[Diy_efi] 4.3L TBI Timing Issues.

[Bret Levandowski]

The knock sensor and knock retard module should be added to that list as well. One other thing; Since your spark table is based on MAP vs RPM, if your MAP sensor has a fault reading high vacuum (low MAP) at idle and/or slightly above, or has a dead spot off of idle the ECM won't see the change and advance timing accordingly.   Ski

David Daniel <ss396 at pinn.net> wrote:  Thanks, David
I know the CEL is working... it's been glaring at me intermittently while I
was chasing an EGR problem. I had been getting an intermittent code 32, but
I think I have that fixed. No CEL since I replaced the EGR solenoid, and
the stutter was there before and after I replaced it. I just checked the
"Set Timing" connector tonight, and it's good. I thought I may have knocked
it loose last Friday when I replaced the cap/rotor/plugs/wires, but it's up
out of the way. I'll pull the cap in the morning to verify that I didn't
loosen anything while I had the cap and rotor off.

Good thought on the ignition module...I've seen them do some crazy things.

Thanks,
Dave

> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
> Behalf Of David Allen
> Sent: Saturday, December 10, 2005 12:28 AM
> To: diy_efi at diy-efi.org; GM-ECM
> Subject: Re: [Diy_efi] 4.3L TBI Timing Issues.
>
>
> It sounds like the ignition moule is running in timing bypass
> mode. This
> should flag a code and turn on the check engine light but there are
> instances where it might not.
> I would verify the check engine light is really working and there are no
> codes. After that make sure the 4 wires between the ECM and
> ignition module
> are good, and the "Set Timing" connector is not unplugged.
> Maye someone else will think of something else to try too!
> David
>
>
> ----- Original Message -----
> From: "David Daniel" 
> To: 
> Sent: Friday, December 09, 2005 6:57 PM
> Subject: [Diy_efi] 4.3L TBI Timing Issues.
>
>
> > I recently transplanted a TBI 4.3 out of a '85 Monte Carlo into my '81
> > Malibu. I've been trying to diagnose a slight stutter under light
> > throttle conditions. Tonight I hooked the timing light up to check the
> > spray pattern on my TBI injectors. They looked fine, so I took a look
> > at the timing. I could increase the throttle slowly, holding steady at
> > several points, and the timing was not advancing at all. Then, once I
> > get to a certain point, I see the timing advance all at once. I know
> > it shouldn't jump like that, but what could be causing this to happen?
> > I can feel it when I drive, too. It kinda stutters as I roll on the
> > throttle, then it smooths out and takes off once the RPM's come up a
> > bit. I don't have a tach yet, so I'm not sure what RPM range this is
> > happening, and the CEL is not lit. Any ideas?
> >
> > Dave D.
> > '81 Malibu Wagon <-4.3 TBI, the st-st-stutterer
> >
> >
> >
> >
> >
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