Engine 1993 2.3L LX Cold Starting Issue Below 20 Degrees Fahrenheit

DOHCobra

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Sep 16, 2018
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My first winter with this 93 2.3L and I am struggling to understand why it will not start when temps drop below 20F? Above 20F the car fires up from a cold start within one or two revolutions of the crankshaft, the warmer the outdoor temperature the quicker it starts. It will start immediately from a hot start condition. Below 20F the engine cranks harder and slower, almost starts, but not quite. Acts like when the timing is off on an adjustable ignition car, too advanced for winter. No codes.

Thinking of temperature related items I checked the ECT and IAT sensors and both are good. I tried starting fluid and no affect, no start below 20F. Through the process I have changed out and changed back, the DIS, Coils, Crank pickup sensor, none of these impacted cold start below 20F and all performed the same and well on warm weather starts above 20F.

Anyone else experience something like this?

Only modifications are 11:1 compression, mild hydraulic cam (pulls 19-20 inches of vacuum at idle), K&N filter in factory air box and about 8K miles since rebuild, all else is factory stock.

Thanks,
 
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DOHCobra

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Sep 16, 2018
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Good thought. The battery was changed in December. New battery has a few more CCA which helps but not so much below 20F. I tried jumping the battery also without any change in cranking/starting condition.












f,
 

DOHCobra

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Sep 16, 2018
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I checked resistance and voltage drop across all battery cables to be sure nothing has changed, temperature in the teens. Battery terminals 12.25V, Battery to engine ground 12.25V, Starter relay post 12.25V, Starter post 12.25V. Resistance was zero ohms across all cables. Note: Starter is a newer unit when engine was rebuilt last year and was/is an improvement of the 100k mi Motorcraft starter.

Open to any other thoughts?
Thanks,
 

DOHCobra

Member
Sep 16, 2018
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NE Wisconsin
Starting to get cold again in mornings up north and cold start issue is recurring same as last winter season. I also see a few others now have threads with potentially similar issue - no solutions yet. Hard to start cold, fine when engine or outdoor temperatures are warm.

To pick up on last question above - volts are 12.4 on Battery, Key on 12.2V, Crank 11.9V, recovery to 12.4V in 2-3 seconds after cranking. I have substituted this battery with other 2.3 and 5.0 mustangs I have and all other cars start in cold with any of the batteries, this particular 2.3 cold start issue is unaffected by battery change.

Being an old school carburetor guy, the engine is acting like it has too much advance in colder temperatures. During cranking the engine locks up due to pre-ignition condition when starting. On non-computer controlled cars you would retard timing in winter to get engines to start more quickly in cold temps. I am sure my higher compression is not helping the situation. I have tried all octanes of fuel, with and without ethanol, 87-105 octane and the result is no change in the cold start issue. When warm (outdoor temp or engine temp) the engine cranks and starts as if it were showroom stock.

Here is what else I can share
1. all ignition components are known to be good from crank trigger to spark plugs
2. fuel pressure is normal and constant with engine on or off, takes a day to bleed down
3. new injectors this summer - engine may run a little smoother, but no significant difference in mpg and cold start issue remains
4. using starting fluid does not affect the cold start issue
5. replaced the ECT sensor earlier this year with no affect on cold start - I found the resistance of old and new sensors to be identical (when heated in pot of water)
6. No codes

Being temperature related, which temperature sensor(s) is the ECU relying on to determine ignition timing?

I am considering to measure ECT resistance when car starts normally and substituting a resistor for the ECT to see if cold start improves.

Open to any new ideas or thoughts to explore next.

Thanks,
 

91TwighlightGT

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Off the wall suggestion...

you are running higher than stock compression and your starter can’t keep up when the air is colder and more dense.

edit: I realize your starter is newer but maybe it just doesn’t have enough power.
 

DOHCobra

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Sep 16, 2018
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NE Wisconsin
Actually at the time you wrote your suggestion yesterday I was changing the starter. When I started to troubleshoot in the afternoon I noticed the starter was weak and bendix kicking out prematurely. New starter is much better now, but still no start with temperatures in the 30's F.

I did a KOEO scan for codes after starter install and trying to start the car, Codes 114, 116 came up with 118 in cache. All pointing to temperature sensors. Anyone know the resistance expected at lower temps, all the tables I found only go down to 50F and the resistance on ECT and IAT are reasonably close to expected values at ambient warm temperatures. But at 30F I measure 91K ohms on IAT and 83K ohms on ECT? Just don't know if that resistance is reasonable or not.

Voltage between sensor lead and ground is 4.6V for both sensors. Wonder if voltage loop with ECU is weak?

Thanks for thought.
 
Last edited:

junkyardwarrior

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Jan 10, 2011
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The voltage reported to the EEC is relevant, moreso than the sensor's resistance. Back probe the ECT wire at the EEC and see what the sensor and wiring are reporting to the EEC. That is what's important. There is another way to do it (quarterhorse, etc) but if you don't have that, it's easier to backprobe. I do not remember exactly, but I think pin 7 (lt-grn/red).

I've had this issue. I've also had a starter get weak and cause same problem; although you've already addressed that.
 

DOHCobra

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Sep 16, 2018
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NE Wisconsin
After the starter change and no start condition with temps in 30's outside, I found the ICM was not getting a signal from the crank position sensor. A new crank position sensor took care of that and it now starts as before at warm temperatures.

Regarding voltage to sensors, reading Ford Manual the voltage to sensors can be in range of 4.5 to 5.0 volts, so all good there.

I also found in the Ford Manual that the PCM has a Dual Spark Inhibit feature which at temperatures of 20F and below only uses the right side coil pack to start the engine. Got me thinking I should check the coil packs, especially the right side. Sure enough I found the secondary resistance on both coils to be 60% of the expected 13,500 ohms. Replaced old coil packs with new FOMOCO coils (with correct resistance), starts quicker and runs a little smoother, just waiting for temps below 20F to verify the cold start fix. Expected to be below 20F the next couple of mornings.

Will report how it goes.
 
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DOHCobra

Member
Sep 16, 2018
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57
NE Wisconsin
After the starter change and no start condition with temps in 30's outside, I found the ICM was not getting a signal from the crank position sensor. A new crank position sensor took care of that and it now starts as before at warm temperatures.

Regarding voltage to sensors, reading Ford Manual the voltage to sensors can be in range of 4.5 to 5.0 volts, so all good there.

I also found in the Ford Manual that the PCM has a Dual Spark Inhibit feature which at temperatures of 20F and below only uses the right side coil pack to start the engine. Got me thinking I should check the coil packs, especially the right side. Sure enough I found the secondary resistance on both coils to be 60% of the expected 13,500 ohms. Replaced old coil packs with new FOMOCO coils (with correct resistance), starts quicker and runs a little smoother, just waiting for temps below 20F to verify the cold start fix. Expected to be below 20F the next couple of mornings.

Will report how it goes.
Dropped to 15 deg F this morning and engine fired on first beat. Weak right side coil (and Dual Spark Inhibit feature) are reason the engine would not start below 20F for so long. Hope this experience helps others chasing similar cold start issue on dual plug 2.3L.
 
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91TwighlightGT

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Thanks for letting us know the answer. Too many times these threads just fade away with no resolution, but this information always helps others out with confirmation.
 
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