'07 Ranger 3.0L stumble on WOT, backfire, random misfire

The 2007 Ranger Sport I bought in October this year has been a money pit. I am ready to sell it and keep my '98 Ranger.

Haven't solved the random misfire and stumble on acceleration problem yet. I have fixed several others. I am surprised the PO was able to drive it. It was short 2.5 quarts of oil when my mechanic looked at it before I bought it. I should have run away then.

Problem 1: Misfire Cylinder #3 code popped up driving the truck home. It got much worse and started the flashing MIL after several weeks.
~Solution: Replaced Plugs with Motorcraft SP-413 gapped to 0.052" per owners manual (notice this conflicts with the Ford Workshop Manual)
~Solution: Replaces OE plug wires with Airtex wires.
Resolution: No more specific cylinder misfire or code. I can drive it now.

Problem 2: Random mild misfire, runs rough, poor acceleration, loud screaming noise near Cylinder #3.
Paid a Mechanic to check transmission codes with expensive Scanner. Asked him to find squealing noise near rear of engine.

Diagnosis: Vacuum leak in upper intake manifold gasket, sticking injector, misfire at startup (no cyl given)

Recommendation: Fuel rail flush first then replace injector(s) if still bad. Replace upper manifold gaskets (figure 8 shaped rubber)

~Solution: Replaced Fuel filter with Motorcraft. 3 fuel treatments added to gas.

~Solution: Found noisy Crankshaft Synchronizer, replaced with Motorcraft part. I did not replace the sensor. I reused the old undamaged sensor. The Sync was only noisy without any damage or excessive play.

~Solution: After not being able to find anyone to do a fuel rail flush correctly (I paid Valvoline quick lube place here $65 to do what they told me was a fuel rail flush, but was not. I found out after I paid.) I pulled the injectors, ohm tested them (12.4-12.6 ohms), then had them cleaned and flow tested at a local marina. Flow test before 77,77,77,76,76,76, replaced baskets, ultrasonically cleaned, replaced o-rings, flow test after 77 all.

~Solution: Replaced upper intake manifold gaskets, replaced valve cover gaskets since I had the plenum out of the way. They were leaking a little oil and I wanted to see the valves anyway. Cleaned out the electric heated PCV valve with brake cleaner (did not remove valve from cover). The oil on the valves was dark near the PCV valve (cyl 5+6). Replaced the PCV hose on the other side as well with Motorcraft part.

Resolution: No more squealing noise. Fuel pressure steady at 68psi, 5+psi shaking needle gone.

Problem 3: Random misfire that does not set a code, runs rough at idle, stumbles at WOT from fully closed (before rev limiter kicks in) cold, warm, and hot. KOEO Fuel pressure 10-30psi (not sure what this means, haven't found any significance to it yet), KOER fuel pressure 65-68psi, Ford Workshop manual says both between 65-75psi. Fuel pressure bleeds down to 0 after about 30-45 minutes after shutting off the ignition. Driving fuel pressure steady at 68 psi did not notice any variation. The needle started shaking a little over 2-4psi range can't tell if it happens when the engine shakes from the misfire.

~Solution: Tested TPS resistance with analog meter and voltage KOEO with digital meter. No abnormalities found 0.9-4.6VDC, ohm test moved needle steadily.

~Solution: Ran fuel pump on override switch key off for 5+ min, disconnected ignition from coil, turned over engine to get any leaking fuel into cylinders, checked for wet plugs. No plugs were wet or smelled of gas. The fuel pump pulls 6.4 amps KOEO and 7.4 amps KOER. I suspect the fuel pressure regulator and/or pump check valve are leaking, but I cannot confirm it.

~Solution: Check compression: Completed test then read more carefully that test should be done at operating temp. I drove truck for 20 minutes. Then put a fan over the exhaust manifolds to lessen the burns and blisters. Compression test results: 10 cycles cold, 6 cycles hot, cyl-dry cold/wet cold/dry hot/wet hot 1-190/250/200/230, 2-192/260/207/240, 3-185/255/197/232, 4-162/210/190/211, 5-198/280/200/228, 6-190/285/207/235. Hot-dry test showed 8.2% H-L well within spec. Hot-wet test showed 13.7% H-L again well within spec. Cold tests showed 19-36% H-L assuming invalid. I don't have enough experience to interpret beyond.

~Solution: Check for vacuum leaks with water, can't find any, check EGR for leaks/ malfunctions. EGR appears to be working normally. Replaced DPFE sensor (I discovered it wasn't causing the problem when I left the vacuum line off the EGR solenoid, but I broke the old one removing it). I cannot verify the EGR solenoid function because my vacuum gauge does not read in the operating range of the solenoid (0-10 inHg). No vacuum leaks found.

~Solution: Check IAC valve. Tested OK according to manual. Cleaned it out with carb cleaner. No change. The engine nearly stalls when IAC is disconnected. Normal function as far as I can tell.

~Solution: Checked for bad plug wire from new set by replacing wire one at a time with old OE wire. No change. Re-gap plugs to 0.043" per Ford Workshop Manual (conflicts with owners manual, emissions sticker says see specifications for gap). Stumble on WOT improved. Possible backfire still present, but harder to get.

~Solution: Tested coil pack with 2 OTC HEI testers. Showed plenty of spark all 6 cylinders.

Resolution: Need help. Light backfire still present or worse back pressure from plugged cats. Could really use some help on this. I don't want to destroy my cats. It is possible the cats are already clogged from the fuel treatment done by the Valvoline quick lube place or from spraying a small amount of carb cleaner onto the valves when the injectors were out. I would not be opposed to cleaning the cats with the lacquer thinner method, but I am a little unsure about it damaging something in the fuel system.

Next step(s): Remove O2 sensor(s) to observe back pressure, any other suggestions??? Tried removing O2 sensors. I don't have a wrench big enough to get leverage.

I am sure there are things I've done not listed. I've been beating my head over this for 3+ weeks. I am out of money replacing parts and buying testing tools. My code reader does not take live data, it only reads engine codes and clears codes.

I just found a very small exhaust leak at one of the flanges. I know that an exhaust leak on my '86 ranger would cause backfire so bad it blew open 3 mufflers. Don't know about the 3.0L. On my way to parts store to get a new gasket for it.

Replaced leaking Catalytic Converter gasket 5E241 with Fel-Pro 60641. No significant change. The stumble on acceleration seems to be getting harder to produce or just more intermittent. The backfire is still there, but is also harder to produce now.

Still stumped. Will try removing forward O2 sensors again later to see if there is excessive backpressure from cats.

Only thing I can provide is encouragement.

Not that you need it because you sound like someone that likes to complete things.

Some real smart people here so they will probably start checking in, probably still at work.

Ray

I read as much as I could before I posted anything. I've seen some very good tips and troubleshooting.

I gave up for the night.

Summary of problems:
-KOEO fuel pressure significantly lower than spec. Fuel pressure when pump on override switch within spec. Fuel pressure KOER within spec. Don't understand if it is a problem or not.

-Needle on fuel pressure gauge started bouncing a little over ±2psi after having the injectors cleaned. Can't take the connector off #4,5,6 because the plenum is in the way. Anybody have another way to isolate the FI? Is this normal or does it indicate a bad injector? I listened to all of them with a mechanics stethoscope and they all sound fine as far as I can tell.

-Stumbles slightly and seems randomly now on snap to WOT from closed throttle only. Sounds like a light backfire through exhaust or intake after snap to WOT. Would really like to stop this as it may fry my cats. This got better after I gapped the plugs to 0.043" as the Workshop Manual says instead of the Owners Manual (0.051"-0.057").

-Has a random misfire that does not throw a code. It has been bad enough to notice while driving at highway speed.

Tests Completed:
EGR valve function: pass
Expensive shop computer tests: misfire at startup (no MIL), no other codes
Fuel pressure test: KOEO: low, KOER: pass, driving: pass
Injector coil resistance: pass
Injector flow test (bench test at 35psi): pass
Compression test: cold wet & dry: out of spec?, hot wet & dry: within spec
TPS resistance: pass
TPS voltage KOEO: pass
IAC Valve function: pass
EGR solenoid function: inconclusive, don't have a gauge to read 0-8 inHg
Spark test: pass

Cleaned:
throttle body
MAF Sensor with CRC MAF cleaner
Plenum (lots of oil residue from pvc)
PCV valve
IAC valve


Parts Replaced:
PCV inlet hose
Oil fill cap
Plugs w/ Motorcraft SP-413
Wires with Airtex
Crankshaft syncronizer with Motorcraft (not sensor)
DPFE Sensor
Valve cover and plenum gaskets

Tests still trying to do:
Check exhaust back-pressure ahead of cats. (Don't know spec for backpressure. 0-4 psi?)
Bore-scope cats from O2 hole: waiting on scope
Bore-scope cylinders from spark plug hole: waiting on scope

Will this help?!?:
Replace all plugs again?
Replace crankshaft position sensor?
Re-align crankshaft sync (there was some slop in the alignment tool I used from parts store)?

Don't want to do:
Take to Stealership for $100 "Don't have a clue" response.

No MIL or misfire codes since I replaced the plugs several week ago. Looking for cheapest options. I am not too afraid of having the heads rebuilt, but the compression test ruled that out as far as I can tell. Anybody that can interpret my results, please chime in.

I appreciate any help.

I didn't see any mention or a fuel quality test. if there is excessive ethanol or water in the fuel there can be some pretty goofy symptoms. also I would verify the cam synchronizer alignment. it's easy to get that wrong. also you have a mechanical returnless style fuel system on that truck. any pressure concerns should be rectified by replacing the pump assembly.

Thanks for the suggestions. I have not done any fuel quality testing. I don't know of any company in this area that would do this service. For the amount of fuel treatments I ran through the last tank of gas I am less concerned about water. Ethanol or dirty gas may be a concern. Would you have suggestion for what type of company could do the fuel testing?

The sending unit assembly is only available as an entire unit for this vehicle. I am hesitant to replace it unless a part is bad. The pressure readings I've been getting seem to indicate the pressure regulator is bad or going bad. The fuel pressure KOEO is 10-30 psi after the 1 second burst the PCM gives it initially. If I override the relay is stays at 68 psi then drops to about 58 psi when I shut off the fuel pump. That tells me the KOEO pressure is still low discounting the short on burst. What I don't know is what effect it will have with the issues I am experiencing. Driving fuel pressure holds steady at 68 psi.

Just got back with speaking with some long time mechanic acquaintances. They suggested checking the EGR valve, which I am doing right now. I pulled it off and cleaned it as much as I could. I am waiting to see if water will hold in it. Next is to block the EGR altogether and see what happens.

They also suggested the backfire sounds like a lean condition and check the MAF data and O2 data live with a ODB reader. Looks like I get to buy a nicer code reader now. Any suggestions on a brand that works good (Actron, Innova 3160, laptop based). I don't really like the idea of having the laptop riding with me to diagnose.

To update drive-ability: I was able to drive a highway speed for long enough today to determine a few things. The stumble on snap to WOT is still there, but not nearly as bad. The random misfire is still clearly there, but not a bad as last week.

Will update as I continue.

After cleaning the EGR valve with Gumout, water, and a brass brush it leaks water very slowly. I will try blocking the EGR completely and see if that works. Looks like I am replacing the EGR valve.

I blocked off the EGR valve with a piece of aluminum can. It did not improve anything. The stumble on snap to WOT is still there, backfire out the tailpipe is still there, random misfire is still there. If anything they're worse, but I don't think it is related.

The backfire happens after snapping WOT 2-3 times. This was done after the initial high idle drops down to ~750 rpm.

Next is testing cat backpressure. I will wait until it cools down.

Found an Autozone with a Camshaft Sync tool (Cardone 84-8400T) in stock to loan. Will be going to pick it up and recheck the camshaft sync alignment. Will be picking up a rental OBDII scann tool with live data from Autozone tomorrow morning.

Is it normal for an EGR valve to leak water about 3 drops in 30 minutes? I don't want to replace a $90 part 20K miles too early.

I just re-checked the timing of the camshaft syncronizer using the Cardone 84-8400T tool. There is some slop in the tool.

When I first put the sync on with the tool last week the bolt that holds in in place spun the washer and sync and jammed the tool. I had to pull hard to get it off and loosen the bolt to put it back on. Be aware of this if using this tool.

Giving up for tonight. Will pick up the loaner scan tool with live data tomorrow. I will post some data for those who know how to interpret better than me.

Got the OBDII Scanner from Autozone this morning. Hooked it up and it reads perfectly. I forgot to pull the O2's and check cat backpressure. I'll try that now.

Problem!!! I don't know what to look for...

I don't know what parameters to diagnose MAF or O2's. I did notice the O2 bank 2 reads 0 volts.

http://easyautodiagnostics.com/ford/4.0L/index-of-articles-1 http://troubleshootmyvehicle.com/ford/4.0L/index-of-articles-1