Vac leak?

[FLSHBCK]

Just rebuilt the engine in my GTP and trying to get it back on the road. I've sorted through a number of problems from putting it back together and am (I hope) getting close to being done with it.

During the rebuild, I replaced the cam sensor, crank sensor, and the timing set, so I took it for a CASE learn this morning and was unable to do it. Falls on its face typically around 2500 - 3500 RPM and can't get to the target RPM for the CASE learn.

Scanner indicated miss on #5 and to a slightly lesser extent #3 at those RPMs. Idle is fine. Also stumbles and misses under load like starting from a dead stop - I was hoping the CASE learn would help.

Buddy and I just went out to take a look in the parking lot at work and what we noticed was a whistling sound when it starts to stumble... says vac leak to me.

Anybody have any suggestions on how to hunt this down?

Oh, almost forgot... threw a P0420 Catalyst System Efficiency Below Threshold (Bank 1) on the way in this morning, but not sure if that's cause, effect, or not related.

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[02BlueGT]

If your running the stock cat, it may have clogged up, it is common on these cars for the substrate inside to become loose, and the engine normally can't function under load, and won't go over 2500 - 3500 RPM's..... I'd look into that judging by your symptoms and DTC

 

[bikrboy128]

If your running the stock cat, it may have clogged up, it is common on these cars for the substrate inside to become loose, and the engine normally can't function under load, and won't go over 2500 - 3500 RPM's..... I'd look into that judging by your symptoms and DTC

disconnect the downpipe from the exhaust manifold and try it again. it will be very loud, but just might work.
as for the vac leak, i would suggest picking up a can of brake parts cleaner and spraying around in the engine bay (near vac ports, on vac lines, near gaskets, etc etc). if the idle speed changes when you spray a certain part that is where the vac leak is.

 

[FLSHBCK]

OK... finally got back to it.

Right after I posted this, I ended up having to have gallbladder surgery, so I was out of comission for a couple of weeks.

Over the weekend, I decided to bite the bullet and pulled the LIM off and redid the gasket. Seems to have helped with the whistle but still cant hit enough RPMs for a CASE learn.

Only code it's throwing now is random misfire (don't recall # off the top)

I took it to a local Goodyear (that seems to have a clue) for the CASE learn because I didn't want to try to get it all the way to Mundelein with the way it was running. He said it acted like the cat was clogged without it throwing the cat code or me mentioning it.

Any possible negative consequences to trying to run it without cat (or in this case everything from the manifold back) other than annoying my neighbors? I was thinking just to try it out (like bikrboy128 said) to see if it helps driveability before I go spend a couple of hundred on a new cat...

Thanks for the responses

 

[RebelGTP]

get a ZZP catless DP...

 

[FLSHBCK]

Pulled the DP off and the cat is indeed plugged. Bit the bullet and ordered a bolt-in catted DP from ZZP.

Thanks for the responses! Hopefully this finishes it up...

 

[FLSHBCK]

got it put back together tonight - what a difference! Don't think it's ever run this well.

CASE learn hopefully tomorrow...

 

[Yaj Yak]

whos helpin you with that..