Contour Enthusiasts Group Archives Forums General Troubleshooting low rpm bucking, all people reply w/ your thoughts

this problem dates back till last year. the car was out of commission for the last 3 months, as i was installing a new tranny.

the car hestiates/bucks/misfires at rpm's under 3000. im using 87 oct fuel, changed teh spark plugs 5 times usually helped but this last time it didnt. new spark plugs are 4 days old and i made sure not to over tighten them they are at the right torque specs. the wires have 4 months on them. as well as the ingition coil.

from reading the website on a similar problem, some one suggested carb cleaner and spray around the vaccuum lines to see if the car chokes. i did this yesterday, and the car didnt choke.


at high rpm the car seems to run and pull just fine. or it just cover ups the misfire. but the car seems to be running high and revs up pretty quicky after 3k. but its takes a long tiem for it to get to 3k.

so now the question is what can this thing be. its not the fuel filter or the fuel pump as the car would have a bad tiem at high rpm as well as low.


thank you very much, i welcome all responses as long as they dont hijack topic.

-walter


edit here is a topic i found that replicates my problem.(im not the only one)

http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=trouble&Number=291034&Forum=All_Forums&Words=misfire&Match=Entire%20Phrase&Searchpage=0&Limit=25&Old=allposts&Main=285441&Search=true

What year and which engine might help us to understand your problem.

On a V6 with manual trans, especially the SVT, there is sometime a little bucking or surge with closed throttle or nearly closed throttle in 4th or 5th gear at about 25 to 40 MPH.

On those it helps to confirm the condition of the plugs and wires and then clean the throttle body and injectors. Often cleaning the throttle body and injectors will make a big difference. If it persists, do the throttle hang fix described in the FAQ section. Sometimes this is caused by the PCM trying to lift the idle speed while you are coasting or nearly coasting. The throttle hang fix settles the idle down.

You may have other problems, but if it acts like I described, it is worth trying.

My SVT was bucking when I let off or cruised around 2600-3000 rpm. It seemed fined at higher rpm like you describe. The problem turned out to be the fuel pump. They swapped it under warranty.
My $.02

Cheers

i have a 96 duratec atx.

try testing your EGR valve and sensor. It is what fixed my car when it did the same thing ,,, that and new wires...

sistence but if they are the original set, it is just as easy to replace them. That fixed my missing problem.

Coil Pack

Mine jerks a little when i let off the gas , but its not close to being a serious problem "yet"

I had that same problem....... but mine was a fuel pump going bad...... when I was a 1/4 of a tank of less the car would hesitate at higher RPM's..... But no matter how much gas I had in the car the idle what jump by itself.... it would "hang" and then drop back to normal... I took out the fuel pump..." another bad design by FORD" and the screen for the pump on the bottom of the pump was sitting on the bottom of the gas tank.... I tried to put it back on it wouldn't go back on.... So, I bought a new pump and installed it and the hesitation went away... the throttle hang went away...

I figure the reason that the rpm's where reving up by themselves is that the computer was trying to compensate for the lack of fuel.... I took apart the pump and there was a lot of dirt and such in it... So, I guess the best way you can figure out your problem would be for you to get a fuel pressure check..... I don't see how jamming a copper pipe cap into a hose would fix the problem?????? I think it just masks the problem........ It may not be the fuel pump.... but maybe something else... anyway you loose power with that copper cap....