Intermittent 0 Vac Reading

[Knox Joe]

So this is weird. Every now and again I'll start the car and the boost gauge will stay at zero. No vac and no boost.

The BOV stays open a long time and I get a super long turkey. It almost dies at idle and the rpms surge.

After I get going though, and get on it a bit, it seems to get back to normal.


I am so confused.(boom07)

I checked the vac lines, and everything seems fine. I've replaced all my clamps with t-bolts so it's not pressure loss. I'm lost.

[mp5_tunerx]

hmmm...mine idles at 100 then bounces back up...that my problem sorry to hijack thread but i think we might have the same problem

[Knox Joe]

No mine idles fine normally, just when the boost gauge zero's out it starts running weird.

Morning BUMPAGE!!!

Someone help me before I spend lot's of money bringing it to one of the local SUPA TOONERS.

[Brian MP5T]

There has to be a problem with the guage. If your car was actually at zero, it would bounce off the rev limiter like it was at WOT.

[Knox Joe]

There has to be a problem with the guage. If your car was actually at zero, it would bounce off the rev limiter like it was at WOT.
That's what my mechanic said. He also said it could be just from MAF.

Would that cause the car to run funny though?

Cause when it does it the car acts weird.

BTW it is tapped at the same place the AFC is, so maybe that is having an affect on how it runs when this happens?

[Brian MP5T]

MAF?

An electronic boost?...

If it is, then it's your boost, and it would be a MAP snesor not MAF

[Knox Joe]

MAF?

An electronic boost?...

If it is, then it's your boost, and it would be a MAP snesor not MAF

no mechanical. He was saying MAF vehicles are weird, and that they run funny.

I'm starting to think it's a bad toon (supermap, with all my mods prolly not too great)on the AFC because I just drove it the gauge went to zero, and it drove fine.

so I'm gonna replace the gauge next week, and I'm probably going to ditch he AFC for a Unichip as well.

[terbow]

if its running wierd when it hits zero thats probably not the gauge. if it was just the gauge, the car wouldnt run wierd.

I have the same amount of mods as you and my afc runs just fine, so its capable. Did you try reloading the map? Hows the wideband look when you hit the stumble? Hows the wideband look when going into boost etc, etc?

based on the bov issue and the super long turkey, it sounds like something is affecting the vac really bad, not the tune. how are ur vac lines run (source, t'd, etc)?

[Brian MP5T]

Or even there could be a leak in the wastegate or BOV that is causing it. You should be able to hear a vac leak that big when the engine is running.

[terbow]

indeed.

[Knox Joe]

No, there's no leaking sound.

I blew into the wastegate and it's fine.

I drove it again this morning, and the gauge went to zero and it ran fine.

Being so intermittent I'd say it's gotta be the vac lines.

[Knox Joe]

if its running wierd when it hits zero thats probably not the gauge. if it was just the gauge, the car wouldnt run wierd.

I have the same amount of mods as you and my afc runs just fine, so its capable. Did you try reloading the map? Hows the wideband look when you hit the stumble? Hows the wideband look when going into boost etc, etc?

based on the bov issue and the super long turkey, it sounds like something is affecting the vac really bad, not the tune. how are ur vac lines run (source, t'd, etc)?

I can't reload the map, I have a Mac.

The wideband is at 12-13 going into boost then it goes rich to 10-11 as I get on it more.

It seems like the longer I stay in boost the weirder it gets. It starts to slightly stumble.

[Brian MP5T]

Drive conservatively until this is resolved..

Wierd A/F can lead to long evenings under your car and an empty wallet.

[Knox Joe]

Drive conservatively until this is resolved..

Wierd A/F can lead to long evenings under your car and an empty wallet.

It's not my daily driver, so I'm gonna bring it to the shop next week and have them go through it.

I'll go ahead and get it tuned on a dyno so we can work out all the bugs. I'd rather spend a few hundred now getting it straight, than possibly buying a new motor.