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Thread: SVT is idling better with no MAF hooked up??? Reply to Thread
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Topic Review (Newest First)
02-06-2013 07:39 AM
Nyberg Just following your thread did you ever resolve your problem I am having the same issues with my sons svt
12-22-2012 05:17 PM
1turbofocus If you had a Vac leak you would have high idle

Tom
12-22-2012 04:23 PM
sweetnlo
Quote:
Originally Posted by whynotthinkwhynot View Post
Well with an SVT manifold you have lots of places where you can have vacuum leaks. There is a vacuum line diagram under the hood on the VECI (vehicle emissions control information) sticker. Most vacuum will come off of the throttle body, but a few come directly off of the intake manifold- like the PCV and brake booster. A rusty brake booster will cause a very annoying vacuum leak coupled with weak/hard brakes. A bad check valve- the 90 degree connector where the hose goes to the booster- will do the same thing.

Trace down each vacuum line using the VECI diagram to help you locate them. You should have about 5. The longest one will be the one that goes to the EVAP system. It should connect to the TB, then go to the purge valve, and from there to the carbon canister. That one won't be it unless it's not hooked up at all- or the purge valve is stuck open. I'd give a stuck purge valve a 10% likelihood. It's really uncommon. The most common issue is the PCV line, but I'm not sure where it connects on an SVT manifold- if there is one at all. Check your VECI, and then look for what is on there.

1Turbofocus is right, the MAF is not your problem, what's happening with the MAF is a result of another problem. Stop throwing parts at the car, and work from the cheapest fix up, or diagnose it properly. We can help you with diagnostics- one of which is listening for the hissing sound indicating a vacuum leak. The best way to figure that one out is to simply remove each line, inspect visually for dry rotting or damage, replace if needed, and re-install. I have stopped recommending starting fluid or WD40 sprayed around the inside of the engine compartment to help find vacuum leaks because of the dangers involved- and it's a subtle change in rpm that most people will miss. In the end you just have a lot of flammables in a confined space without much new information.
i only hear the hissing sound when i start up the car and then it stops.. Also, i dont have the o.e. hood from an svt and im having a hard time figuring out the lines. i need to find the pcv line..
12-22-2012 04:20 PM
sweetnlo
Quote:
Originally Posted by 1turbofocus View Post
He has a rich or lean condition and by unplugging the MAF it goes into the failed MAF tables
Wish I could help more but cannot do much with out a datalog

Before this have you changed ANYTHING even anything small ?

Tom
i am running reaally rich, just had to replace my o2 sensor again. what do i need to do to data log? i dont know what that is
12-22-2012 12:23 PM
whynotthinkwhynot Well with an SVT manifold you have lots of places where you can have vacuum leaks. There is a vacuum line diagram under the hood on the VECI (vehicle emissions control information) sticker. Most vacuum will come off of the throttle body, but a few come directly off of the intake manifold- like the PCV and brake booster. A rusty brake booster will cause a very annoying vacuum leak coupled with weak/hard brakes. A bad check valve- the 90 degree connector where the hose goes to the booster- will do the same thing.

Trace down each vacuum line using the VECI diagram to help you locate them. You should have about 5. The longest one will be the one that goes to the EVAP system. It should connect to the TB, then go to the purge valve, and from there to the carbon canister. That one won't be it unless it's not hooked up at all- or the purge valve is stuck open. I'd give a stuck purge valve a 10% likelihood. It's really uncommon. The most common issue is the PCV line, but I'm not sure where it connects on an SVT manifold- if there is one at all. Check your VECI, and then look for what is on there.

1Turbofocus is right, the MAF is not your problem, what's happening with the MAF is a result of another problem. Stop throwing parts at the car, and work from the cheapest fix up, or diagnose it properly. We can help you with diagnostics- one of which is listening for the hissing sound indicating a vacuum leak. The best way to figure that one out is to simply remove each line, inspect visually for dry rotting or damage, replace if needed, and re-install. I have stopped recommending starting fluid or WD40 sprayed around the inside of the engine compartment to help find vacuum leaks because of the dangers involved- and it's a subtle change in rpm that most people will miss. In the end you just have a lot of flammables in a confined space without much new information.
12-22-2012 12:02 PM
1turbofocus He has a rich or lean condition and by unplugging the MAF it goes into the failed MAF tables
Wish I could help more but cannot do much with out a datalog

Before this have you changed ANYTHING even anything small ?

Tom
12-22-2012 02:48 AM
sleepyboy
Quote:
Originally Posted by whynotthinkwhynot View Post
There's something else you're missing. Do you hear any loud hissing when the engine is idling? Do you have any way to data log? That's what 1TurboFocus needs to be able to help you diagnose this issue.

It's nagging the hell out of me because I've seen this before, but I can't remember what it was. Sorry Paul, I don't think it's the TPS. If it was, it would be drivable with or without the MAF unplugged.


Yea I don't think it was, I'll be honest was just making a quick suggestion.
12-22-2012 12:15 AM
sweetnlo no i dont have a way of data logging and im unfamiliar with what that even is.. Ive read alot about getting the svt tuned. Any info on this?
12-22-2012 12:13 AM
sweetnlo
Quote:
Originally Posted by whynotthinkwhynot View Post
There's something else you're missing. Do you hear any loud hissing when the engine is idling? Do you have any way to data log? That's what 1TurboFocus needs to be able to help you diagnose this issue.

It's nagging the hell out of me because I've seen this before, but I can't remember what it was. Sorry Paul, I don't think it's the TPS. If it was, it would be drivable with or without the MAF unplugged.
Im goin to check for vacuum leaks again. I feel like i have a vacuum hose crossed or something. I DO HEAR HISSING when i start up my car for a little while till the engine calms down. Do you happen to have pictures of vacuum lines/hoses? That would help me eliminate an easy fix. Also my car backfires alot when shifting.
12-22-2012 12:05 AM
whynotthinkwhynot There's something else you're missing. Do you hear any loud hissing when the engine is idling? Do you have any way to data log? That's what 1TurboFocus needs to be able to help you diagnose this issue.

It's nagging the hell out of me because I've seen this before, but I can't remember what it was. Sorry Paul, I don't think it's the TPS. If it was, it would be drivable with or without the MAF unplugged.
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