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96 OBD II engine misfire codes and rough idle

Ecomike

NAXJA# 2091
NAXJA Member
Location
MilkyWay Galaxy
I need some ideas guys! My sons Ford Taurus, 96 lost the coolant recently due to a hose rupture. We fixed that. Now it wants to throw random cylinder # misfire codes, and it idles real rough especially when its cold, first start of the day. The idle smooths out when it warms up, and it stops throwing codes once it is good and hot!
I have a code scanner, and I have cleared the codes, and run it hot and cold, running tests in the driveway in gear and in park after clearing the codes. Only codes it has thrown so far are engine missfire cylinder numbers, and not always the same cylinder. It also posted a single Cl-fault on fuel system #2 once, but has not repeated that code since I cleared it.

Ideas????

My problem is I think it is the HV coil or secondary system, wires or ECM for the spark based on some other tests ( Iam planing more tests there right now), but it started right after it overheated???

Any good Ideas out there???

Oh, And just pretend it is a 96 Jeep 6 banger I am asking about!
 
Hmmm...Ignition system damage from the hose rupture, etc...

So... I am thinking all the typical stuff...plugs, wires, cap, rotor, coil, etc...maybe a/some sensors got wet with coolant and is/are now performing erratically until they warm up...intermittent connection problems...

might want to change all the hoses...if one went...who's next?

Good luck with it...McQue
 
The hose that leaked was at the very bottom of the entire system, bottom of the radiator, and nothing above it got wet. Rest of the hoses seem OK.

I just ohmed three of the six HV wires, I got 5,000 to 8,000 ohms, or about 5,000 ohms per foot. I also just used an inline lighted neon spark intensity tester on Cyl 5, and it looks real good. There is no typical cap, rotor or distributor on this beast, just a box with 6 HV secondary wires.

I found a realy cool ford OBD-II manual that describes how the 1996 year OBD-II system works. It is quite revealing.

http://www.motorcraftservice.com/vdirs/diagnostics/pdf/obdsm962.pdf

McQue said:
Hmmm...Ignition system damage from the hose rupture, etc...

So... I am thinking all the typical stuff...plugs, wires, cap, rotor, coil, etc...maybe a/some sensors got wet with coolant and is/are now performing erratically until they warm up...intermittent connection problems...

might want to change all the hoses...if one went...who's next?

Good luck with it...McQue
 
I just dug this out of the manual, looks like its not spark related after reading all this,

It has an Electronic Ignition systems (Electronic Distributorless
Ignition System - EDIS) systems.

The EDIS system uses a chip to process the 36 (or 40) tooth crankshaft position signal, generate a low data rate
PIP signal for the PCM microprocessor and control a 4 or 6 terminal coil pack which fires a pair of spark plugs. One
of these sparkplugs is on the compression stroke, while the other is on the exhaust stroke. The EDIS chip can be
incorporated within the PCM or in a separate ignition control module.
The ignition system is checked by monitoring three ignition signals during normal vehicle operation:
Profile Ignition Pickup (CKP, commonly known as PIP), the timing reference signal derived from the
crankshaft 36-tooth wheel and processed by the EDIS chip. PIP is a 50% duty cycle, square wave signal
that has a rising edge at 10 deg BTDC.
Camshaft IDentification (CMP, commonly known at CID), a signal derived from the camshaft to identify the
#1 cylinder
Ignition Diagnostic Monitor (IDM), a signal that indicates that the primary side of the coil has fired. This
signal is received as a digital pulse width signal from the EDIS chip. The EDIS chip determines if the
current flow to the ignition coil reaches the required current (typically 5.5 Amps for COP, 3.0 to 4.0 Amps
for DIS) within a specified time period (typically > 200 microseconds for both COP and DIS). The EDIS
chip also outputs status information when the engine is not running.
First, the relationship between successive PIP events is evaluated to determine whether the PIP signal is rational.
Too large a change in 3 successive PIP indicates a missing or noisy PIP signal (P0320). Next, the CMP edge
count is compared to the PIP edge count. If the proper ratio of CMP events to PIP events is not being maintained
(for example, 1 CMP edge for every 8 PIP edges for an 8-cylinder engine), it indicates a missing or noisy CMP
signal (P0340). Finally, the relationship between IDM edges and PIP edges is evaluated. If there is not an IDM
edge (coil firing) for every PIP edge (commanded spark event), the PCM will look for a pattern of failed IDM events
to determine which ignition coil has failed. If the ignition coil cannot be identified or if the engine is running and
there are no IDM edges, the IDM circuit is malfunctioning (P1351).
I starting think it may be clogging fuel injectors, but who knows.
 
to me it kinda sounds like it was a fluke that a hose blew out then started missing.
be sure to check simple things that can bite you too. such as fuel pressure, spark plugs, etc.
i would say it sounds like an injector, but that wouldn't make sense because injectors usually open up after it gets hot (heat + coils = higher resistance.), but be sure the check those too, sound to me like you've got one hell of problem.
 
Thats a pretty descriptive manual you found...I have been reading through it. If you are thinking injector problems keep in mind that I read "If a single cylinder is indicated to be consistently misfiring in excess of the catalyst damage criteria, the fuel injector to that cylinder may be shut off for a period of time to prevent catalyst damage. Up to two cylinders may be disabled at the same time. This fuel shut-off feature is used on many 8-cylinder engine and some 6-cylinder engines."

Since the problem seems to be temp related, your gonna have to remember to do your testing when it's failing, but you already know that....hate to rule out something that tests good when it's all warmed up...

McQue



 
3.0 v6's in the taurus cars a notoroius for headgasket leaks,I've done 4-5 in the last year,alot of them started just as your's did..........blown hose,missfire,overheat,etc. Like yours it was not always the same cyl,but in most of the one's I did the rear cyl were the one's with the problem,also IIRC 2 of the engines wound up needing at least one head and I know 1 needed both
 
Just an idea. But glycol is insidious stuff, it is a pretty good conductor. Anything it gets into is likely to short, much more so than regular water. It only takes a little film or residue to do it. When I get a coolant spew, I wash the motor with hot whatever and then repeat, I've learned that lesson the hard way.. When it gets hot and dries it conducts less. Glycol is a desiccant, if it dries out it reabsorbs moisture from the atmosphere.
Could also be a head gasket like mentioned. Sometimes the misfiring plug will show a slight tint the same color as the coolant.
The coolant may foam and bubble with the radiator cap off. You can sometimes pump some air into a suspicious cylinder and get the coolant level to rise and/or bubble.
If it gets really bad you can have drops of moisture coming out of the exhaust, often with a tint the same as your coolant color. I sometimes use a white piece of toilet paper to check this.
 
What is really weird is that it almost immediately throws a misfire cyl code on cold start up, at ECT = 60 F. Then if I clear the code after it warms up and restart it, I can not force it to throw a misfire code again, even with multuiple restarts until it cools down to say 70 F.

The Coolant temp is running about 210 F with out any fans on at all. Takes about 20 minutes of idle at 80 F ambient just to trigger one elec fan to run for about 30 seconds, which drops the ECT from about 220 F to about 190 F in just 30 seconds. One electric fan runs on the ECT switch through the PCM, the second electric fan is operated with the A/C on. There is no fan clutch, or mechanical fan on this beast. I see no signs (yet) of coolant / head gasket leaks in either direction, and the misfire code switches between at least 3 (or 4?) cylinders so far. It has not thrown any other codes at all after 16 restarts and about 60 minutes of idling during those start run operations.

I did find a disconected vacuum hose to the fuel pressure regulator during the first test, fixed that, but the codes did not change, except for the freeze frame data which went from Fuel sys #1 reading "CL" to reading "OL" now, ????

Fuel sys #2 in the freeze frame of the missfire code is always reading CL-Fault, but I have not been able to find any references yet that tell me what " CL, OL, or CL-Fault" in the Fuel Sys means, nor why, or what the 2 fuel systems are, like what is the difference between fuel sys #1 and #2?

Thanks for all the replies and help guys!

I am going to run fuel pressure and vacuum tests today.
 
I have told my son repeatedly not to run the fuel tank dry, but alas Humans seem to learn many lessons the hard way. Trash in the fuel system is a high priority possiblity in my book, but if I am right it is only part of the poroblem, and is a roaming trash in the fuel injectors problem that is coming and going with this tank of fuel.
I did notice in that on line manual I linked to at Ford, that this beast fires the spark plugs on both the compression stroke and the exhaust stroke (unlike the Jeep which has a camshaft position sensor) , so it is concievable that a stuck opem FI that is leaking might ignite on the exhaust stroke and throw a misfire code????


codyj86 said:
to me it kinda sounds like it was a fluke that a hose blew out then started missing.
be sure to check simple things that can bite you too. such as fuel pressure, spark plugs, etc.
i would say it sounds like an injector, but that wouldn't make sense because injectors usually open up after it gets hot (heat + coils = higher resistance.), but be sure the check those too, sound to me like you've got one hell of problem.
 
Yes I found that OBD-II ford feature description quite enlighting too! I wonder if OBD-II Jeeps do that too?

McQue said:
Thats a pretty descriptive manual you found...I have been reading through it. If you are thinking injector problems keep in mind that I read "If a single cylinder is indicated to be consistently misfiring in excess of the catalyst damage criteria, the fuel injector to that cylinder may be shut off for a period of time to prevent catalyst damage. Up to two cylinders may be disabled at the same time. This fuel shut-off feature is used on many 8-cylinder engine and some 6-cylinder engines."

Since the problem seems to be temp related, your gonna have to remember to do your testing when it's failing, but you already know that....hate to rule out something that tests good when it's all warmed up...

McQue



 
98XJeep said:
3.0 v6's in the taurus cars a notoroius for headgasket leaks,I've done 4-5 in the last year,alot of them started just as your's did..........blown hose,missfire,overheat,etc. Like yours it was not always the same cyl,but in most of the one's I did the rear cyl were the one's with the problem,also IIRC 2 of the engines wound up needing at least one head and I know 1 needed both

Your giving me HEAD ache :eek: with this, LOL, as I already have my first head gasket job waiting for me on the 89 XJ, but thanks for the feedback, even if I don't like the answer.

So since this is a V-6, it hads two heads. The codes I recall were 1, 2 and 5 so far, and I think 4 once, but more often it has been #1 and #2, say on 3/4ths of the codes thrown so far. 1,2 % 3 are on the rear side.

Now, correct me if I am wrong here, but I know that antifreeze (silicone) is death to an O2 sensor, but so far I have no O2 sensor or Cat codes and no signsd of coolant leakage or overheating. Also, it only throws codes at cold start up, never when it is heated up. Also it has the rough idle ALL the time, and smooth as silk at other rpms with one exception. He has had this beast for 12 months, and 20,000 miles and it has always had problems getting over 3,800 rpm in park, or in drive, where it rapidly runs up and down in RPMs like a really bad TPS on a jeep would do.

So does this still sound like a head gasket. Also he said it died and coasted to stop when it starting leaking and overheating, and he did not try to restart it. The way he explained it, it sounded to me like it did not run long enough to damage the heads.
 
8Mud said:
Just an idea. But glycol is insidious stuff, it is a pretty good conductor. Anything it gets into is likely to short, much more so than regular water. It only takes a little film or residue to do it. When I get a coolant spew, I wash the motor with hot whatever and then repeat, I've learned that lesson the hard way.. When it gets hot and dries it conducts less. Glycol is a desiccant, if it dries out it reabsorbs moisture from the atmosphere.
Could also be a head gasket like mentioned. Sometimes the misfiring plug will show a slight tint the same color as the coolant.
The coolant may foam and bubble with the radiator cap off. You can sometimes pump some air into a suspicious cylinder and get the coolant level to rise and/or bubble.
If it gets really bad you can have drops of moisture coming out of the exhaust, often with a tint the same as your coolant color. I sometimes use a white piece of toilet paper to check this.

Come to think of it, the O2 sensor is low enough and close enough to perhaps have seen some antifreeze on the outside, which I know is death to an O2 sensor. Hmmm!:doh:
 
I found some of the fuel system details at:
http://findarticles.com/p/articles/mi_qa3828/is_200503/ai_n13486252/pg_3


UEL STAT 1 = Fuel System 1 Status: Fuel system status will display more than just Closed Loop (CL) or Open Loop (OL). You might find one of the following messages: OL-Drive, indicating an open-loop condition during power enrichment or deceleration enleanment; OL-Fault, indicating the PCM is commanding open-loop due to a system fault; CL-Fault, indicating the PCM may he using a different fuel control strategy due to an oxygen sensor fault.

But still looking for more details on this.
 
I think I just hit pay dirt!

http://findarticles.com/p/articles/mi_qa3828/is_200503/ai_n13486252/pg_1

"No matter what the driveability issue happens to be, the first parameters to cheek are short-term fuel trim (STFT) and long-term fuel trim (LTFT). Fuel trim is a key diagnostic parameter and your window into what the computer is doing to control fuel delivery and how the adaptive strategy is operating. STFT and LTFT are expressed as a percentage, with the ideal range being within ±5%. Positive fuel trim percentages indicate that the powertrain control module (PCM) is attempting to enrichen the fuel mixture to compensate for a perceived lean condition. Negative fuel trim percentages indicate that the PCM is attempting to enlean the fuel mixture to compensate for a perceived rich condition. STFT will normally sweep rapidly between enrichment and enleanment, while LTFT will remain more stable. If STFT or LTFT exceeds ±10%, this should alert you to a potential problem.
The next step is to determine if the condition exists in more than one operating range. Fuel trim should be checked at idle, at 1500 rpm and at 2500 rpm. For example, if LTFT B1 is 25% at idle but corrects to 4% at both 1500 and 2500 rpm, your diagnosis should focus on factors that can cause a lean condition at idle, such as a vacuum leak. If the condition exists in all rpm ranges, the cause is more likely to be fuel supply-related, such as a bad fuel pump, restricted injectors, etc.
Fuel trim can also be used to identify which bank of cylinders is causing a problem. This will work only on bank-to-bank hiel control engines. For example, if LTFT B1 is -20% and LTFT B2 is 3%, the source of the problem is associated with Bl cylinders only, and your diagnosis should focus on factors related to Bl cylinders only.
The following parameters could affect fuel trim or provide additional diagnostic information. Also, even if fuel trim is not a concern, you might find an indication of another problem when reviewing these parameters:
Fuel System 1 Status and Fuel System 2 Status should be in closed-loop (CL). If the PCM is not able to achieve CL, the fuel trim data may not be accurate."
Now my last 2 freeze frames read:

STFT B1% 17.1
STFT B2% 1.56
LTFT B1% 17.19
LTFT B2$ 1.56
So the LTFT (Long term fuel trim) and STFT )Short term fuel trim) for each bank is the same! And there is a huge difference between the two banks!
I need to recehck and see if these fuel trims were all positive, I think they were.
 
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I just tried cleaning the outside of the lowest O2 sensor nearest to the colant leak. I used scotch bright and a hyrocarbo solvent (non chlorinated, non fluorinated, mostly hexane aerosol while it was cold).

I tried the OBD-II relearn procedure by warming up the engine, clearing the latest misfire codes, and then following the published relearn procedure steps (see the link in prior post of mine here).

I got all the way to locking in the final emissions monitors which were the catalyst "C" and the EGR "E" monitors. The other emission monitors locked in 5 to 10 minutes earlier with no problems including the oxygen sensor monitors, fuel system monitor, Misfire monitor, Oxygen heater sensor monitor, Comprehensive component monitor and the heated catalyst monitor. Shortly after which it threw its first misfire code at normal operating temperature in about 2 hours of run time tests at normal engine temeratures. It threw no codes before then or during a 15 minute stop and go drive test at speeds up to 50 mph, once it was warmed up.

Shortly after cold start up I checked the exhaust and again after running and driving it for over 30 minutes, and I saw and smelled nothing, NOTHING in the exhaust. Coolant bottle coolant level is rock solid, not going up or down after an hour of runing and driving.

At the begine of todays tests it cold started and threw two missfire codes, Cyl #2 and #5. Got the folowing Freeze frame data:
STFT B1 +32.81%
LTFT B1 +0.78%
STFT B2 +9.38 %
LTFT B2 +0.78
EDT = 78 F
Fuel sys 1 CL
Fuel Sys 2 CL-Fault

I shut it down, restarted it, cleared the codes, and it idled smoothly all of a sudden, at 1000 rpm in park, apx 110 F, for over 2 minutes with no DTCs, after which I drove it as described above. After 15 minutes of driving with no codes, after the last IM locked in, I got 3 separate cyl 1 missfire codes, after clearing the codes and reseting the monitors. Once a misfire code was set it never triggered any more misfire codes.
The last misfire codes had thi freeze frame data, which varies from one the next!
The fuel trims on this one were all negative, prior ones had been positive!!!!
(1) Cyl #1 misfire! With all I M monitors locked in and running.
STFT B1: -1.56%
LTFT B1: -10.94
STFT B2: -0.78 %
LTFT B2: -10.94
EDT = 203 F
Fuel sys 1 CL
Fuel Sys 2 CL-Fault
Vehicle speed = 0
RPM = 696

(2) Cyl #1 misfire! After clearing, and resetting the monitors, and clearing the DTC code for the misfire.
STFT B1: -1.56 %
LTFT B1: -9.38 %
STFT B2: -2.34 %
LTFT B2: -9.34 %
EDT = 215 F (I am not sure I beleive it is getting this hot, CTS sensor may off a bit, I never got over 195 F with an IR external sensor)
Vehicle speed = 0
36.08% load
RPM = 707 (Note all the missfires up to this point were ALL at idle!!!, May be programing lock out codes that do this)

(3) Cyl #1 misfire! With C E emission monitors still not locked in, the rest locked in and working.
STFT B1: -9.38 %
LTFT B1: +0.78 %
STFT B2: -9.38 %
LTFT B2: +0.78 %
EDT = 204 F
Fuel sys 1: OL - Fault (this was a first!!!!!!)
Fuel Sys 2: CL-Fault
Vehicle speed = 13 mph (this was first, always was at idle before)
RPM = 2349 RPM
80 % load

At this point, about half of all the misfire codes have been cyl #1, so I am going to try and look closer at that cyl tomorrow, but it is buried under stuff and will be very hard to get to. Not looking forward to it. I may try new plug wires as a desperate last attempt to avoid lots of disasembly work just to get to the rear spark plugs and injectors (1,2 & 3). I already love my Renix jeeps again, LOL.

Does anyone see a pattern in the data that I am missing so far????


I see the following differences, Fuel system #1 was typically Ok, but Fuel system 2 (I am guessing bank 2, and further guessing bank 2 is where cyl #1 is). Fuel system #1 read a single OL fault during the final missfire, after the car ran for nearly 30 minutes, a first so far. Prior to that it was normally CL with no fault during the missfires. THe consistant fuel faults on sys #2 make me suspect a leaking fuel injector on the bank 1,2,3 side, possibly #1, or week spark on that cyl on occasion.
I just figured one odd thing out. The service engine light (or MIL Malfunction Indicator Lamp) would on occasion flash, and on other occasions be on but not blinking, my scan tool manual says the light blinks when it is sensing the cyl misfire and it continues to blink during the misfire, if the missfire stops the MIL light stops blinking! I has been doing both, so now I know what it means when its flashing!!!!
 
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From the manual specifically..."Since inaccuracies in the wheel tooth spacing can produce a false indication of misfire, the misfire monitor is not active until the corrections are learned. In the event of battery disconnection or loss of Keep Alive Memory the correction factors are lost and must be relearned."...So, here is what I heard ...you did all the right things...cleared the codes...and went through the "relearning process"... only after that did you start to collect new, real, and relevant data...but you already know that...
SO..you then pulled some misfires...and your analysis of the data collected after that seems right on except the part about negative fuel trim...were the codes logged while decelerating?
In any case...keep smiling!...( does it seem odd to you how the misfires seem to show up on cyl #1? (all of my life, cyl #1 is the guy that pulls a code...probably just a coincidence) .but forget I said that...believe the data...believe in technology...but in the end, your gonna have to pull out a wrench and change those plugs to start..
Yes, you are correct...the manual states.. "If the misfire threshold is exceeded and the catalyst temperature model calculates a catalyst mid-bed temperature that exceeds the catalyst damage threshold, the MIL blinks at a 1 Hz rate while the misfire is present. If the threshold is again exceeded on a subsequent driving cycle, the MIL is illuminated"..I would interpret this as possible damage to a piston if it continues to happen long term...(weeks/months)
Get the wrench out...let us know what happens for sure...
McQue

 
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It's not the piston they are worried about, but overheating the Cat converter due to excess unburned gas.

Right now I am trying to figure out how to test this 3 coil beast or block in this year model that fires the plugs. It is a direct ignition three pack coil, if I got the terminology correct. Seems it fires opposing cylinder plugs at the same time, one postive one negative of the same coil. How do you test one of these?

My other problem is it looks like you need to remove the intake manifold just to reach the fuel injectors and spark plugs on the rear bank which houses cyl 1,2 & 3. So I am trying to do as much thinking, reading, and diagnostic work as possible first.

I am reading tons of horror stories where people had this same problem and replaced everything including head gaskets finaly, with out ever solving the problem.

Somebody please tell me what or where this consistant Fuel system fault, bank 2 is coming from?
 
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you don't have remove the intake to change the plugs, but you do to replace the injectors.........is this car a dual fuel setup? it will have a green leaf badge on the side or trunk......had a ranger 3.0 that had problems with missfire's. it turned out that the sensor that tells the pcm what kind of fuel it was running on wasn't working, it was telling the pcm it was on reg fuel and the customer was running on E-85
 
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