So a couple weeks ago I started my car after sitting overnight and I experienced the dreaded misfire. We had a torrent of rain a couple days before which is unusual in the PNW for this time of year. So I’m thinking I somehow got moisture in one of the caps. Drove it to the end of the driveway and the misfire quit. Thinking nothing ever fixes itself I started planning to spend time to diagnose and repair. Problem was still random for the next couple weeks till I could work on it so I decided to park it till I could work on it.
Fast forward to last Saturday I was making plans to look and and probably buy a R129 a few hours away and thought the perfect car to road trip was the 400E. So I pulled it into the shop and removed the air cleaner. I remembered I never saw the production label on the injection harness so I better pull the boot on one of the injectors connector. Turns out I still have the original harness! So off it came. Then I pulled spark plugs looking for traces of arcing. None were found so next order was to remove the caps. No problems found there as well And even though the plugs were not bad I had a new set so at the minimum it was going to get plugs. Then while I was in there i thought don’t half ass it fix the power steering and what appeared to be a leaking cam cover seal. So while I’m there I noticed the VVT cam magnet was leaking oil. Might as well clean and reseal that. So by 6PM it’s all buttoned up and I start the engine. Runs great and no more oil leaks but after a minute or so I start hearing a misfire again. Quickly traced the problem to #3 cylinde. This was best accomplished with the wheels blocked and brakes set with the engine running in drive. Swapped plugs. Still there. Listened to the injectors with a screwdriver and could not discern a fault injector but one thing I noticed is there was a pattern to the misfire. The misfire was cycling with the O2 sensor. At that point the LH control unit was pulled and my spare was installed. Misfire gone!
So now that I have driven the car a couple of days I can stick a fork in that problem. Disassembly of the LH did not reveal any any capacitor damage. It’s going to get new caps to see if that fixes it but I’m having doubts. While I was in there I discovered the EEPROM was socketed Which is great because I do not have to get another WOT cont unit but a 93-95 and swap the EEPROM from the bad to the new.
Fast forward to last Saturday I was making plans to look and and probably buy a R129 a few hours away and thought the perfect car to road trip was the 400E. So I pulled it into the shop and removed the air cleaner. I remembered I never saw the production label on the injection harness so I better pull the boot on one of the injectors connector. Turns out I still have the original harness! So off it came. Then I pulled spark plugs looking for traces of arcing. None were found so next order was to remove the caps. No problems found there as well And even though the plugs were not bad I had a new set so at the minimum it was going to get plugs. Then while I was in there i thought don’t half ass it fix the power steering and what appeared to be a leaking cam cover seal. So while I’m there I noticed the VVT cam magnet was leaking oil. Might as well clean and reseal that. So by 6PM it’s all buttoned up and I start the engine. Runs great and no more oil leaks but after a minute or so I start hearing a misfire again. Quickly traced the problem to #3 cylinde. This was best accomplished with the wheels blocked and brakes set with the engine running in drive. Swapped plugs. Still there. Listened to the injectors with a screwdriver and could not discern a fault injector but one thing I noticed is there was a pattern to the misfire. The misfire was cycling with the O2 sensor. At that point the LH control unit was pulled and my spare was installed. Misfire gone!
So now that I have driven the car a couple of days I can stick a fork in that problem. Disassembly of the LH did not reveal any any capacitor damage. It’s going to get new caps to see if that fixes it but I’m having doubts. While I was in there I discovered the EEPROM was socketed Which is great because I do not have to get another WOT cont unit but a 93-95 and swap the EEPROM from the bad to the new.
