flechebleue

Hello
I've exchanged the complete ignition module on my 1989 v6 2,8 Firebird as the old one was corroded and pickup coil was shorten.
I've reinstalled the new one at the same position than the old one and the engine has restarted with no issue. The car was running smoothly.
I've then checked the ignition timing and set it to 10 degree as specified (est cable disconnected). With this setting the engine starts but as really low power. The car is accelerating very slowly and has no torque (like if the timing was too late).
I had to go back to 20 degree advance timing to recover a smooth behavior. Is there something I'm doing wrong? I've seen in some manual that the aldl diagnostic has to be grounded for the timing optimization? But in the manual they said no to start the engine when all grounded!!
Thanks for your help

RBob

iTrader: (1)

It may be you are using the wrong mark on the damper. I recall that there are three or four marks, with one being wider then the others. The wide mark being the one to use.

It may also be that the outer ring on the damper has slipped. If the rubber is protruding out from between the hub portion and the outer ring, need a new damper.

RBob.

flechebleue

I am using the large mark (there are 3 marks at 120 degrees). The rubber on the damper seems to be ok. I've checked the position of the mark when in front of the 0 degree and it corresponds exactly to compression of cylinder 1.
I've optimized the timing at 36 degree at 3000 rpm. The car run smooth but the timing at idle is around 20 degree!!

Gfunkill

Since mine is a 3.4 damper, there are no timing marks.
The only way I got around it after a week of messing around, was to find the spot when it was hard to start, then slowly back it off until it wasn't struggling.

knightinblackar

It wasn't the larger mark on mine, it was one of the other two thinner lines. I know this because I painted the larger mark silver and couldn't get anywhere near timed up on that mark. As soon as I timed it from one of the narrower lines all timed up perfectly!

Six_Shooter

iTrader: (2)

The 3.4 damper most certainly has timing marks. I have pulled 3 of them in the last year (replacement and spares) and they all had timing marks, along with every other 3.4 damper I've looked at.

The thicker timing mark IS the one to use for TDC #1, if you're finding that to not be the case your outer ring has slipped or you're not using #1 for timing check reference.

flechebleue

I don't think this is the problem that I have. The mark are at 120 degrees from each other. I'm only off by 10 degrees.
I have optimized the timing to obtain 36 degrees at 3000 rpm. In this condition the engine runs smoothly and the car is quite responsive. I think I will let the setting like this.

Gfunkill

@sixshooter,
Dude, the only mark on my damper is the notch that is cut into it, and it doesn't correlate to #1 being at TDC.

Six_Shooter

iTrader: (2)

Then you have a problem with the outer ring having moved, if you are indeed lining up TDC #1 correctly.

The 3.4 damper has the timing mark that correlates with #1, there is even a small indicator mark on the 3.4 timing cover that lines up with that mark at TDC #1. This could be used with a dial back timing light, but the wasted spark generally makes that difficult.

Six_Shooter

iTrader: (2)

You mean when you are setting base timing the mark is 10 degrees BTDC? Then that would be good, if that's the case.

If that's not what you are saying then how have you verified that the timing mark is 10 degrees off?

flechebleue

When I check timing at idle I have 20 degrees instead of 10. So I am 10 degrees off from the optimal timing. However when I check for compression on cylinder 1 the mark is on 0!
With 20deg at idle I have 36deg at 3000rpm.

RBob

iTrader: (1)

OK, there is definitely something wrong here and I think I may have figured it out. You replaced both the ICM and pickup coil. Now you need to advance the base timing to get the engine to run with power.

Try this, disconnect the EST/BYPASS connector and check the base timing. Should be at 20* BTDC as you set it. Shut the engine off and reconnect the EST/BYPASS connector.

Start the engine and check the base timing. Did it go advanced or did it retard some from the 20* BTDC (engine still at idle)?

Another item that came to mind is that you are not on #1, which is on the right hand side front of the vehicle (passenger side for those that drive on the correct side of the road).

Common mistake as the majority of American engines have #1 on the left hand side of the engine.

RBob.

flechebleue

When the est cable is disconnected the base timing is around 30degrees. When the est cable is reconnected the timing goes to 20 degrees at idle. If I increase to 3000 rpm, it goes to 36 degrees.
I am pretty sure I'm taking the right cylinder (first front on the left when you look to the engine).

RBob

iTrader: (1)

Yes, as I expected the pickup coil is wired backwards. Need to pop the two wires out and reverse their positions within the connector housing. Then reset the base distributor timing to 10* BTDC. With the EST/BYPASS reconnected the idle SA should be about 28* BTDC.

You have the correct cylinder for the timing light. Although it is easier to use cylinder #4, center drivers side. No need to drape the cord over the engine to get to #1.

RBob.

flechebleue

Ok I will try to do that. This is quite strange as I bought the complete assembly ( distributor, I miss, pickup coil..) already mounted.
If I understand right the timing should advance by 18degrees when est cable is connected ?

RBob

iTrader: (1)

Yes, this is the key, once the EST/BYPASS is closed and the ECM reset (key-off for 10 seconds), upon restart the spark advance should go advanced from the base setting. If it retards from the base setting the pickup coil wires to the ICM are reversed.

RBob.

flechebleue

Ok, I have exchanged the two wires on the est cable. That's a little bit better but still not as it should be. At 10 degree the engine is still not working properly. A good setting gives 18 degrees at idle (est disconnected), 28 degrees at idle (est connected), 38 degrees at 3000rpm.
Any other idea?

RBob

iTrader: (1)

From here it sounds like the new distributor is totally foo_bar. At least it is now advancing once under ECM control. Was the distributor a GM unit or aftermarket? I only use GM distributors, ICMs, and ignition coils.

I will use premium aftermarket parts for the cap, rotor, and pickup coil.

RBob.

flechebleue

It's an aftermarket part. The coil is a GM part. Does it means that I have to replace the icm by a GM one or can I keep the setting as it is? When I drive the car I don't see any difference compare to what it was before (the old distributor was the original GM)

flechebleue

I've tried to replace the ICM by a GM part but I don't see any change on the behavior. What else could be wrong?