lately my truck has been sputtering. I've mostly noticed it in the mornings.

The exahust smells like fuel, a lot. the truck hasn't been making as much as I think it should be lately, and my MPG is a bit down. Is the base timing adjustable? what should it be if it is?

any suggestions?

 

Sounds like it's getting too much fuel and almost flooding it out.

 

that's kinda what i'm thinking..

does the computer start using data from the O2 right at startup or does it have a warm-up period?

What about a Fuel pressure regulator?

 

It does have a warm up cycle called open loop. these o2 sensors have a heating element on it ot reduce the open loop time. you sensor could reading a wrong number as well as the coolent sensor or sticking or clogedfuel injector or fuel pressure reg or low engine vacuum

 

okay, i figured it used open-loop mode during warmup.

how can I test or check the injectors? I'm thinking pull spark plugs or check exhaust port temperatures after generating a load on the engine. hotter cylinders = lean, colder = rich sort of thing. i'll start by pulling plugs to see what they're saying.

does the coolant temp sensor that the computer reads for management also drive the gauge? I'm askinng because my mustang had two. Although, it doesn't get better or worse (much) with engine temperature but i'll pay closer attention to that tonight on the way home from work.

Can I read the voltage from the multimeter at the computer (to ground, right)? what should the range be?

 

Don't know what year truck you have but on the magnum you do have two sensors. One for the sending unit on the gauge and a seperate one for the pcm. If the coolant temp. sensor is bad it should be setting a code.

 

You'd think it'd trip a code, but if it's simply reading the wrong range like most failed temp sensors i've seen they don't throw codes.

my saturn did it, my mustang did that, and now it seems like my truck might be too.

 

Had a similar problem on a different vehicle, it was a vaccuum leak. Caused the vaccuum advance to malfunction, advancing the timing and running too much fuel to the engine. May not help, but just something to check.

 

thanks, i'll check that!