Hi all,

1992, F150, 302, AT, 2wd

Finally broke down and put truck in shop...results are plenum leak and no compression on #7 cylinder. 75 psi at all other cylinders.

So, truck doesn't smoke. No other problems besides the miss...

What would cause no compression and no smoke? Is there some other reason, besides valves, rings, pistons, etc. that could cause a no compression on a cylinder?

Looking for the best and cheapest fix here....

As always, any and all help is greatly appreciated.

Thanks,
Rick

 

From what I've been told, sounds like it's about worn out. Was told that 70 lbs. is the bare minimum for it to fire & that's borderline. A trick I've heard is squirt a little oil in the cylinder & re-try. If it comes up, then it's rings. I'd say at best, you're probably looking at a rebuild.

 

X2 I am amazed the engine starts and runs at all. 75 psi is way low.

 

No compression is either a broken ring or stuck valve. You're going to have to take it apart to see what's wrong with it. 75 PSI is way too low. If those are accurate numbers then you need a new motor.

 

I dought it would run with 75 psi comp , but you said it broke down , check the timing chain that will cause low comp on all cylinders , # 7 may have a bad valve . You can put some oil in the cylinders & test again like old man said , if its rings the comp will come up ...Lew

 

Thanks guys. Well, the truck does run and quite when when getting into it. The miss is very bad at idle though, when warm. But, I have been driving the truck since this first happened in July.

I had a crossfired (7,8) issue...would that cause this?

What questions should I ask the mechanic before I get it back? I reckon that I need to verify his compression numbers as well...

Thanks to all on this gloomy day...

Rick

 

Good thing for you that 302's are cheap and plentiful

 

Wanna send one my way?

Cheap and plentiful is what I need given our current economic situation...

But, thanks to all for the input...onto to find a new motor! But, the mechanic had the gall to say it was driven to long with the plenum leak and that burned the valve...while possible, I parked the truck the day it started idling rough...which was the same day that I believe I created the vacuum leak!