Hey all, I could use some expert assistance here.

I have a 2004 MCS with 110K miles. Just had a ton of maintenance that I had to do and got the car back together and there are major problems. The first round of repairs went fine. New clutch and flywheel, new Control Arm bushings, Cranks sensor position O-Ring, and Oil filter housing gasket.

The 2nd round wasn't quite so smooth. I installed a new serpentine belt, and while I was in there added a new Alta 15% reduction pulley. Then replaced the valve cover gasket. I got it all put back together and started up it seemed fine. So I took it for a drive. Within a mile it started running horribly, at idle pulsing from 2K to 3K rpm and then drops to under 1K misfires and sputters, then repeats the cycle. And the brakes were super hard to stop. If I kill the ignition and start again it starts up with a high rev right up front then revs between and starts the cycle. I got it back in the garage and noticed that even at idle the exhaust manifold is GLOWING hot.

Its throwing the following codes:

P1109 - Manifold air pressure too high in deceleration
P1237 - Secondary Upstream Manifold Air Pressure Sensor Low Input
P1242 - Secondary Upstream Manifold Air Pressure Sensor Too High in Deceleration
P0300 - Random/Multiple Cylinder Misfire Detected
P0107 - Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

So like most people the first thing I think of is a vacuum leak. I have chased down every vacuum hose I can find. I started at the brake booster since I know its not getting vacuum (the booster wasn't working). Traced that to the supercharger inlet tube and it all looks fine. Ive tried a stethoscope I can't find this leak.

Any suggestions on methods to hunt this down would be greatly appreciated.

D.J.

 

Are the intercooler boots seated correctly? Mine was cracked on the driver side, car was running like crap and lean enough to make the exhaust manifold glow red. It does sounds like a vacuum leak.

 

Did you ever figure out the answer here? I have a similar problem I just posted about before finding your thread. I'd replaced the valve cover gasket, buttoned it all back up and got symptoms just like yours.

I'm going to check my intercooler boots...

 

Slightly embarrassed, but all it was was a improperly seated intercooler boot. Fixed that and it works like a champ.

 

Was going to suggest the same ...intercooler boots. One of mine developed a tear in it and car ran exactly the same. Glad you figured it out.