GT-40 PCM Running RIch, sometimes

You’re right. PN is capable of being good for troubleshooting at times. There are a few guys on this site that never fail to get folks across the goal line though 😃

KENO wrote: There's a guy with the same name on PN with the same problem, but he posted more info over there like a trouble code.................why is that?

PN is a waste of time for technical help on GT40 and other engine troubleshooting issues. Good place for stereo advice and ballast system engineering!

Compression test is tomorrrow

Nothing, still goes it and cant figure it out. Low vacuum is main concern now. If it wasn't for you I would have forgot I posted that, i cant remember 2 hours ago

video

The video above was taken yesterday. I decided to check vacuum.

I know bad gas can cause issues, and granted this stuff is old. However, it was doing the same thing all last year with new gas

Fuel pressure is fine, checked that as well.
Im.more concerned about the vacuum issue. And, no obvious vacuum leaks. Which points me to a leaking valve, rings, etc. I suspect I have a valve to tight. However, these rocker arms are non adjustable. I'm doing compression test today to try and find out of my thoughts are correct.

This vacuum.leak takes priority right now.


New stuff within the last year
New fuel injectors
Fuel Pressure regulator
Low pressure pump
IAS idle air thingy
Water temp sensor
Plugs, wires, cap, rotor
MAP
Relays both ECU and fuel

Within the past 2 years
GT40X Aluminum heads
PIP Sensor
New shift and throttle cables

My son runs a Corvette with Twin Turbo's, on premium gasoline he makes 738 HP at the rear tire. On the E85 he can run higher boost and more timing with no detonation. The Horsepower jumps to approx 900 at the rear tire. No joke.   You can make great power on E85 but the alcohol can be corrosive and hard on the fuel system. He can flash his computer in about 5 minutes to run on either gas. He has developed 2 separate tunes.
I think with E85 he is running 21 pounds of boost and recording zero detonation.
Not so sure it would work that well with carbs.

Getting back to the issue and question at hand ...   bad gas aside (or just crappy gas depending on who's speaking) two things pop into my head, that haven't already been mentioned anyway. Overpressure in the fuel rail.    Or you may have a few injectors getting old and starting to drip. I've been told when this starts to happen it is more prevalent at idle and very low rpm which can load up fairly quickly and cause just the issue you're having.
Just a thought.

8122pbrainard wrote: tryathlete wrote: 8122pbrainard wrote: tryathlete wrote: I ran only ethanol free premium always because I don’t like what happens to ethanol over the winter even with stabil. Why risk it? Ethanol is junk. I've run ethanol in everything since it's inception and haven't had one problem. It's great stuff. Hope you’re not serious. Maybe just run straight ethanol then Pete. Great stuff! Peter, I'm very serious. Again, I've used it since it's inception and NO problems.

You know I hate to agree with you Pete (Brainard), it really pains me at times

But I'm feelin' real pained right now since I completely agree with your ethanol experiences all year round. And I'm being serious.

I'm talking about today's gas with 10% ethanol No issues

8122pbrainard wrote: tryathlete wrote: I ran only ethanol free premium always because I don’t like what happens to ethanol over the winter even with stabil. Why risk it? Ethanol is junk. I've run ethanol in everything since it's inception and haven't had one problem. It's great stuff.

Hope you’re not serious. Maybe just run straight ethanol then Pete. Great stuff!

I ran only ethanol free premium always because I don’t like what happens to ethanol over the winter even with stabil. Why risk it? Ethanol is junk.

workky wrote: Hey guys I have the first year GT-40 in my boat with no FCC. We have had quite a few issues in the past with the engine management. I will someday replace the crappy ECU with something i can control from my laptop. Now, the issue i will describe is unusual Boat runs fine, cranks up fine, drives fine, does everything fine because it's mine. However, at Idle after a while it starts running rich. Rich enough to see black smoke coming out the exhaust. When you raise the RPM or get under way to about 2k RPM is goes away and does not come back. It will come back after an extended IDLE It only does this at IDLE for extended periods of time, it may or may not do it, there is no consistency. Whats wrong???

Since your issue seems to be related to idle why not see if your IAC is dirty? I’d pull the flame arrestor and see if cleaning up the IAC will fix it.

Look for a few other easy places like your cap and rotor.

Finally; another easy one; how is your fuel? Do you have last years gas still in there with ethanol degrading or water trying to get through your injectors?