Misses/Stalls on hot restart

[TedJ]

I've got a 94 Sport with around 64k. It's got new plugs and wires (motorcraft), all the filters are new (air/oil/gas), and the coolant was just changed. No lights are on.

The problem I'm having is very intermittent. 99% of the time my truck starts and runs fine, but every once in awhile, after it's been fully warmed up and then allowed to sit for maybe around 30min it occurs.

The truck starts on the first try, but it starts to run really rough, not like a dead miss but very rough. Usually if I give it some gas it will smooth out, or sometimes I have to shut it off and start it again, which fixes it as well. Yesterday I thought I was not going to get it running. I started it, and it was ok for a second or so, then began missing. I had to put my foot on the gas to keep it running, and it just kept missing more and more till I had my foot on the floor and it stalled totally. I started it again and did the same thing.

It feels kinda like turning the ignition on and off rapidly, like it runs in spurts.

Then I got out, popped the hood and looked around for a minute, and not seeing anything I tried it again. It started right up and ran fine as usual. I drove it home (45 min) and it was fine, started it this morning and went to school, and it was fine.

Any ideas? Crank sensor?

Thanks, Ted

 

[manaen]

oh boy, those intermittent problems can be a bear, I would do the usual diagnostics, fuel pressure, test the coil pack, clean IAC and MAF it would be nice to have a computer hooked up while it was acting up but thats probably not going to happen. Did you ever change your fuel filter? if not I would do that as well.


in general electrical component tend to fail more when they are warmed up because solder joints stretch when warm

 

[TedJ]

Yea it's so intermittent. Yesterday was the first time it's happened in over a month. The strange part is that its like an on/off switch. It runs perfect as soon as it decides to. The fuel filter is new, mentioned that in the original post.

-Ted

 

[manaen]

I guess I would go over all the connections on the engine compartment, clean them, use tune up (dielectric) grease in everything, and see what happens. It could be many things, and sometimes just a good once over on the wiring harness cures the problem, and you may find some corrosion or shorted wires or something.

 

[mawrazen]

O2 sensors?

 

[manaen]

O2's wouldnt cause such a severe miss. sounds more electrical.
are there any codes at all?

 

[lofton316]

My 91 does the same thing. Im sure its a fuel thing. It only happens sometimes when its hot!

 

[manaen]

Maybe try replacing the fuel pump relay, they are cheap.

 

[lofton316]

Maybe try replacing the fuel pump relay, they are cheap.

Its Not The relay!

 

[manaen]

How can you be so sure it is a fuel thing, have you checked the pressure when the problem occured?

 

[TedJ]

Probably not the O2, i wouldn't think that it would even be closed loop yet. The relay works ok because as soon as it dies you can hear the pump running. I would think more towards electrical... but besides bad/corroded wring are there any sensors I should look at?

Can there be codes that will not turn on the CEL but that I would be able to get if I read the codes?

-Ted

 

[lofton316]

Probably not the O2, i wouldn't think that it would even be closed loop yet. The relay works ok because as soon as it dies you can hear the pump running. I would think more towards electrical... but what should I look at?

Can there be codes that will not turn on the CEL but that I would be able to get if I read the codes?

-Ted

When the last time you had your Pcv valve changed?

 

[TedJ]

Hmm....I'm not really sure, It could be original for all I know. How could that cause the symptoms I'm experiencing? Not that I am doubting what you are saying, just that I would like to understand it better.

-Ted

 

[manaen]

Probably not the O2, i wouldn't think that it would even be closed loop yet. The relay works ok because as soon as it dies you can hear the pump running. I would think more towards electrical... but besides bad/corroded wring are there any sensors I should look at?

Can there be codes that will not turn on the CEL but that I would be able to get if I read the codes?

-Ted

yeah there are soft codes that the computer will only show during a KOER test.

 

[lofton316]

Hmm....I'm not really sure, It could be original for all I know. How could that cause the symptoms I'm experiencing? Not that I am doubting what you are saying, just that I would like to understand it better.

-Ted

My pcv value is the orginial or hasnt been changed in Years, There is rust all over the top. I changed it out for one day but then everytime i start the car it would sound like its choken, it would die out every few starts and once i put it in drive it would act like it doesnt want to go anywhere. So i switched the old one back in. And with that one it it stalls when its hot and randomly between starts it dies out or act like it doesnt want to move unless i floor it.

So im going to try something. I am going to change the pcv again to see if that changes anything. If the pcv is not in, the car would either not start or began to jump up in down like hydraulics installed So that may be the problem. I will test the new one out for a week and see if the problem cease, but if yours is the original you should look into replacing it anyway!

 

[manaen]

the EGR can be tested to make sure it is working properly, it is also monitored closely with the DPFE sensor so if it is not opening or closing at the appropriate times the computer should throw a code.

 

[TedJ]

OK good stuff guys, thanks a lot. I think I'm gonna go find that thread on reading codes and see if there is anything in the computer...

-Ted

 

[TedJ]

Update: I didn't get a chance to check the codes, but I realized that I have the ORIGINAL PCV valve....It still rattles but it didn't seem as fee as it could be. I cleaned it a bit, and I'm gonna go to the store and get one in a day or two, I've been really busy. I never realized that the PCV was so essential for it to run right, and I totally forgot about it when I did the tune-up.

And manaen, don't you mean EGR, not PCV?

-Ted

 

[manaen]

And manaen, don't you mean EGR, not PCV?

-Ted

Yup, I did, sorry bout that, thanks for the catch

 

[TedJ]

Ok, so I went to the Ford dealer today, got a new PCV valve, which came with a vacuum tee and cap, which I didn't need (but who doesn't love bonus parts). Is it just me or do you feel good when you open up a Motorcraft box? I save the boxes too... maybe I have a metal problem, but I digress.

I put it in and now I will wait and see. It could be awhile before I can be sure that it's fixed, it happens so rarely. Thanks everyone!!!

-Ted