2001 Explorer Sport 4.0 SOHC Cylinder Misfire Codes

[ironhed85]

Hi, I'm new to this site and this vehicle as well. I purchased it with 106,000 mi., and a number of problems. I am hoping that someone can shed some light.

Besides the low speed firing of the ABS system that is bugging me, I am pulling numerous codes on bank two for random misfire, cyl 4,5,6 misfire, and rich condition (5 codes). At one time I was pulling a lean condition but that was before I replaced the plugs. All the other codes were in the system before I tuned the vehicle. The engine doesn't make a ton of power, it shakes a fair bit at idle, and only pulls codes when it is idling not on the highway. (if I reset the codes while on driving, they dont come back until it has idled some)

Yes, I replace a set of Autolite double platinum plugs with a set of Bosch single platinum plugs gapped @ .045". I also replaced the aftermarket wires with a new set of Duralast wires from Autozone.

From what I understand, the Bosch plugs disagree with the 4.0 SOHC motor; but I have never seen a set of plugs set off an OBDII misfire code unless something else was wrong.

The last plugs were gapped @ .045 as well, I didn't think that the Ford coil pack could fire across a .054" gap consistently and that the plug gap that I got from Autozone was dislexic. I can't imagine that aftermarket wires would contribute to this problem but I am open to suggestions.

I don't have any reason to suspect the charging system or battery however the battery weighs less than my head so I don't think I will be keeping it for too long, even though I haven't had a problem with it yet.

I plan to swap in a set of Motorcraft S400 plugs gapped @ .054" unless anyone has some personal experience to convince me otherwise. I have read that the V6 cylinder heads are prone to cracking between the valves, but why would I get all 3 cylinders reading misfire?

I expect to disasemble and clean the IAC with carb cleaner which may reduce the misfire at idle. I am currently getting bad gas mileage (15-18 mpg highway) I expected better.

[2000StreetRod]

The PCM computes the power of each cylinder and when one is low reports a misfire for that specific cylinder. The PCM tests the CMP and CKP sensors before reporting a misfire. The PCM does not always detect a bad sensor. Typical misfire sources are ignition, fuel injection and compression.

Ignition problems could be due to a bad plug, wire or coil. Make sure to "read" your old plugs when you replace them.

Fuel injection problems could be due to a bad injector, pressure regulator, fuel filter or pump. The only problem that is cylinder specific is a bad injector.

Low compression could be due to worn/broken rings, worn or sticking valves, blown head gasket or cracked head. Replacing your plugs is an opportunity to do a compression test. You didn't mention an engine oil change. A sticking valve is hard to detect. I suggest that you flush the engine oil and then change it. I believe the SOHC heads are less likely to crack than the OHV heads.

I suggest changing your fuel filter if it has been more than 30,000 miles since it was changed and then adding fuel injector cleaner to your tank. (I use only Techron). See this link: Why change fuel filter?

After performing the above (if appropriate) I would clear the DTCs and start fresh.

If you still have problems then perform the TPS Test Procedure

followed by cleaning the MAF sensor and performing the MAF Sensor Test Procedure

and then the Fuel pressure test procedure

[ironhed85]

Thanks for the response StreetRod. I did flush the engine oil; didn't get the fuel filter out though, couldn't get the rear flex fitting off of the filter. I'll try again next weekend, never had a problem with any fuel fittings before.

If I can get the fuel filter replaced, what should the fuel pressure be?

Too bad my lift is clogged w/my 1 ton waiting for a new oil pan, I don't expect a 100 K fuel pump to be that strong, or the regulator to be functioning properly.

Haven't decided on a plug yet. AutoZone says OE plug is irridium.

Cheers

Ironhed85

[FexplorerV8]

it all points to the wires being plugged on the wrong spark plug, misfires and a rich condition indicate that you have unburnt fuel going out of the tail pipe.

check the wires and make sure they are connected to the right plug, gap the sparkplugs to the oem spec and get motorcraft iridium plugs. bosh plugs are for german cars.

has the check engine light flashed at you?

[2000StreetRod]

Originally Posted by ironhed85

. . .
If I can get the fuel filter replaced, what should the fuel pressure be? . . .

Cheers
Ironhed85

1999 and later models have a returnless fuel system. The pressure should always be 60 to 65 psi.

[ironhed85]

Thanks again StreetRod. Yikes, a one way trip for fuel, haven't seen much of that.

I'll follow up after this weekend with results.

Ironhed85

[ironhed85]

Thanks for the replies, unfortunately I am no closer to acheiving my goal of an inspection sticker.

I got the fuel filter swapped, a fresh set of front sway bar end links, and a set of Motorcraft plugs ( gapped @ .054") that I got from my Ford Dealer. No changes in how the vehicle starts or runs.

P1000 System not ready

4 Codes presently
P0175 System too rich Bank 2
P0171 System too lean Bank 1
P0306 Cyl 6 misfire
P0305 Cyl 5 misfire

probably

P0304 Cyl 4 misfire coming soon.

I ran out of time Saturday to test the fuel pressure; next Sunday I guess. If the fuel pressure is low, I will first swap in a new regulator and test, and then a pump if necessary.

I am suspect of the TPS. The code scanner shows 19% for the throttle position at no throttle, and about 46% at WOT. That is under driving conditions. I will do a voltage test on Sunday as well.

I'm sure that the IAC could be disassembled and cleaned, and the MAF meter should be hosed with cleaner.

I would like a procedure to test the coil pack for internal resistence. If it is bad, AutoZone offers an aftermarket product. I'm a little leary of using cheap aftermarket ignition parts, but I won't go crawling to my dealership to fork over my weeks pay either.

Ironhed85

[2000StreetRod]

Something is wrong with your scanner TPS readings. 19% is normal for closed throttle but WOT should be at least 80%. You need to perform the TPS Test Procedure.

Since you have a scanner, are your short term fuel trims consistent with the reported DTCs? Your misfires are on the bank that is too rich which makes sense. Have you looked at the voltage swing on your pre-cat O2 sensors?

[2000StreetRod]

I checked one of my past generic scanner log files and my absolute throttle position value at WOT was 93%. When the ignition key is switched to On the PCM reads the TPS value and assumes it to be closed throttle. Since the PCM provides the reference voltage to the TPS, it is able to compute the WOT value. The PCM tests the TPS output to make sure it is not too low or too high. The PCM is also supposed to compare the reasonableness of the TPS value with the MAF sensor output but the tolerance is large.

You mentioned that you plan to replace the fuel pressure regulator (FPR) if your fuel pressure tests too low. Since 1998 the FPR is located in the fuel tank with the fuel pump. There's a photo in the Fuel Pressure Test Procedure. The device on the fuel rail that looks like an FPR is a damper. I suspect it is there because fuel is basically incompressible like water. In your home plumbing there is probably a device that contains air to absorb the shock that occurs when water is turned off and off.

[ironhed85]

Well,

I finally got around to checking the fuel pressure after changing the fuel filter...65 psi @ idle.

I am still getting misfire codes on bank 2 and now some on bank 1 as well as rich condition bank 2.

The TPS is apparently functioning within the correct range (19 -89%) as read from my scanner. I was previously mistaken.

I have now officially become a parts changer instead of the diagnostician that I aspired to be. The only thing that may cause this that I haven't replaced is the coil pack.

It is worth noting that the idle quality is terrible, not to mention the terrible valve train rattling. (both at idle, and at 2500 -3000 rpm) I am considering re-habbing the timing chain tensioner system in the spring, but for now will suffer through it. My gas mileasge was 17m MPG average on the highway which I believe is poor.

I'm sorry to be a burden to this site. When I do the V8 conversion to my X Sport, I will be sure to post the steps.

Ironhed85

[2000StreetRod]

What did your Bosch plugs that you swapped look like?

Did you perform a compression test while the plugs were out?

Did you clean and test the MAF sensor?

Did you add fuel injector cleaner after replacing the fuel filter?

What is your spark advance and knock retard at idle and at cruise?

[2000StreetRod]

Originally Posted by ironhed85

. . . I still have misfire codes, and lean/rich condition. I stopped our correspondence because the driver's side timing chain guide became much too loud to drive the vehicle without risking valve interference. I took the vehicle out of service and performed a complete timing chain replacement with an offshore timing kit. (4 chains, tensioners, guides, casettes, etc...). Now I am reasonably sure that the cam timing is correct as the engine runs like a raped ape at WOT but I haven't worked out any of the bugs I started with. . .

Congratulations on pulling the engine and successfully replacing the timing chain related items! Was there much sludge accumulated in the heads?

Did you ever perform a compression check or happen to pull the heads while the engine was out and look for cracks?

Did you try fuel injector cleaner?

Does your scanner show unusual long and short term fuel trims?

[1998Explodasport]

So I have a very similar situation than you except bank 2 on my truck runs lean not bank 1 and after watching my fuel trims I should also get a bank 1 rich code but I never do. I get alot of misfire codes, most start on bank 1 and eventually I will get codes for almost every cylinder missfire. Like you I replaced my plugs, wires and coil with no change. The only difference with my plugs is I used the OEM iridium.

What state are you in?? I was able to get an inspection sticker on my truck a few months ago. I drove around with my NGS scanner hooked up and I was able to monitor my fuel trims and keep them where they needed to be so I wouldn't set a code. I'm in Mass and my truck doesn't need to finish the EVAP part of it's readiness to get a sticker.

[ironhed85]

Thank you gentlemen for your continued correspondence, I am still obviously frustrated with my vehicle and looking to take it out rather inappropriately. Sorry for that.

I just got through the last of the fuel with sea foam in the tank to clean the fuel system. Even before the sea foam, the exhaust smelled like a charcoal grille, evidently running rich and possibly contaminated from before my purchase of the vehicle.

It is running better but still weak in the midrange. I will get a better idea of the codes it is throwing by tomorrow and post again.

Honestly, I need some explainaton to understand the fuel trim or fuel maps on this engine. Some of it may be available on my code scanner, I will do my work to better use the information available to me. I could use an overview of the fuel trims.

It would also be helpful to know the three O2 sensors, as to where they are located on the system. the scanner sees the drops on the wiring harness as Bank 1 - Sensor 1, Bank 2 - Sensor1, and Bank 1 Sensor 2. the latter I expect is rear of the front cat. Bank 1 the passenger side and bank 2 the driver's side. It is possible to have the passenger's side connector (S2S1) swapped with the B2S2 connector. I need to know which two locations are on the Y pipe and that they should look similar when in live data output mode.

Certainly there is sludge in this engine as it was a leased vehicle and oil changes were not considered important. I am sure that was the primary contributing factor for low chain tension, and slappy chains destroying their respective guides. I cleaned the pans and the timing cover, however the block and heads have a healthy dose of sludge. I figure to do frequent oil changes with kerosene added to the oil just prior to oil change. This should cleanup the valvetrain and loose stuff anyway. The heavy stuff will just have to stay put like a heart attack waiting to happen.

[2000StreetRod]

I believe that a defective crankshaft position sensor can result in the PCM detecting a misfire. The sensor is in a position exposed to the elements. You might try cleaning the connections by disconnecting and reconnecting the connector a couple times. However, a defective CKP sensor shouldn't result in the misfires always being detected on only one bank of cylinders.

[swetrid]

Do you have rich codes on one bank and lean on the other bank?

[2000StreetRod]

Originally Posted by ironhed85

. . .
It would also be helpful to know the three O2 sensors, as to where they are located on the system. the scanner sees the drops on the wiring harness as Bank 1 - Sensor 1, Bank 2 - Sensor1, and Bank 1 Sensor 2. the latter I expect is rear of the front cat. Bank 1 the passenger side and bank 2 the driver's side. It is possible to have the passenger's side connector (S2S1) swapped with the B2S2 connector. I need to know which two locations are on the Y pipe and that they should look similar when in live data output mode. . . .

Your O2 sensors are different than mine. I have two cats that feed a dual inlet/single outlet muffler. There are O2 sensors prior to and after each cat. As I recall the passenger side precat O2 sensor is B1S1 and the post cat O2 sensor is B1S2. On the driver side the precat is B2S1 and the post cat O2 sensor is B2S2. In your case with a Y pipe I assume the single post cat sensor is B1S2.

I was thinking that you might have a blocked cat on the driver side bank until I learned that you only have one cat.

[2000StreetRod]

According to the 2001 Model Year OBD System Operation Summary:

"Long Term Fuel Trim correction cell currently being utilized in conjunction with Short Term Fuel Trim:
Lean malfunction: LTFT > 25%, STFT > 5%
Rich malfunction: LTFT < 25%, STFT < 10%"

I think the Rich malfunction above should be:
LTFT < -25%, STFT < -10%

I've seen my LTFT change as much as 31% in 1 second and my STFT change as much as 25% in less than 0.7 seconds.

The following observations are for my Sport:
LTFT is computed by the PCM and stored in KAM for the next engine cycle. It will not change while the engine is idling. When engine speed exceeds 3200 rpm, LTFT becomes 0%. When A/F ratio is lean, LTFT is positive. When A/F is rich, LTFT is negative.

Engine started & idled with A/F ratio = 16.0:1, LTFT = +25%, STFT = +42%, no DTC
idled with A/F ratio = 14.7:1, LTFT = +10%, STFT = +42%, no DTC

The above were before I installed my 00M12 kit.

[1998Explodasport]

Like I said I have similar symptoms and codes, I replaced almost all sensors on this motor (don't waste your time or money doing the same, our motors are junk and need to be replaced) with no change. I am almost positve I have an internal vacuum leak and most likely you do too.

[ironhed85]

Well, I pulled the latest codes from the PCM from a 50 mile drive yesterday.

Codes that were stored:
P1132 Lack of H02S11 switches - Sensor indicates rich
P1151 Lack of H02S21 switches - Sensor indicates lean

Codes that are pending:
P300 Random misfire
P302 Cylinder 2 misfire
P303 Cylinder 3 misfire

Freeze Frame for DTC P1151:
Fuel System 1 - closed loop
Fuel System 2 - not supported
Calculated load value: 59.61%
Engine coolant temp 88 C
STFT Bank 1: -23.44%
LTFT Bank 1: -4.69 %
STFT Bank 2: 42.19%
LTFT Bank 2: 3.91%
Engine rpm: 2113
Vehicle speed sensor: 82 km/hr