94 5L: starts but stumbles/stalls out

[Stangarossa]

Looking for some expertise on a problem thats may have me beat.
Vehicle dies out while driving a week ago, and would not fire again, until trying the car a week later.
Now the car will fire, but quickly stumbles out and stalls.
I got spark at the coil. I got fuel at the rail - but no fuel pressure gauge. Out of a week of screwing around, I actually got the car to run smooth for about 4 minutes b4 dying out again.
I pulled out my basic OBD 1 code reader and got a 121 code : Throttle Position Sensor fault.
So here is what I have done since, with no luck:
Installed a new TPS, Installed a new fuel filter, Installed a new cap/rotor, cleaned the MAF and AIT, cleaned the Throttle body. Fuel pump was replaced about 1500 kms ago, plugs and wires replaced with factory motorcrafts about 8000 kms ago...... Do you guys think I have a faulty pump, or is it electrical related????? Any help would be appreciated....

 

[desertcox05]

You say you have spark to the coil, do you have spark to the plug?
When you changed the cap and rotor did you notice a lot of black dust in the bottom of the dizzy?
I'm thinking your dizzy is taking a dump. $120 for a remanned and $20 for just the PIP inside the dizzy.

 

[Stangarossa]

the inside of the distributor looked clean. However, the elextrodes on the cap and on the rotor where dark black.

 

[HankyGT]

I second the dizzy. Most electronic stuff wont fail fully until it gets hot. Like he said, you can't just check spark at the coil.

 

[Stangarossa]

Thanks guys, I appreciate the insight. Since I am no mechanic, I am pretty much running out of ideas and'or how to accurately test the electrical pin outs/etc.... I guess I should just call the tow truck already and get a shop with the right equipment to fully diagnose..... At least I won't being flying blind when they give me the diagnosis.... Thanks for your help.

 

[BlackVert]

i'd try a new distributor cap and rotor first ... they are not expensive and you can save yourself alot of money if that is all it is.

i'm no mechanic either, but some things are easy enough to do yourself

case in point ... my wife's cabrio had a check engine light and the shop determined that a rubber pcv hose had rotted out and was letting un-metered air in. they quoted me a price of about $150 to replace it: $75 for the part (including another plastic piece ) and $75 for the labor to replace it. i said no thanks and went to a car parts place and got a 1 foot piece of hose for $1 and replaced it myself. saved $150.

good luck bro and let us know what happens

 

[HISSIN50]

Fuel at the rail but no fuel pressure concerns me. Retest it and figure out why you have no pressure registering on the gauge (even if you need to borrow a gauge to ascertain if your gauge is bad). You can have a decent amount of fuel squirt out but not have enough P-V (thus cranking fuel) to start the car.

And FWIW, if your TPS shorts and reads over ~3.7V at rest, the injectors will shut off and it won't start.

Matt or Paul, please move to this to Tech.

 

[toyman]

Fuel at the rail but no fuel pressure concerns me. Retest it and figure out why you have no pressure registering on the gauge (even if you need to borrow a gauge to ascertain if your gauge is bad). You can have a decent amount of fuel squirt out but not have enough P-V (thus cranking fuel) to start the car.

I think he said he doesn't have a fuel pressure gauge not doesn't have fuel pressure at the rails.

And FWIW, if your TPS shorts and reads over ~3.7V at rest, the injectors will shut off and it won't start.

That would imply that the injectors won't pulse if you try starting with the throttle fully open? Not having a stock EMS I can't try doing that but I recall reading not too long ago someone could only start his car at WOT. Just curious as to how the PCM recognizes the difference.

I would as Hissin suggests confirm with a gauge that you have 38+ psi with the engine off. If you do have pressure I like others would suspect the PIP sensor on the distributor shaft since you have replaced the basic tune-up items.

 

[HISSIN50]

I think he said he doesn't have a fuel pressure gauge not doesn't have fuel pressure at the rails.

No one said I could read.
Thanks for the catch Richard.

That would imply that the injectors won't pulse if you try starting with the throttle fully open? Not having a stock EMS I can't try doing that but I recall reading not too long ago someone could only start his car at WOT. Just curious as to how the PCM recognizes the difference.

Yep, you're right. WOT shuts off injectors on Stangs (and almost every EFI car - we're talking stock EFI systems) to clear a flood condition.

When there's too much cranking fuel (i.e., running 30+ pound injectors without a tune to reduce Cranking Fuel), it fouls the plugs. Cranking at WOT at that point clears the flood and the remaining fuel lights off, allowing the car to start.

It's not uncommon to have to do a gas pedal dance to get such a vehicle to start.

 

[Stangarossa]

Thanks guys - You where correct, I have fuel at the rail - but do not have a gauge to diagnose how much pressure. The car will start most times without touching the gas pedal, but starts to stumble out to a stall within about 20 seconds or so. "If" i give the gas pedal a shot to try and get it to run better, it immediately stalls out.
I am thinking you guys are dead on about the PIP, for this reason. I had the car in the shop the week prior to this incident as the car failed emissions test due to hi-flow converters. Before the shop diagnosed the converters where the issue, they adjusted my timing a few times. Initially it was at 16 degrees running on hi-octane, but they adjusted another three times or so, from 5 to 10degrees, (than running mid grade fuel)noting that the changes did not help the emissions much. So today I am running 10 degrees with my factory OEM cats (passed emissions with flying colors). Too cut to the chase, I am thinking having the timing adjusted three or 4 times over the course of the week, might of effected the distributor/sensor on a 15 year old car???

 

[HISSIN50]

Did it do this before it went to the shop?

 

[Stangarossa]

No, this happened on the way home from the shop. The car ran perfect for the entire 1 hour commute home. The car died as I was turning onto my street. I had to push it the rest of the way home (200 meters). When I picked it up from the shop, I filled it with mid grade fuel and added fuel stabilizer before my 1 hour commute home, so I could cycle the stabilizer through the engie/fuel lines as this commute was the cars last drive home before being parked for the winter.

 

[Stangarossa]

I want to thank everyone on this thread. You guys know your stuff. I dropped in a rebuilt distributor lastnight (complete assembly with PIP,etc). The car runs like a champ! Again - Big Props to your guys!!!

 

[desertcox05]

it's no problem eh
That's a common problem with the 5oh's. If you haven't had to replace the pip/dizzy yet then your on borrowed time. (unless it has supper low miles)

 

[HankyGT]

Good deal man! Mine's on the to-do list here over the winter