94 Explorer VIN X V6 runs for a minute and dies

Hi Jim:

For the time being, I would not invest any more time in things that have to do with the ignition.

I would concentrate on why the injectors are not getting the proper juice. From what I know, the CMP is critical for the injectors though not for the spark.

I see you tested the circuit to the CMP but did not mention anything about testing the CMP itself.

Can you identify the positive in one of the injectors and measure the voltage against ground when the car dies? Is the 12V present all the time when the ignition switch is on? Remember, the injectors have the

Temperature, MAF, throttle, pressure, etc. sensors when defective, make the idle and running of the engine irregular but do not kill the engine.

Yes the PCM controls the injector activation but it requires signals from the CKP to know when to inject and CMP to know which cylinder to inject.

Is the ambient temperature any lower? This could explain why it took longer for the car to die.

I am sure you will find the problem pretty soon.

This forum is scary:

J Adams wrote:

Hi Alex:

Found this on the internet: "Double check all grounds.Does it have a cam sensor as well? The PIP signal goes from ignition module to PCM.If there is a conflicting angle signal between cam and crank it will can set this code" Regarding the 211 code I was getting.

As I have refined my testing procedures it has become obvious that CMP circuit (somehow) is the culprit. I can test the CMP and PCM, but the testing procedures require a backprobe. Any idea how the tests can be run without one?

Just gained access to Mitchell on Demand and found the section you mentioned on engine performance. Very detailed! Especially the testing procedures. Also, much better wiring diagrams than my Haynes book and includes the location where grounds are terminated. I did a quick check of grounds for corrosion and didn't find any, now on to the circuits. It's California car that has been in Arizona for the last five years. I bring that after the reading the thread you posted below and today intend to be more thorough in testing. Pulling the CMP requires removing everything down to the heads, as it is located behind the intake manifiold and there is only about 4 or 5 inches of clearance. All those new gaskets ....... :-( Plus the CMP is the single most expensive item at a little over $400 and the PCM is only $165. So I obviously am willing to do more testing before spending that on top of the money I have spent replacing good components. Education is never cheap and I have to admit I understand how the 'modern' engine works and why it was designed that way.

I can do that, but I'm not clear about how to do it. I assume I'm looking for a voltage drop. I have to be careful about which tests to run because of the time lag to be able to restart the engine. When it won't restart the injectors not activating is very obvious and clearly the problem. At the point, now that I have injector signal as the source, should I do these test on each injector?

That should be easy enough to determine. What would that tell me?

CKP has been replaced, but not CMP.

Yes the temperature is lower. And I thought I had done something to affect that.....

Lets go over the basics for the fuel injectors:

They are 12 volt solenoid valves, when the ignition switch is on, +12v is always applied and the ground is switched on and off by the PCM to inject the fuel as needed.

So, to identify the +, disconnect one of the injectors, turn the ignition switch on and with a voltmeter or the lamp, find out which terminal shows 12v (or makes the test light glow brighter) with respect to ground. Once identified, you need to make sure that the 12 volts is is there at all times when the vehicle is running or cranking. If this voltage disappears you may have a defective relay or ignition voltage (think switch). Measuring just one injector should suffice.

The negative (ground side) is controlled by the PCM. That means, that the PCM grounds need to be clean and tight. Make sure that you have unplugged and plugged the PCM connector(s) as to guarantee good electrical contact there.

For the PCM to control the injectors, it needs signals from the CKP, CMP. The PCM will use other signals like the MAF, Barometric Pressure, coolant temp sensor, TPS etc etc to determing the length of the pulses.

Given the difficulty in replacing the CMP, lets wait until you can be sure it is the culprit.

As far as test> >

Hi Alex

Here's the latest:

Used the backprobe at the connector base of the PCM. Just tested the CMP circuit using this and the Mitchell specification 6.8VDC at idle and the rest below from the Autozone site:

1. With the ignition OFF, disconnect the CMP sensor. With the ignition ON and the engine OFF, measure the voltage between sensor harness connector VPWR and PWR GND terminals (refer to the accompanying illustration). If the reading is greater than 10.5 volts, the power circuit to the sensor is okay.
2. With the ignition OFF, install break-out box between the CMP sensor and the PCM. Using a Digital Volt-Ohmmeter (DVOM) set to the voltage function (scale set to monitor less than 5 volts), measure voltage between break-out box terminals 24 and 40 with the engine running at varying RPM. If the voltage reading varies more than 0.1 volt, the sensor is okay. Fig. 3: CMP sensor wire harness connections for the 3-wire sensor VPWR - Black/White PWR GND - Red CID / CMP - Dark Blue/Orange

Both tests 1 and 2 came back OK. So now I'm back to why does it run for a short period of time and then the injectors loose their signal but I still have spark. Can start it twice OK, but the third time No Go. Just intermittent signal to the injectors. Also hooked up the DVOM to the injector and voltage was present even when the engine died (so not the ignition switch?). The CKP is also fine, does that leave the PCM?

I did not replace the Oxygen sensors.

Jim

I am glad the CMP was not defective (the cost thing).

At this point the PCM seems to be the one telling the injectors to stop working, either by being defective or by getting signals that tell it to do so. I would check the power and grounds for it.

Most likely you will need to replace the oxygen sensors, antrifreeze poisoning of O2 sensors is almost a given in your case. The antifreeze residues will cover the O2 sensor, not allowing the O2 in the exhaust to reach the sensor. I think that if this is the case, they could be telling the PCM that the engine is too rich, forcing the PCM to lean out the mixture. O2 sensors begin to work after they reach operating temp and this takes a couple of minutes. Disconnecting them should force the PCM to operate in open loop and should allow you to see if the engine runs longer. It is worth a try.

Almost at the bottom of the linked page, there is a very nice description and test procedure for O2 sensors:

Good luck Jim, you are (should be) almost there.

J Adams wrote:

Hi Alex;

Just tried quick start/off cycling. I was able to get 12 cycles and ran KOEO at the end and the 211 code reappeared. The first 6 or 8 starts I didn't have to touch the accelerator, each start after that a light touch was required to start. I checked the TPS for dynamic response with a DVOM and received the voltage variation expected from RPM change.

Apparently the problem is when something is getting warm/hot because I went from 2 starts and letting run until it died to 12 quick starts/off. Also tested continuity/ground of PCM and everything OK included voltage test of each ground and all came back well under one volt (per spec).

The 211 code requires at least 2 starts/runs before it's generated. So the multiple start/st>I am glad the CMP was not defective (the cost thing).

found this .... where a truck would run for a while and then die. He eventually took apart the ECM and replaced the electrolytic capacitors in the ECM which fixed his problem. It is possible that the problem is related to a leaky electrolytic cap that will charge properly when first powered up, and then lose it's ability to store charge as it heats up. Metal can electros have an expected service life of 5 years, and anything past that is a gimme. I'm not saying that this IS the problem, but it is definately something to suspect, but unfortunately if you are not "into" electronics the only way to test for this would be to replace the engine control module.

Wouldn't leaning or enriching the mixture be a matter of pulse duration? I will try this, disconnection, but I might try the testing procedures in the link you furnished first.

Did you align the CMP properly? This could cause the code and all the problems.

Yes, leaning or enriching the mixture is a function of the pulse length, and normally, this should not cause the engine to stall, but we are not dealing with a normal situation. Unplugging the O2 sensor is easy enough.

J Adams wrote:

Hi Alex

I think the problem has been found ..... using a hair dryer...

Stuck a hair dryer on the PCM, started the car took it to 1800 RPMs (simulates 55mph). It ran for 18 minutes.

After holding the hair dryer for 10 minutes it become too hot to hold so I shut it off. Sprayed some compressed air to cool the PCM, but it was very very warm. Ran it at the 1800 RPMs for another couple of minutes then let return to idle and it ran for another six minutes very smooth. Then missed a couple of times and died. Touched the PCM and it had cooled considerably, well at least I could touch it.

Next

Tried to start it, wouldn't start.

Heated the PCM and it started, ran for 15 minutes varying the RPMs and smooth as kitten. I kept heating it up with the hair dryer every few minutes. Shut it off. Started it up again without touching the accelerator.

Just inspected the board, nothing comes back as obvious and I used a big magnifying lens. No cracks, loose connection or such that I can see. This is a problem that got progressively worse starting a couple of months ago. More like something going bad than something loose.

Don't capacitors behave that way? A little $2 item if I knew which one and if that is indeed the problem.

Oh, I forgot, tested the oxygen sensors and they were OK.

The reason for the hair dryer was to induce a failure quickly and just the opposite happened. Net result was the same.

Jim

Congrats!!

Yes Capacitors can behave this way, I call them the plague of the electronic devices. I have a small box with all the ones I have replaced over the years. The Electrolytics have a rather short life span if used at the max ratings. Designers can improve their life by choosing capacitors with higher than required ratings, but i guess cost kills the good will.

When electrolytics fail they normally bulge or leak mainly by the leads rusting the lead and sometimes the pcb (printed circuit board). Some other times, they do not show signs at all.

Because the PCM failed when cold, i would rather think that the problem is a cold solder, either at the point where the plug terminals are soldered to the pcb or at any of the bigger components, resistors, power transistors, etc. When looking for cold solders I use a magnifier at least 10x, but prefer to use a stereo microscope that gives me 20 or 40x.

Keep in mind that the problem could be one of the components being defective itself vs a cold solder. In diagnosing this kind of problems, technicians use a source of hot air or cold spray that can directed toward individual components.

The local junker sells the PCMs for about $30.

If you do not have it already, a Craftsman tester with capacitance measurement goes for about 20-30 bucks. You will need to take the capacitors off the board to test them and this can be a pain, particularly with poor quality boards in which the copper tracks become detached from the pcb when heat is applied. A good desoldering tool is worthwhile if you plan on doing this yourself.

How long have you had this problem?

Good luck!

J Adams wrote:

running and

engines don't

Hi Alex

Thanks for all your help.

This problem actually goes back further than I initially thought. The reason I say that is about 6 months ago I would get a miss at idle and not at any particular interval. Then about a month and half ago I had an episode of severe missing and then no problem the next day. Maybe a week later another episode. The frequency began to increase and the stalling started. Then finally I didn't trust it at all and decided to rebuild the upper engine because I knew I was leaking antifreeze into the cylinders.

So today when the heat test worked and I had no missing at all, which tells me the problem crept up quite a while ago.

I've taken the PCM apart and looking at solder connections and components. Nothing looks like what you're describing. I'm using a Photographers Loupe 8X for inspection. Getting apart to look at the pins connections may damage it because of the way its assembled.

If I did find one I might be willing to troubleshoot this one to satisfy my curiosity as to the cause of the failure.

What tests could I run, cold I assume, to see if a cold solder connection is the culprit.

Jim

running and

engines don't

Hi Jim:

You are welcome, I am so glad you found your problem.

You should be able to see a cold solder with the magnifying glass, you will see the lil crack, around or under the component leads.

Usually the larger components carry bigger electric loads and those are the ones that normally get cold solders or solder fatigue (repeated heating and cooling cycles).

For now I think it is worthwhile checking with your local junkers. This next weekend I may go with a friend to the one around here and even though I doubt that i will find a California vehicle, I will check the PCMs.

Good luck!

Alex

J Adams wrote:

running and

engines don't

Thanks Alex

Local guys here not much help.

I'm still going to try and isolate the problem.

Jim