Cold Start Issue... ACT Sensor? '89 LX 2.3L

ChillPhatCat

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Apr 22, 2002
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I'm partly looking for simple confirmation here and partly looking for additional ideas. So the car will crank and crank and crank and after about the 4th time I give it a 10 second burst, it will fire a little while cranking, then within a couple more tries the car will grudgingly come to life, where I can rev it up to about 3k for a minute or so and then it will eventually settle into a high 1,500 RPM idle and then after a few minutes it lowers to 800-900 RPM and it will idle there indefinitely as far as I can see (10 mins+). And after that, if I shut it down and try to start it again any time in the next couple hours, it will start up on the first or second shot and continue idling at 800-900 RPM.

So it seems I've got a cold start issue... When I got the car it didn't run and the owner said his son said there was a faulty "switch" under the drivers seat, so I replaced the fuel pump relay and it showed me signs of life and I got it started in the same manner as above. Since then I filled the tank with ethanol free gas, replaced wires, plugs, coil, and the ignition switch... and although it runs a little smoother with the new coil and sparky bits, it has mostly not changed it's behavior. The oil is clean and the coolant looks good... runs at normal temp once it warms up.

My main question is if this car actually has an ACT sensor? None of the parts carriers give me the warm fuzzy that the parts that come up in searches will actually work with my car.

What else could cause this issue? Can the EEC fail in a very specific manner like this?

Update: Not ACT, as was suspected, but it was cheap so I changed it while I had the upper plenum off. Ordered a new fuel pump, waiting for the neighbor with a lift to lend a hand dropping the tank.
 
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ChillPhatCat

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I'll have to check next time go out there... found a wiring diagram for the engine and there is supposed to be an ACT... I'll be doing some good old fashioned poking around this weekend.
 

Mustang5L5

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Run the engine codes. If it is an ACT sensor you will have a code for it. You can also resistance check the sensor to determine if it is bad.

I second checking the fuel pressure and confirming you have proper pressure
 

ChillPhatCat

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Apr 22, 2002
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Yeah I've got the reader, I tried to use it at one point and thought I was not getting any codes... looking at the online how-to use it, I may have just screwed that up. I'll give that another go as well.

Edit: Just noticed my "5 year achievement" for 300 posts. lol How many do I need to fulfill 17 years as a member? :D
 
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ChillPhatCat

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I pulled the codes with the engine off and it read 84 then 10 and then 11... so it currently is reading code 84 but the continuous memory code is “all clear”. 84 is an EGR failure so I guess I should look at the EGR circuit, though I don’t know I’ve ever heard of that causing a hard cold start. I did locate the ACT sensor so I’ll check that next time for proper resistance just for the hell if it... You never know.
 

junkyardwarrior

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Jan 10, 2011
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ACT won't cause hard starting.

ECT will and it won't always throw a code.

Ditto on the fuel pressure check. Why? Past experience. I've had more than a couple that the pump "sounded" fine yet wouldn't pressurize the system. There's a hose between the pump and the hanger, had several of them bust. Also have had a couple pumps that the impeller was not tight on the shaft, meaning the armature would spin but the impeller wasn't tight enough on the shaft to build enough pressure to run.
 
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Boostedpimp

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Bet if you turn the key on a few times back to back without actually starting the car it'll fire right up. If so then your pressure is bleeding off due to a crack in hose in the fuel tank that connects the pump to sender. They crack do to age and lose pressure but this could be confirmed by motoring your fuel pressure at the rail as well.
 

ChillPhatCat

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It’s only hard to start cold. It takes 4-5 tries and then it floods a bit as it grudgingly comes to life and then I need to keep RPMs up for a minute or so and then it runs and idles fine. If I let it warm to operating temp and then shut it down, it will then fire right up without a problem for the next hour, or as long as the block is warm.
 

91TwighlightGT

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I had the same basic issue on my car, and ultimately it ended up being faulty fuel injectors. You can buy cheap reman's on ebay. If the car sat for an extended period of time the ethanol based fuel is very hard on the injectors.
 

ChillPhatCat

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Thanks for the ideas, I will test the fuel pressure I swear, just did not have time to do it yet. The fuel injector thought is interesting... it did sit for 2 years before I got it so maybe. Still gathering ideas for everything to investigate.

So related fuel injector question... if I upgraded the injectors to 36 lb or 42 lb will the computer be able to meter the fuel correctly as is or is it going to need to be tuned? Some day I might turbo this thing... I know it won't do me any good at present and the fuel pump would need upgrade to actually get anywhere near 85% duty cycle. Not like they aren't dirt cheap but I always like to buy once if I can avoid buying twice.
 

Boostedpimp

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Verify your fuel pressure is where it should be and doesn't drop off instantly after the car is shutoff. I wouldn't worry about the fuel injectors yet and if one was bad you would have a very noticeable miss. Upgrading injectors if your car is mass air equipped would require a mass air sensor swapped in calibrated for that size injector your going with not a tune. If your cars speed density and your trying to upgrade the injectors then you'll need a tune but in either case upgrading the injectors is pointless and a waste of money if the car doesn't need the larger injectors.
 

91TwighlightGT

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Verify your fuel pressure is where it should be and doesn't drop off instantly after the car is shutoff. I wouldn't worry about the fuel injectors yet and if one was bad you would have a very noticeable miss. Upgrading injectors if your car is mass air equipped would require a mass air sensor swapped in calibrated for that size injector your going with not a tune. If your cars speed density and your trying to upgrade the injectors then you'll need a tune but in either case upgrading the injectors is pointless and a waste of money if the car doesn't need the larger injectors.
So, just to be clear, my car was presenting with very, very similar issues that the OP is battling. Mine is a '93 2.3L with dual spark and distributor-less ignition, so there is a slight difference in our cars, but not much.

My car sat for a long time while we were doing body work, and eventually it fell into an extremely hard to start and poor running condition. We replaced coils, wires, plugs, and I thought we had it nailed after that because it seemed to run a bit better. The next week it fell back into the same pattern, and we started thinking fuel pump as well - but after investigating it had plenty of fuel pressure. Seeing as how the car had run well before, we didn't really suspect a low compression issue. We ended up spraying starting fluid in the intake and the car ran well, then would die. Finally, we turned to pulling the fuel rail to replace the injectors. The car has never run better since.

My theory is that the injectors had become partially clogged, and because the Engine is asking for more fuel on a cold start it simply couldn't supply enough fuel for a reliable cold start. Once you got it running, eventually it would warm up enough and the semi-clogged injector would provide enough fuel to idle smoothly. In my case, over time the clogging continued to build until I had a complete no start situation.


To the OP - Since this is an unknown car, it would not be a bad idea to do a compression test to have a baseline. There are several things that could be going on if the engine has low compression.

#1 - It is simply worn out and needs a rebuild due to worn piston rings. This is the least likely scenario.
#2 - You have a car with a blown head gasket. If the plugs are getting wet from coolant, it can create this situation. Blown head gaskets are not unheard of on 2.3L engines, but you will also have other signs. If you have access to a boroscope you could see if there was any evidence of coolant in the cylinder, including particularly clean piston tops or actual water in the cylinder. The plugs also usually have signs of anti-freeze contamination.

Realistically, I don't have any reason to think you have a head gasket problem at this point. If it were my car, I would spray it with starting fluid and see if it fires up easily. If so, you can presume to have a fueling problem and go from there.
 

ChillPhatCat

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Apr 22, 2002
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I’d be surprised if the engine has any major issues but I have a pressure gauge somewhere kicking around to test compression, I’ll put it on the list. It has 98k miles on the clock and I would be hard pressed to believe it had rolled the odometer just because the car is really clean with virtually no rust and fairly tight in most respects. The engine oil is clear of water and the coolant is clear of oil, and the exhaust is normal when it runs, no hint of oil color or smell, no sweet smell of vaporized antifreeze... and when I pulled the plugs they looked normal, slightly brown, and free of oil or water droplets. Currently it has about 8 gallons of ethanol free 90 octane in the tank, which was nearly empty when I got the car.
 

junkyardwarrior

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Jan 10, 2011
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So related fuel injector question... if I upgraded the injectors to 36 lb or 42 lb will the computer be able to meter the fuel correctly as is or is it going to need to be tuned? Some day I might turbo this thing...

The right way to do it is to find a turbocoupe and rob the engine and all sensors, and computer from it. They come with forged pistons (your factory pistons are cheap cast pistons which will last about 2 seconds with anything more than 5 psi boost). 5 psi is a waste of time on a 2.3. You don't even notice it. 10 and you have something, but most run 15+. 87-88 urbocoupe's come with 36lb low impedence injectors. Your mustang has high impedence injectors and the computer won't recognize the low's from a Turbocoupe. I suggest not "turbocharging" the stock cast piston engine, just pull it out & put the thunderbird engine in as mentioned. You'll be further ahead in the long run; in other words a lot less headache.
 
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