98 Intermittent P0305 - Lots of troubleshooting

[94LebConv3La604]

Alright, let's see if I can get everything down in one post.

Been trying to figure out the source of an intermittent misfire for at least a month now. Like the title says it's a 98 Deathstar with a P0305, misfire in cylinder 5. The engine has just over 100k miles on it and I've done quite a bit of work so far trying to figure it out. The misfire seems to not care what temperature it is or whether the engine has been run recently. There was one instance where I was turning into my alley after a spell of misfiring and stalled. When I restarted the car it ran without a hiccup the rest of the day. I mostly have problems when the engine is under light load and the engine starts to buck. Sometimes if I give it a decent amount of additional gas it will even out, other times it makes it worse with the CEL flashing and huge loss of power. I know it's not good for the cat, but I have gotten frustrated before and simply rode out the misfiring without changing pedal pressure and it will get its power back. Also of note, the engine will perform and respond well in park or neutral throughout the RPM range, however in drive it will begin to noticeably miss around 1500 RPMs. Park and neutral RPMs are steady around 1000 to 1100 when first started cold and drops to around 750 to 800 after a minute or two. Idle RPMs in gear fluctuate between about 450 and 650 and will occasionally nearly stall. The van mostly stalls during low speed maneuvering in both reverse and drive gears. If I give a quick press of the gas pedal in drive the engine bogs down and 75% of the time will stall. It will stall maybe 5% of the time doing this in park or neutral.

Work I have done thus far to try to solve this problem:
New fuel filter
New plugs (Bosch platinum plus, not the double pronged ones)
New wireset
New coil pack
New PCV valve
Dry compression test with all cylinders measuring between 180 and 185 PSI
Fuel pressure test (idle = 28 PSI, vacuum removed/plugged from FPR = 38 PSI)
Exhaust backpressure test stayed under 1 PSI
Removing EGR vacuum and plugging did not help and EGR valve checks out
Gave it an at-home smoke test with no leaks detected....at least the cigar was good
Power brake booster is air tight
IMRC bushings are still in decent shape, the actuators hold vacuum, and the butterfly rod moves easily and the butterflies are able to close completely.

I've torn the engine apart down to the lower intake manifold without actually taking them off. All vacuum lines seemed okay. Upper intake plenum had about 1/8 inch of carbon build up where the EGR ports expel. There is only a thin film of carbon from what I can see in the lower intake manifold. While the plenum was off I cleaned all of the EGR ports, only #3 was actually plugged.

I replaced some other items about a year ago to take care of a P0174 I think it was. DPFE and EGR solenoid are the only things I can remember doing for those.

As a side note, I will be doing CV axles when it gets a bit warmer as I have started to hear a click when turning every now and then and I get a slamming when I hit the gas after decelerating. I am also assuming that I have a cracked tone ring or two, but haven't had a chance to verify as my ABS tries to engage almost as soon as I start moving forward and turns off, lighting the ABS light, after about 75 or 100 feet.

I left my scan tool in the car and I'm tired so I'll post some of the captured data tomorrow morning.

I THINK that's it, but we'll see what memories comments will jog....

[tempfixit]

Originally Posted by 94LebConv3La604

Alright, let's see if I can get everything down in one post.

Been trying to figure out the source of an intermittent misfire for at least a month now. Like the title says it's a 98 Deathstar with a P0305, misfire in cylinder 5. The engine has just over 100k miles on it and I've done quite a bit of work so far trying to figure it out. The misfire seems to not care what temperature it is or whether the engine has been run recently. There was one instance where I was turning into my alley after a spell of misfiring and stalled. When I restarted the car it ran without a hiccup the rest of the day. I mostly have problems when the engine is under light load and the engine starts to buck. Sometimes if I give it a decent amount of additional gas it will even out, other times it makes it worse with the CEL flashing and huge loss of power. I know it's not good for the cat, but I have gotten frustrated before and simply rode out the misfiring without changing pedal pressure and it will get its power back. Also of note, the engine will perform and respond well in park or neutral throughout the RPM range, however in drive it will begin to noticeably miss around 1500 RPMs. Park and neutral RPMs are steady around 1000 to 1100 when first started cold and drops to around 750 to 800 after a minute or two. Idle RPMs in gear fluctuate between about 450 and 650 and will occasionally nearly stall. The van mostly stalls during low speed maneuvering in both reverse and drive gears. If I give a quick press of the gas pedal in drive the engine bogs down and 75% of the time will stall. It will stall maybe 5% of the time doing this in park or neutral.

Work I have done thus far to try to solve this problem:
New fuel filter
New plugs (Bosch platinum plus, not the double pronged ones)
New wireset
New coil pack
New PCV valve
Dry compression test with all cylinders measuring between 180 and 185 PSI
Fuel pressure test (idle = 28 PSI, vacuum removed/plugged from FPR = 38 PSI)
Exhaust backpressure test stayed under 1 PSI
Removing EGR vacuum and plugging did not help and EGR valve checks out
Gave it an at-home smoke test with no leaks detected....at least the cigar was good
Power brake booster is air tight
IMRC bushings are still in decent shape, the actuators hold vacuum, and the butterfly rod moves easily and the butterflies are able to close completely.

I've torn the engine apart down to the lower intake manifold without actually taking them off. All vacuum lines seemed okay. Upper intake plenum had about 1/8 inch of carbon build up where the EGR ports expel. There is only a thin film of carbon from what I can see in the lower intake manifold. While the plenum was off I cleaned all of the EGR ports, only #3 was actually plugged.

I replaced some other items about a year ago to take care of a P0174 I think it was. DPFE and EGR solenoid are the only things I can remember doing for those.

As a side note, I will be doing CV axles when it gets a bit warmer as I have started to hear a click when turning every now and then and I get a slamming when I hit the gas after decelerating. I am also assuming that I have a cracked tone ring or two, but haven't had a chance to verify as my ABS tries to engage almost as soon as I start moving forward and turns off, lighting the ABS light, after about 75 or 100 feet.

I left my scan tool in the car and I'm tired so I'll post some of the captured data tomorrow morning.

I THINK that's it, but we'll see what memories comments will jog....

Have you tried moving #5 injector to another clyinder to see if misfire moves to clyinder you move it too?? What brand spark plugs where in at time of change?? Lots of engines do not like Bosch plugs.

[12Ounce]

I would suggest an easier first step: Because cyl#1 and cyl#5 are fed off of opposite ends of the same single ignition coil, merely swap the ignition cables for those two cyls at the coil pack .... and see if the problem moves to cyl#1.

If it does not, I would repull the plugs on cyl#1 and cyl#5 ... just for an inspection.

Good that you did the compression test. Of course, the readings depend on the gauge ... and gauges vary ... but your numbers seem a bit low. Was the throttle plate blocked in the full open position when the test was made?

[94LebConv3La604]

temp,
I had taken the fuel rail off and inspected all of the injectors, but none of them looked in the least bit dirty or gunky except on the outside where they are exposed to the engine compartment. All of them ohm out with readings very close to one another and all tick as they should with the engine running. I really should have swapped a couple just to make sure, though. There were motorcraft plugs in before I changed them, but as soon as I put the new ones in the engine ran 10 times better for about a week. Then it went back to Ford so they could finish up work that they screwed up. When I got it back it was back to same old same old. It was the FOURTH time going back to them so they could fix botched work and I refuse to bring it back to them any more. It seems every time I bring it back something else is wrong with the car. They even broke my radiator and tried to fix it with some sort of grey adhesive....looked like JB weld....I didn't have it for a day before my engine compartment was covered in coolant.

12Ounce,
I have taken out the plugs for a close inspection and even swapped them to different cylinders. I haven't tried swapping the cables, however both the cables and coil pack are also brand new. I will swap them anyway just to rule out a defective. And GAH....forgot to block the throttle open.

[94LebConv3La604]

Instead of blocking the throttle open could I just take the throttle body off the plenum?

[12Ounce]

Originally Posted by 94LebConv3La604

Instead of blocking the throttle open could I just take the throttle body off the plenum?

That would be even better.

[94LebConv3La604]

I haven't had time to do any other TS on the van, but I promised some diagnostic readings so here they are:

Freeze Frame Data:
Trouble Code: P0305
Eng Speed RPM: 2815
Calc Load %: 82.3
Coolant °F: 201
ST FTRM1 %: 3.9
LT FTRM1 %: -1.0
ST FTRM2 %: -4.9
LT FTRM2 %: 0.0
ST FTRM3 %: -70.2
LT FTRM3 %: -80.1
LT FTRM4 %: 57.0
ST FTRM4 %: 83.5
Veh Speed MPH: 31
Fuel Sys 1: CLSD

Those last 4 fuel trims are way out.

I also have some recorded data frames, but I think I will zip them first.

[12Ounce]

If you do get around to removing any/all injectors again; give each a sideways blast in the inlet end with aerosol brake cleaner. And then drip a drop or two of clean motor oil into the inlet. If possible, rest the injectors several hours vertically on work bench.

[94LebConv3La604]

Should I just immerse them all in some B12?

[12Ounce]

Never, never immerse injector bodies in any cleaner/solvent!!!!

[94LebConv3La604]

Good to know, thank you much.

[12Ounce]

BTW, are those fuel pressure readings a bit low for your model?

[94LebConv3La604]

It is the low end, but it is within spec. The specs for my 98 3.8L are:
28 to 45 with vacuum attached
38 to 50 w/o vacuum attached

[12Ounce]

Could be low-spec fuel pressure is a co-conspirator. It may be varying ...

A fuel pump replacement may be in your near future.

[olopezm]

I agree about the fuel pressure, it seems a bit low and a new pump might be needed in the future. Hopefully not.

About the STFT3 and 4 don't worry; that's a regular problem with generic OBDII readers. These engines have only 2 banks.

Try sticking a long screwdriver (which will work as a stethoscope) at the injector and you should hear a constant clicking sound. You can compare it with the rest.

Oscar.