98 Intermittent P0305 - Lots of troubleshooting

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.... :confused::runaround:
:1zhelp::feedback:

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.... :confused::runaround:
:1zhelp::feedback:

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.

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?

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. :swear:

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. :banghead:

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

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

That would be even better.

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.

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.

Should I just immerse them all in some B12?

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

Good to know, thank you much. :cool:

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

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

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

A fuel pump replacement may be in your near future.

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.

I saw the new fuel filter in the list.....and most other routine maintenance items.
The only thing that I would add is the Berryman's B-12 Chemtool in the gasoline tank.
From the reading that I have done......it does the most cleaning when it is not all used in a short time, like on a trip.
Having it in there to soak for a while is a good thing.
Even though you have had the injectors off.....there may be some stubborn deposit....or like I had once when I had serious misfires right after I had had the injectors off and clean them (when I replaced my lower intake manifold gasket)......something worked loose and lodged.....patience with the Berryman's was what solved it.

The flashing does indicate a condition that could cause damage to the catalytic converter, misfire being 1 big one.
However, the PCM does not know the cause of the misfire (would make your job a lot easier if it did).
If the cause is due to lack of spark, you have raw fuel going into the catalytic converter.....which is bad.
If the cause is due to lack of fuel to that cylinder, such as a dirty injector, then it is not so bad for the catalytic converter.


One other thing that can go bad.....though one would expect a code....is the Camshaft position sensor.
This is easy to change and not expensive.
You ONLY remove 2 small bolts and an electrical connection.
The actual pickup part of the unit, which is what you are changing, can become brittle and crack from all the heat cycles.
The camshaft position sensor is located on top of the syncro gear.....all that is left of the old time distributor.
You DO NOT want to mess with the sychro as that can be difficult to get back into the correct setting.....but changing the CPS does not require any messing with that part.

Rockauto has this part listed under "Ignition"....a Genuine Motorcraft CPS is $60.79 plus shipping.
You will want to check to see if you have the 2 pin or 3 pin connector.

Here is a picture of the CPS on my '96 3.8L.

http://inlinethumb17.webshots.com/48720/2804003860011220610S600x600Q85.jpg (http://rides.webshots.com/photo/2804003860011220610IkRBFJ)

So far I've put in a can of seafoam and a can of B-12. I was considering the CKPS as well or possibly the TPS, but I can't seem to get a good probe on it for testing. This is our main vehicle, but a tank of gas usually lasts a few weeks as I mainly just take the wife to work, kids to work, a trip to the in-laws each weekend that is only 10 miles away...it's mostly short trips and I am still getting over 200 miles per tank. I was planning on putting another can of B-12 into the tank next fill. There definitely isn't lack of spark. I bought one of those crappy spark testers from autozone and made some modifications to it so that it actually works reliably and it has a strong blue spark. Admittedly I have not tried this with the car in gear...my wife doesn't like helping me work on the car and I don't trust my kids to have their foot on the brake. :headshake

Our engines are pretty much identical...even down to the broken alternator + boot. :rofl:

The 2 weeks is GREAT.
I used to think that using the cleaner when I went on a trip was good....but the 2 week soak is what I'm told is what will get the most out of it.
I would put ONLY the B-12 in......it is a solvent based cleaner, where as most are detergent based.
The B-12 is the ONLY cleaner that would work on my injector deposits.....and I tried a LOT of different ones.

Yeah, I tried the Seafoam first, but it seemed to only make it worse. I will never use it again.

The Throttle Position Sensor (TPS) should not cause a missing.
I once forgot to plug mine in....gave me a code and the thing that I really noticed is that I did not have that downshift when I romped on the accellerator.
However, the vehicle did not run rough at all.

My '96 was really prone to building up deposits inside that cap over the end of the fuel injectors.
Later years did not seem to have the same issue, but it was an issue that would come up about 1 time a year for me......very slight miss that most people would not notice.
It would take a couple years to get bad enough to light the CEL, but it would drive me crazy until then.
MANY parts were replaced and finally I figured it out.
Then when the problem came back very suddenly, my local mechanic handed me a can of the Berryman's B-12 Chemtoool and told me about it being a solvent based cleaner vs the detergent based.
I add a "maintenance dose" of Redline Complete Fuel System Cleaner because the fuels in my area are not the best in terms of additives.
The Redline gives a boost in detergency and also provides an upper cylinder lubricant.
I will be first to say that it is overkill, but I DO tend to keep my vehicles a long time.

On the Windstar, I STILL needed to run the Berryman's about 2 times a year.

This is a fuzzy picture, but you can see the cap on the left and the dirt deposits right on the outlet of the injector on the right.
The combination of oil from the PCV line and the EGR carbon........
Although I would NOT want to reduce the PCV flow as that is super critical.
I did add a catch can, don't know if it was of any help or not.

http://inlinethumb15.webshots.com/31822/1345071487011220610S600x600Q85.jpg (http://rides.webshots.com/photo/1345071487011220610UQRjYi)

Here is a clear picture of the end of the injector after I sprayed the end off and you can clearly see the spray holes.
Again, the dirt was over the end....and also built up inside the cap.

http://inlinethumb09.webshots.com/49608/1345076747011220610S600x600Q85.jpg (http://rides.webshots.com/photo/1345076747011220610JjMqaP)

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?

why do you say that? I ran a dry one-that means with the spark plugs out, right? My haynes book said anything over 101 psi was good, mine were all over that 120-130 psi.

It stopped the popping noise when it did that, too.

...........I ran a dry one-that means with the spark plugs out, right? .......

It stopped the popping noise when it did that, too.
.
A dry compression test is just that ... no oil has been dropped into the cyl to "seal", possibly worn, rings. ( I will never again try a wet test ... too indefinite,and likely to damage the gauge.)
.
What stopped what popping noise?
.
I think I remember approx 175 psi when I tested my 3.8 .... but that may just be my gauge ... or bad memory.

Haven't had much time to try any other troubleshooting as the damn deathstar blew the power steering return hose...it was pretty badly rusted and took the better half of a week to get replaced due to weather, replacement not being in stock, and an overall PITA of getting the old out and the new in. Good news is that it has been mostly sitting in the driveway with only a few test drives after replacing the power steering return hose and bleeding the air out of the system. I think I will take it for inspection before the misfire comes back so I have a bit more time to figure out what is going on.

Some additional info: my scanner picked up a pending code for failure to bleed up fuel tank pressure....I forget the code....P1450? Pretty sure it's not the FPS going wonky since I have on occasion heard a growling sound come from the fuel tank. It has a nearly brand new gas cap on it so I'm thinking vapor canister as the most likely culprit and if that isn't it, the lines to and from it. Would this contribute to the misfire situation?

Also had a pending code for TCC solenoid being stuck in the open position I believe....only pops up after a long drive, which is not often for me. If it pops up again I will make sure to take note of the exact code. :banghead:

Went through inspection today successfully. So far it has been driven 30 or so miles with no sign of misfire, but the guy at the inspection station managed to stall it out stutter stepping the gas pedal. I swapped the 1 and 5 wires at the coil pack before heading out so we'll see if the misfire switches cylinders once it starts to act up again. The van was sitting w/o being started for about a week and it didn't start misfiring for a few days the last time I allowed it to sit that long. We shall see.