Weird Problem - New ECM & MPG Loss

[cascadiarunner]

Long story short a rodent chewed an injector cable and fried my ECM. I got it replaced and I've lost about 2.5 MPG average since. It's been about a month and I've probably driven 1,000 miles or so. Also got the spark plugs replaced at the same time.

I know correlation =/= causation but the timing seems to indicate something related. Anyone ever heard of anything like this or have any ideas?

Thanks!

 

[Skidmarcx]

Doesn’t sound normal... do you have access to a scan tool that can display fuel trims?

 

[fkheath]

Long story short a rodent chewed an injector cable and fried my ECM. I got it replaced and I've lost about 2.5 MPG average since. It's been about a month and I've probably driven 1,000 miles or so. Also got the spark plugs replaced at the same time.

I know correlation =/= causation but the timing seems to indicate something related. Anyone ever heard of anything like this or have any ideas?

Thanks!

Try resetting the average MPG. Sometimes there is some old data in the memory that makes the reading look low to what it really is.

 

[flyrv9]

You could do a basic fuel calibration. Make sure all tires are the same pressure. Fill tank and drive a set number of miles (let's say 100). Fill tank again and compute MPG. You could run the test a couple of times under the same conditions; with the same loading in the truck. Compare that to what you were getting with the old ECU.

Another thing to check is that both ECU's are the same part # and have the same software load.