Hello!

I have an on again, off again problem, and the only consistent OBD code is "cat convertor below threshold". 2005 E350 5.4.

I noticed this first on the coldest day of the year, after the van sat for three days. The engine would turn, but would not start. I had it towed to the local mechanic. He didn't know what the problem was, but he said it smelled like I burnt the starter motor from all the cranking. Not starting is the first symptom, a burning smell is the second.

The next time this happened, it was cold again. I took off the air filter and tried to start it. No luck. I put a space heater up and blew hot air into the intake. After five minutes, it started right up. There was no burning smell this time.

The next time, it was warmer, and I had driven about a half mile. The engine died. I had a misfire code and the cat code. I pulled off the air filter, and she started right up. I ran it up the road to a parking lot, and put the filter back on. This time, the burning smell was back.

The mechanic replaced the little circuit box inside the air intake. I assume that is an air flow sensor to control mixture. He also replaced the sparkplugs.

A second mechanic replace the #8 coil, and the plugs on the drivers side. When I told him that the plugs were new, he was surprised. I mentioned the air flow sensor, and he suggested that I clean the contacts.

Any ideas? Is there some way to check the Ford TSB database?

Michael (this is my seventh ford)

 

If you can, check the wiring harness that goes behind the EGR supply pipe for a burn thru condition. Can cause a series of different problems among which could be the burn smell you notice.