TruckStang

For the tired/worn motor or with a radical cam...that's not this car. I just swapped my engine for a 5.4 a few months ago, it has maybe 5000 miles on it. As for the cam, I only have a stage one, but it was already accounted for with my first dyno tune. I have clamps around the vacuum lines that aren't srewed into the tb and plenum. I'm really running out of ideas. I tried the sensors, checked and rechecked the vacuum lines, tried the ether, again...rechecked the vacuum lines, tightened all of the bolts, checked the gaskets. I just don't know anymore. I'm really considering the dyno tune, but like i said before, I don't want to waste the money until I am absolutely sure that's the only thing I can do.

Poobs

Well, it is not unusual for a car's idle to go lumpy when the carburetor is too large. This is more so when a non stock cam is added. You basically went to a bigger carb.

Lets try some home brewed logic.

A) The 75mm Tb caused the rough problem entirely. This would mean that anybody with a 75mm TB will have the same problem.

B) The 75mm Tb combined with the cam and maybe the condition of the engine causes the rough idle problem.

C) The instalation of the TB left something misadjusted, loose or otherwise created a leak etc.

D) The problem is actually something else that just hapend to take place when the TB was installed.

What I would do :

Replace the TB going back to the previous one.

Check the vacum while the engine is cranking and running.

Check the compression.

If the above tests come out ok then you have engine controls to check out.

2 low 4 you

Sounds like a vacuum line is loss or off and make sure that the intake is sitting all the way down. My buddy got a bad intake and it didn't sit right and did almost the same thing.

lizzyfan

Ford racing 75mm? No such item.

TruckStang

My fault, It is a a bbk. I read the listing wrong when I was buying it.

Poobs

How this this turn out ?

TruckStang

There was a computer error, so I ended up putting a diablo chip on it to fix everything.

Poobs

Great !!!

TruckStang

Thanks for checking back with me though. I really appreciated all of the help.

footpedal

im curious, you think it was just a coiencidence that when replacing the TB the computor showed a error? I wonder did you still have the battery hooked up when you did the work? or did you notice that the car had a little rough idle before the replacement and the new TB just brought it about more,,, i know you already have fixed the problem, but i was curious as to what you may have noticed.