Post Transwap Timing

Lost Bushman · Mar 26, 2014

I switched to a FM146 from an A4LD.
.. tech article suggests timing change, but doesn't say what to adjust it to. It idles high and has weak top end...

Help?

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RonD · Mar 27, 2014

Idle should be 1,000 cold, 700-750 warmed up
IAC(idle air control) valve on upper intake is used by the computer to set idle level.

10deg BTDC is normal, advancing will raise idle, but computer should lower it if IAC valve is working.

Lost Bushman · Mar 27, 2014

Ok, the reason I ask is because the tech article fro the swap clearly says re-time the engine because the timing is different between manuals and autos...

Is this not true?

RonD · Mar 27, 2014

I wouldn't think the spark timing would be different as that is an engine parameter, engines method of driving the wheels shouldn't come into play.
You want idle speed to be slightly higher with automatics, and electronic ignition would adjust timing for that.
Your '89 computer would be setup for auto so idle will be higher

The electronic module that controls the spark timing could be different for manuals and automatics but I don't think that is the case for the Ford TFI ignitions.

Assuming 2.9l engine, some prefer up to 14deg BTDC although you can start to get "pinging" as you retard timing.

Remove SPOUT connector,
set base timing at 10-12deg BTDC
Reconnect SPOUT
and see how it runs

Module controls spark timing on the TFI which is why you need to disconnect SPOUT to set base timing

Lost Bushman · Mar 28, 2014

Ok, first, it is a 2.9...

timing is set at 10deg BTDC and it idles better when warmed up, but struggles when cold and puffs a fair amount of smoke. But only until it warms up.

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RonD · Mar 29, 2014

Cold start reads like you may have a bit of oil coming in from worn valve guide seals, which happens as engine miles go up.
When running this oil is burned with the fuel/air.
When engine sits a little oil collects on the top of the intake valves and on cold start it is just a little too much oil to burn easily so you get misfires.

Try gaping the spark plugs a little wider, 2.9l looks to be 0.044, try 0.049

Spark plug gaps are determined for best overall performance and longest life, not for optimal performance, and, of course, determined based on a new engine with perfect rings and seals, lol.
The larger gap will give you a hotter spark and better lower RPM performance, but will wear out spark plug faster, not alot faster.
Narrower gap gives harder cold starts but better high RPM performance.

General rule of thumb is an adjustment range of +/- 0.01 so in your case 0.044 could be adjust from 0.034 to 0.054

Lost Bushman · Apr 2, 2014

RonD said:
Narrower gap gives harder cold starts but better high RPM performance.

General rule of thumb is an adjustment range of +/- 0.01 so in your case 0.044 could be adjust from 0.034 to 0.054

Interesting. I'll re-gap the plugs and see how that works, I did just put all new plugs in there, and noticed an improvement on startup. Maybe a re-gap will further improve the situation.

Thanks! :icon_thumby:

Lost Bushman · Apr 3, 2014

Well, I re-gapped the plugs to .049, and it runs rougher, so I guess close them up a bit?

RonD · Apr 3, 2014

Yes, close it up a bit, the TFI ignition system coil can have a weaker spark so larger gap can cause misfires.

MSD makes a $40 replacement coil(Part No. 8227), for the Factory coil, it will have a stronger spark, mostly because it is new, but also has a better "turn count" than Factory coil.
The "Blaster" version would require new wires as well, and not sure it would be much of an improvement over just the new coil.

Lost Bushman · Apr 4, 2014

RonD said:
Yes, close it up a bit, the TFI ignition system coil can have a weaker spark so larger gap can cause misfires.

MSD makes a $40 replacement coil(Part No. 8227), for the Factory coil, it will have a stronger spark, mostly because it is new, but also has a better "turn count" than Factory coil.
The "Blaster" version would require new wires as well, and not sure it would be much of an improvement over just the new coil.

I closed the gap from .049 to .047, and it seemed to smooth out. I'll look into that MSD coil in the future, I'm getting ready to move back home to AZ, so I'll have to put any non-essential expenditures on the B2 on hold until I get re-rooted. Thanks for your help, RonD! :icon_thumby:

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