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View Full Version : 97 Ford Ranger 2.3 engine/misfire question



potshotscott
05-09-2017, 10:34 PM
Good evening,

I'm stumped. I'm working on a 97 Ranger 2.3 that has a misfire problem. It has coded out for misfire on #2 cylinder in the past but since I disconnected the PCM to Ohm out some wires the codes are gone and have not come back. Things I've already done:

1. Verified resistance within 3K Ohms on all plug wires (except #4 intake side since it's nearly impossible without taking off the intake manifold)
2. Verified resistance of all fuel injectors
3. Verified wiring to injectors both 12V supply and signal wires all the way back to the PCM
4. Measured pulses at coil packs to determine that the timing to them seems normal (they get signal to fire)
5. Swapped each coil pack out one at a time with a known good unit (no significant changes)
6. Inspected all plugs (except #4 again) set gap to ~1.10mm in accordance with Ford specifications - plugs were fairly clean

I drove the truck today for 20 minutes total time and codes did not set. Once above about 1200 RPM the engine runs seemingly smooth. Idle's like it's missing. Was going to pull the MAF out of the loop next to see if default inputs to the PCM clear it up. Anyone else have any ideas? I'm thinking about shotgunning plug wires and coil packs.

Scott

KMT
05-10-2017, 12:24 AM
I'd check all the vacuum lines/connections over real well and then do coil packs...

Be sure to inspect the old ones (top/bottom) for cracks in the epoxy. Hit them with a spray bottle & water when running to see if you can out one or the other.

Still no joy, run a compression test.

potshotscott
05-10-2017, 12:30 AM
Edited - ahh cracks in the epoxy in the old coil packs!! Was confused for a bit.

KMT
05-10-2017, 01:11 AM
That large seldom seen strange yellow ball in the sky today will do that...

potshotscott
05-10-2017, 03:21 PM
No vacuum leaks, no change in performance with water on packs. Ordered coil packs.

Thanks Ken

KMT
05-10-2017, 04:09 PM
I hate to see parts thrown at it w/o cause, but cps are fairly inexpensive these days, I guess. I had to replace the one on my Windstar a few months ago and it was only $18.

Know how to do a cylinder power balance check with a code tester?

Can't wait for OR cities to move to summer fuel blends, BTW.

potshotscott
05-10-2017, 04:48 PM
I have a simple Bluetooth OBD2 scanner that I connect to via Android and an app. I have no idea how to run a cyl pwr balance test.

Also - had NO idea there were summer/winter blends

KMT
05-10-2017, 05:05 PM
Cylinder balance test is described here http://www.corral.net/tech/maintenance/eecivtest-balance.html - requires sequential fuel injection, which I believe your ranger has. Might be worth a try, considering the #4 plug access p i t a.

I have both a plugin OBD-II tester and a wi-fi tester - not sure if you can kick that test with any of the wireless testers. You might be able to get away with the method where you jumper the test connector to force a test.

Winter grade fuel might as well be water - my MPG gets worse, idle and starting suffer, etc. And while they both have the 3.8l V-6, my SC dislikes it more than my Windstar, for some reason. I believe OR's schedule mirrors national, so we should be on summer grade from June 1 to end of Sept, I think.

potshotscott
05-10-2017, 08:20 PM
Thanks for the link. Will have to figure out how to run the KOER test with OBD2 on this thing.

sam jones
05-10-2017, 11:41 PM
Good evening


As as been mention by members get an OBD II scanner. I would check Long and short term fuel trims. Could be the intake manifold gasket has failed.

See video. https://www.youtube.com/watch?v=qJWnpiCj-6A&index=9&list=PL_jEaS-po9vA_ZvIphGhAFbSoos98bMr6




Good Luck.

potshotscott
05-11-2017, 12:24 AM
Is the OBD2 scan tool that talks to my droid phone not compatible Mr. Jones?

KMT
05-11-2017, 12:45 AM
I've read trims w/my wi-fi reader. I'd be surprised if your BT reader didn't offer to read them too.

Should be fairly straightforward to check vacuum and fuel related issues, keeping in mind which mechanicals can affect fuel (a faulty coil can influence fuel trim, but not throw a code...). Be sure engine is warmed up and readings/swings are consistent. The trick is being able to accurately interpret them. (https://www.youtube.com/watch?v=mzsOY_AhgY4)

If you can gather them and post them here, I'm sure someone can help decode, etc.

Example: idle~2,500 rpm:

For a suspected vacuum leak, note the fuel trims at idle and increase engine speed to 2500 RPM and hold. If the STFT immediately decreases and moves to acceptable levels and the LTFT slowly starts to come back down, you have a vacuum leak.

Just remember...higher (than normal) means LEAN.

Example: idle
Use Fuel Trim to Diagnose Vacuum and Fuel Delivery Leaks. With the engine idling, look at the Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT) values. Normal range may be high as plus or minus 8, but closer to zero is best. If the numbers are +10 or higher for STFT and LTFT, your engine is running LEAN.