97 GST runs lean at low boost

[xxd1ab0licxx]

Hey guys

So the car is a 97 GST Spyder with 160,000 miles, it had not been started for almost 1 year at purchase. Also the car is completely stock. It runs great, doesn't miss, or cut out, has great acceleration.

I have auto meter boost and AF ratio gauges already so I installed them, it is a narrow band (I know there not very accurate) Under very low boost it shows rich for about 2 seconds then drops to the lowest lean point on the gauge. This happens under half throttle or full throttle doesn't matter. I have to let off throttle for a couple seconds before it will show rich again.

I pulled the plugs to verify, they are all white. I installed new NGK plugs and wires, new fuel filter, new Walbro 190 fuel pump, new idle air control valve, new battery, k&n drop in air filter, new thermostat, checked for vac leaks, checked fuel lines for leaks/bent. I pinched the fuel return line from the FPR no change, have Snap-On scanner no codes, voltage at fuel pump is 11.7 to 12.5

Had this problem with the original fuel pump and thought the Walbro would fix it but nothing has changed. Pulled the new plugs after 1 week and they are all very white. I may have let out something

Any advice is appreciated! I am out of Ideas! Thanks

 

[Rikolas]

Have you checked your injectors? They could be clogged. Give them a cleaning and see if that helps.
http://www.dsmtuners.com/forums/bolt-tech/400962-diy-testing-cleaning-dsm-fuel-injectors.html

Hmmm...maybe your gauge could be bad also?

 

[xxd1ab0licxx]

Gonna check them tomorrow while I'm off work. thanks for the info, very cool videos! I will let you know the results. Thanks

 

[Rikolas]

Good luck with it! Hopefully it fixes the problem. But you said there nothing going noticeably wrong with the car other than thever gauge ? If this doesn't fix it then maybe check your gauge/sensor?

 

[xxd1ab0licxx]

I thought it was maybe the gauge at first. I pulled the new ngk plugs and there all extremely white.

I also had a bg fuel injector service done yesterday and there is no change at all. I still run very lean at 3lbs of boost.

The car starts, runs, and drives excellent.....I just cant boost at all

 

[Rikolas]

Is your wastegate stuck open?

 

[xxd1ab0licxx]

I went out and checked, I don't know a great deal about wastegate operation. The arm from the actuator to the wastegate moves freely from closed to open, with me guessing about 20lbs of pressure applied moving it to open.

 

[DSM1G90]

Bet the diaphragm assembly is bad which is causing the WG to remain open, or open under simple exhaust pressure .. and this disables turbos in a heartbeat.

You mentioning of moving the actuator rod to open and close the WG. Odd that this can be moved freely - is why I mention a bad diaphragm assembly.

 

[xxd1ab0licxx]

It takes quite alot of force to move the actuator arm to open. It moves freely, not sticking or anything.

 

[92awddsm]

The car boosts just fine, correct? Just shows a lean condition at low boost? If this is the case, why are you chasing boost problems? What does it do when you go wot?

 

[Rikolas]

..I just cant boost at all

Says he can't build boost.

 

[xxd1ab0licxx]

It boost fine, its all stock so boost is 12psi at wot. It goes lean at 2 or 3 psi and stays lean at any amount above that.

I'm worried about how lean it is, and the plugs being solid white. I don't want to ruin the engine. So Ive been trying to stay out of boost until I can resolve the issue.

 

[92awddsm]

Says he can't build boost.

I saw that. But he hasn't said anything at all about not being able to build boost, he has been talking about being lean when he does build boost. I was under the impression he can't build boost because he is afraid of causing engine damage.

 

[92awddsm]

Have you replaced the o2 sensor?

 

[xxd1ab0licxx]

Yeah it boost 12 psi at wot, sorry about that. I meant I cant boost without fear of engine damage.

I had a shop watch the o2 sensor on a snapon scanner and they said it was reading like it should. Don't know much more on it than that. I have access to a scanner tomorrow and may look at it myself.

Thanks

 

[92awddsm]

Yeah it boost 12 psi at wot, sorry about that. I meant I cant boost without fear of engine damage.

I had a shop watch the o2 sensor on a snapon scanner and they said it was reading like it should. Don't know much more on it than that. I have access to a scanner tomorrow and may look at it myself.

Thanks

Well i wouldn't worry about looking at the wg or vacuum lines because that obviously isn't your problem.

Has the mas been modified at all? I would suspect that or a failing o2 sensor if it really is lean. But then again, a narrow band is nothing more than a flashing light that is powered by an o2 sensor.

 

[Rikolas]

It boost fine, its all stock so boost is 12psi at wot. It goes lean at 2 or 3 psi and stays lean at any amount above that.

I'm worried about how lean it is, and the plugs being solid white. I don't want to ruin the engine. So Ive been trying to stay out of boost until I can resolve the issue.

I guess you're right. He can boost but will lean out. I thought maybe a new symptom was not building.

 

[xxd1ab0licxx]

I checked the mas it is clean and not been modified. I will try a new o2 tomorrow and keep you all posted.

Thanks

 

[xxd1ab0licxx]

I ordered a new mas and o2 sensor monday, got them in this morning. I first tried the mas and there was no change, I fought to get the old o2 out and finally got the new one installed. It runs perfect now!!! Didn't think a bad o2 would make it run lean!

Thanks again for all the help!!!!

 

[92awddsm]

I ordered a new mas and o2 sensor monday, got them in this morning. I first tried the mas and there was no change, I fought to get the old o2 out and finally got the new one installed. It runs perfect now!!! Didn't think a bad o2 would make it run lean!

Thanks again for all the help!!!!

Awesome, I'm glad to hear that.