Hey folks, my first post here but I have lurked around for a while and picked up a lot of good info. I am just not finding what I need to know this time...

So I have a 91 Dakota with the 318 and about 120k on it. And I have been fixing the little annoying issues with it one by one - more then enough of them. But I really like this little beast and it isn't my regular daily driver so not a big issue. I guess I would like some other peoples thoughts more then anything...

I am stuck on a smoking issue. I can run it 3000 miles and not have any noticeable oil usage. However, if I let it idle for even a minute or two it starts to burn oil. A little at first (notice a little puff when you take off) to clouds of it when you take off after idling for 5 -10 minutes. I find it hard to believe it would be rings since I do not go through oil and it runs strong.

I am thinking it is a vacuum related issue. Of course some of the symptoms I have can come from different problems as well. It has done this since I bought it. I bought it from a guy I know and he said the vacuum cables were all screwed up when he got it and his mechanic patched it back together. I think they may still be messed up. For instance when I go to flip from Cold to hot air it is usually pretty much all or nothing and a tough "flip". Also I have replaced the PCV valve and checked all the hoses I can see on the top of the engine for leaks but found nothing.

The diagram that is normally under the hood is long gone. I used the link under the 1st gen FAQ to try and track down a diagram but they didn't have one for my particular year and the one for an earlier model (89) and the one for they year after. They had the 91 360 also. Is either of these right? If not does anyone have any idea where I can get a vacuum diagram?

I think there may be a vacuum issue for other reasons as well: Mileage is horrid - 11 mpg at best sometimes as bad as 9. - City and/or HW but that can go with bad rings or at least fouled O2 sensors. Cap, rotor, wire and plugs are all fairly new. I know mileage isn't going to get a LOT better but it's rated at 13/17.

It also usually has hesitation when the air is dry, but when it is raining absolutely no hesitation - Runs like a beast. I have sprayed around the lines and Throttle Body but didn't notice a change in RPM. I think it is a connection issue - they are not run correctly - or there is a leak not on the top of the engine.

So what do you think?

By the way - what should the idle be in gear and out?

 

You say you're not going through oil. What color is your smoke? If it's white/gray it's a coolant leak.

 

No, it's definitely oil. But I used less then a quart (maybe less then half a quart) over the last oil change and I ran it about 3500 miles. That's why I find it so strange. If I was going through oil, I would assume it was rings.

 

1 quart in 3500 miles is considered within tolerance of oil consumption. Hell, Ford lets a quart go every 1000 miles before they look at warranty.

 

I know all too well about the older Ford engines. I had an 89 302 Mustang that went through a lot more oil when it was new. When the dealer told me a quart every 1000 miles was when they started looking and mine was only every 2000 miles I was more then a little surprised. But it never smoked.

The Dakota smokes at idle and it is definitely oil that is burning. I just don't let it sit and idle; but it is really annoying when I forget.

 

Check your plenum gasket for leaks. Seems to be the culprit.

 

One year too old for a true plenum gasket. However I took a good look at the TB gasket and it looks suspect. I didn't get any rpm in crease spraying around it but it looks like it has some leakage. Might solve some of the vacuum issues...

 

My 91, 318 4x4 also did this. I read that the intake manifold gaskets shrink and suck oil at idle ( highest vacuum level )
I figured that I'd try re-torquing the intake manifold bolts first before I replace the gaskets. Much to my surprise, half the bolts were finger tight. The truck hasn't smoked since and all appears OK with the motor...so I guess I'm not changing the gaskets ( at least not until I change the cam )