2G Idle O2 variation, fine under boost until it shutters.

[hystericfox]

Alright, I was having trouble with my O2 trims at idle. It varies from ~0.02 to ~0.96. Under boost, it's fine, logs fine until about 3400 RPM, where it shutters really hard and loses about 7 pounds of boost. There aren't any boost leaks, I haven't found any vacuum leaks. Vacuum at idle is about 18, about 24 on decelleration. EGT at idle rarely goes above 900, and occasionally when I'm on the highway the O2 will go way lean again. Mods are in my profile, and I just rewired my fuel pump. Any suggestions on what else I should be looking for?

 

[steve]

Alright, I was having trouble with my O2 trims at idle. It varies from ~0.02 to ~0.96.

That's what it does in closed loop. The ECU varies the mixture around 14.7:1 and watches for the O2 sensor to switch.

Steve

 

[oldman]

There aren't any boost leaks, I haven't found any vacuum leaks.

Is that the results of a REAL boost leak test? Have you check the plugs and wires?

 

[hystericfox]

I haven't changed the wires, but the plugs are new NGK BPR6ES, gapped at .028. It was a real boost leak test, and I tested it to 25 pounds without any leaks.

 

[oldman]

it's fine, logs fine until about 3400 RPM, where it shutters really hard and loses about 7 pounds of boost.

What happens after that? Does boost build back up? Only during wot? Give us as much detail as you can.

 

[hystericfox]

It builds boost fine until about 3400 RPM, then it shutters violently, then will start to build boost back up. If it isn't under full boost, i have been able to rev it to 5000 RPM under load, but only partial boost.

 

[oldman]

What happens if you floor it again after 34k? Will it wot to redline or will same thing hapeen again at a higher rpm?

Also, what boost do you have set at?

 

[hystericfox]

It goes up to about 4300, and does it again, if it manages to get past 3400. It also seems to do it at lower engine speeds in higher gears, in 2nd, it does it at about 3400, in third at 3100, in 4th at 2900. In 5th, about the time it gets boost it starts to. That's about the time the O2 drops to ~0.04, and the EGT starts to climb ofer 1450 degrees.

Oh, boost is set at 14 now, but it doesn't matter what the boost is set to, it does it anyway. I've had it set at 17, 14, 12, and 10, and it kept doing the same thing.

 

[oldman]

It sound more like boost or ignition related. Change the wires if they're old, if problem persists I would do the following.

1. Compression test. If numbers are good, go to 2.

2. Disconnect the hose to actuator and test run. Boost should shoot straight up so feather the throttle and keep it at around 12 psi. If problem resolved, there're issues with either the actuator or the mbc. If problem persists, either the turbo or you need to dig deeper into ignition.

 

[hystericfox]

Disconnected the actuator, still did it. Going to order another set of Magnacor 8.5 tomorrow, which are what were on it when I got the car.

 

[hystericfox]

Update:

Installed a B&M fuel pressure gauge on the fuel filter, and my base fuel pressure is 54 psi. I was wondering why my pump started whining after I rewired it, I'm guessing it isn't stock. That answers my question on the rich issue, which has gotten worse in the last 2 days. Time for an AFPR.

EDIT: Forgot to add that I got a code today for Fuel Pressure Solenoid Malfunction, which is odd, because it is disabled, but I left the electrical connector plugged in.

 

[hystericfox]

Update:

I installed an Aeromotive AFPR and got my base fuel pressure back down to 45 pounds (a little over stock). Replaced the coils, and it is still happening, but a little higher in the RPM range and isn't quite as violent. I'm starting to run out of things to replace. Any more suggestions on this would be greatly appreciated.

 

[hystericfox]

Problem fixed. Finally mounted the AFPR properly, and re-set base fuel pressure to 43 pounds. Set base on the MAFT, and it ran perfectly. Did a few 3rd gear pulls, and tuned it as well as I could with the MAFT. Thanks for everyone's help.