As some of youknow I got a new pcm from pcmforless and had a checkengine light/service engine soon light, well now I know what the problem is I have to switch the knock module from myold pcm to my new one because the one I got from them is bad. Its easy and quick, however, I noticed on my trip out of town my highwaymileage was down to about 17mpg or 18mpg. Could this be due to the knock sensor? I generally got about 25mpg or 26mpg before this. I was driving at 81 or 82mph, which is about where I normally drive. I'm thinking it could be the sensor or the way the pcm was programmed, slowing down to maybe 75 could help depending on how it was programmed...suggestions? thoughts? Comments?

 

If it's pulling timing out because it thinks it hears a knock, then you're getting worse mileage. If it's running open loop because the knock sensor's totally failed, then it's using a "safe" timing map which gives worse mileage. Try an LT4 knock module for cheap HP. Good luck

 

Excellent, I'm glad to know I am not the only one thinnking that...I'm going to switch it tomorrow and see what happens on the trip home...I was expecting a minor drop in mileage with the pcm change but damn near 10 mpg was wayyy too big a difference...thanks for the input.

 

Switched the knock sensor but still have the service engine light, I'll swing by my mechanics tomorrow or tuesday and have him clear the codes and see if that takes care of it. I think it will, I called him this weekend he said it was necessary for him to clear the code and that would probably take care of it.

 

Clearing the code takes all of 30 seconds of having the PCM BAT fuse out. On a 1995, it is in the underhood fuse/relay panel.

 

cool, I did that and same thing, service engine light was on took it by my mechanics and he cleared and it came back, its something with the pcm, I've tried three different knock sensors and when I put the pcm into another 94 car it did the same thing. I called pcmforless they were more than willing to help, I'm going to ship it back and he'll get me another out. This sucks but at least they're really easy to deal with.