Thread: Odd vacuum leak?

Just installed my IC and I'm having a weird problem. Watching my boost gauge, I start the car and the gauge shows around ~10inHg, after a few seconds it will pull down to ~20inHg (normal). It will continue to do this until the car gets warm, take it for a drive and at stops and off the gas its pulling ~20inHg, on some occasions it will jump up to 10inHg while at a stop but rarely. This isn't a slow transition either its a jump in inHg like a switch is being flipped or something is cycling if that makes sense. Car idles fine, I've checked all the vacuum lines and replaced a bunch. I just can't figure out why it is jumping back and forth. I pulled the IC today and resealed just to make sure, but no difference. Anyone else seen this?

No i haven't, I have to buy some I'm out. But if I have a vacuum leak it should always be there right? Not coming and going like its doing? Right?

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Originally Posted by BillBoost37

Does the odd usage of vacuum coincide with you using the brakes? Vaccum assisted brakes..

No, the brakes have no effect on it. If this means anything while the gauge is showing 10inHg if i crack the throttle plate slightly the gauge drops to 20inHg then continues to rise as i give it more gas, like it should. I'll try to get a video of it later.

This morning on the way to work it through a P0171 code. So I guess I need to continue my vacuum leak search.

Originally Posted by BillBoost37

Does the odd usage of vacuum coincide with you using the brakes? Vaccum assisted brakes..

Ha, stalling the car by pumping the brakes.

My ic leaked with garleaks, didnt respond to brake clean. Replaced with rtv and the vac was gone.

Yes, i do work for brool story co.

I removed the gaskets and used RTV, but still getting the same results. I've done a visual inspections of all the hoses and all look decent. I'm trying the carb cleaner tonight.

Finally got back around to the leak search. I started at the "T" under the snout and started capping the vac lines and watching the vacuum gauge. I got all the way around to the MAP sensor, pulled the line, capped it and the vacuum dropped to 20inHg (normal). Plug the MAP back up and the vacuum leak is back (10inHg), so my current assumption is the MAP sensor is causing the leak. I'm getting a replacement today unless someone has any other input? BillBoost37 or matt5112 ever seen a MAP sensor cause a vacuum leak?

Anybody have any idea why capping the line to my MAP sensor would correct my vacuum leak issue? I tried a new MAP sensor and the leak still shows up when I connect the vac line. Anybody?

that doesnt make much sense.

Where in the line to the map are you capping it?

I pull the hose directly from the MAP and put a cap over the line end. Gauge pulls down to 20inHg, plug line back to MAP gauge goes to 10inHg. Tried a used MAP, same results, bought a new one AutoZone same results. I'm stumped.

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Are you able to see what the map is reporting?

Nope, what do I need to be able to view it? Dealer scan tool?

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A scan tool that can show live data.

What does the rubber connector look like that you are connecting to the MAP. You could try a zip tie on the rubber connector