Hi,
I am working a 1990 3.0 with less than 1000 miles on a rebuild. The engine is running rich when it is cold. After start-up, the is a noticable loss of power until I travel a few miles or the truck warms up. I also have a slight exhaust backfire at low RPM's when I let of the throttle. The backfire is only happens when the truck is cold. After the truck is warm it runs good with no backfire or loss of power. Any ideas on where to start? Would an EGR that is stuck cause this problem? Thanks

 

I just did some checking on Yotatech and believe I found the issue causing this problem. I am not running a cat on the exhaust. I installed new exhaust and when installed it the pipe going to the muffler was too long. I assumed that it was meant to have the cat removed as it fit perfectly, well.... I hypothesis this is causing operating issues with the emissions such as, EGR, AS systems and possibly the O2 sensor. The reduction in exhaust backpressure is messing up the 3.0 emissions and the way they were designed to operate= crappy performance when cold. In the old days, cat removal was not that much of an issue as the engine and emissions(and computer) were not as advanced and designed to operate with the cat and the increased backpressure. So, the cat is getting replaced. Anyone know of a good spot to get a high flow cat?

 

summit racing.com just gut a magnaflow high flow cat. it will work like a charm, the o2 sensor might like it too.

 

Thanks, $53.95 for a universal cat, $85 and some change for a direct fit, not a bad price for a high flow converter. Thanks again