My dads 1990 Dodge D250 with that ghetto TB injection backfires at low rpms... I have searched the forum and havent had any luck.

The truck was running great ever since he got it. One day he was driving and he went to go and it started messing up. When idling it runs ruff, and when you rev it, low or midrange it will backfire. It backfires when you try to drive it. When you get into the higher rpms, it screams without backfiring. Around about 3K rpms it seems to just clear up by itself, even noticable when you are just reving it.

Also would like to check to make sure the vacuum lines are on at the right place. Would be great if someone could show me the vacuum diagram, or a picture of one of these engines without the air filter housing on.

Any ideas on the backfire?

Thanks, Andrew

 

Screwed up injector? If it's sticking open then it'll dump too much fuel at idle and off-idle but at WOT it'd probably run fine. Screwed up O2 sensor? Or you might be on the right track with the vacuum system. Happy hunting man. Pull the codes if you can.

 

The distributer had couple of the magneto pickup "fins" bent with the cap throwing fire everywhere. The throttle body also had a huge leak...

It runs a helleva lot better with those things fixed, but still not like it used too...

Its running extremely rich at idle. When you initially go to take off, it back fires, usually a tiny pop out of the exhaust, sometimes it will let one rip out the intake and stall. With every back fire the truck jerks the **** out of you... once you get rolling to about 20 mph, its fine, only occausionally cruising will it backfire... When you poke it to the floor it does good, but sounds like its bogging...

I guess the tps, map sensor, or maybe the o2 sensor is fuber'd.

Any ideas, suggestions?

Thanks, Andrew

BTW the MAINTAINENCE REQ. light is on since it was bought, it used to flicker on and off, now its stuck on.

 

Did you set the timing? Mine does equally lame things when it's cold. It backfired once so hard the choke plate wedged shut and I couldn't get it to start until I poked it back down.