Idle probelm after MP install

joedpl

joedpl

Member
I finally found the time this week to install the MP that I bought. When I first started the truck up it ran just as good as the eaton was on it. I drove it around for about 5 miles going easy on it just so I could make sure everything was installed correctly. I did 1 WOT run and now the truck won't idle for crap (300-1000rpm). Here's the weird thing, above 1000rpm, it runs great and very smooth but as soon as it drops below 1000....****. At idle my wideband will be pegged lean (16.0) and I will be pulling only 10 in HG of vac but if I rev it up a little bit it will go to 20 in HG of vac.

I've checked all the vac lines that I had to unplug during the install and they are all good and tight. I've check a couple other things that might be causing the problem but none of them did anything to change it.
1-Replaced IAC valve with a known good valve, started truck, no change, reinstalled.
2-Bypassed oil seperator incase there was a vac leak there, started truck, no change, reinstalled.
3-Uploaded predator canned tune to eliminate any potential problem with custom tune, started truck, no change, reinstalled tune.
4-Bypassed MAFIA in case that had gone bad, started truck, no change, reinstalled.
5-Unplugged battery for 2 minutes to let the computer reset, no change.

I wouldn't think that my mass air flow meter would be bad because then the truck would run like crap all the time and not just below 1000rpm (correct me if I'm wrong)

I plan on changing the front O2 sensors this weekend but I don't think thats going to change anything, but thats just 1 more thing I can eliminate.

If anyone has any ideas please throw them my way, once I get the problem figured out then I'll post the install pics.
 
Did you check where the vac hose for the PCV connects to the lower intake? What you describe is either a vaccum leak or a bad EGR controller. You can eliminate the EGR controller by disconnecting the vaccum hose that hooks to the EGR valve and plugging the hose. If that doesn't fix it I bet that you blew a hose off somewhere.
 
Dr. Matt said:
Did you check where the vac hose for the PCV connects to the lower intake? What you describe is either a vaccum leak or a bad EGR controller. You can eliminate the EGR controller by disconnecting the vaccum hose that hooks to the EGR valve and plugging the hose. If that doesn't fix it I bet that you blew a hose off somewhere.
Click to expand...

I'll check out the hose beneath the lower intake manifold, I'm willing to try anything at this point. It can't be anything EGR related since its all been deleted.
 
I never had an issue like that...well after I remembered to hook my catch can vac hose back up. I removed my EGR though.
 
My truck idles the same with the KB as it did with the MP and that was the same as the P.E. No "learning" to idle with a new blower.
 
Have you checked your spark plugs? Since the Magnum is supposed to move more air, you might have damaged a few plugs during your WOT run.
 
My2004FordSVT said:
Have you checked your spark plugs? Since the Magnum is supposed to move more air, you might have damaged a few plugs during your WOT run.
Click to expand...

I plan on pulling the plugs when it warms up this weekend, no point on going out in the garage when its 45 degrees when in 2 days it'll be 70. I'm also going to try and get my arm between the firewall and lower intake manifold to check and see if the lower pcv hose blew off somehow.
 
Zimmer said:
Come on 45* and in a garage:headscratch: lol
Click to expand...

Yeah, I know, I don't like to be cold when I'm working on the truck

I'll do a little update over here since I didn't keep up with this thread. I pulled the s/c off to check the rubber 90 degree elbow on the back of the lower intake manifold, it didn't come completely off the fitting but more like exploded off, meaning that 1/2 of the rubber was still on the connector and the other 1/2 was still on the PCV line. I replace the entire PCV system and reinstalled everything only to start the truck back up and have no difference in the way it was running. I took some time to look over everything again but at this point I was more frustrated than anything so I shut the hood and didn't open it again for another week. Here the conclusion to my problem which I originally posted over on NHTOC......

Finally had some time to work on the truck today and decided to hook up my fog machine to the truck to check for any other vac leaks that I hadn't been able to locate yet, here is how it looked hooked up:

View attachment 21888

I turned on the fog machine and it stated pouring out underneath the plenum:

View attachment 21889

So I pulled the plenum off and I found this:

View attachment 21890

I have no idea how this happened and definately wasn't expecting it since I had replaced the TB gasket, Plenum gasket and EGR gasket when I installed the MP. So I ordered a new Plenum gasket and I noticed that when installed there was a section of the gasket pertruded into the intake tract and I've come to the conclusion that there was enough gasket that it somehow was able to get sucked in and cause the idling problems that I've been experiencing. I'm sort of kicking myself for not checking the simple things like this gasket and instead removing the s/c assembly 3 times, I would have saved alot of time had I completely disassembled everything (instead of removing the s/c, plenum and tb as 1 piece.) It also leads me to believe that the 90 degree elbow on the back of the manifold had been on its way out for some time and it just so happened to go when the plenum gasket also went. Now that a new gasket is installed the truck runs great and the vac reading on my boost gauge is back to where it should be. I want to say thank you to everyone that helped me out diagnosing this problem and it feels great to have a fully functional truck again. I'm waiting for it to get back into the 60's before I do any WOT runs but I am curious as to what it'll produce now that everything is sealed up properly.....
 
Last edited:
Just FYI, when I had a MP with a C&L plenum I had to notch the blower to get the front of the plenum to sit flush against the blower case. I posted about this back then and others with the same parts did not have the issue. If that gasket goes out again you might check to see if the plenum sits flush without hitting the front of the blower case.

Here are some pics of what I had to do to make it clear. You can see by the pics of the plenum installed that without notching the blower snout that there is no way my plenum could have sealed to the case.

newunsorted076.jpg


newunsorted078.jpg
 
Charles sent the snouts out with a notch cut out in the upper left corner so that the plenum would clear but I'll double check to make sure that the notch is enough so the plenum can clear.
 
You must log in or register to reply here.
Back
Top