2003 3.0L automatic with Multiple Misfire Codes
 

Hello, My 2002 3.0L with 344K miles has been throwing Check Engine light recently with these codes:

P0316 = Misfire detected on startup (first 1K RPM)
P0306 = Misfire Cylinder 6
P0305 = Misfire Cylinder 5

I have swapped and tested coil pack, crank position sensor, plugs, plug wires, and injectors to no avail. I have also cleaned the MAF sensor and replaced the fuel filter and air filter. This truck gets regular service thereby why it is still going at 344K miles, so not poorly maintained.

It happens intermittently mostly after it gets up to temperature. Cold starts are right away and mostly without issues. Occasionally it will start to misfire on cold startups. I have not done a compression check yet but that is next.

It always starts right up, no issue starting. It idles fine cold most of the time but as it warms up and I start getting a miss and when stopped at lights I sometimes have to keep the RPMs at 1000 rather than 750 to get it to smooth out. When it starts misfiring the check engine light will start flashing.

Performed a compression test, here are my numbers.

1- 115
2- 120
3- 110
4- 115
5- 98
6- 100

Observation while testing compression on number 5 and 6 is once the gage started moving above 30psi as it cranked I can hear a whistle or a squeaky sound (almost like a belt slipping) all the way until the needle stopped progressing. These are the only 2 cylinders that made that noise while cranking.

Any input on what that whistle means, (guessing valves not closing)??

Any and all input and suggestions are greatly appreciated.

Thanks,

compression test should be done, all plugs out and cold motor. compression is low but could be the gauge. at 3k plus mi im sure a valve job would help. what did the plugs look like? did the motor smoke at all? look into doing a leak down test.

docm, Thank you for your reply.

I did remove all plugs while performing the test on a cold motor. As you said could be the gauge but at least the same guage is used so there is consistency there. All plugs looked fine and the engine did not smoke, it never has. Indeed a leak down is my next step.

At 344K miles I am not complaining as this truck has served me very well and in turn I have kept up on all maintenance. Thanks again for your feedback!

i had to replace heads on my 01 3.0 at about 165k. it had misfires and low compression and it cyl 5. not sure if it was burnt valve or cracked head. no machine shop close to me so i opted to buy online and ended up getting from Rock Auto. that was the only real choice i had. so when i replaced them i did the water pump, thermostat and a few other things since it was apart. been running good for 5yr now. oh and do the O2 sensors too. i did just the upstream.

Reviving an old thread since my truck is similar.

I just bought a '95 4.0L OHV @215K mi. While doing tune-up to try and pass DEQ (I believe it's IAC/MAF related), I swapped plugs/wires and decided to check compression.

Plugs 4,5,6 were far worse at .070" gap.

Compression:
1 150
2 150
3 150
4 142
5 120
6 135

I saw another thread with similar degraded values on the right bank with cyl 5 being the outlier. Is this a common thing for both 3.0 and 4.0 with known cause, or just coincidence? Someone said Chilton manual says max. 20psi between min/max, so it's officially out of spec.

Assuming I can get tuning fixed to pass DEQ, would next be a wet test to isolate rings vs.valvetrain? If the valvetrain, probably worth servicing (DIY or otherwise) whereas if rings maybe just run it until it dies. Truck is otherwise clean, all manual trans, transfer case, hubs. I noticed it can be a hard to get into first from neutral at a stop w/o going into 2nd first, whereas my brother's '94 2wd doesn't seem to have this issue.

Thoughts on this from you experienced Ranger folks? Thanks!

BTW, for anyone doing compression test with the $35 HF tester, the adapter threads aren't deep enough to bite. I found the advice on another thread to use the Dorman Anti-fouler (p/n 42008) from Autozone as an adapter instead. I used both of them together with pipe tape, cutting the nut portion off the upper one to get just the right length that worked for all 6 cylinders. Also helps to run Gorilla tape around the joints to ensure the whole assembly comes out at once when unthreading.

easy one first, replace the clutch. is there misfires, or how does it run. im not that familiar with that motor, burnt valves is common with the 3.0 have you cked codes.

A bit of rpm hunting at idle, otherwise seems fine.

There's also a howling noise coming and going from the intake at idle, which appears to be the IAC from other posts I've seen. I don't think the solenoid is able to fully close the valve, even after cleaning, since I can still blow right through it when connected to battery. New motorcraft one is on order as I saw mixed results from aftermarket.

The only code I'm getting is P0102 (MAF sensor low). When I view live data, it shows 0.4v at idle, and smoothly ramps up to about 4.5 at WOT, so it's clearly functioning. 0.4v is normal from what I can tell, but maybe marginal enough to trip it?

the IAC should fix that when its warmed up unplug the IAC, idle should drop or stall. that means it is working. could be a small vacuum leak too but i doubt.