I Just got back from a drive to the Oregon coast. About fifteen minutes away from home my car starts hesitating, felt kinda like missing when I would accelerate. I figured it was my plugs since they needed to be changed anyway. Today I replaced them but it didn't fix the problem. But I did notice the manifold has a nice four inch crack in it. Could this be the problem? Injector related maybe? It idles perfect and at cruise it's fine but whenever I start to push it even the slightest towards 0 vacuum it jerks and hesitates. Any advice?

 

Do you have a CEL? Have you hooked up an OBDII Scan tool?


My educated guess would be that your car is misfiring on one or all cylinder due to a dirty or bad MAF. This usually happens when you don’t have oil catch can and some of the oil comes back into your intake tract and your MAF can get covered in this flow causing the car to misfire / lag towards 0.
Hard to say with such limited information.
Hook up a scan tool and let me know what codes your throwing if any.

Best of Luck

 

has to be the crack, that would explain the higher rpm stutter.

 

You mean the intake manifold?

If there is a crack in the manifold then it will not hold a positive or negative vacuum. Your car's ECU is confused. You need to fix or replace that manifold.

 

It's funny cuz I had this on my regular turbo setup and now again on the built motor setup. The tuner said it's compression surge. Something like to much air coming into the small turbo and it hesitates.

Others have said that it's tuning related.

 

Forgot to mention it's the exhaust manifold. and I think it could be the maf as well, that was my other guess. And I'm going to check the codes tomorrow but the CEL didn't flash, but then again it was already lit because of my non catted setup.

 

The exhaust manifold wouldn't have a bearing on it. If you have a crack in your exhaust manifold, you're just gonna be really loud, and if you're turbo'd, your spool time will suffer.

Compressor surge happens when you let off of the throttle. The BOV doesn't bypass all of the air, and it flows back into the turbo. This WILL destroy a turbo. But that isn't causing hesitation.

 

Having a clogged cat will do it too. Trust me I know. Repair your intake mani and you will be good to go

 

Your advice would be much more helpful if you read the thread. I'm non catted and my intake manifold is fine...

 

Well fix what you know is broken then and report back then.

 

1. Are you on FI/C or emanage or some EMS ( hydra ect) ?
2. have you tried unplugging the EMS then plugging it back into your harness?

One of our customer cars did this EXACT thing yesterday and it was because the AEM FI/C was loose at the harness.

also keep an eye on your wideband (if you have one ) and make sure your AFR is okay at cruse as well.

Feel free to PM or email me at Bardia@dezodwest.com if you have any questions regarding the above or your turbo setup

 

I'm on the emanage. Haven't tried that yet, but I was thinking about it on the way home. Had the manifold fixed. Also, I'm on new stock plugs now so they need to be gapped correctly. Cleaned the MAF sensor as well.

 

also my AFR is fine 14.7 ish but just stutters and goes lean once in a while. it does this the most at over 60mph. and it does not throw a code.

 

Thats so way to lean its not even funny. Unless your sitting at a stop your lean as ____. Anything over 13 I was told was to lean. 12.5 even

 

14.7 is perfect if you are in vac.

 

sorry man my post said expert not I've browsed the fi section and want to get my average posts up...not trying to be a jerk or anything but you have no idea what you're talking about. In closed loop 14.7 is the factory AFR. now if you're gettin on it I would say yes 14.7 would be lean, but if that was happening do you think my block would even be intact lol...

I'm thinking dirty Primary 02 sensor, Bad injector, or bat Emanage connection..

 

Check your intake for boost leaks - that's always the first thing I do when I start bucking under load, especially if it's not done it before.

And as far as 14.7 being lean - 14.7 is stoich - the ratio at which every mole of oxygen is balanced with fuel and you get a complete burn. At idle this is what you want, and as you put more load on the engine you should go richer. Boosted I'll run about 11:1.

 

Good call I'll check that!

 

Is this when you get one the throttle OR back off OR get on, back off then back on.

 

I want to say both but it's much more pronounced when I'm getting on the throttle.