misfire under no load?

[TooManyRangers]

1996 2.3l ranger. 286,000 mi. starts and idle's like a champ. accelerates as good as a stock 2.3l can.
misfires after reving the engine from idle for 1-2 minutes while the engine is cold, 10-30 seconds warm. giving a little throttle does'nt seem to affect the miss.
misfires after acceleration ie after i have shifted into another gear.
cleares up after 2-5 seconds of acceleration in the next gear.
compression test results:
1=135
2=145
3=145
4=142
have not checked fuel pressure yet but the problem is not with foot on the throttle. so i do not think it it is the problem.
spark is strong on all cylinders and even while the engine is missing when a plug wire is disconnected the engine rpm slowes reguardless of the cylinder. so i have not been able to narrow it down to a specific cylinder.

plugs and wires are new.

air-cleaner in new.

fresh oil change+filter

i have had the code p0301 appear once but not while the engine was missing. when i cleared it it did not come back.(500 miles ago).
i have not noticed any outside conditions affecting the condition(rain, damp, hot, cold, etc).

any ideas?

 

[Lemondrop]

Very similar problem with a 97 2.3L automatic ranger .
Difference is the PO301 keeps coming back.
Also shows a lean condition on bank one code.
When you disconnect #1's injector it misses worse, can't get to others to check them in the same manner.
Compression on this engine is:
1.138
2.135
3.155
4.155

I don't know if the cranking put raw fuel in 3+4 that aided in the slightly higher numbers. No known vacuum leaks, had one under the intake (small hose broke that connects the steel line that bolts to intake manifold joint), but repaired that early on. Tonight disconnected the upstream O2 sensor to see if it would help the miss,incase it was a rich/lean condition from the O2. That did not help, the miss was still there.
Also connected a vacuum gauge and the needle was pretty steady so I doubt valve issues. IIRC it had about 18 inches of vacuum. The fuel pressure was 30PSI and went to 33PSI when reved. Driving down the road the engine runs fine. When you stop the engine starts shuddering and the CEL starts flashing(for the PO301 #1 cyl misfire). I also cleaned the MAF back a week ago when I changed the plugs and wires. I removed the upper intake manifold for easy access to the plugs but the miss was the reason I wanted to change the plugs, so there is no problems from that.

The EGR makes the engine stumble when you apply vacuum to it at idle. I also replaced the PCV valve when the intake was off. The coils seem to fire very good..........

We thought of buying 1 injector and swapping #1 and then swap hole to hole but would prefer an easier fix.

 

[jubangy]

Very similar problem with a 97 2.3L automatic ranger .
Difference is the PO301 keeps coming back.
Also shows a lean condition on bank one code.
When you disconnect #1's injector it misses worse, can't get to others to check them in the same manner.
Compression on this engine is:
1.138
2.135
3.155
4.155

I don't know if the cranking put raw fuel in 3+4 that aided in the slightly higher numbers. No known vacuum leaks, had one under the intake (small hose broke that connects the steel line that bolts to intake manifold joint), but repaired that early on. Tonight disconnected the upstream O2 sensor to see if it would help the miss,incase it was a rich/lean condition from the O2. That did not help, the miss was still there.
Also connected a vacuum gauge and the needle was pretty steady so I doubt valve issues. IIRC it had about 18 inches of vacuum. The fuel pressure was 30PSI and went to 33PSI when reved. Driving down the road the engine runs fine. When you stop the engine starts shuddering and the CEL starts flashing(for the PO301 #1 cyl misfire). I also cleaned the MAF back a week ago when I changed the plugs and wires. I removed the upper intake manifold for easy access to the plugs but the miss was the reason I wanted to change the plugs, so there is no problems from that.

The EGR makes the engine stumble when you apply vacuum to it at idle. I also replaced the PCV valve when the intake was off. The coils seem to fire very good..........

We thought of buying 1 injector and swapping #1 and then swap hole to hole but would prefer an easier fix.

I've got a 94 2.3l that acts very similar. Mine so far has not acted up only in the winter. In the summer I never have an issue. Now in the winter, after the truck sits all night I don't have a problem the first time I start it up and drive it. Now if I let it sit for more then an hour it seems, and start it up and drive it after about a minute or 2 of driving it starts stumbling, the idle when sitting at a light will stumble to almost stalling but it don't stall. When driving when you hit the gas it starts to miss and it will pop out of the exhaust. If you push the pedal to the floor it will straighten out and go, this happens for about 5 minutes or so then after it warms it up straightens out and is fine the rest of the trip. Occasionally if you let it sit and idle for to long, it will start happening again, but not too often. But, like I said in the summer it never does this. The only thing thing I have found is that when the coolant is low it does it more. Awhile back the thing the engine coolant temperature sensor screws into broke, so I took it out and just put a tube in there to connect thehoses so there was no sensor, that didn't work out so well as the idle was high and startign was rough. I couldn't find the part at the part sotres so I went to Hovis and got one basically pre-fabbed. It's a bit bigger then the original and I have no idea if it's actually holding enough coolant so the sensor can actually get a good read or not, but when I check and fill the coolant the problem does not seem as bad or as frequent. It may just be coincidence I don't know. I do know that before I had the newer engine put in, it never did this. The guy that put it in said the tube from the cat or whatever that goes to the egr was not hooked up, but now it is. So that may be part of it to I am not sure, but you would think that it would affect it in the summer as well and it don't. Hopefully everyone can figure this out so we all can fix our trucks.

 

[TooManyRangers]

I rechecked the compression with the throttle open this time and did a wet test as well i also ohmed out the fuel injectors and switched ports they were going into these are the numbers:
dry wet ohm
1) 180 191 14.5
2) 180 190 14.4
3) 180 196 14.5
4) 181 190 14.5
I replaced the o2 sensors after I hooked up Auto-tap scan tool software and saw that they were responding slowly. That did help, but not much.

Plugs and wires are new along with air filter.

I did a driving test with auto-tap hooked up and found that i am getting misfires in both cylinder 1 and cylinder 2 but #1 is the worst.

I checked for vacuum leaks using the spray and listen method there are none.

I checked the coil packs resistance primary is 1 ohm on both coil packs and secondary is 13.5k to 13.8k ohm's.

MAF is functioning well ranging from .10 lbs per minute to 8.9 lbs per min.

Ignition timing seems to respond ok it ranged from 8 to 25 btc.

Short term fuel trim is around +1.0 at clean idle and +19 at rough idle.

can any one think of anything else to check. I am about at my wits end. please ask any question you want and I will try to find the answer or do the test.

 

[squishyss]

p0301 is a obd-II code for cylinder #1 misfire. this is probably your problem cylinder.

 

[Lemondrop]

You swapped the injectors around? The truck we are working on our last thought was to replace the injectors. Still has #1 missing on this ranger also.

 

[TooManyRangers]

problem is missing/worn valve seats in cyl 1 and cyl 2. head shops say that is a problem with the 2.3 heads. it looks like the seats are just cast iron.

yes i did and the problem did not follow. i took it to a mechanic and the cpu showed cyl 1 and cyl 2 loss of compression while it was missing.

the seats are so worn that at certain rps the valve wont close because in my case it has .025" further to travel. i found worn valve guides also.

 

[Lemondrop]

Strange that the compression was ok but the seats were toast. I hope it's not the same case on this truck Im working on. I checked with a vacuum gauge and the needle is steady, unlike what one would expect with a burnt valve or seat.

 

[zamos]

Just for laughs - why don't you try switching out the coils - maybe get a couple out of the boneyard - I know you tested the ohms but one or more of the towers might not be putting out any voltage- I had this problem with my 89' - Primary (drivers ) side coil #2 & 3 not output voltage

 

[eddieo64]

I to am dealing with a misfiring #3 cyl it seems to be worse when its cold and gets better when it warms up but does not go away. I have done so far the
1 computer
2 cps
3 injector
4 wires
5 plugs
6 tps
i read on another site to try the EGR VALVE POSITION SENSOR its fairly cheep so i will try it it also said that it could be the Differential Pressure / Feedback Exhaust Sensor this part is expencive if anyone has an idea please let me know.

 

[TooManyRangers]

had the head redone. it is back on and works great. the valves were seating but the seats were so fare gone that the valve was floating on the camshaft at higher rpms(this also allowed the valve to rotate a little and leave the normal position). as the rpms came down the vale took a little time to work back into plase. this was added to by the worn guides.
i had heard from several head shops that this was a common issue with the 2.3 soc heads.
out the door for guides, seats, seals bearings, macine work, magnaflux, hottank, and slapping it togeter $457.00 pluss $100.00 for gaskets, etc and 7 hours time off and on.

that is almost what i spent on swapping out parts and much less than what i spent diagnosing the problem.