Post Plenum Pull Problem

[pantera1683]

I just finished with my plenum pull, changed alternator, wires, and coils. Now I have a misfire and backfire through the exhaust that is getting progressively better. My idle goes between 1300 and 750 and I do have a slight vacuum leak at the fuel pressure regulator that I will address this afternoon. I am just worried about damaging the car and want to make sure that the vacuum leak is my problem. Any ideas?

[LGAFF]

Pulling any codes.....misfire could be vac leak or ign wire crossed, I would not drive it with the misfire....

[pantera1683]

I think the vacuum leak is worse than I thought, there is a loud howling whistle coming from underneath the plenum.

[bldavis11]

Double check, and then tripple check, the MAP sensor hose at the very rear of the plenum. Another vac leak source (that you swear is under the plenum and actually isn't) to check is the PCV valve hose on the driver's side towards the rear of the plenum. You might actually have to pull that hose to investigate for a crack/split in the rubber... very, very common.

Let us know.

[pantera1683]

Map, PCV, and all external hoses look good

[tomtom72]

I know there is one vac hose at the right side of the T/Body....it's off all by it's lonesome at the right side lower rear of the T/Body... a nipple that faces backwards on a 90 anyway(?). That one is easy to have come undone while you are reconnecting the DIS stuff.

:cheers:
Tom

[pantera1683]

Turns out I crossed #6 and #8 plug wires. It runs really well now. As for the loud hissing sound, turns out it's the LT1 alternator touching the plenum and causing a vibration. I will have to lift the plenum and clearance the alternator a bit with the grinder. As soon as I get my stock alternator rebuilt it goes back in.

Thanks to everyone for the help.:salute:

[tomtom72]

Good deal. I love repairs that don't cost anything.:cheers:

[bldavis11]

Glad it worked out with an easy fix.