I have a '95 F150, 4x4 Auto, with a 300 Straight 6. Everything is completely stock/original. Recently I went to do a tune-up and that is where the headaches began. The truck has 77,000 actual miles, and ran so nice, smooth, and quiet I would be checking the tach to remind myself it didnt stall! Anyways, I started to do basic "maintenance" stuff to keep it running good, oil change, air filter, tune-up, etc. BASIC stuff.

Anyways, I went to take the screws out that hold the dist. cap on, and snap-snap they both break, ok, I wasn't too angry, I went and got another dist from the autozone, checked everything out, looks and feels absolutely identical. I marked where the old one was (AND took a picture of it) before I even loosened the hold-down. Then I dropped the new one in EXACTLY where the old one was, put everything back together, and checked the timing (pulled the "jumper" thing before it). Shows about 60*+ off... can't be possible, so after screwing with it for a while I figure out the damper has to be slipped. The other problem was the EGR valve opening wasn't detected (KOEO code), so after chasing vacuum lines for a while, I by-pass the vacuum reservoir and engine light stays off, hopefully meaning the EGR is working.

ANYways, so I go to drive the truck and now the check engine light is off, but it stumbles under load, about 1200-1600 RPMs, and gradually gets worse until I drop the hammer and force it to downshift. Its odd, when it starts to stumble, the truck has no power to pull out of it, so I barely maintain my speed. It feels like a bad U-joint, the whole truck vibrates, but not violently and the engine doesn't make any weird noises. When it downshifts, its fine above 2000+ rpms (or so it seems). Once it a while it also stumbles at low engine speeds, when I put it in D or R when standing still, but this seems to be only when its warmed up- the lights dim and the charging gauge shows a low reading that bounces around a bit.

What I have done so far: changed timing (seems to make NO difference) checked plugs (all are gapped at factory spec, with no burns, damage, or cracks) tried better plug wires (no difference) pulled dist to inspect for anything wierd (nothing) Chased vacuum lines (no leaks) Hooked the vacuum reservoir back up (no difference) I think the vacuum reservoir is bad, either leaking or the one-way valve in it is bad, but either way, makes no difference.

I can't imagine it being anything other than what I've listed since I haven't touched anything else... and this happened immediately after doing what I listed above... nothing seems to make a difference, and it doesn't show any other symptoms- while its stumbling all the gauges show thier normal readings, the speedo and tach don't jump around, there is no pinging, it doesn't heat up... no funny noises... no check engine light... I've been lurking around this forum and a couple other ones looking for tips and so far everything checks out... so please help me! My last F-150 was a '94 that was identical to this one except it had A/C and the 5.0. That damn truck never broke anything and ran to over 350K!!! Why is this one beating me up at only 77K?!

PS- One thing I did read about is the MAP sensor, they said one symptom is hard shifting... not sure if this is true but my truck does shift a little hard, so I will try unplugging it and driving it like that tomorrow.

Thanks in advance for any and all help... I just want this thing to run right again so I can get to work and back without worries or it vibrating my teeth loose on every hill...

 

When I was chasing down a loss of power and stumbling on my truck I ended up swaping out the MAP sensor from a JY and that was it. I was a little surprised that no MAP sensor trouble codes ever set even though the truck was running rich.
YMMV
rikard

 

Whats a JY? I'm hoping to keep the gas mileage where it should be- the truck used to get 13-16 mpg which isn't great but with me having to get it revving and downshifting to climb hills (I live in upstate NY so this happens a LOT) its not even doing that, about 10-12 mpg tops which is crazy thats what my '95 3500HD with a 454 gets.... The torque of this engine used to pull me up hills at 12-1500 rpms which was great, because the greatest factor in gas mileage is the driving style, and I'm pretty good at "miser-driving".

 

Junkyard....

 

Doh! I'll try unplugging it and see if it changes anything. If it makes it better a new one will be going on there. I'm gonna try a couple different things today and see if it helps any.

 

One thing you might do on an old truck like this is clean ALL the electrical connections on the engine-control devices - anything connected to the computer.

 

You have to ask yourself, "What changed?" Since it was running perfectly before the Autozone distributor - and with only 77K miles - you may want to consider putting the original distributor back in. Get the broken distributor cap screws out of the old distributor and reinstall it. Take it to a machine shop and have them extract the broken screws if it comes to that.

 

Aye!

Reps for this.

You change something, it behaves not like you wanted, so CHANGE IT BACK HOW IT WAS.

 

I'm betting the distributor is off a couple of teeth. You need to find TDC (top dead center) with the piston, and see where the rotor is pointing.

 

The distributor is my last-ditch option, I've changed many distributors just like I did that one, marking where the rotor was pointing and where the "ear" for the screw was pointing and such, then taking a picture with my digital camera just to be safe- saves time over finding tdc and all, especially now that I know the damper has slipped. The old distributor is gone (almost $80 core charge) and the rounded ear that was closer to the "top" of it was broken off anyway, so no saving that one. That is what I've been asking myself- "what has changed?" and it seems to be narrowing down to that...

ctubutis, I have been looking for any dirty or loose connectors with no luck, this thing is pretty clean under the hood for a 16+ year old truck, only corrosion so far is the dizzy and the vacuum reservoir. Most connectors have a little bit of dirt on the outside, but when unplugged the inside is nice and clean.

I tried two things yesterday- The first was unplugging the MAP sensor which did nothing except make it want to stall. I read on another forum that someone was having trouble with it stumbling with no check engine light, and unplugging the MAP made it run good again but now I know thats not my problem.
I also replaced the vacuum reservoir, as the old one was rotted out down on the bottom where I could not see it. I put in a good aftermarket one that is about the same size, leftover from one of my hot rods and it seems to help a little- so after work tonight I'm going to try to see if I can find any more vacuum leaks- it would be great if that was the culprit, nice and easy...

ONE more question- is there any adjustments or calibrations on these distributors? I compared the A-zone one the old one and could not find anything different, except for the broken screws and some dirt and grime. If all else fails, I have had trouble with some A-zone electrical parts before so maybe getting one from carquest and getting my money back on the A-zone one would help...? Or does anyone have a better recommendation on the best place to get an OE replacement dizzy for this thing?

Sorry for writing you guys a couple of volumes here, but this is my first 300 or any straight six for that matter, so I did not know if there was something I was missing... thank you for all the help so far though!

 

You can slip a tooth or 2 when putting in a distributor. I have changed them like you did as well, and had some good luck, and some bad luck. It just depends where the oil rod was sitting when the gears started down. You say the damper has slipped, so that's more reason to find TDC. pull out #1 plug. stick your thumb over the hole and have someone bump the key until the air blows your thumb off the hole. TDC found. now look where the rotor is pointing. To set timing with a bad damper, use a vacuum gauge and look for the best reading. make sure to take the spout out just like you were setting the timing with a light


If the timing is too far retarded, it will act just as you say, and not leave codes.

 

Rock Auto:

MOTORCRAFT Part #DA2061 [Wholesaler Closeout - 30 Day Warranty] $110.79

 

OK, so far I have replaced the balancer- the old one was slipped only a tiny bit. Now with the new one on, I found TDC by hand-rotating the engine with the dist cap off until the rotor was pointing at (very close to) #1, and looked at the timing tab, sure 'nuff, the dist was off, but not from my tinkering, it was in the same exact position when I got the truck. I removed the distributor and backed it up a tooth, then set the timing at 10 degrees BTDC, factory spec. Wierd thing is, at the correct timing, the dist seems to be "maxed out" to advance, it doesn't seem to want to turn any more... and the "ears" that house the screws that hold the cap on are at (about) the 3 and 9 o'clock positions. Is this correct or at least close?

Anyways, I test drove it and as soon as it got into 2nd gear, pinging like a SOB... so I backed off the timing little by little until the pinging went away, and the shaking came back, so I found a "happy medium" to where I could safely drive it, with no pinging and a little shaking (again). I then checked where the timing was... about 2 to 4 degrees ATDC... what the hell? So I filled it with 93 (had 87 in it before) figuring that would help temporarily (only $3-$4 more anyway) and sure 'nuff- I could advance the timing to ZERO with no pinging and no shuddering. I have been driving it a couple of days like this and it just barely pings a little when climbing a steep hill.

I tried un-plugging the MAP, truck would idle rough, but go into gear it stalled out. I guess that's doing it's job.

So next question... would the knock sensor be causing this? Obviously the timing was not set right when I got it, but somehow it ran perfect on 87 and even got about 14 mpg, now I'm lucky to get 12 and can't make it run right... I called a few auto parts places today and they were saying they can't get it and one even tried telling me it doesn't have one because it's not in thier computer... only reason I mention this is I found another thread on a different site where someone was having similar problems with an 80-something F-150 with a 300, combined with a slight "miss" at idle. They were discussing the knock sensor causing it. My truck does this as well, but I can live with that if I can't fix it- the lack of power, mileage, and pinging not so much.

BTW, thanks for the help so far!

 

This may seem like a dumb question, but did you make sure to plug the SPOUT connector back in after timing the engine? That's the little grey piece that you had to remove originally to time the engine.

Also, you need to remember these engines (or any fuel injected engines, for that matter) don't like to be off very much on the distributor timing. They just won't run correctly.

 

Yeah, really.

This is the exact opposite of what the common knowledge about EFI out here says - basically, stab the distrbiutor somewhere in the ballpark of 10° - and the computer will compensate to a reasonable degree.

What that degree is is uncertain, but I would imagine 5 teeth off would be too many.