Weird boost hesitation

[Doat]

So on my way home tonight it's a cold night mind you and usually the car feels like a beast straining the leash and this guy in a modded MazdaSpeed 3 wanted to run me, so we do a 40 or 50 roll and as I gun it the boost builds but when I am at full tilt it feels like the boost or turbo is switching off and on off and on off and on then it stays on. It doesn't feel like fuel cut there wasn't a sudden cut no CEL or anything it just felt like the power was being turned down and up I felt it pull then let off repeatedly. I am not sure if it's tied into my exhaust leak but I bet that doesn't help either, still trying to figure out what the hell is causing the exhaust to leak hopefully not a warped manifold. Any ideas on what could cause boost hesitation?

Mods:
550 CC injectors
Lex AFM
Full 3in exhaust
Blitz Dual SBC boost controller

 

[BryanDyer]

A boost leak between the turbo and throttle body. Exhaust leak before the turbo will cause a lot of lag and you won't be able to hit full boost. A gasket could always fail or bolts aren't tight enough. Code 52 can cause hesitation like that because of the rich fuel mixture and retarded timing

 

[IndigoMKII]

Honestly, it sounds like a boost leak.

 

[Doat]

Thanks guys I'll be checking those out soon.

 

[Doat]

Well I figured out my problem turned out I had my boost up too high and I think it was verging on that borderline to fuel cut would possibly explain why that night it was acting like a soft fuel cut. I turned it down and did some pulls to see what psi it was at and set it to 14psi and it felt strong and that night while leaving work I had to quickly exit the parking lot and get on the entrance ramp of the highway, so naturally I boosted in second and it threw me back into my seat and scared the crap out of me. For profile 1 I have it set to 12 psi for daily and profile 2 at 14psi for some fun. I really need to move my boost gauge to the stock location so I can keep an eye on it while boosting. I am glad it was something that simple.

 

[IndigoMKII]

IIRC there isn't a 'soft fuel cut'. I'd still check for boost leaks.

 

[Doat]

What I meant by that was it felt like fuel cut but wasn't as harsh like it was on the verge of fuel cut but not enough to cause it to fully cut and turn on the CEL if that makes sense. I'll still check for boost leaks when I can but ever since I turned it down a bit it's been boosting really strong.

 

[atmperformance]

What I meant by that was it felt like fuel cut but wasn't as harsh like it was on the verge of fuel cut but not enough to cause it to fully cut and turn on the CEL if that makes sense. I'll still check for boost leaks when I can but ever since I turned it down a bit it's been boosting really strong.

fuel cut is fuel cut, there's no half cut unless you really want to melt a piston. I'd check for a boost leak while the car is warm and also check your wastegate actuator. It's possible your waste gate is flying open then closing.

 

[Doat]

fuel cut is fuel cut, there's no half cut unless you really want to melt a piston. I'd check for a boost leak while the car is warm and also check your wastegate actuator. It's possible your waste gate is flying open then closing.

Will do but my wastegate actuator is new I got it from DM it's 11psi. It could be hitting the downpipe since I have an ebay Justspeed divorced downpipe I know fitment is not the best on those that is why I want to get a BIC ddp.

 

[stolensupra]

I thought I hit fuel cut before when my car stuttered; I found out what fuel cut is when I put on a MBC got to 14 psi in 2nd gear on a CT26 and almost hit my head on the steering wheel from the force differential. I had a similar loss of power that was intermittent. Turned out my exhaust studs were slowly working their way out, failing helicoils mind you. Check your exhaust stud nuts for 29 ft/lb. Good Luck

 

[Doat]

is there a way to check the studs without removing half of the motor? I am really tired of doing that now lol. I know there a few nuts I can get to with an extension or I can just use a deep well socket. It could be that they are backing out because after I changed the studs and such then went for a test drive I did not hear any ticking then after a day or so it came back. The boost comes on strong and doesn't creep or go wonky but when I boost I can smell the exhaust inside of the cabin.

 

[shiftysupra]

Did you figure this out? If not, do you have an aftermarket boost controller by any chance?

 

[Doat]

It seems that my problem is solved I think it was because my boost was turned up a little too high i had it set around 15psi or so and when I hit boost it would hesitate and not pull as hard as I expected. Now I turned it down to a solid 13-14psi and it goes like a stabbed rat and boost just come on strongly. I have a Blitz Dual SBC controller and figured it out when I was testing some daily driving boost settings and noticed when I had it at 12 psi it did not hesitate and pulled harder than when I had it set too high, so I just kept increasing it until I got to a stable setting. If you are having the same problem with a similar setup to mine then I suggest turning down your boost a bit.

 

[shiftysupra]

I was going to suggest fine tuning the boost. Your wastgate was probably stuck open. I figured that out when I did a NA-T swap. The car would buck like a bull. I have the AEM Tru-Boost.

 

[Doat]

I replaced my actuator with the 11psi one from DM

 

[berniek]

Just curious about your 12-14 PSI boost. Seems low considering the potential with turbo/AFM/550 injector mods. Is your turbo stock? If so it is probably inefficient at those or higher boost levels. I got mine modded to 57 trim. no turbine clip, but had the wastegate passage bored out instead. With the Lex AFM/550 injectors/3" exhaust it runs fine at 17 PSI, except for initial hot air under the hood (using an HKS air cleaner). It will start to break the rear tires loose in second gear at around 4K RPM.

BernieK

 

[Doat]

Yea I just have the lex/550 mod with 3 in exhaust on the stock turbo. I do want to upgrade the turbo but I am on the fence about it since I want to build my 2jz and might as well buy a turbo for that instead.