Ignition System
NOTE: The following data only apply to the '88-'89 4A-GE. They may be similar to earlier 4A-GE ignition
systems, but use at your own risk.
| Firing order |
1-3-4-2 |
| Timing |
T-E1 diagnostic terminals shorted
Diagnostic terminals not shorted |
10° BTDC
> 16° BTDC |
| Spark plugs |
OEM (Platinum) |
ND PQ16R
NGK BCPR5EP11 |
| Suggested (Copper) |
NGK BCP6ES |
| Factory spark plug gap |
0.043" |
| High tension cords |
Maximum resistance |
25 kOhms per cord |
| Ignition coil |
Primary coil resistance (cold)
Secondary coil resistance (cold) |
0.4-0.5 Ohms
10.2-13.8 Ohms |
| Distributor sensor air gaps |
Ne Pickup (cylinder TDC)
G Pickup (#1 TDC) |
0.008-0.016"
0.008-0.016" |
| Distributor sensor resistance |
Ne Pickup (flatter/wider plug)
G Pickup (rounder/narrower plug) |
140-180 Ohms
140-180 Ohms |
Words of advice...
If you're thinking about getting "cheap horsepower" and advancing the ignition timing over stock specs... DON'T!
Unlike most car manufacturers, Toyota actually did their homework and came out with the best timing. I've seen some dyno
print outs where only the ignition timing was changed and the best power was indeed at stock specs. If you're still a hard-ass
and plan to advance the timing anyway, don't go any more than 12° BTDC. Sure, you may gain a teeny-weeny bit of power, but
any more than that and the engine will ping at certain loads and rpm. Trust me, I've tried!
Thinking about aftermarket ignition coils, modules, etc? Fuh-getaboutit... Honestly, they're a waste of money on naturally
aspirated motors with more-than capable ignition systems like the 4A-GE. I'd recommend upgrading the ignition system if and
only if you are:
- Experiencing crappy gas mileage and lousy power because your OEM ignition system just plain sucks (this doesn't particularly
apply to Toyotas I've worked on),
- Running forced induction at > 14 psi,
- Running high cylinder pressures because of forced induction and/or domed pistons,
- Running a Formula Atlantic-type motor that regularly sees > 9,000 rpm (10,000 rpm to be exact).
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fsp14@ae92gts.com