sudden change in idle vacuum after repaint...(long!)
 

So my reman has ~8000 miles on it. Everything stock but for reliabilities. Pass fender got hit by... well... someone, and I just got the car back last night. Looks fairly ok, just not in any way perfect. Not the point of this thread, though...

When I started it up, it started right up. No stumbling (didn't have any problems before it went in for the repaint), but the idle sounded weird. I know that seems strange. It sounded... strained? Anyway, it's idling a little lower than before I dropped it off. Typically, it runs 750 right on the money, unless you give it an electrical load, whence it shift to 850, right on the money. Just like it is supposed to. When I started it last night and got it warmed, it idles at 600, bumping to 700 with load. Here's the weird thing: idle vacuum was 13 inches. Since I started the new motor, it has run 17 inches of vacuum at idle. So idle speed is ok, but the vacuum is not. So I of course had to drive it the 5 miles home. By the time I had it idling in the garage, the vacuum was at 15 inches. Hmmm...

As an interesting experiment, I pulled the BOV vacuum line right next to the boost gauge line, at the UIM. Predictably, the idle went up for a few seconds, then came right back down to the 700 or so (lights on). Just sat there idling with the little hiss from the manufactured leak. I went around and checked the boost gauge: 15 inches of vacuum. More Hmm...

So the ECU is compensating for the increased air flow and lean idle by changing the idle speed control solenoid, fuel injected, and probably timing for all I know, just like it's supposed to. Placing the vacuum line back on, the idle drops a bit, then recovers as the ECU adjusts. OK.... hmmm...

SO my question (finally!!) is this: Should I suspect sudden vacuum leak caused by body shop? OR, is it possible they started it to move it a few times, it got real close to flooding, and the rotor seals are having a hard time getting back into "shape". This would reduce compression, I would think, and therefore drop the vacuum at idle. That the value changed over a driving cycle makes me think this is the deal, and I shouldn't worry. But I wanted to ask those who'd gone through a flooding situation if they'd noticed the vacuum at a different point once they got it restarted? I looked at all the vacuum lines I could get at, they are all where I put 'em at rebuild time, so.. hmmm...

As an aside, I know overall vacuum readings are NOT a good diagnostic of engine health on our engines, if for no other reason than the above stated ECU fumblings. But a 4 inch change after not so minor body work raises red flags... no more hmmm's :)

Bueller... Bueller.... Bueller...

Did you check your odomoeter before you dropped it off ? Think about it if you worked at an auto body shop and someone dropped off an FD or a TII could you resist ?! If you didnt have one already ofcourse...

True dat.

so true!

then again, they could have just taken off the cables to the insurment pannel and reved the crap out of it...

When I had my car in the shop for total repaint, I fixed it so boost could not go over WG spring default, and set the rev limit to 4K, love the PFC!

Mileage was fine. Obviously, they could have revved the hell out of it and all that, but lets give them the benefit of the doubt just for kicks... Let me ask this, then, the other question was not covered. Is there a way to defeat the ECU correcting for vacuum leak? Like a jumper position on the diagnostics box?

i would pull the spark plugs and check them.

Update (like 'yall care!): After sitting for a couple days, the vacuum will now pull to 17 most of the time at idle. Every now and then it will slip up to 15. Quick blip of the throttle will get it back down to 17. So it's the ISC playing around with the mixture. More later if it warrants...