93 Legacy Cold Start Problem

[soobenthusiast]

I have a 93 Legacy (auto) that doesn't start well cold. I've already replaced the coolant temperature sensor, and cleaned the IAC. Neither really made a difference. The usual starting attempts go like this.

 

When I first crank it cold, it may fire once or twice, but doesn't really do anything.

 

Short pause, press throttle to floor for a second or two, release and crank again. will usually fire a few times but not start. 

 

Another Short pause, press throttle to floor for a second or two, release and crank again. Usually starts almost normally this time. 

 

When the car is warm/driven recently it's usually fine, even if it's been 8 hours since it ran. When outside temps are colder it's much harder to start. 

 

 

What should I check next?

[grammajudy]

Know nothing about mechanical things but has the coolant sensor replaced on mine and now it works fine.

[wtdash]

they've done that:

 

I've already replaced the coolant temperature sensor

I'd be looking @ the cam or crank sensors and the MAF. Has it ever just stopped running, but then start right back up? sure sign of a bad MAF.

 

Check your codes here: http://legacycentral.org/library/literature/codes.htm

 

If the CEL is NOT on...do it anyway as there's likely something stored - per the instructions.

 

GL,

TD

[soobenthusiast]

they've done that:

I'd be looking @ the cam or crank sensors and the MAF. Has it ever just stopped running, but then start right back up? sure sign of a bad MAF.

 

Check your codes here: http://legacycentral.org/library/literature/codes.htm

 

If the CEL is NOT on...do it anyway as there's likely something stored - per the instructions.

 

GL,

TD

 

I can't remember it ever stalling out, after it's started everything works extremely well.

 

Pulled the codes and got:

12 - Starter Switch - I've already converted to a push-button, so I'm not concerned about that

22 - Knock Sensor

32 - Oxygen Sensor

35 - Canister Purge Solenoid

 

This car sat for a couple years before I got it, and this problem appeared within the first several hundred miles I put on it.

[GeneralDisorder]

12 - Starter Switch - I've already converted to a push-button, so I'm not concerned about that

 

First of all that's a problem for startup. The computer uses the start signal from the ignition switch to know when the engine is cranking. This changes fuel enrichment and timing to compensate for the low RPM of engine cranking and it tells the computer you are attempting to start the engine. If it does not know this it cannot help you. 

 

The O2 and knock codes will dramatically affect your fuel economy. Fix them. 

 

Second - which coolant temp sensor did you replace? There are two. 

 

Third - depressing the accelerator prior to starting a fuel injected engine does absolutely nothing but wear our your shoe. If you HOLD the pedal > ~75% throttle *during* cranking it will shut off the injectors and put the computer into flood clear mode. Pumping it does nothing except confuse the computer. It is designed to start without any throttle input. 

 

GD

Edited June 21, 2017 by GeneralDisorder

[wtdash]

^+1

 

I don't see that #12 code often, and the #35 is a common 'extra code' caused by something else - Fix the  Knock Sensor and O2. The KS frequently CRACKED  and there was a Recall (?) for the '90-'95 version. I'd check it ...as a bad one will put your car in 'Limp' mode but shouldn't affect starting.

Edited June 21, 2017 by wtdash

[soobenthusiast]

First of all that's a problem for startup. The computer uses the start signal from the ignition switch to know when the engine is cranking. This changes fuel enrichment and timing to compensate for the low RPM of engine cranking and it tells the computer you are attempting to start the engine. If it does not know this it cannot help you.

This was GOLD. If I hold the key in the start position while pushing the push-button for the starter, it starts right up perfectly!

 

I love how much simpler fuel injection becomes as soon as I learn the logic it was programmed with.

 

The O2 and knock codes will dramatically affect your fuel economy. Fix them.

Now I'm stoked; I've already gotten 33mpg in this situation, the future looks bright!

 

Second - which coolant temp sensor did you replace? There are two.

The one with two wires on the right rear side of the intake manifold. I had the code for the temp sensor, and now I don't

 

Third - depressing the accelerator prior to starting a fuel injected engine does absolutely nothing but wear our your shoe. If you HOLD the pedal > ~75% throttle *during* cranking it will shut off the injectors and put the computer into flood clear mode. Pumping it does nothing except confuse the computer. It is designed to start without any throttle input. 

 

GD

I had thought this as well, but there was a slight whine as if fuel was flowing. I know the Bosch CIS system allows fuel through in this situation, so it didn't seem too strange to me. But of course this system is quite different, and clearly my mental models were incorrect.

 

 

Obviously I'd like to be able to start my car with 1 hand rather than 2...Is the start signal to the computer also coming from the ignition switch?

 

 

 

^+1

 

I don't see that #12 code often, and the #35 is a common 'extra code' caused by something else - Fix the  Knock Sensor and O2. The KS frequently CRACKED  and there was a Recall (?) for the '90-'95 version. I'd check it ...as a bad one will put your car in 'Limp' mode but shouldn't affect starting.

Right on, my knock sensor certainly has some cracks. I'll order one soon!

[GeneralDisorder]

The noise you hear when depressing the throttle is the transmission line pressure duty solenoid ramping up the line pressure in anticipation of a shift event. The TCU is a pretty dumb critter. It sees TPS voltage go up and adjusts the PWM signal to the trans line pressure to keep the trans from slipping.... It does this regardless of if the engine is running or not.

 

GD

[Gloyale]

This was GOLD. If I hold the key in the start position while pushing the push-button for the starter, it starts right up perfectly!

 

 

 

Simple fix would be to put a "double up" spade on the starter terminal.  Connect both your pushbutton wire, and the original starter wire to teh spades.

 

 

Now when you hit your pushbutton, the current will also be passed to the original system and the ECU will see the starter signal volts.