87 B2 2.9 efi, misfires, lags with throttle

[CurtisP87]

I'm having some problems with my bronco, and cant for the life of me figure out whats going on...When i turn the key it fires right up, no problems, every time. When idling its obvious that its missing on a cylinder or two. As soon as i touch the throttle, the rpms drop, motor begins shaking violently, and it sounds like its missing on three or four cylinders. Earlier today I replaced distributor cap, rotor, plugs/wires, throttle position sensor, HP fuel pump, and the filter down the line from it. Air filter is good....

I tested fuel pressure, via the schrader valve in fuel lines....35 psi at idle, and 40 psi when on throttle, despite the rough idle. This makes me think my fuel delivery is just fine (i.e. ruling out a problem with the low pressure pump or its filter), so its got to be a timing or spark issue. The plugs i took out earlier were all in o.k. shape, slightly corroded, but wet and gooey, like the engines been running rich.

Ive been doing some reading, and it almost sounds like I could have a faulty TFI. However, everything Ive been reading seems to imply that the engine should perform fine when cold, and the problems arise when it warms up, and Im having these problems when cold, the engine isnt running well enough for me to leave it on long enough to get hot.

Like i said, Im totally stumped....Has anyone else ever had similar problems?
Thanks in advance for any help or opinions!!

 

[CurtisP87]

Bump

 

[Brownie Mobile]

I've had a similar problem, not to the letter but pretty close. The problem with mine was the tranny fluid was low, my throttle was lagging a lot and the engine seeemed to be running badly mines a 2.8 carbed but its worth a shot checking the fluid level because after i filled it properly( let it heat up to operating temp for 10 mins or so) it was fine and the sputtering in the engine subsided also adjusting the timing is something to look into make sure you read in the manual how to adjust it its not as simple as running it and looking at marks you have to unplug some electrical connections to get an accurate timing.

 

[adsm08]

The TFI has many many many modes of failure and half-operation. Working fine when cold and then cutting out at temp is just one. Check your spark quality. If it is crappy the TFI is the most likely suspect. On a vehicle as old as yours I would recommend replacing the TFI, stator, and coil as a set. I've seen only doing one of the three cause issues as the older components will draw too much power and burn up the new piece.

 

[sjr53]

Try a new MAP sensor. That fixed my 88 BII that acted similarly. I did get a lean code shortly before fixing it. I have 2 BII's so I was able to swap sensors around until it worked.

 

[CurtisP87]

Update: I changed the tfi, didn't help. When the new one was in, I turned the engine over. She started right up, and ran real nice for about 10 seconds, then died. Now it won't start at all without the spout plug disconnected (in which case it runs beautifully).

Completely stumped...

 

[Mike828]

Pretty sure 2.9 fuel rails have rust issues. I've taken mine off twice in the last year or so to find injectors plugged and rust in the gas that was in the rail.
Your symptoms are almost exactly the same as mine were and the first time I went all through the ignition too.
Something to think about....

 

[littlezell]

try the iac.... and egr valve..... unplug the vaccum line running to it plug off the line so you dont a have a vaccum leak...