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GT-40 PCM Running RIch, sometimes

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workky View Drop Down
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    Posted: July-05-2019 at 10:57am
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???
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tryathlete Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2019 at 10:50am
Originally posted by workky 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?
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workky View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2019 at 11:57am
It is last years gas!!!!!
However, it did the same thing last year. I'll clean the IAS or whatever it's called.

Thanks for the suggestion, I'll do it today and report back
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tryathlete Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2019 at 12:52pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2019 at 1:32pm
Originally posted by tryathlete 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.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote tryathlete Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2019 at 3:39pm
Originally posted by 8122pbrainard 8122pbrainard wrote:

Originally posted by tryathlete 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!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2019 at 3:50pm
Originally posted by tryathlete tryathlete wrote:

Originally posted by 8122pbrainard 8122pbrainard wrote:

Originally posted by tryathlete 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.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2019 at 5:57pm
Originally posted by 8122pbrainard 8122pbrainard wrote:

Originally posted by tryathlete tryathlete wrote:

Originally posted by 8122pbrainard 8122pbrainard wrote:

Originally posted by tryathlete 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



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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2019 at 6:58pm
When the "mechanic/tech" can't figure out the problem, it's typical he blames it on bad gas!!


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Post Options Post Options   Thanks (0) Thanks(0)   Quote gt40KS Quote  Post ReplyReply Direct Link To This Post Posted: July-06-2019 at 9:07pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: July-07-2019 at 1:09am
I think GT40KS is correct. I'd look at the fuel injectors and associated systems. When the throttle-body fuel injection was failing on my 1994 PCM, I first noticed black smoke at idle. There was so much black smoke that I had to wipe the black soot off the stern after skiing. A dirty, clogged or failing injector that isn't properly atomizing the fuel certainly can cause an over-rich air/fuel ratio at idle.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: July-07-2019 at 3:46am
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tryathlete Quote  Post ReplyReply Direct Link To This Post Posted: July-07-2019 at 4:12am
Originally posted by MrMcD MrMcD wrote:

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.


Hopefully he doesn’t fill up his gas tank in September and plan to use it in June the following year like many of us do up North. Phase separation of alcohol from gasoline and water absorption don’t work well with SOME of our marine engines.

My local small engine repair guy won’t work on chainsaws and line trimmers without changing the fuel to ethanol free premix gasoline.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: July-07-2019 at 11:45am
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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-07-2019 at 5:03pm
What was the outcome of this thread in the link below, where you had intermittent smoke and one fouled plug. ?

Sounds like things could be related

link
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Post Options Post Options   Thanks (0) Thanks(0)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: July-07-2019 at 7:23pm
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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-07-2019 at 8:53pm
So.........putting the 2 threads together, you suspect issues with one cylinder and you have one with a loaded up plug.

Sounds like a good place to start looking

Is that pitch black plug oil covered or fluffy black and gas fouled?

That would probably help you figure out if you should be looking at injector problems or mechanical issues with that cylinder

Maybe a compression test will be informative
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Post Options Post Options   Thanks (0) Thanks(0)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: July-07-2019 at 11:26pm
Compression test is tomorrrow
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-08-2019 at 8:07am
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?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tryathlete Quote  Post ReplyReply Direct Link To This Post Posted: July-08-2019 at 8:30am
Originally posted by KENO 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!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-08-2019 at 9:24am
Originally posted by tryathlete tryathlete wrote:

Originally posted by KENO 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!


I don't quite think I'd say that

Just as one example, where did the GT40 ECU fix come from ?

I figure Workky can.t figure out how to post a picture here but I'm not sure.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tryathlete Quote  Post ReplyReply Direct Link To This Post Posted: July-08-2019 at 6:23pm
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 😃
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slmskrs Quote  Post ReplyReply Direct Link To This Post Posted: July-08-2019 at 11:36pm
Originally posted by workky workky wrote:

video

New stuff within the last year
New fuel injectors


Not to sidetrack your thread, but I'm looking at replacing my injectors. Where'd you get yours? I'm not going to pay PCM's price....

Thanks,

Gordon
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: July-09-2019 at 12:14am
Let's see what he used but Ford Motorsport M-9593-LU24A are a good choice.Many places have them- around 215 a set,just google them. Will need EV-1 to EV-6 adapters for the wiring harness also.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: July-09-2019 at 1:59am
I dont remember where we got them, I think summit racing. I believe they were around 200 hundreish a set, for some reason I remember something like what Gary said about the connectors, and for some reason I think the injectors are pink.
I'll look at them tomorrow
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Post Options Post Options   Thanks (1) Thanks(1)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: July-09-2019 at 2:07am
Originally posted by KENO KENO wrote:

Originally posted by tryathlete tryathlete wrote:

Originally posted by KENO 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!


I don't quite think I'd say that

Just as one example, where did the GT40 ECU fix come from ?

I figure Workky can.t figure out how to post a picture here but I'm not sure.


KENO, you are quite the investigator. You are right, I have no idea how to post a picture here. As I've said many times, I can't remember 2 hours ago. So if I post so.ething on PN I cant even tell you what I posted, hell I do t even remember what I posted here, I forget and dont do searches like I should
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: July-09-2019 at 4:06pm
Your idle vacuum at 15 is not terrible, you may have weak compression or maybe your timing is a little retarded.   The fact it is bouncing between 15 and 15.5 is not an issue.
Bouncing vacuum would refer to bouncing between 12 and 17, you don't have that.
How did your compression test turn out.
!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: July-11-2019 at 12:02am
150 psi on 6 cylinders
155 psi on one
And 147 on one
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: July-11-2019 at 7:11am
Originally posted by workky workky wrote:

150 psi on 6 cylinders
155 psi on one
And 147 on one


No problem with those readings as far as consistency from cylinder to cylinder.

Which reading was from the cylinder with the black plug

Have you tried the vacuum gauge on another engine to see if maybe the little fluctuation is due to bad dampening or if it's steady on the other engine?

Or hold your RPM's steady at say a couple thousand and see if the gauge is fluctuating slightly or does it smooth out.

Just me thinking but I think you have a bit of a misfire on the cylinder whose plug is black if the fluctuation is real
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Post Options Post Options   Thanks (0) Thanks(0)   Quote workky Quote  Post ReplyReply Direct Link To This Post Posted: July-11-2019 at 11:53pm
I hooked it up to my Honda accord , it was steady at 22.

You are right about the misfire. Number 6 plug wire is bad according to the om meter. Replaced the wire and plug in number 6. However, it still smokes, but not as bad.

I looked at the injector and its pink, the others are blue or black I cant recall. It is clear that we have changed it at some point, and it may have been the wrong one or is leaking. But I cant freaking remember when we did that. As is said many times I cant remember crap anymore, and I'm in my 40's.

I ordered a set of injectors 15 minutes ago. I know they are all not bad, but they sure are old and probably need replacing. A leaking injector is the only thing else I can think of that would be causing this.
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