Misfiring Ranger with the 3.0L Vulcan - diagnosis steps?

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A friend had someone in the family with a late 1990s Ranger with the Vulcan 3.0L V6. Owner states random misfire. Shop sounded like they went parts cannon with it, it got new plugs, wires and coil assembly. I know the cam synchronizer is a sore point in these. He wants me to diagnose it, the plan is to eke out a few more years out of this until used truck prices or a new Maverick is in range.

My plan was to do a compression check, check for spark, fuel pressure and use the Power Balance test in either ForScan on a Windows PC(if I can find my Carista OBD-II dongle) or download the Ford software for my ThinkDiag2 and run the test from there. I’ll rent the testers from AZ or buy them from HF. I’ve been reading recessed valves or dropped valve seats are a fact of life on these Fords. Am I on the right track to chase down the misfire here?
 
Cam synchronizer should only occur over 3000 or 3500 rpm.

If that's where it happens, good bet. You can then run the test to graph the output of the signal. I don't have the technical document in front of me but essentially it pegs at some weird max value like 99787 (or something)
 
How many miles? Recessed valves are more of a high miles issue, I think.

The dollar bill test on the exhaust is supposed to help find valve problems (bill gets sucked in when exhaust valve leaks)
Mileage is an unknown - I’ll find out on Saturday.

I was reading up on the dollar bill/plastic bag test as well.
 
I would think that a dropped valve seat would be readily apparent. Just because X number of parts were replaced doesn't mean those replacement parts were good parts.
You can get the torque pro app and download the Ford specific PIDs. That is how I diagnosed a misfire on our 04 3L escape...just ended up being a COP for me.
 
Apparently the TSB states '00-03, so we'd need clarification on "late 90's"

See:
 
I would think that a dropped valve seat would be readily apparent. Just because X number of parts were replaced doesn't mean those replacement parts were good parts.
You can get the torque pro app and download the Ford specific PIDs. That is how I diagnosed a misfire on our 04 3L escape...just ended up being a COP for me.
The Escape's a different family, no?

Duratec vs Vulcan? I think....
 
When these synchronizers go out too many throw the kitchen sink at it: plugs, coils etc.

Then it doesn't work and they give up

Synchronizers often squeak, too, but not always
 
When these synchronizers go out too many throw the kitchen sink at it: plugs, coils etc.

Then it doesn't work and they give up

Synchronizers often squeak, too, but not always
And I’m hoping it’s the synchronizer - Rock doesn’t show an Motorcraft part, so it’s an OE Ford one if still available. Else, it’s gambling with Chinesium.
 
And I’m hoping it’s the synchronizer - Rock doesn’t show an Motorcraft part, so it’s an OE Ford one if still available. Else, it’s gambling with Chinesium.
I ordered a Motorcraft on ebay thru Quirk Parts. They're a Ford dealer in MA IIRC

Was about $180 but I wasn't going to use an O'Reilly special
 
Also the Motorcraft won't come with the alignment tool. If you don't have them and need them this deal still stands at RA, looks like it's dropped from the $4.53 I paid to $4.41 :D
20230301_135216.jpg
 
Apparently the TSB states '00-03, so we'd need clarification on "late 90's"

See:
The truck is a 1998, so the TSB doesn’t apply.

I got the truck today. I didn’t work up to fuel pressure or compression but I pulled codes, P0302, P1000 and P1151/P1152. Checked for spark - good, strong spark. Pulled the plug - sooty but intact. All Motorcraft was used. I decided to pull out my stethoscope, injector #2 is dead. The adjacent ones click. Gonna pick up a noid light to rule out wiring or PCM.

Gonna order new Bosch upstream O2s, one new Motorcraft injector, new seals for the remaining injectors, and a new fuel filter. I’m debating sending out the remaining 5 to @Trav if I have the fuel rail and plenum off but it all depends on how much time I have with the truck.
 
Compression and fuel pressure testers from AutoZone were a dud.

But my question - replace all 6 injectors, replace only the one and have the rest flowed/cleaned/resealed or let it ride and replace just that one?
 
When I did injector o-rings on an '05 Duratec 3.0 (so, yeah, different family) O'Reilly had a weird listing where a 2-pack of o-rings was actually more expensive than a 6-pack. Something to consider when shopping.

I also have these giant Q-tips I got at TSC and they were perfect for cleaning the injector seats. I'd douse them in solvent of my choice and spin around in the bore. More random musings that might be helpful.
 
Key question: under what conditions is it misfiring?

no load / load?

hot/cold?

rpm?

one thing I’ll do is run a tank of premium fuel in it. If that settles is down, I start looking for reasons something would be too hot (balve problem, carbon issue).

misfire under high load / low rpm tends to indicate a high voltage (high tension) issue.

ive seen misfire/stumble at idle/no load related stretched timing belt
 
Key question: under what conditions is it misfiring?

no load / load?

hot/cold?

rpm?

one thing I’ll do is run a tank of premium fuel in it. If that settles is down, I start looking for reasons something would be too hot (balve problem, carbon issue).

misfire under high load / low rpm tends to indicate a high voltage (high tension) issue.

ive seen misfire/stumble at idle/no load related stretched timing belt
It’s missing at idle and load. Spark is good. #2 injector is dead, I took my stethoscope to the #1 and 3 injectors and can hear them click.
 
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