where the injector harness meets the main harness.

I’m wondering if anybody knows of any particular problems with the injectors on this engine, beyond the electrical connections. If cleaning the connections doesn’t work out, should I just go ahead and replace the injectors, or would there be any other clues to follow up on first?

Well, it’s been a while, so here’s an update for the car that misfires at will, then runs nice, randomly, like a light switch:

It’s been to the same shop three times in an attempt to diagnose the problem (one time diagnosis fee, it’s cheaper than switching mechanics all the time). I told them the same as above, and mentioned that the fuel filter had not yet been changed. The service advisor didn’t think it was the fuel filter, based on the very on-off nature of the problem.

  1. Discovered that the injector wiring loom had been cut near the main harness at the back of the engine, and put back together with “butt-joints” (explained to me as basically wires crimped together.) So they soldered the wires back together. We picked it up, the wife drove to work the next morning, and the misfire came back.

  2. Brought it back to the shop, they found more butt-joints, and fixed them. They gave it back, it messed up the next day.

  3. The third time, they had the car for 3 days, trying to trace the problem. They say they took it for SIX test drives, and the problem didn’t come back, so they gave up and gave it back. They test drove it so much that it was nearly out of gas.

The misfire came back in the 3-minute drive to the gas station.

The wife and I started brainstorming with the service advisor, and he started to think that the problem was… wait for it… the fuel filter. So I got off my butt that evening and changed the danged thing. Chrysler’s quick connects didn’t disconnect so I had to recycle some hose, but the new filter went in and seems to be holding.

In the 24 hours since then it’s been driven a fair bit, and hasn’t misfired yet. In fact, I think the engine runs smoother after the whole tune-up than the previous year we had it! The wife thinks the problem is solved, but I’m willing to bet we’ll be back at the shop in a few days. I’ll let y’all know.