Check for pending codes.
Check the purge valve by blowing through it
Check for boost and vacuum leaks
Etc

 

sorry im not trying to jack this thread from theOP

i check purge vallve and i CANT blow through it.

im on stock intercooler/cold/hot pipes and still hold 20psi while in boost.

and no CEL

how do i check for a CEL it may not be on,on the dash but maybe something is set in the memory??


is there a way to look on my interceptors for pending codes,not an actual check engine light

 

aha! i was playing with my interceptors and i got a p0497!

so i checked my purge valve (on the intake mani) and i cant blow through it. where is this vent valve located at??

 

the vent valve is in the charcoal canister under the car by the gas tank. my vent valve was deffinitly bad. it sounded like a bag of marbles inside of it. it was deffinitly causing my stalling on cold start up. as well as throwing my furl trims off a bit. but my ltft is still abit off. so I am going to be checking for a leak asap.

Kind to think of it. what should a stock car with only gms1 be running for both ltft and stft ? For all three , acceptable highs and lows as well as an average. and when a car says its say running a stft of -2%. is that -2% of fuel it is removing or air ?

 

Thank you sir.

Well I'm GMS1 but I have the K&N sri and hahn catless dp and cat baxk. My LTFTs are -3.9 but when I do WOT pulls it usually bounces back close to 0. I know that my STFTs bounce all over the place

 

Im also gms1 with a kn sri. But I took my intake off a week ago or so to clean the filter and havnt put it back on yet. My stft is also all over the place. And my ltft seems to bounce in around -5 to -6 at the moment. but its still a lot better then the -9.8 I was running before the vent valve replacement.

 

Did you replace the purge valve on the intake manifold? Or did you replace the canister be the gas tank?

 

so since the purge valve on the intake mani is working (i took it off and couldnt force air through it) it would point to the canister on the gas tank,right?

 

I picked up both the purge solenoid and the vent valve because they arnt to pricey. However, gm decided to update the vent valve to a new unit and you will also need to ask your dealer for the pigtail adapter. It will plug into your wiirjng harness and then into the new design plugin. Also, from what I have been told. Although it is a good indicator that your purge should be okay if you can't blow through it. It is possible that it is stuck closed and still needs replacement. This why for the extra $30 I replaced both.

 

Maybe I will replace the one on the intake mani and see how that goes. I left the car parked and took my othet car to work today. Ill pick up the purge valve while I'm at work today, good thing my buddy works in parts at the dealership I got to

 

I would buy both. Install one on the intake manifold first. Then see if it's fixed. Then vent valve if it's not.

 

The car shouldnt have an issue if the vent valve is busted (one in the gas tank) The Purge valve is only a problem because it because a leak where measured air can escape away from the engine.

Vent valve opens once a certain pressure is reached in the gas tank as the fuel vapor builds up. The vent valve opens and allows the fumes to travel into a charcoal filter and then after that it journeys all the way to the intake manifold where the purge valve "purges" it.

I call it my factory NOS system

 

I can't think of anything else that would have been causing my cold start issue ? Espeically when I take my vent valve out and it is all busted inside and sounds like a bag of marbles. Sense replaceing it the car has been good so far on cold starts as well as my fuel trims are SLIGHTLY better. Improved for sure. As well every time my car stalle dI got a fault code I could see in torque on my cell phone that said p0494 Evap system low flow . Or something like that anyways. So I just went ahead and replaced both the purge solinoid and the vent valve. And when I pulled the vent valve out. It was all busted up. Made sense to me I thought ?

 

100 $ for the 2 parts from a dealership!

50 for both of them from oriley. I have the updated gm part number if anyone wants them

 

I think the worse thing that could happen with the broken vent valve is that when you open the gas tank lid to put gas in the car, you kill the ozone alittle faster.

Since you replace both, I bet there was something fishy with the Purge valve and you fixed it.

 

Agreed. Thats why I mentioned to other guy to start with purge valve first. Then you have diagnosed which was the issue

 

i ordered both parts. the purge valve on the intake with the pigtail,i will try that first and see what that does. if the code still pops up on my interceptor i will change the canister on the gas tank

 

From what I understand from the gm dealer I got the parts from. They have sold a huge amont of the pruge and vent valves with the pigtail. They stock a lot of each. They said they have never sold the actual canister according to there records. I was always under the impression they didn't go bad very often ar all. Not unless you over filled your cars gas tank after it clicks off alot.

 

I'm still wondering what it is removing when my ltft are at -4.5. Is the ecu removing fuel or air ?

 

It is removing fuel.

 

How do I get my ltft to go positive? Fix the leaks if I have any ? My concern is if I don't have any boost leaks then what ? And if I do... and it is around the maps can I use some high heat etc sealant around the seat to try and seal them up if the o rings are proper and in good shape. I really hope I have any easy to fix leak at my injen coupler at the ic and I can just put a new one on.

 

Wait, you want a negative fuel trim. Slightly less than 0 means it's a little rich. Which means safe. I don't think you are that far off from normal. Obviously not a major leak.

I don't remember my exact trims before K&N intake but I do know they were slightly negative. Within 5% is not bad at all for a GM tune.

Try running some 93 or 94 octane. It should raise your LTFT a couple points. I also use a splash of E85 sometimes and it raises my fuel trim a bit.

 

I thought ltft in the - meant the ecu was removing fuel ? Making it run leaner ? Or is that the piont ? Its removing fuel because it is running to rich ? Im at a ltft of -5.5. So your saying that isn' too bad for a gms1 ltft ?

 

Yes it's removing fuel because it's running too rich. -5.5 is a little on the low side, but it's honestly not that bad to be running 5% rich. I'm running +7% on GMS1 with K&N and I know it's too much but don't have the option for a tune just yet. But I think Termi is the only guy I would allow to tune my car.

I'm trying to figure out the rough cost i would need with HPTuners and tune. Also not sure if I need or want PRO.

 

Quicksilver-did you receive the updated canister part from gm? Mine cam with a new pig tail