Question to the board:

I took the truck out on a road test for the first time since I owned it. I've done plenty of engine runs in the driveway and garage and never saw this problem. I got about 10 minutes out and it started hesitating to the point of near engine stop. I was able to get it home but almost any throttle advance would cause the hesitation. I'm leaning towards ignition, specifically the TFI module since I have had to replace the entire fuel system to get the engine running and most threads I have researched make this suggestion.

Any info or help is appeciated.

88 F150 I6 4spd
4WD

 

No, a blind guess isn't likely. Start testing things: fuel pressure, spark energy, ignition system, fuel contamination, spark plug gap/buildup, compression, vacuum leaks, MAP sensor, battery terminals & grounds...

 

Thanks Steve83, appreciating your input!!

Fuel system checked and repaired, pressure good,no fuel contam, compression good, battery terms replaced and grounds good, vacuum system checked and repaired with good vac all around.

This leaves MAP and ignition.

I checked the wires for crossover and errant sparks in the dark, all look good. I suppose I could replace parts of the secondary like plugs, cap, rotor to rule out, I was planning on replacing them anyway.

Found this test on FSB for spark energy:

Install a NEW spark plug in the distributor end of the coil wire, rest its shell on a bare-metal part of the engine, and then have someone crank the engine while holding the accelerator all the way to the floor. The last part is to prevent the injectors from firing (also known as 'clear-flood mode'). The spark kernel at the spark plug MUST be white to blue. Any other color (usually orange, yellow, or red) indicates a weak coil, or possibly bad coil primary or battery/engine ground connection(s). It was dark out when this was happened.

Not sure how to test the MAP sensor, any info is appreciated.

 

http://fordfuelinjection.com/?p=27 I've never done it though.

 

What is the fuel pressure? What were all the compression pressures? How many & which ground points did you inspect? New battery terminals aren't necessarily good ones - read the captions below. A spark tester is inexpensive & easy-to-find in parts stores. To test the ignition system, follow the procedure in Haynes Ch.5 (usually Sec.5 or 7). It also shows how to test both types of MAP, but yours is probably a frequency-varying. Duck into a junkyard & snag a few used OE ones from the newest vehicles you can find them on. If swapping it makes a difference, put your original back in. If the symptom returns, drive on the used one in until you buy a new one.

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Thanks for the info, I am going to go back and check fuel pressure again, it was good before, but something may have failed. I went and got the tester from AZ but couldn't get to it this morning, I got called in for OT at the unreal job. I will go back and check the compression values again, they were good so I didn't save the numbers,(silly me) something may have changed.

I don't have the Haynes manual, but instead have a set of factory manuals. Vol 1 and 2, Emissions/diagnostics, and wire diagrams. I'm thinking about buying the Haynes, it sounds like diagnostic routines are easier to find in there?

 

Had time for some testing today, putting in lots of hours at work. Haven't had time to go to the junkyard for a MAP.

Fuel Press readings:
KOEO- 54 (VIP FP lead grounded)
KOER- 45
KOER- 54 (FPR Vac line disconnected and plugged) - Pressure has 1-2psi varience with throttle increase (didn't try a road test).

Bleed down is within limits. Holds pressure within 3 minutes and past
All pressure readings are steady with the exception of the following:

As the engine stalls the fuel pressure decreases to 25-30 psi.

There is a new fuel pump relay, socket, and Motorcraft High Press pump that has not seen road use, could it be bad from the factory? I'm thinking to back probe the high pressure pump during KOER to see if I'm losing power?

88F150 6cyl man 4wd

 

You still have spark when the engine stalls?

 

Does the pressure drop occur BEFORE the stall, or after? I'm talking fractions of a second here. If the pressure falls & then the engine sputters, the pump is weak. If the engine sputters, and & then the pressure falls, the PIP signal is failing.

 

Fractions of a second ... engine sputters,, pressure drops

Anyone have a Motorcraft number for the distributor? Also, I read alot of guys complain about the Cardones, any info on the Autoline?

 

Stop buying/replacing parts. Get a Haynes manual & follow the ignition diagnostic procedure.

 

Ok, thanks Steve, I hear ya and appreciate and will follow your direction....

I'm not doing to badly for a noob. So far I the only thing I have replaced that didn't need it was the EVP sensor to clear the DTC 31 which turned out to be the valve itself. Everything that I've replaced was either cobbled or didn't work.

The only other thing I could have done better on was the fuel pump relay socket, I bought one from RJM and crimped it all in there, I should have followed your advice and just dyked one at the junkyard. (which I did anyway, they ended up giving it to me and it's sitting in a box for later use because the one from RJM doesn't fit a stock relay or have the same mount sytem as stock)

 

As an update to this thread, the intank pumps that I replaced only a couple months ago and had never seen any use other then idling in the driveway were bad. They worked when I first installed them. I had to drop the tanks and replace them both AGAIN.

For information purposes to other members of the board, they were Carter- Federal Mogul pumps.. Made right here in the USA. Sad......