Trouble With Rebuild

Bronce George · Jun 29, 2004

Hey guys&gals heres the question:

89 Bronco 351w/c6

Just instaLled my rebuilt motor hooked up(i belive) everything and the motor almost fails to crank starts to stumble (runs really rough) then it jumps to sumpin like 3000rpm(smooth) scarein the hell outa me. It does this everytine i try to start it I dont let it run long liek that maybe 3or4 sec but i cant get to run rite Ive set everything rite(i hope) and iam about to pull my already thining hair out over this anybody got any ideas?

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BigNasty · Jun 29, 2004

Sounds to me like the carb has its throttle linkage opened a bit and is just running fast.
Can't run without fuel and air

so something is making it happen, whether its a bound/bent/sticky or maladjusted linkage or if FI, all the above and possibly the ECM or a sensor.
I had one that stumbled, started and sputtered before racing to around 3grand before dying but with yours continuing to run, I doubt a vacuum leak is to blame. (289 with a Holley intake and carb.. but the gasket was shy about 1/4" on the back side)

Similar can happen to FI also.
Bent and binding linkage on an 86 cav Z24 tried to take me to the next plane of existance a few years back

hawk2100n · Jun 30, 2004

check your timing, sounds like it is off pretty far but not that far. at least it runs. if it is running real rough at idle and then surges to high rpm, sounds like a lot of unburnt fuel is collecting in the cylinders and then it starts to burn off.

Bronce George · Jul 1, 2004

yah but see i dont let it run wth the rpms shooting up that high on my rebuild kinda scares me its practilly never ran for no more than 5or6 secs since i set the timeing. Because of the spike in rpms. Arggh i'll just let run for a little whille maybe it'll flatten out after it warms upa lil. :unsure:

Bronce George · Jul 1, 2004

lol "wheres my hammer" this dam truck has driven me and my brother nutts I drive a 90 eddie bauer his is the 89 xlt wth the trouble. Its been a patio queen for a month now and its my patio to boot too.

Broncoholics · Jul 1, 2004

Well, we can rule out the distributor not being 180 out if its running smooth @ 3000 rpm's. I bet its something to do with the auto choke dumping too much gas, starts to flood (runs bad) then revs up (runs better) as it burns off. I'd call Ford and talk to one of their mechanics. They will tell you exactly whats going in just a few minutes. Did you cleanthe corbon out of the throttle body? Could be a pice of crap stuck in there. Does it ever idle? Also did you have the injectors cleaned? Look for a vacume leak, spray some carb cleaner around the engine and see if it revs up. Then find where the leak is. Other thanthat maybe its the computer sending false singals. I'm out of ideas. Good luck! b-(

Broncoholics · Jul 1, 2004

Forgot to mention if you have vacume advance on the distributor it will throw off the timming when running if its bad. You are suposed to take off the vacume advance when setting the timming so when its plugged in it advances. Not sure if you have this on yours but if so suck on the hose going to the vacume advance and hold your tounge on the end of the hose. If your tounge sticks to it you know you have good vacume and its working. Or a vacume gage will work.

FLYFSHIN · Jul 1, 2004

It's not a bad thing to let your engine run a little high at a rebuild. When I have a new motor done, I always stuck the throttle open at around 2500 for no less than 5 hours. This ensures that the crank and cam pick up oil and throw it around inside the motor before you subject it to load. It takes alot less gas and makes alot less heat than driving it around town slowly for two weeks.

broncoxlt89 · Jul 3, 2004

ok here is the deal .... i Cn crank it up with stArter fluid ... then it runs at 3000 rpm , but w/out the starter fluid it wont crank it'll fire on intial fire but wont turn over (I found the computer ... thanks a lot ford in a very screwed up plaCE) some times it'll fire after a while but only a burp... still workin on it

here what was done ... the block wasa bored out .30 over notmuch else a large cam the size i forgot the machnist doesn't recall.... i was wondering if the stationary postion has caused a bad set on the truck's computer miss fires w/ the distributor or is the fuel injector not spraying ... the injectors have been cleaned i'll kee wrking and checking bak thanks guys [-o<