Ok, I'm baffled.

[osiris_9510]

Well...it runs great, really. But every now and then it wont start up. I'd say the problem occurs 1 time in 5 cranks. If you let it sit a few minutes (up to an hour!), it will start up again. The mechanic has checked just about everything, and has no idea whats going on with it. Here's what he's replaced (all used parts, for diagnosing the problem. He's not charging every time he replaces a part, he's just trying to rule things out.):

Plugs, Wires, Coil Pack (I already paid for these 3, this was an unrelated problem. he even tried different ones to rule out the new parts.)
Mass Airflow Sensor
Crankshaft Position Sensor
Fuel Filter
Fuel Pump

He also checked the fuel line, cleaned the injectors, cleaned the intake/throttle body, replaced air filter, etc. Computer shows no error codes, even the dealership's big computer. Otherwise it runs fine. When it won't crank, you can smell gas, so its getting fuel. And there's plenty of spark (new plugs), and the intake is clean. I'm just as clueless as the mechanic. Its been at another place for 2 weeks now, another guy is looking at the electrical parts in it. But I'm just fed up now.

Could this be a faulty security chip in the key, or on the computer?

Could it simply be a faulty computer?

Could this be a loose wire in the steering column?

 

[osiris_9510]

Forgot to mention:

2001 Ford Explorer XLT, V6
2WD
SOHC

 

[osiris_9510]

Any ideas???

 

[corkey]

could be the key chip,
when it won't start try taking the key out , and putting it back in again, or using a different key, that will tell you ,,

 

[osiris_9510]

Tried my spare key today. Got left stranded at the Post Office for an hour. lol

Here's what happened. Cranked it up, went to the store. Came out, cranked fine. Got to the Post Office, came out, and it wouldn't start. After an hour of flooding and fantasies of tumbling its iron carcass off a cliff, it started up. Put it in reverse, began to back out, and it quit. Would not crank for another 15 minutes. Started it up again, backed out, went to the office, giving it gas the whole time, even at the stop sign. Put it in park, let it idle. It quit in 4 seconds flat. Would not crank again. Here I sit, finally eating my lunch. I notice that it runs very rough right now. But this morning and last night it was fine. No rough idle and no cutting off.

 

[budwich]

I think that you need to clarify your "would not crank" statements. "Not cranking" normally means that your starter is NOT turning and thus the motor is not being cranked... just like in the old days... when you went and cranked on the front of the engine with a crank. IF this is the case (ie. not cranking), then you likely have an electrical issue going to the starter. IF the starter is turning along with the engine, then you have a different issue as opposed to "not cranking". Suggest that you read a few "no start" threads and ensure that you follow some of the normal steps for trouble shooting "no start conditions".... CEL light on with key on, CEL light then off with starting attempt, fuel pressure, spark, etc.

 

[osiris_9510]

Ok let met clarify. The engine will turn over. If you hold the key long enough it will flood (you get a strong smell of gas, anyway). CEL light comes on when key is in. CEL light goes off when attempting to crank.

My mechanic had this in at his shop for 3 months. He told me:

It has spark.
It has fuel pressure.
It is getting air flow.

To trouble-shoot, he replaced the following with spares:
Plugs, Wires, Coil Pack (I already paid for these, this was an unrelated problem. He even tried different ones to rule out the new parts.)
Mass Air Flow Sensor
Crankshaft Position Sensor
Fuel Filter
Fuel Pump (It did have low fuel pressure. He replaced this. Fuel pressure reads higher.)
IAC Valve
Spare Key

My mechanic's computer showed no error codes.
The Ford Dealership's big computer showed no error codes.

My mechanic gave up. He sent it to someone else who deals with automotive electronics. They checked the computer and wiring in the steering column. Mechanic #2 could not fix, did not charge me any money. All in all, my mechanic only charged me $100. He told me it wasn't fixed, and said that he did have to charge me something. And the fuel pump needed replacing, if not now then soon. I think he was just glad to be rid of it.

Edit:

He did a compression test.
He replaced the EGR valve.
He cleaned the injectors.

 

[budwich]

thanks for the clarification and re-iteration.... so definely cranking but no start. OK last question what is the "observation" on the theft light??? and one more clarification, when the key is put in and turned JUST TO ON.... and left there for a long period of time... the CEL stays on for the WHOLE time... right???

 

[osiris_9510]

thanks for the clarification and re-iteration.... so definely cranking but no start. OK last question what is the "observation" on the theft light??? and one more clarification, when the key is put in and turned JUST TO ON.... and left there for a long period of time... the CEL stays on for the WHOLE time... right???

When key is in ON position (not cranking, just in the ON position), Theft light comes on for 2 seconds, then goes off. When key is removed, Theft light blinks every two seconds.

When key is in ON position, CEL comes on and stays on. CEL goes off once the engine is running.

 

[budwich]

again... some more clarification... good on the theft part.... likely means that the key is detected and everything is "good" on the theft side... probably... maybe.... but on the cel stuff not quite sure what you mean. You said.... "CEL goes off once the engine is running.".... BUT we are discussing a NO START so are you saying when the engine is running... you mean the engine is turning via the starter and not actually running which would normally mean started / normal firing... right???

You also mentioned "flooding"... how have you determined this... pulled a plug... its wet????

Certainly a tough problem if you can't readily reproduce a "predictable" outcome at any given instance. IF plugs are wet, you are likely looking towards electrical based issues.

 

[ranger7ltr]

Have you or your mechanic checked the camshaft position sensor

If that sensor doesn't function the PCM will not be able to determine when to start to fire the plugs...

And I can't remember if an intermittent/defective camshaft position sensor will throw a CEL or not...

 

[swetrid]

Did he put a used or new fuel pump in? If new pump what brand? Most aftermarket fuel pumps are junk. I still say fuel pump.

 

[2000StreetRod]

test equipment

Intermittent problems are the most difficult to diagnose. Since you know that you have good compression (on all cylinders) from a previous test by the mechanic that leaves ignition, fuel and timing of both. I suggest that you install an under-the-hood starter control as in my thread: Remote crank control installation

Then purchase an inexpensive fuel pressure gauge, noid light and ignition tester. Keep these items in the vehicle so you can use them the next time the engine won't start. Even if you have new spark plugs, wires and coil pack that doesn't guarantee you have spark to the plugs. Even if you have a new fuel pump, fuel filter and clean injectors that doesn't guarantee there is fuel to the injectors and they are firing.

Once you verify that there is spark, fuel pressure and the injectors are firing that leaves timing of the spark and the injection pulse. The PCM and the crankshaft position sensor control the spark timing. The PCM and the camshaft position sensor control the injector timing.

My guesses would have been a faulty crankshaft position sensor, a faulty fuel pump or fuel pump relay, or a faulty camshaft position sensor.

You may want to swap the fuel pump relay with the blower motor relay. Also, make sure the spark plug wires are routed so they aren't shorting out to ground between the coil pack and the plugs. If your new spark plugs are Bosch platinums I would replace them with Autolite or Motorcraft.

 

[osiris_9510]

Its fixed!

I'm no mechanic but the 2nd mechanic told me that it was the sensor inside the manifold, which I *think* would be either the MAF sensor or the MAP sensor. On a 2001 Explorer XLT 4.0 SOHC, what would be the sensor in the manifold?

 

[swetrid]

He probably replaced iac valve.