Ok, I've searched for days, convinced that someone else has had this problem, but to no avail.

When ever the boost preasure turns positive, the car feels like its hitting fuel cut; it bogs down and hesitates terribly. Before my rebuild and rats nest removal, this was not a problem.

Things I done/checked:
Replaced all vacume hoses on the block
regounded preasure sencsor
tried with FCD unplugged
checked all intercooler conections
added a restrictor pill ( I just cut a small piece of a 1/8 vacume tee and shoved it in there, how small should this opening be?)

I'm out of ideas now. Maybe the waste gate line being capped, instead of going to the stock Boost controler?

 

Also the TPS is functioning perfectly.

 

Sounds like a boost leak to me, especially if it runs ok without boost. I would double check all the vacuum lines again. Also, building a boost leak tester can help narrow down a leak.

 

Boost leak..

 

mine did this the other day. it was running real lean..??? I let it sit for a couple days and now it drives right. check your compression. Mine did this after it knocked on the freeway.

 

Possible boost leak sources would be where?

I can think of the intercooler,intake, BOV, and all related piping. Anyother places I should check?

Wouldn't a boost leak also be a vacume leak when not at positive preasure?

 

Still no dice. I examined all the piping on the intercooler, all vacume tubing on the turbo, and pretty much everthing that sees preasure. It still does hesitates very badly when ANY positive preasure come on. It could be .1 pounds or 6 pounds, same effect. Any other places to check?

S5 Turbo, emissions removed, Rb exaust, SP, S-Afc 2, cleaned injectors, hks intake

 

I would also say from my experience that it could be a boost leak, that is not a vacuum leak. If you have an air compressor, remove your TID and fabricate a coupler for the turbo's compressor inlet, that leads to a regulator and your air hose. With the room very quiet, slowly raise pressure with your regulator, and listen for any escaping air. It's normal for a little air to escape the fittings and such, but as pressure increases, you may find a leak that would not otherwise have been visible. It's worked for me a few times.

 

I love Kevin..

 

IS it the backwoods country accent, the improvisational smartass comments, the backyard ingenuity and troubleshooting methods, or my ability to promptly bitch out, without reservation, any newbie posting some stupid ****?

 

I've had a similar problem on my S5 FC and once on my FD.First thing is check that the HT leads are going to the right spark plugs,especially if you have just remove spark plugs.On FCs if the TPS is not working properly it will do the same problem.Try setting it with the proper mazda LED TPS Checker or just disconnect tps connector and go for a drive(FC3S ONLY).....Hope it helps.

 

"IS it the backwoods country accent, the improvisational smartass comments, the backyard ingenuity and troubleshooting methods, or my ability to promptly bitch out, without reservation, any newbie posting some stupid ****?"


you forgot your elaborate use of commas. =D

 

friends s5 tII has the same problem i heard it wasnt boosting at all for some reason, though i never saw it myself...this was after it sat for a long time (6 months or longer) and wouldnt start up probably flooded ... then it finally started up...hes actually looking to sell it for about $5000 ...it has a 1/2 bridgeport, front mount intercooler, hks dual exhaust , fuel cut defender, and lots of other ****, from what i heard it was like 450hp@19 psi and ran 11's or something like that using a stock turbo modified to handle more boost

 

Id check the voltages going across the injectors from the ECU.

I had something like the problem you had, anytime I would go into boost the car would pop and cut out. turned out to be a loose injector connection. I didnt notice it down low but when the car needed extra fuel it would *** out on me.

 

This is also a possible failing fuel pump. When the engine requires the extra fuel for boost it cant send it.

 

same thing happened to me last week ..

check your plugs ... thats what i did, they were coated in **** ... replaced them and the car screams again

 

so just unplugging the tps and do a testdrive is safe to do? have a s5, gonan have to try that cuz i have the same problem and think its becuz of my tps. checked it yesterday and sits fine att 1kohm but as i acc it just keeps going past 6kohm on to infinity(well atleast more than my dmm can handle)

anything that should change with tps unplugged? idle etc....

 

ok tested to drive it with tps unplugged and all hesitations were gone this means that the tps was the cause of my problems right?

allthough i didnt have an idle after the car reaches normal temp, is that ann effect of having the tps plugg pull or something else??

had good (warm) idle before the hesitations started, although pulsating while cold)