Folks,

I have been recently hitting limp mode while just driving. Spirited acceleration seems to trip it. I'm thinking bad check valve or split hose somewhere. Visual inspection has revealed nothing so far. Symptoms are hesitation on hard acceleration and limp mode after about 2 restarts / 1 hour of driving. Not your normal hesitiation like a misfire, but a loss of boost and then immediately getting it back. This is what makes me think it's a check valve taking too long to close, but I could really use some input.

Codes: p0171 system too lean (I know, it's an air leak)

Thanks for your help.

Ian

 

Code could also point to a bad MAF. Try driving with your MAF unplugged. With the MAF unplugged you will get a CEL and the ECU will use the default fuel/air maps. If power seems to be normal then you have a bad/dirty MAF.

Limp mode is a condition where upon overboosting you will go into a "SAFE" mode where the boost will not exceed 5-7 psi, essentially dumping any boost you make. Turning the car off/on will normally clear this until you overboost again.

 

MAF was replaced within 3000 miles... no overboosting condition exists. Turning car off and on again doesn't clear limp until codes are cleared. Only clearing the codes will release limp. This is hard limp right? I think I might have found a leaking check valve, but I won't know until I run the car some more... I work only 1 mile from my apt... Doing some driving for Christmas tomorrow so i'll see then... Happy Christmas everyone!

 

What values are you seeing on your boost gauge in a WOT third gear run? Peak, sustained?

 

Boost seems normal, peaks 13-14psi holds ~12psi. Vacuum is what's on the fritz... sometimes as low as 13inhg then I drive for 5 minutes and we're back at 18inhg. I'm sure now it's a tear in a hose somewhere. I'm getting an oil burning smell that I wasn't before. It's probably one of the breather hoses torn. Maybe one of the check valves is doing its job and cutting off boost, which is why I don't see a reduction in boost as the result of a leak. Makes sense to me at least.