Still dealing with a nagging poor running, stalling problem...

D

Doc

True Classic
Hey fellas-- happy July!

I'm still dealing with the nagging poor running problem and occasional stalling that has been going on for the last few years, and it's keeping me from driving the car very much.

I have a staycation next week, and time to work on this, so I want to get to the bottom of it once and for all.

From cold, the car starts right up and purrs like a kitten. After a few minutes of running, as things start to come up to temperature, it will begin to buck and want to stall. I've tested the injectors, the coil has been replaced, and otherwise everything seems tip top.

Today, as I was playing with one of my old cars with a mechanical choke, I forgot to turn the choke off, and that car began to act exactly like the X as it loaded up with fuel... and it got me to thinking-- is there any sort of electronic choke or cold start valve that might be failing/have failed on my X? I took a quick look in the FSM, and I didn't see anything, so I'm hoping one of you guys might know.

I'm also open to any other ideas you might have.
 
I've never had an FI X but I believe that system has a cold start valve. If it is not turning off, I would expect it to run too rich, just like leaving your mechanical choke on. Maybe you can try disabling it and see if it runs better when warm, Better yet, wait for someone who has expertise with the X FI system and see what they recommend.
 
The first thing to check when dealing with a temp related issue is the water temp sensor. It's easy to get to and it has a major influence on the amount of fuel injected into the engine. Don't forget to check the wires/connection too.
 
The cold start injector could be leaking, some crud could be in there causing it to dribble fuel. As a CSI is intended to dump a decent amount of fuel its ‘dribble’ can be substantial.

They sell aerosol injector cleaner units to clean injectors with a 9v battery. I would try this.

The warm up regulator may be working incorrectly, it controls the CSI. It is bolted to the head to get heat but also has a built in heater to close it thermostatically and shut off the CSI. A way to test this is to unplug the CSI electrical connector and see if the problem persists. (Plug it in to start and then immediately unplug it at the injector). You can then use a noid light to time the period there is electricity being run to the CSI.

Following the injection system trouble shooting guide carefully would be a good thing for you to do. The procedures are intended to parse out any problems and written so that an idiot like me can find a problem.

You can find the guide in the WIKI
 
Thank you gents! I've read the FI manual, and I think I understand what I need to do, but there are no pics of the CSI- what am I looking for?

Similarly, where is the water temp sensor and what does it look like?
 
The cold start injector is in the left end of the intake log looking from behind the car. Its body is generally blue.
IM002908.JPG
 
Water temp sensor is in the top half of the t-stat body. You can see the white electrical connector in this picture. CSI is barley visible at the top of the photo.
IM002529.JPG
 
The cold start injector is a stand-alone system; the only thing it shares with the rest of the injection is it's fuel supply. It is controlled by the thermal time switch.

If there's a problem after the car runs, it's more likely the temp sensor (in warm weather).

Starting for my '86 usually involves cranking for about 5 seconds (edit: really closer to 3 seconds), pausing (when I usually put on my seat belt), and it will start instantly on the next turn of the key. In warm weather, it may catch in the 5 (3) seconds.
 
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Thanks Jim!

Jefco- car starts fine. It does this no matter the outside temp as the car warms up.
 
Ok… so I was able to detach the cold start valve- it wasn’t that. Though curiously, it didn’t spit and sputter like it usually does. After a few minutes of running, it just stalled and wouldn’t restart.

I see the white temp sensor- I couldn’t get the connector off (though I really couldn’t see what I was doing once my hand was in there. Is there a truck with that one? Also, would that sensor send the engine temp to the gauge on the dash? That gauge has always worked fine, but I noticed today it hadn’t moved at all, even when the car had been running for several minutes.
 
Doc said:
Ok… so I was able to detach the cold start valve- it wasn’t that. Though curiously, it didn’t spit and sputter like it usually does. After a few minutes of running, it just stalled and wouldn’t restart.

I see the white temp sensor- I couldn’t get the connector off (though I really couldn’t see what I was doing once my hand was in there. Is there a truck with that one? Also, would that sensor send the engine temp to the gauge on the dash? That gauge has always worked fine, but I noticed today it hadn’t moved at all, even when the car had been running for several minutes.
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No, the H2O temp sensor only feeds info (resistance values) to the ECU, there is a separate sensor for the gauge. The H2O temp sensor is the sensor that has the most influence on how much fuel the engine receives, so if it's bad it can have a real impact on how the engine runs. They have been known to go bad, but because of the location, the wire connection is prone to damage too.
I can't remember the resistance range (changes with temp) but the FI troubleshooting guide will have it. You don't have to take the connector off to test it, you can test it at the ECU connection. The FI diagonstics will tell you which pins to test.
If my memory serves me, the resistance goes down as the coolant heats up. That means that if the sensor isn't working the ECU is receiving information that tells it to send MORE fuel to the engine - as if the engine was still cold. I think you're having symptoms like this - you're getting more fuel than the engine needs as it warms up. It runs OK when it's cold - right?
 
Mike is 100% correct, as the temp goes up the resistance reading goes down. The sensor is of the NTC variety.

The PREFERRED (aka "smart" way to ohm out the CTS (coolant temp sensor) is at the big plug on top of the FI controller in the spare tire compartment. Why? Because with one test you evaluate the CTS and the wiring from the FI controller to the CTS to its ground on top of the cam box.

If you test only by testing resistance at the CTS's plug, you only evaluate the CTS itself and may miss an issue with the wiring.

The roadside repair for a CTS that fails with a too-high resistance reading (and would therefore encourage the FI controller to increase the injector duty cycle, resulting in a too-rich condition) is to unplug the harness from the CTS and short the harness plug leads together, effectively delivering a low-to-zero ohm reading to the FI controller, telling it the engine is well-warmed up and no mixture enrichment is necessary to compensate for low engine temps.
 
MikeHynes said:
It runs OK when it's cold - right?
Click to expand...

Correct-- it starts without hesitation when cold, and idles beautifully until it starts to warm up. I'll need to spend a little time dissecting the rest of your post and Dan's, as I'm not really sure I understand what I'm being asked to do. The wiring to that sensor looks fine... not frayed or cracked, and the boot is still soft and supple.
 
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Understood. I’m not terribly mobile these days (need both knees replaced), so path of lease resistance (pun intended) is easiest, and I don’t mind spending a few bucks to avoid crouching or bending.

Am I correct in thinking I’ll have antifreeze spewing out when I swap this? I’ll need to prepare accordingly. Teflon tape on the threads of the sensor, or no?
 
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