1991 3.1 with 148k miles tends to "diesel" spit and sputter after shut off for just a moment. Any one else ever had this problem? If so what do I need to check?

 

Checking the plugs is the first step..

Possible issues:

Crappy gas.

Carbon buildup on the plugs

Carbon buildup in the cylinder (on piston or in cylinder head)

Plugs too hot.

System running lean (injectors are weak or dirty)


If your plugs ends are coated in thick carbon there is a good chance the cylinder and pistons are also. You can add some seafoam to the fuel then run the **** out of it and blow the carbon out of it. If the issue is lean when you pull the plugs they will be white-ish and may show signed of pitting.


Warn: just taking it out and running the crap out of it could fix but if the issue is due to a lean issue and you run the crap out of it you could burn a hole in a piston. Make sure you pull all the plugs to make sure you don’t have a failing injector or some other issue with a single cylinder.

 

Ok got it. Idk why I didn't think of carbon buildup. 1st thing I did was check the timing but it was fine. I just replaced the fuel filter and idk if I've ever seen a filter that was in this bad of shape. Just bought the car and I'm trying to get all the neglected issues fixed. I've been running seafoam, marvel, and Lucas threw it. "Not all at once". The knock sensor was out when I first got it and who knows how long it had been ran like that so I do imagine everything is fould out.

 

Ok update on what I have found. #1,3,5 all a Carmel color. #2 was wet and black smelled like fuel, #4 was dry and black still smelled fuel, and #6 was ghost white

 

If I remember right the 3.1 was a throttle body fuel injection. The first thing I would check is for a vacuum leaks around cylinder 6 and the spray pattern of the injectors.

Timing would be a human error, very possible, missing knock sensor, defiantly in the future let us know you know nothing about the car, I assumed it just started doing on its own.

A good tank of fuel of high grade fuel may help.

 

Yes I have been told that the lower intake is prone to leaking on these cars, but I have taken 3 cans of carb cleaner and sprayed around the intake and can't find any leak.