stall while coasting on neutral coming to a stop

[whitebroncoii87]

Hi, my 87 bronco ii drives for about 10 minutes and once warmed up the engine stalls out when the car comes to a stop in neutral. I put the gear in neutral (manual trans) to let the car coast the last bits before hitting the breaks to a standing stop. It stalls out while the car is coasting not while it's already stopped and idling. It doesn't stall out when it's idling or when the car is cold the first 10 minutes or so. Only when warm and after downshifting to 2 and then neutral to coast before applying the brakes. It dies while coasting before the brakes. Any ideas? And what is the correct vacuum reading should I see from the intake while the engine is warm and cold? Thank you!

 

[whitebroncoii87]

P.S. After the car stalls I turn the key, it would struggle to start, I had to pump the gas a lot to get it to start. After it started back up I notice the engine while idling would alternate between wobble and steady. It wobbles like it's about to die then I hear a vroom sound like the throttle opened up and the engine stops wobbling then the vroom dies and the engine is wobbling again, repeat. Also I notice a constant hissing sound, it's not from the intake because I checked all the vacuum ports. Intake reads about 15 on the gauge when the engine is cold, didn't get a chance to read it again when it was hot. Couldn't drive it home, left it on the street.. Need to figure something out to fetch it back..

 

[redhurricane]

You have a vacuum leak somewhere, start at the main vacuum tree on the intake and trace each line for the "hissing" sound you hear. You can use brake kleen (the flammable version) and spray around each of the vacuum connections. If the idle goes up when you spray a spot, you've located your leak(s).

 

[whitebroncoii87]

I see, all the vacuum port on the intake is plugged so I assumed no leaks, but I'll try brake kleen as you said when I go back to fetch my car later. Any idea what kind of vacuum reading I should get when it's warm and when it's cold? What about the air filter box, I have two small tubes on the topside that are connected and a larger tube on the back that's not connected, should it be connected or it's just for vent?

 

[enjr44]

If the engine is getting un-metered air from anyplace it is going to run like crap (that is why the first guess is always vacuum leak). The amount of air getting into the engine must be measured so the computer knows how much fuel to add to the mix.

 

[swynx]

my 4.0 used to die when i would iether run it hard and start coasting or downshift into 2nd then come to a stop it ended up being the fuel pressure regulator, if i was you i would pull it off and smell the line, if it smells like fuel... replace it.

 

[whitebroncoii87]

i replaced air charge temperature sensor and tfi same time and it seems not to stall now when its warm. its prob just the act sensor thats bad but ill leave it be

i have oil sitting around the distributor hold down bolt, maybe o ring worn, anybody ever just replaced o ring or must replace whole distributor?