🔧 BUILD Twincharged 3800 Malibu

[ASlowV6]

I’m just using the 3x signal with custom ignition parameters that someone else figured out and I found on a forum. It was running reasonably decent with these settings previously. It’s the same parameters bs009 is using as well.

 

[sktchy]

You sure somethin else isn't the issue? Possibly even grounds or losing key power when turning the switch or somethin stupid?

 

[sktchy]

I guess I just went through alot of bs to get a sniper to work right with a hyperspark and run it's own timing and they're really particular and sometimes the directions are off from what makes it actually run. Assuming it's similar I remember Somethin about a brown and green and gray wire that were my culprits with that.

 

[sktchy]

3x seems like a gell of a Los of resolution in my mind. But if you guys are making it work then by all means. I guess where it has signal maybe I'd look into a lingenfelter box or somethin trying to convert if you've exhausted all else

 

[ASlowV6]

I really don’t think so. I’ve tried grounding to the ECU, grounding to the battery, running shielded wire, trying to start it with my fluorescent lights off, removing the alternator exciter wire… I’ve done tests turning the engine over by hand and reading volts with my meter, a test light test, and now this oscilloscope test. I’ve tried setting the cam sensor parameter to “not used” and running batch fire. I’m getting no RPM signal whatsoever.

 

[ASlowV6]

I think at this point I’m going to mail the ECU in and see what Holley says.

When I was having no start issues before my problem was a bad cam sensor, even though all the faults I was getting were for the crank sensor, but when that was the case I was at least getting some RPM.

 

[sktchy]

You double check all your pinouts? I remember a local tuner mentioning somethin about flipped injector wires and I've found flip flopped tps and iac wires but those instances were pre-made harnesses

 

[sktchy]

I've also had about 1 in 5 cam sensors be good in these engines. You think maybe your magnet in the timing gear is pushed too far back to pick it up?

 

[ASlowV6]

The signal and reference wires were flip flopped and that has been corrected. I have a double roller. I verified the magnet is there, but I guess I’m not sure if it’s too far back or not. I did verify 12v drops to zero on the cam sensor pin when I rotated the engine by hand, but I never tried to see what would happen with an oscilloscope.

Are you saying most 3800s are driving around with bad cam sensors?

 

[sktchy]

The signal and reference wires were flip flopped and that has been corrected. I have a double roller. I verified the magnet is there, but I guess I’m not sure if it’s too far back or not. I did verify 12v drops to zero on the cam sensor pin when I rotated the engine by hand, but I never tried to see what would happen with an oscilloscope.

Are you saying most 3800s are driving around with bad cam sensors?

Yes and as long as they're under 4000 rpm which most are no one ever knows the difference if the icm picks up the crank signal and guesses with alpha n. This goes back to all the nightmares I had when my car ran perfect until I hit boost and then it would machine gun at me because timing was so retarded.

 

[sktchy]

On the contrary I've seen many a gen4 ls not switch to the ls2 chain when putting a cam in so they lose cam signal and then it's a really long start or no start condition at random. Sometimes you get lucky and hit the sweet spot.

 

[ASlowV6]

Interesting. I guess with the dual reluctor the stock PCM should be able figure out where it’s at based on 18x pulses per 3x pulse window.

I wonder how vital the 10v reference that the sensors want to see is. I’m sending them 12v. I wonder if it would be worth it to hook them up to 5v and see what happens.

 

[sktchy]

Worth A shot I suppose. I can't imagine it likes overvoltage on a signal line

 

[Turbocharged400sbc]

The icm uses the cmp 1x and ckp 3x/18x to create a 7x signal to pcm for sequential injection

 

[sktchy]

The icm uses the cmp 1x and ckp 3x/18x to create a 7x signal to pcm for sequential injection

Tries to pin it at 10⁰ total timing when its a in a situation that it's not seeing a signal right?. I wanna say zeph said you don't even necessarily need pcm control for the icm to actually function and it made for easy testing on junkyard shit or somethin along those lines.

 

[ASlowV6]

Tries to pin it at 10⁰ total timing when its a in a situation that it's not seeing a signal right?. I wanna say zeph said you don't even necessarily need pcm control for the icm to actually function and it made for easy testing on junkyard shit or somethin along those lines.

Yeah he has a video somewhere of him firing an engine hanging from a cherry picker with nothing but 12v and ground to the ignition harness, ether, and a bump to the starter lol.

 

[sktchy]

I'm not super surprised his bursts of knowledge are about the only thing I miss as far as the fb 3800 scene goes

 

[ASlowV6]

Well, tried a new cam and crank sensor, hooking both to 5v rather than 12, and no change. Cam is triggering the LED on the ECU same as it was before. Crank sensor works the same on 5v as it did on 12, which is cool because it means I cut my harness in about ten different spots for no reason if this wasn’t a wiring issue.

 

[sktchy]

 

[ASlowV6]

Holley got back with me today. Email said “it looks like there’s an internal ground fault on the O2 circuit.”

So, good to know there is a legitimate issue and I’m not just completely retarded. I know in the equipment I deal with (HVAC), ground faults can cause all sorts of seemingly unrelated issues. It was not made clear how we move forward from here, but I’m hoping Holley will be cool and just take care of the problem.

 

[Turbocharged400sbc]

Signal ground or heater ground?

 

[ASlowV6]

Turbocharged400sbc he didn’t specify. I’m hoping they’ll give me a report of what all they went through and what they found.

 

[ASlowV6]

Good guy Holley coming through for me!

 

[ASlowV6]

I went to go out the new ECU in and figured I’d check over a few things to make sure I don’t accidentally fry it. Found the ground side of the coil for my relay which powers my key-on bus bar was intermittent not making contact. Upon further inspection I found some wiring had been chewed. My antenna wire for my power steering pump module was also chewed. Cool.

Well anyway, I’m taking it as an opportunity to clean up my absolute shitshow of wiring. It was intended to be temporary just to get the car running anyway. I wanted to do a center console anyway since I’ve put these seats in, and the plan is to hide all my electronics inside the console.

I bought this off a guy locally for cheap. It’s out of a second gen F Body. I’m going to put cup holders in the front opening and a hinged armrest on the rear so I can access my electronics. And obviously it will be cleaned up and painted.