Good morning,
Have read many post on this issue with none matching exactly. So this is what I have from the beginning.
Unit once warm would begin to misfire so bad you could barely keep it running.
before I got to this unit another tech had read code po352 and replaced the following
coil,plugs, wires and crank sensor. No change at all
1:once I received unit I dropped off at dealer to have tested. Dealer stated bad computer
2:I picked up flashed computer at Napa and installed
the very next day same issue came up.
3: swapped around plug wires with no avail
4: performed compression test and found one cyl at 60 and the rest 140-180
5: removed heads and had rebuilt. 7 bent intake valves and 7 bad guides
6: installed rebuilt heads , plugs along with new cam/ distributor sensor. Test ran same issue
7: tested each wire with spark tester ok. replaced injectors and still same issue.
NOTE: issue primarily arises at 25mph but will act up in park as well..
8: with stethoscope I listen to injector click ok until it misfires. Then only injector #3 doesn’t fire, no pulse.
any advice?

 

Welcome to the forum

2004-2006 Rangers with 3.0l engines had an issue with recessed exhaust valve seats, bad batch of seats at assembly plant, wrong size
So your 2005 is in that range

Bent valves????
The 3.0l OHV Vulcan engine used in Rangers is a non-interference engine, meaning at no time can a valve strike a piston, so valves can not be "bent"
So maybe you misunderstood what was done?
And there are only 6 intake valves and 6 exhaust valves in this 6 cylinder engine, 1 of each in each cylinder

If heads were not fully rebuilt, i.e. new exhaust valves and new exhaust valve seats and guides then you could still have the bad Exhaust valve seats

So to start with I would do another compression test, all spark plugs removed and then test each cylinder DRY and write down results, then test each cylinder WET(add oil) and write down results
Compression will go up on all cylinders on WET test, but by how much determines if compression leak is in Rings or Valves
Expected compression on 3.0l Vulcan will be 160-170psi with calibrated gauge and fully charged battery(crank/starter speed)
But a lower PSI(above 150psi) is OK across the board as long and its consistent on at least 4 cylinders

Any cylinder lower than average would be from possible valve seat issue

The computer will often shut off a fuel injector if a cylinder is misfiring so cylinder doesn't get "washed" with unburned gasoline and exhaust doesn't get unburned gasoline that could be ignited by the heat, so check #3 cylinder it may be the one misfiring regularly

2004-2006 Ford Ranger 3.0l TSB seen here: https://www.therangerstation.com/for...n-tsb-05-26-3/

 

Thank you, I will check. True it is 6 valves. Machine shop did complete rebuild but found it odd only intake valves had issues. He also made me aware of seat issues but was able to grind them all. Question, if compression issue, would it not continually shut injector 3 down? Again thank you for your help!

 

is it sequential fuel injection? Where each injector has it's own ground wire?

 

Each injector has its own plug with 2wires

 

Yes, 2005 used sequential injection, all 1995 and up Rangers did, just FYI

Computer would test if a cylinder was misfiring and shut off injector then retest over time by turning it back on

Computer uses Cam sensor to "see" a misfire, the rotation of an engine, and cam sensor vane, will have a "known time" if all cylinders are firing, if a cylinder misfires then there would be a time lag, because one cylinder didn't add power/spin to crank so slowed it down
It then does a power balance test where it shuts of each injector to see which one doesn't slow the engine down further, it can then ID which cylinder or cylinders are misfiring
This all happens in seconds and on the fly so you would never notice it happening

Compression is Black and White, and mechanical, so not a come and go issue
So it always best to do the test and either take compression off the table and move on to something else, or find out it is a compression issue and not waste time and money on non-fixes

 

Ok finally got back out to unit, performed compression test.
cyl. Psi
1. 160
2. 157
3. 155
4. 125
5. 149
6. 157

 

Yup, #4 has bad valve seal and #5 looks like its on its way

2 New heads are in your future

 

Heads are rebuilt, # 3 injector is the one that shuts off after warm?

 

Then one head is defective, but I would suspect both, you could re-test 4 and 5, and maybe do a WET test after to see if its valves or rings

It could be a leak in the head gasket between 4 and 5 and it hasn't reached a coolant passage yet, so no overheating, when there are adjacent cylinders with low compression thats always a possibility

Injectors have no effect on compression

 

Thanks, Sony believe injector #3 is being cut out because of compression on 4and 5?

 

Compression prior to head repair
cyl. PSI
1. 120
2. 160
3. 160
4. 120
5: 70
6. 150

I never did it wet unfortunately

 

Compression prior to head repair
cyl. PSI
1. 120
2. 160
3. 160
4. 120
5: 70
6. 150

I never did it wet unfortunately

 

No, computer wouldn't turn off #3 injector because of misfires in 4 and 5, that would be an unrelated issue

Compression is a mechanical issue no electrics involved
Lower compression can be piston rings or valves in the head, valves are the more common issue, that's what the WET test is for, it seals leaking rings but not leaking valves
So while the compression will go up during a WET test on any engine, it would need to go up above 160, in your case, to indicate a ring issue

A head gasket issue can also lower compression, but its a moot point if WET test shows a valve issue, since the heads need to come off and new head gaskets used regardless

You could pull the valve cover on bank 2, 4 5 6 cylinders and check the rockers, its possible that lifter, pushrod or rocker is causing lower compression, not likely, unless engine is really noisy/ticking, when running, but possible

 

Thanks, lifters are quite. Runs good enough for ranch work until injector shuts off. Any ideas as to what I can check for the injector issue?

 

Not really, if the actual ground pulse is being cut off then the PCM(computer) can be the only issue, each injector has its own "transistor" inside the PCM that grounds it to open it, so it is possible for that to fail, but would be a rare failure

Firing order for the 3.0l Vulcan is 1-4-2-5-3-6
So in theory you could cut the #3 ground wire in the injector harness and connect/splice it to #5 injector's ground wire
So #5 and #3 injectors would open at the same time, this would give #3 a squirt of fuel just before it needs it
You will get a code for #3 injector when its ground wire is disconnected from computer

Injectors all share a red 12v wire, so the other color wire is the ground/computer wire at each injector

 

Wow, awesome! I will try that! Thanks again

 

Ok, both # 3 and 4 cylinders loose pulse at injectors and loose spark at coil. If I shut engine off and re fire ok til I reach 1500 rpm then missing starts up again. I check signals at pcm plug for injectors. 3 and four show to be companion cylinders in my book

95 and newer

 

Code p0352 came up??? So lost I am.

 

Hi,

I'm having the exact same problem here. A week ago, my truck started misfiring and showing code P0352. Would still run, but very little power, and would stall often. I changed the coil pack, the spark plugs and the wires, and still the same problem. I took it to an electrical auto shop and when I came back it wasn't even starting. Guy said the computer was burnt so we changed it, reprogrammed it, still the same problem, in the same cylinders. After this, we switched the injectors on cylinder 3, but they didn't seem to be the problem, so we ran a compression test which gave 60 on that one. I took it out of the shop because it was late, and the next day I found when turning the engine on and unplugging the wire from the coil pack, no spark was coming out of the connectors to cylinders 3 and 4. I called a guy who tested the cables from the computer and the ones for cylinders 1; 2; 5 and 6 were fine, but the one for 3 and 4 showed very little voltage. Still, the guy said that the cables were fine, that it must be the computer. But I already changed that! Also, he couldn't understand why was I having the exact same problem if it wasn't a computer issue. Any help? Thanks!

 

Finally after 2x computers from Napa,Injectors, Valve job and numerous sensors I gave up! Told the customer he’s on his own and wrote off 26+ hours of labor and 4 hours of forums. Advised him to take to Ford dealer that originally told us it was the computer. Guess what they said it was the computer again lol . They ordered own computer and installed. Unit has been running great. Whoever builds napa computers for these rangers are, well let’s just say we were told (by Napa’s computer rebuilder)and billed from them twice and told twice there is nothing
wrong with the computers and we were doing something wrong. Truth is they were right, we were wrong buying a computer from napa. Not saying this is your issue but if you have a decent dealer pay $150 to have diagnosed