Vacum/idle?

akmud · #1 (**permalink**) 02-16-2004, 04:18 PM

I have a '95 Bronco with a 351W with speed density. I bored .030, new rv cam, gasket match. Ever since the rebuild I have had problems with the idle. I used a Snap-On scan tool to find any codes and found none. I thought I might have a vacum leak so I used propane, water, starter fluid and checked every vacum line with a hand held vacum pump and no vacum leak to be found. I put a vacum gauge on it and it tells me I have a vacum leak. Someone told me I may have got a to egressive cam for the computer for the speed density system to compensate for. Can someone clear this up for me? I don't have the cam info here at the house. It it is needed I will put it on next time.

87MarkVIILSC · #2 (**permalink**) 02-16-2004, 04:21 PM

with that hot cam you might need to add a bigger vacuum canister or even a vacuum pump off a diesel.

akmud · #3 (**permalink**) 02-16-2004, 04:34 PM

Which would be better the canister or the pump? A vacum pump off a dieseal? I have never heard of that!!!! Which one do I get it out of and is it a direct hook up?

fordeverpower · #4 (**permalink**) 02-16-2004, 05:52 PM

i thought rv cams are practically stock and if anything your engine should have more vaccum.

akmud · #5 (**permalink**) 02-16-2004, 06:58 PM

That's the problem I think the place I got the cam sent me the wrong one.

fordeverpower · #6 (**permalink**) 02-16-2004, 07:12 PM

call them and check your spec card again if you have it.

78fordman · #7 (**permalink**) 02-16-2004, 09:07 PM

You would know if you got that big of a cam. Usually when the cam is having vacume problems, it will lope at idle, atleast in my expiriences, but the efi might be compensating. That could be your idle problem too.

akmud · #8 (**permalink**) 02-16-2004, 09:43 PM

I did call and they told me that their computer listed the cam as the one I wanted.
I do have a slight "lope" and I do think that is what is causing my vacum problem.

jwtaylor · #9 (**permalink**) 02-17-2004, 08:48 AM

What is the lobe seperation of the camshaft?

beartracks · #10 (**permalink**) 02-17-2004, 10:21 AM

On some engines it's not uncommon to get a vacuum leak under the intake manifold.Check inital timing. What is the vacuum gauge doing? Does it run OK above idle?

akmud · #11 (**permalink**) 02-17-2004, 11:11 PM

The needle on the guage is towards the bottom of the guage. Like I said the guage says that its got a pretty bad vacum leake. The way the guage reads you would think that the leak would be easy to find.

akmud · #12 (**permalink**) 02-17-2004, 11:13 PM

sorry did not answer the whole question. Above idle it's better but I don't think it's where it needs to be.
Oh yeah, sorry for not paying attention to how I spell gauge.

rainbowATF · #13 (**permalink**) 02-18-2004, 01:33 PM

The actual vacuum reading at idle and the behavior of the needle; and at opening of throttle would be more helpful in diagnosing a problem.

akmud · #14 (**permalink**) 02-19-2004, 12:54 AM

I will get it this weekend and post it. dont forget about till then

DW2455 · #15 (**permalink**) 02-19-2004, 01:21 AM

it would help alot to know that actual vac. readings and the cam specs. but just for the record, there are very few after market cams that will run with speed density system with out causing problems. DW