Time to start a new post. I have subject Exp that starts normally and idles for a few seconds then abruptly dies. Cold or warm, makes no difference. Codes don't indicate anything. Fuel pressure normal, vacuum normal, new plugs, wires, o2s. MAF, IAC, TPS all checked good. Static code check nothing. Can't get through a running test as engine flucuates and dies. When it does make it through the codes that show don't really mean anything as engine rpm was so erratic.
Any movement of accelerator caused engine to gasp and stall unless I let go back to idle and it will recover.

Question is how can I isolate this? Changed the pcm two months ago and car has run good for that long.

 

Air, fuel and spark - need all 3 for an engine to run. PIP codes is suspicious. Did you check for spark at every plug? Specs are around somewhere but ther's a coil resistance spec that can be checked.

 

It really sounds like it's starving for fuel. If pressure is within specs at idle and beyond, test your TPS.

 

I will recheck as much as I can, tomorrow, when off. Before, fuel pressure was 40 static and 31 at idle. When car died, you could see fuel pressure climb as engine rpm decreased. I believe it to be ok.

Vac was at 20-21 and relatively stead during smooth idle. I don't believe I have a vac leak. If I did, I'd expect it hear something and see it effect idle consistantly, not every 20 seconds or so.

If air was issue, opening throttle seemingly would take car of that, but engine acts as its stalling, like said before, for fuel. Don't know if timing would cause such a reaction.

This leaves me with the spark side.

I'll pull plugs again tomorrow to see if there's anything to see. There wasn't when this first started occuring.

I'm at a lost as how to proceed with troubleshooting the icm/pcm. I'll see if I can pull spark plug wires off and check for spark at each cyl.

I don't think an internal problem would manifest itself like this, so am leaning toward a controls issue. As said before, MAF, TPS and IAC checked good according to the mx manual, but this is an intermittent problem and these tests might not show the malfunction. That said, I don't see how the MAF could cause engine to die. I don't see how the TPS would be the culprit when cracking open the throttle causes the engine to starve/decay. That would seem to be bypassing the IAC, taking it out of the equation, too.

What I think I'd like to know, is what pins I could monitor at the pcm that could help me determine if signal/voltage/ground is being lost causing ignition to drop/kill engine. sorry for the rambling, but this is the basic question.

 

IM me your email address and I'll send you a document I put together with the PCM pinouts. It's got both CA and Fed so scroll down to the Fed.

Also, there is a device called a break out box. Rutunda made for Ford techs. Might be other manufacturers too. It runs in series between the PCM and the wiring harness and lets you tap into all pinouts while the PCM is still hooked up and running the car. There's a little breakout board with the 60 pins accessible. Have seen them on eBay from $50 to $200 depending on the shape of the unit and that particular auction.

There was a post a few months ago where a 4.0 had bad idle and stalling problems. Ended up being a corroded wiring connection at the coil. Since you got a PIP code, I'd check all the connections that control spark. You know where the crank position sensor is, the ICM is located in front of your battery, coil is obvious. I'd take the connections apart and clean with carb or electrical contact cleaner, visually inspect and try again. Intermittent problems can sometimes be as simple as a bad connection and can come as abruptly as you mentioned - working in the morning then afterwork, started acting up.

 

Just read through your first post. Man you've been through the wringer on this. When you changed your crank sensor, I think when you first jiggled the old one, it lost signal to the PCM. The fuel pump may have been thinking RPM's were >0 and thus kept driving the fuel pump. Fuel pump realy did not stick but pulling and replacing PCM relay shut off fuel pump after 2-3 sec's. Maybe the new sensor and cldeaned up oil gave a better connection to PCM.

Then on the 522 code, if your nuetral switch on the passenger side top of tranny is stuck open or wires borken off, you'll always get that code. Is this a 4x4, I can't remember. If so, I bet you can't get into 4x4 low range. I just found tht my switch was stuck closed so the PCM always though it's in nuetral. And since my rebuilt tranny had no port for the nuetral sensor, I just cut off the connector and jumbered the wires. Somthing els to look at when you get this straightened out.

Verified all spark connections as discussed and if you are getting wet plugs when it stumbles and dies, those plugs are not getting a spark. I chased this issue on my 2 stroke JetSki for a couple years - bad coil. Worse case, is the PCM you bought under warranty?

 

The neutral switch is another story. I put a new transmission in about three years. It was a new unit. The only thing different was that the electrical harness didn't have but one switch to hook up to. There was no place to swap over the old switch, so I found out that the backup switch worked ok and everything else (at that time) seemed ok, so I just bagged up the extra connector and tied it off above the tranny. That was what was causing me the 522 all along. Way back when we were first looking at it, I sorted it out, but didn't want to divert the subject, so didn't mention it. I crawled under car and shorted the connector and the KOEO and other tests then worked correctly. I currently have it jumpered, but didn't know if I could/should leave it that way and drive the car or not---what it might to to pcm/program/etc.

 

The only thing I can see the transinission mounted nuetral safety switch do on a manual trans like you and I have is to lock you out of 4W low. I know this used to work, years ago. I tried to put it in 4W low while in gear and no doing (obviously with the clutch pressed in) - only worked in nuetral. The start/no start is only hooked up to the clutch petal 3 position switch. In fact when I asked autozone for a nutetral safety switch, they pulled out the 3 position switch. Napa only had auto tranny nuetral switches. Ford looked like the right one on the microfish but it was $118 and 3 days out. Glad I didn't order it since my new tranny doesn't have a port in the shift rod cover for it - sounds like yours doesn't either. When I pulled the tranny last week, I tested the back-up and nuetral switches. Back up was OK but the nuetral switch was stuck colsed. So the PCM thinks it is nuetral all the time. I figured, if everything works like this, jumper the harness and have one less leak potential on the tranny - just like you did. I'll have to see how my 4W low engagement works now -in and out of gear. Haven't used 4x4 for a while, boo hoo.

 

I have only a 2WD Exp, so it sounds like I can just leave the harness jumpered. I wasn't sure it would somehow tell the pcm, "Hey, he's in neutral, even though I think he's going down the highway at 60," and adjust fuel and air like the car was stopped, etc. Guess I'll find out, once I get it to run.

 

No. Nuetral switch does not play into the tables like that. Engine load calculated by actual air flow / TPS opening and RPM give the main A/F. Coolant and air temp have a lessor affect.

OK one other area where the switch comes into play, KOER tests. I guess if the clutch is engaged and the PCM thinks it's in gear, it doesn't want to rev the engine up and do all those tests if the car will lurch forward. That's all I can think of. You should be safe.

 

Yup. 4x4 will now go into low while in gear. Still need the clutch pressed in though so there is at least that level of safety. Nuetral switch on tranny then good for just 2 things 1) locking out 4W low and 2) allowing for KOER tests. Well at least the old switch didn't get stuck open and not allow 4W low. I'd have been scratching my head on that one since I've already rebuilt the shift motor assembly.

 

You might check your engine temperature sensor ( for the PCM) I say this because the other day when flushing my warm engine and waiting for the air to burp as I refilled the system, any quick throttle movement would kill the engine. Slow throttle pressure would bring the engine speed up ok. Once the coolant was circulating the engine ran fine. I flushed this engine 3 times and each time same thing, the last time I pulled a heater hose to bleed out the air quicker, these things are finicky. Last night same thing with the wife's Aerostar 3 litre. Hope this helps.

 

Thanks, I wouldn't be surprised, but this afternoon I pulled plugs and found bank 2 plugs carboned up. Tomorrow, I'll swapout both o2s as they are still under warranty and see if that helps/fixes, at least for a while. Not sure how much further I can get with this old car. I had wanted to make it to 300K but I'm about 4K short right now.

 

Talk about going the extra mile - or 4000 of them! yeah if the drivers side O2 don't fix it, you're looking at some other mechanical thing.

I am at a loss as far as the long term correction factors in the PCM. You ran OK for 1,000 miles with a new PCM then bang, it crapped out again. Maybe a long term correction factor kick in after so many cold starts. maybe the new PCM was collecting data, collecting data, and then said - OK we need a change.

Let's see what happens with new O2's. Post results!

 

Can't say definitively it's fixed, but swapped out both o2s, reset computer and it's running ok. Drove it a few minutes and it seemed pretty smooth after warming up. I pulled codes and got nothing. Cross your fingers. Thanks all.