MS3 Gold Box 5.3 Turbo running extremely rich.

[ryder2shae]

Hey guys, am new to this forum. I have 1967 Impala with 5.3 with GT35 turbo. has 80 pound injectors and running on 91 octane. Car has PNP MS3 golb box. Car has been running perfect for the last few months. but all of a sudden, it started misfiring and running extremely rich and gas started coming out of the exhaust. looks like its only on the left side bank. you can see gas coming out through the manifold gasket. I replaced the fuel pressure regulator,intake manifold gasket, got all my injectors checked out at a local injector place. checked my fuel rail, return, tested the fuel pressure, everything checked out fine. tried to adjust the trim on tuner studio
on both open and closed loop and no luck. I replaced all the plugs and changed the oil a few times. I unplugged all the left bank injectors and the car stops puking gas out through the exhaust and the wide band reads very lean (20.1AFR) when the car is running. checked all my sensors and they all read fine. Am out of ideas here guys. Please help me out. Any help would be much appreciated.
Thanks again,
Arjun

[tryingbe]

Post your MSQ and MSL.

[brianj5600]

Were are where all the plugs on the Left Bank wet?

[ryder2shae]

Yes. they are especially cylinder #3 and 5 plugs soaking wet. I unplugged Cylinder 3 and 5 injectors and the car started running lean. 15.0 AFR. so #3 and #5 is running way rich and all the others fine or lean. Thanks for your reply. Much appreciated.

[goodysgotacuda]

First things first, it sounds like you've honed in on the fuel system being the problem.

...do those cylinders have compression?

Spark?

If you are missing one, you'll dump raw fuel...


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[ryder2shae]

Am just going to do a compression test tonight.didnt have a gauge handy. I pulled the plugs and put my finger in the plug holes and cranked the motor over and it pushed my finger right out. Seems like it has good compression. Going to check the right way tonigtonight.
Thank you

[ryder2shae]

And yes. I have good spark, new plugs and new spark plug wires.

[ryder2shae]

Ok, I borrowed the nitrogen engine smoke tester and found no vacuum leak. But I narrowed down the problem down to cylinder #5.car idles good, and around 13.5 AFR with cylinder #5 injector disconnected. As soon as you plug the injector, the AFR goes to 10 and car runs puking rich. Unplug the #5 injector and car idles good and AFR goes back to 13.5. Tried new plug at #5 and same thing. Did a compression test on cylinder #5 and it's 160 psi. Checked spark at the plug again and it's good. I really have no clue. Gonna do a leak down test tomorrow and see how it goes. But I strongly think it's the megasquirt issue. Thanks for any help, in advance.

[nathaninwa]

Swap injectors around between two cylinders and see if the trend follows. Could be a bad injector

[ryder2shae]

I just got all the injectors flow tested and ultrasonically cleaned . They said all the injectors are in perfect shape. Unless they are wrong. Am going to swapbthem and see how it works. Thanks for the help. Much appreciated.

[nathaninwa]

Did you get a flow chart at all pulsewidths or cleaned at a wide open state? I've had them cleaned at 100% with matching results before on a new motor build, initial fireup the car would not idle leaner than a 12.0afr. However cruising was fine and dyno'd ok till one stuck open and hydrolocked the motor!

[ryder2shae]

Did the leak down test at #5 and it was 8%. So everything is good there. Swapped the injector with #3 cylinder to see it's an injector fault and it's still the same. So basically my motor checked out fine and the injector too. Only thing that left to check is my MS3 box. Wondering a transistor or something is shorting out in the box. I checked the injector pulse earlier with a mood light when the car was not running and they all pissed good. The car starts fine with the injector #5 plugged in and it runs good for few seconds and then it starts running richnon #5. Wondering a transistor is shorting out after its get hot or something. Am out of ideas here guys. Gonna check with a mood light with the car running. Thanks again in advance for any help.

[billr]

Here is an idea, posted before but ignored:

[jsmcortina]

Am out of ideas here guys.

Have you contacted your supplier?

James

[ryder2shae]

No. I haven't.thats the next thing am gonna do.
Thanks

[ryder2shae]

Since in my engine, cylinder #5 and #8 goes into compression stroke at the same time, I unplugged #5 injector and tapped into #8 injector and plugged into #5 ( using the #8 injector to fire #5 injector as well).
Now my car runs fine. Idles around 13 AFR. So definitely my problem is the MS3 box. Gonna contact efi source and see what they say. Hopefully I can run it for a while with #5 and #8 injectors firing on the same signal. Lol.
Thanks everyone for the help. Much appreciated.