pretty bad
Typical Repair Cost:
Average Mileage:
223,000 miles
Total Complaints:
1 complaints

Most Common Solutions:

  1. if replacing cop doesn't work replace connector (1 reports)
1998 Ford Expedition engine problems

engine problem

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1998 Ford Expedition Owner Comments

problem #1

Oct 182009

Expedition Eddie Bauer 5.4L

  • Automatic transmission
  • 223,000 miles


Ok, I bought this car used for cheap with a lot of miles on it. Never had an engine problems till last Saturday when it starts misfiring on one of the cylinders. Went from no problems to a miss in one of the cylinders.

Update from Nov 3, 2009: Last Saturday I took a drive in the morning and all of the sudden on the way back it started to misfire. I pulled over and checked what connectors I could, but didn’t see anything obvious so I went home and parked it. I found out autozone rents OBD II scanners so I rented one. I had code P0354, P0304. Cleared the codes and tried it again. I got 354 again as soon as I started up. This code states that I have a connection problem with the COP on cylinder #4.

One big thing I didn’t know and got bad info on from another was the cylinder numbering. I thought it would be like Dodge and Chevy (and probably others), but oh no, Ford has to be different. Their cylinders are numbered 1-4 on the passenger’s side and 5-8 on the driver’s side.

Anyhow after trying to diagnose a coil that wasn’t bad, I finally figured out to actually look at the manual to find out because it finally hit me when it was throwing out other p035X codes. The #4 is a real pain to get to and actually it was the problem that everyone has which is the coolant leak issue (I’m surprised there aren’t more complaints on here). It leaked into the connector and it actually looks like it could potentially be a fire hazard because part of the connector had been burned away or appeared to be melted in the middle of it. There was a lot of white powder around it probably from the antifreeze or minerals that were burned. I took the plug out and used a small file set to clean it and reconnected it. I didn’t swap coils because the rubber boot was stuck in the hole so I just reinstalled the old one back in the boot and connected it back up. I fired it up again and it checked good! It still didn’t seem to run right so I still ended up getting another used COP from the salvage yard for $20 and installed it. Worked great after that. I also relocated the clamp on the problem hose in an attempt to stop the leak until I get a new hose. It seems to be working for now.

Update from Dec 13, 2009: It seems to be the connection that is going bad (on both the harness and COP side) when the coolant gets on it. the coolant seems to work it's way into the environmental seal and get into the connector and somehow corrodes the connector and makes it not have a good connection. That is most of the reason some people haveq a misfire, but aren't getting a code, becuase the PCM is seeing that it's connected, but it's making such bad contact that it won't fire most of the time. Sometimes when you get a new COP it will solve the problem for awhile and sometimes not because of how bad your harness connector is.

I found it really hard to splice back there and was going to go with inline splices first, but decided against it becuase of space limitations. I used bullet splices which also allow for replacement of connectors if the same thing happens again. so far so good. I've also placed a piece of soft PVC (the stuff pool toys and air matresses are made of) over the connection so if it does drip is should just run off.

- , Panama City, FL, USA

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