Alright drove all day yesterday and today. Almost 500 miles.

It was 100 degrees most of the day no issues. Then after I'm cruising around, I hit full boost backroading. By full boost I mean I visibly saw 24-25 psi.

10-15 min later I noticed the car was running very shitty. It was popping and cracking out of the exhuast, idle was high at 1500-2000rpm and the damn thing would backfire when the car was shut off.

Pulled out the DashHawk and the LTFT and STFT were were negative. LTFT was -15%

Turned off a few times and turned back on same result. I was out in BFE so i watched the DashHawk and babied it around.

Went to dinner at 5, left at 8:30. At this point the car is no longer cracking popping or idling high. The LTFT on the way home moved from 0 to +3%. Did a couple pulls and it boosted fine to 20 psi. I did see a few erratic stft shifts though.

So here is what I was thinking the possibilities:
1. Boost leak that went away went cooled down
2. Evap Purge Valve or Selenoid on the way out ( I have replaced both a year ago)
3. Bad Gas - I don't think is likely.
4. Heat screwing with sensors or somethin

I'm not really in the mood to diagnose tomorrow due to the heat and my dad (AKA lift owner) is in Ireland. Let me know what you guys think. I guess a lot depends on if the problem persists too.

 

I ha the same problem, tranny would be jumpy as well and i would build no boost which is limp mode, i thought a boost leak as well and smoke tested it and it eas fine, fyi most of the time the problem would be gone once i cycled the engine. So i took the bumper off and one of my map sensor wires were actually wearing away at part of my ac unit. So long story short i beleive the map sensor was grounding out on the ac unit and i moved the wire and so far so good, ad well as way better gas milage, like almost double... But good luck maybe this will help!

 

Great post. I never run my AC. I did a bunch this weekend Might be the issue.

 

So the car ran good most of the weekend.

This morning i was on empty. Filled it up and wouldn't hardly even start. I got it to start by pumping the gas. STFT -20% at idle but everything looked good under throttle.

So Evap system? That's the only thing I can think of if it didn't have hard starts before.

This is aggrevating.

No pending codes set yet either. Might be after that startup though.

 

I always view -20% LTFT as running rich and its usually caused by a boost leak.

I had a charge pipe partially hanging off of my coupler (surprised it didnt blow off) and it was causing a boost leak when it got hot enough out that the rubber got super soft and ballooned alittle. You might have experienced a similar issue to that. Oh I still showed a good 20 psi on the boost guage too when that happened.

 

You could be right about the boost leak, I just don't understand why I had a hard start after a fill up. Why would a boost leak cause that on fill up.

 

not sure but like you said, those Purge valves (emission thingys) can be a boost leak too if they are stuck open. Hard start could be from fuel vapor lock from running rich.

 

have you cleaned out your throttle body lately?

 

Nope, but I don't see how the throttle body would cause that.

 

You could have an EVAP solenoid or EVAP valve issue. If your EVAP solenoid is stuck open, you have a vac leak. This also causes long-starting issues after fillup.

 

I was having horrible idleing problems to the point of the car stalling. I cleaned my throttle body out and have had no issues. Now it may not fix your problem, but couldnt hurt.

 

On an LNF? Not sure I have heard many people having this problem. I also don't see weird start up, idling and AFR swings to be affiliated with throttle body. I could be wrong.

I"m going to change the Purge selenoid on lunch break. Went and start the car earlier. Started no problem.

 

Ran to the dealership. $30 later and 5 minutes... I leave this video right here. 3rd one in 3 years. Time to stockpile

LNF Evap Purge Selenoid - YouTube

 

Title of that video should be "how to give your car a proper blow job." It will get more views that way

 

done