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Old 4-27-12, 5:27   #1 (permalink)
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Problem with MX6 Help please

Ok guys, I need a bit of help with an issue with my MX6 2.2T

The car is appearing to (randomly and inconsistantly) be hitting some kind of fuel/ignition cut.

No apparent boost/vacuum leaks
VAF has been removed and cleaned, all "appears" to be in fine working order
Car is not overboosting (only 7-8psi)
Happens at all rev ranges, but moreso on light throttle taking off, or after a quick accel, then back off, hit the throttle again and it hits a wall for 1-2 seconds
Fresh plugs, fuel, and filters went into the car today.
Throttle body was cleaned ... still happens
Idles like a PIG! .... accessing the Idle screw on the VAF does Nothing to the idle.

Any ideas, common faults?

Cheers

Damien
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Old 4-27-12, 6:24   #2 (permalink)

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you have a boost leak somewhere or your VAF is screwed.

Pressurize your intake post turbo and check for escaping air. Common places are intercooler endtakes and the bottom side of the throttle body boot or cracks on the end of it.

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Old 4-27-12, 7:04   #3 (permalink)
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Will check that.

Throttle body boot is near new and not cracked, one of the first things I checked when cleaning the throttle body today.

Do you mean the actual endtanks? ... of where the rubber joins onto the inlet/outlet?

My local forum is suggesting fuel pump/fuel pressure?

The VAF all appears fine, and has a "stopper" placed so that the VAF cannot reach the "boost cut" threshold
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Old 4-27-12, 9:06   #4 (permalink)
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Also, check for massive intake manifold leaks by spraying fuel ijector cleaner around gaskets. I know you mentioned that there are no OBVIOUS leaks but what about those you cannot see/hear?
My MX hit "the wall" with less than 12 psi boost. With a reprogrammed chip, this no longer happens, although I believe my new "wall" is a restrictive exhaust.

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Old 4-27-12, 9:17   #5 (permalink)
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Thanks Automan I'll check again the pipes/hoses tomorrow.

My "wall" is very hard and abrupt, exactly like boost/fuel cut
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Old 4-27-12, 11:40   #6 (permalink)

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Yes, the endtanks can and will crack on occasion. I would pick up an unmodified VAF as well to test it. NA and turbo VAFs are the same.

Also, when hitting the cut, do you hear a beep?

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Old 4-27-12, 14:41   #7 (permalink)

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Quote:
Originally Posted by Zach View Post
Yes, the endtanks can and will crack on occasion. I would pick up an unmodified VAF as well to test it. NA and turbo VAFs are the same.

Also, when hitting the cut, do you hear a beep?
scariest moment of my high school driving was hitting fuel cut for the first time before i knew what it was. i'd already wrecked my fist car twice and thought i'd killed the motor on my 2nd car

as for the fuel cut, pretty much what everyone has said. if you have a boost controller, that's your problem.

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Old 4-27-12, 18:33   #8 (permalink)
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No boost controller, no mods at all.

Also no beep when this "cut" hits
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Old 4-27-12, 18:36   #9 (permalink)

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then pressure test your system and get a different VAF to test with.

Also, how long ago have spark plugs and wires been done? What gap are you running?

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Old 4-27-12, 18:59   #10 (permalink)
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Brand new plugs went in yesterday, not sure on the gap tho.
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Old 4-27-12, 19:35   #11 (permalink)
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Reason I dont see it as a boost/vacuum leak is that its inconsistant. .. Can happily drive and boost the hell out of it for 5 mins, then all of a sudden it hits
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Old 4-28-12, 3:30   #12 (permalink)
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all sorted, ... fuel pump
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Old 7-12-12, 16:26   #13 (permalink)
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how did you figure out it was the fuel pump?
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