Question : Timing SEVERELY Retarded (40ATDC) in order to run?

pgtr · 10-25-2008, 12:22 PM

Timing SEVERELY Retarded (40ATDC) in order to run?

1984 2.8L Auto F-Body E2SE Carb 180k mi, gets (got?) 25mpg, NO codes, smooth high vacuum, but timing @ 40ATDC:

As preventative maintenance I recently replaced the intake manifold gaskets and timing chain set as well as the balancer. I also replaced the EGR valve and installed a new set of plugs. The ignition wires are only a few years as is the cap and rotor.

Prior to all of this the car ran fine and got 25mpg. There was a little looseness to the old chain but not bad. There was some notable corrosion in the intake manifold water port gasket area so this was a well timed project in that regard at least. But unfortunately things are worse off overall.

Upon re-installing of everything I'm finding I can't get the timing mark ONTO the tab at all. In fact the mark is barely visible. I'd estimate it to be about 30 or 40 degrees ATDC (retarded). Let's say 40ATDC is what it is idling at. Timing mark is correct (has not shifted on balancer). This was true before and after the chain replacement.

When I try to slowly work the distributor rotation to where I even 'approach' TDC on the mark - the engine starts idling horribly and eventually will not run at all the closer to TDC I get.

Question: With the 4-wire EST connector disconnected - will the ECM go into a 'dumb' or default mode? Or can other subsystems still potentially affect things? Like the MAP Sensor? TPS? ECM Temperature Sensor? Mixture Control Solenoid? etc...?

Joseph Upson · 10-25-2008, 04:44 PM

Are you sure you are taking the right approach to setting the timing, you have to be in by-pass mode which I do not recall the proceedure for doing on the V6 F-body but if it's like the Fiero the ALDL terminal has to be grounded A-B to remove ECM added timing otherwise you'll see timing similar to what you are describing. I find it hard to believe that you can have that much timing retard in by-pass mode and the engine run normally particularly with good vacuum. With excessive timing retard vacuum will be low.

betterthanyou · 10-25-2008, 08:19 PM

You cannot disconnect the knock sensor module (4 wire connector). There is a single wire somewhere in the car that must be disconnected to set timing. Either under the dash in the engine compartment or near the ECM

Joseph Upson · 10-25-2008, 08:50 PM

Quote:

Originally Posted by betterthanyou

You cannot disconnect the knock sensor module (4 wire connector). There is a single wire somewhere in the car that must be disconnected to set timing. Either under the dash in the engine compartment or near the ECM

In the V8 models it's in the harness on the firewall near the distributor.

pgtr · 10-25-2008, 11:09 PM

Hi Everyone,

I'm following the exact instructions for setting timing as specified in emissions label. It states to disconnect the 4-wire connector at the distributor (the EST wire per the FSM), plug the EGR... I don't recall that it specified grounding the ALDL however I have tried it both ways...

Yep - I find it hard to believe too! Tomorrow I'll review and ensure I'm disconnecting the correct "4-wire" connector for setting the timing. But the label on the car is pretty clear that it's the 4 wire connector coming off the distributor...

FYI it looks like I may have both the Baro and MAP sensors. I saw too identical gizmos on the firewall - 1 w/ a vac hose and 1 w/o.

FYI This car does not have a knock sensor.

Thanks all for the input. I'll review and post any further details tomorrow if I can.

betterthanyou · 10-26-2008, 12:21 AM

Oh right this is a Carbureted vehicle. In which case you do need to disconnect the distributor plug. I wonder if you are trying to time off the wrong plug wire?

Superdave · 10-26-2008, 01:31 PM

dizzy 180 degrees out?

i've done that on a SBC and gotten it to run by retarding the timing all the way..

pgtr · 10-27-2008, 12:52 AM

Just to follow-up (sort of)... I went out this afternoon and finished installing a few things after the recent timing chain swap. Fired it up and voila it was on 8 BTDC (factory is 10). So I set it at 10 and it seems fine. There is slight pinging at partial throttle (spark detonation) but other than that it seems fine. I'll probably back it off a few degrees and maybe run some SeaFoam thru. Bit annoying that I don't see what I did or didn't do that would cause such off readings...

Thanks everyone for the responses!

Time to move on to ball joints and steering linkage...