Fixed: V6 Cutting out at cruising speeds?

Re: V6 Cutting out at cruising speeds?

Sparky, don't take this personally, but new parts can be bad/go bad ...
I wish I had a dollar for every do-it-yourself tune-up Jeep that found it's way to the shop.....
I had to listen as the owners would swear that it couldn't be this or that, and that they had replaced everything already...
for instance, very easy to crack the porcelain of the plug when tightening the spark plug; some folks just install them without checking the gap....
I always took that into consideration, but the truth is, you can't overlook anything....when diagnosing, you have to start from scratch....

 

Re: V6 Cutting out at cruising speeds?

Sparky, I have had this problem when the valve springs were too soft. This can happen with aged springs that have not even run.
The engine can run with out a load and rev. but lacks the torque to keep running under a load. Sometimes called 'floating valves'. The valves do not close fast enough to provide higher rpm torque under a load. Under the right load and rpm the engine will stall due a fast drop in manifold vacume because just a little bit of cylinder gases are leaking back into the intake manifold out of the four stroke cycle. This is because the valves (intake esp and also exhaust) are not closing fast enough and long enough. Lack of vacuum with an aspirated engine, means that the engine does not get enough air and fuel--- and then it stalls. This lack of manifold vacume also affects the vacuum dist timing as well-- retarding the timing, causing more cylinder gas to leak into the intake and futher making the situation worst. Put a vacuum gadge on the engine that you can read under different driving conditions and see of you have a rapid drop in vacume in third gear.

 

Re: V6 Cutting out at cruising speeds?


banging head against wall
good idea, teeing in the vac gauge
I shoulda thought of that....

 

Re: V6 Cutting out at cruising speeds?

Welcome SRedinger! I see that is your first post. Maybe the best first post I have ever seen here.

 

Re: V6 Cutting out at cruising speeds?

I had the same thing happen to me. I would get to a certain speed and the darn thing would just shut down. I changed the usual culprits, fuel filter, fuel pump etc....I finally tracked it down to something very simple. When I was at the Rubicon I thought I turned the idle on the carb up for the altitude. Turned out I adjusted the choke screw a little bit. When I would get to a certain speed the wind would catch the choke and shut completely thus not enough air and way too much fuel. Easy enough fix, I just backed out the adjustment screw and it has never done it again.

Just my $.02!

 

Re: V6 Cutting out at cruising speeds?

would advise checking engine vac before proceding with any tear down.
the vac readings will confirm/deny most valve train/timing issues.
should be able to get at FLAPS.
and there should be several plugged, unused ports at the rear of the intake manifold to hook the vac gauge up to

 

Re: V6 Cutting out at cruising speeds?

this might help

 

Re: V6 Cutting out at cruising speeds?

Any chance you have vacuum-activated wipers? That way you could run w/ 'em on and see if they behave out of the ordinary when the engine probs resurface.