breaking up under boost

[nolanator]

i searched this topic and found a few threads go over similar issues, but i still cant figure it out.

The car drives stop light to stoplight very nicely, and will even go into boost up to about 12psi without any noticeable issues, but seems to hesitate if i stay in it. The feeling of it is similar to driving through puddles. It hesitates and catches up to itself repeatedly. I got into it hard once before I noticed anything weird, and found that it would break up pretty rough at higher boost level 18+psi.

I had this problem once before and i found a vacuum line that was disconnected between my map sensor and boost reference, so the car wasn't getting alky and was compensating for a vacuum/boost leak. I've checked my lines repeatedly, and don't see anything out of the ordinary.

I'm hoping to get this figured out as soon as i can as I am looking to convert to e85 shortly and rather than bandaid an issue, I want to actually tend to it and get this car running well.

Thanks

 

[Phoneguy]

Could be as simple as a bad alky pump , loose hose in the tank for the fuel pump, bad fuel pump.
Good luck

Bryan

 

[getdowngranny]

What coil pack and module are on the car? What plugs at what gap? I see in the Sig that you have a MAF translator, but what MAF are you running? What are your AF reading when the car starts to break up? I had a similar issue in the past while under boost and it was my MAF. Have you checked all of your intercooler/turbo hoses and pipes, if you have a boost leak it can also cause the car to go rich and break up. Turn the boost down to around 15- 17psi or so and shut off your alky system to see if your issue goes away. It may be the Alky punp like Phoneguy mentioned. E85 is a whole new ball game and if your fuel and ignition system arent up to par, you may have more issues up the road. Hopefully its just something silly just being an annoyance.

 

[forcefed3.8's]

What is the afr when it is doing this?

 

[nolanator]

What coil pack and module are on the car? What plugs at what gap? I see in the Sig that you have a MAF translator, but what MAF are you running? What are your AF reading when the car starts to break up? I had a similar issue in the past while under boost and it was my MAF. Have you checked all of your intercooler/turbo hoses and pipes, if you have a boost leak it can also cause the car to go rich and break up. Turn the boost down to around 15- 17psi or so and shut off your alky system to see if your issue goes away. It may be the Alky punp like Phoneguy mentioned. E85 is a whole new ball game and if your fuel and ignition system arent up to par, you may have more issues up the road. Hopefully its just something silly just being an annoyance.

Coil pack and module are OEM, and the MAF is LS1. I just received an AEM UEGO wideband in the mail yesterday, but havent installed it yet. I havent double checked all the turbo couplers, but I am almost certain they are on properly. This setup was running fine at 20+psi up until about 2 weeks ago when a couple studs backed out of my header to turbo flange. I purchased new studs, replaced both turbine gaskets, and then noticed these symptoms.

 

[forcefed3.8's]

Did you verify fuel pressure under boost, and when was the last time the spark plugs were changed?

 

[nolanator]

Did you verify fuel pressure under boost, and when was the last time the spark plugs were changed?

I haven't verified fuel pressure since I didnt want to risk getting into the throttle hard and damaging something. The plugs unfortunately we're put in right out of the box, but the car ran very well with them until I ran into that exhaust leak

 

[Mr.Spool]

The plugs unfortunately we're put in right out of the box,

Gap the plugs,check fp and install wideband to see where the afr is.

 

[forcefed3.8's]

9 out of 10 times it is the spark plugs if it just developes a miss under boost.

 

[nolanator]

9 out of 10 times it is the spark plugs if it just developes a miss under boost.

I sure hope so. I have a set of UR5s at home that I'll be sure to gap tight.

 

[nolanator]

9 out of 10 times it is the spark plugs if it just developes a miss under boost.

I'll tell you what. For being optimistic and helping ease my mind, if that's the case and I change the plugs and the car runs well, I'll PayPal you $8 and you can grab a beer on me.

 

[TurboBuRick]

Another thing to consider is the plug wires. Had a car today that ran fine up till about 18psi boost then started breaking up. Simple stuff first.

 

[Phoneguy]

I sure hope so. I have a set of UR5s at home that I'll be sure to gap tight.

If you are going to change the plugs, get rid of the extended tip style plug.

Bryan

 

[nolanator]

If you are going to change the plugs, get rid of the extended tip style plug.

Bryan

Hey Bryan,
You wouldnt by chance have a part number handy for those plugs would you?

 

[Phoneguy]

I believe the UY5 is the non extended tip

 

[achalmersman]

I believe the UY5 is the non extended tip

Close. It's YR5

 

[Phoneguy]

Close. It's YR5

Thanks for the correction !
I run GN1 aluminum heads so I was unsure.


Bryan

 

[getdowngranny]

X2 on the YR5. It is the same as the UR5 but with a recessed tip. With the OEM coil pack and module you will need to gap them tight. min 28 max 32.

 

[nolanator]

thank you, gentleman

 

[nolanator]

Close. It's YR5

I looked up YR5 and there are a few 4 digit variations of it. Which one am I looking for?