i just got a 1991 d250 ram ,360, auto, and it backfires through the throttle body, it idles rough as well.

it only seems to do it under mild acceleration,if im heavy or light on the throttle it drives fine but seems a little down on power. someone replaced the coil ,cap and rotor and plugs and wires are worn but still in good shape.

i think the brake booster is leaking vacuum and its missing the cat.with a pipe in its place. thats as far as ive gotten in to it right now, if i find anything else ill post it. any help would be great.

heres some pics of my truck i got for $800
no rust ,188,000 miles.

 

Is it TBI or MPFI? Could be an injector problem or a timing problem. Wait till dark and start it up. Pop the hood and look at the wires for arcing. I wish I had a dollar for every time some one said these trucks seemed a little down on power. LOL

 

its tbi,is the timing computer controlled on these or can i adjust it?

 

you can manually adjust the timing by loosening the clamp on the distributor and rotating it left or right.

 

Like crazzywolfie said the base timing is adjusted just like all older engines. It is the timing advance that is controlled by the computer. Take off the air cleaner and look at the injector spray pattern. It should be a cone shape that reaches the sides of the throttle body with no gaps or streams in the cone.

 

ok thanks guys, i will check the spray pattern ,and adjust the timing. anyone know what the timing is supposed to be? my under hood sticker is gone.

 

10 btdc

 

many thanks guys, it was a timing issue. my timing light was broken but i did it by feel and now no more backfiring, and it has alot more power.