Re:Re:Re:Re:Re:Re:Re:Re:Re:99 Explorer violent intermittent shaking

Curmudgeon wrote: The inability to hold a speed just a bit off idle without the IAC setting it back to idle has got to be a clue.
Not sure what that clue IS, but must be.
The more rapid shifts through all the gears has to be related, also.

If the PCM thinks the throttle is closed it'll continue to control idle. Throttle position probably also affects shift points. Personally I'd check Vref, signal, and ground voltages at the TPS as a starting point. Also monitor the TPS PID with the scan tool while testing signal voltage to see if it responds correctly to changes in signal voltage.

TPS might not be causing the intermittent misfire but it definitely sounds like a problem. It's not unusual for a 21 year old vehicle to have more than one thing wrong with it.

Matt T wrote:

Curmudgeon wrote: The inability to hold a speed just a bit off idle without the IAC setting it back to idle has got to be a clue.
Not sure what that clue IS, but must be.
The more rapid shifts through all the gears has to be related, also.

If the PCM thinks the throttle is closed it'll continue to control idle. Throttle position probably also affects shift points. Personally I'd check Vref, signal, and ground voltages at the TPS as a starting point. Also monitor the TPS PID with the scan tool while testing signal voltage to see if it responds correctly to changes in signal voltage.

TPS might not be causing the intermittent misfire but it definitely sounds like a problem. It's not unusual for a 21 year old vehicle to have more than one thing wrong with it.

Oh, I know. In the "old days" when I had my shop, Ford with driveability issues, I told the guys to just replace the TPS then diagnose. Probably 90% of the time that fixed it.
I did monitor the graph on the TPS, which does not give raw data, rather percentages. No glitches. No idea what is normal on percentages. I think, if I recall, idle was 18% TPS.

Yes, probably multiple issues, probably one had been there for a LONG time unnoticed, second one triggered the failure.

My other two Fords are 70+ years old, so I know!

Off to get gaskets now....

in the middle of this...the battery died. At least 10 years old.
But I did clean throttle body and IAC. NAPA gave me FOUR throttle body gaskets. Initially didn't think any were right, as I was looking for black not blue...road test without new seal and it howled.
Blue thick o-ring with kickout for air bypass, fixed that.
NEW battery, road test monitoring TPS...moves where it's supposed to, 18% baseline, no glitches.
However, LTFT B2 is zero. I suppose battery disconnected for an hour while I obtained replacement is an issue there, wiped the LTFT numbers? But LTFT B1 is reading, so not sure.

Drove fine, transmission even shifted right, 40 MPH last shift instead of 28 MPH, OD kicks in and out normally now, like it used to, so tomorrow we drive it from cold.


IAC gasket from NAPA is a gasket. In the car is an almost figure 8 o-ring. Did NOT put the gasket in...yet.

And this morning, 5 miles into the drive, the jerking on load is back. Bad. Since I was a passenger (she insists on driving....) I cannot tell on transmission shifting.
Too much to try to accomplish today, after 10 days of this vehicle.
I'll get some current numbers later today.

Data.
I tested the LTFT values, driving, shaking even, LTFT B1 0 at idle, moves up while driving.
LTFT B2 2.3 at idle, moves up and down a bit while driving.

Did some digging, looking at O2 sensors, and I have a problem.
O2 B1 S2 I thought was stuck at .775, but driving it does move, from about there up to .790.
O2 B2 S1 is .105 to .720 while driving.

This seems to be the one behind the cat...and not sure if that number I'm reading is correct.

Still no codes, trans seems to shift close to what it did last night...4th a couple miles and hour slower (like 38 vs 40)

Went out again, at idle, still warm, o2 b1 s2 now .090 to .100. Holding idle 1800-2000 starts climbing, quit my test at .410.
o2 b1 s1 .085-.765.
o2 b2 s1 .070-.745.
Two front o2 sensors look right.

stft b1 s1 -2.3 to +2.3.
sftf b2 s1 -2.3 to +2.3.
stft b1 s2 99.2%, and I read that is normal.

My readings look good. Other than post cat o2 which is odd. I think I changed that about 6 or 7 years ago. Remember it being a PITA on top.

I scanned most of the thread but not all and i don't know this engine but are we assuming a lean condition on #4?
can we assume to much air to #4 or not enough fuel to #4?


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Road test with scanner (still jerking under load), LTFT B1 at cruise is zero. LTFT B2 is +4.7.
Come back, idle, B1 is 3.9, B2 is 6.9.

Replaced the IAC gasket first.

Sprayed upper end of engine with carb spray while monitoring STFT and LTFT and no change. So vacuum leaks are pretty much eliminated.

can you scope fuel injector to #4

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simclardy wrote: I scanned most of the thread but not all and i don't know this engine but are we assuming a lean condition on #4?
can we assume to much air to #4 or not enough fuel to #4?


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I do not have a lab scope, but the last shop did, and told me they had an occasional misfire hit on #4 (4.0 pushrod).
Since I did new plugs, wires and coil pack, and all voltages are good, both ends of wires, they decided #4 injector must be the issue. We have an injector shop, who rebuilt a same part number injector, installed, same issue.

I have done so much testing and minor replacement (like Throttle Body Gasket) but I am not sure the numbers I am seeing are correct or not.

No vacuum leaks, even using the scan tool and carb spray on upper end of engine.

When it does the shaking, it can be violent, can duplicate under load test in driveway, so not drivetrain.

The odd thing is after the battery died yesterday, no battery in vehicle for almost an hour, B2 LTFT was zero, car ran perfectly.
It appears when LTFT starts adding into the mix, it all goes to heck. Makes no sense.

My next test it to disconnect the battery, short the ground cable to positive, and try a road test again.

Downstream O2 is puzzling, since both upstreams reading normal.

TPS tracks normall while driving, no jumps when it shakes. MAF readings good.

simclardy wrote: can you scope fuel injector to #4

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I have no ability here to do that, I don't think. Have to make an appointment and have them do it for me...and that will take a week.

the temperature test with the high temp on #4 sounds like a lean condition on #4

what else could give this result?
it is puzzling that you have such a violent shake.

did the shop scope it while it was having its seizure?

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simclardy wrote: the temperature test with the high temp on #4 sounds like a lean condition on #4

what else could give this result?
it is puzzling that you have such a violent shake.

did the shop scope it while it was having its seizure?

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The issue has been this is intermittent. Now it's fairly consistent, but when they had it (4 days) couldn't get it to fail on demand.
Temp was puzzling. Yet fuel trims are not pegged.
With a vacuum gauge showing steady 20" or more at idle, smooth while driving, tends to eliminate mechanical issues. Or at least minimize them for diagnostic purposes.

No vacuum leaks, including pulling PCV and spraying down into valve cover (guides, top of intake).

RPM sensitive, 25-35 MPH. Sometimes rough idle, sometimes not. Trans shifts weird, then after the last cleaning and killing memory, trans shifted just like it has for the last 16 years.

The downstream O2 is reading high, I think, and that is supposed to feed data to fuel trims, yet fuel trims are looking good, upstream O2's look good. You would think if it was really lean the Bank2 O2 would be off the charts, but it isn't.

They did scope it. I saw the screen one trip down....I think it was spark on six screens. I suppose on a 99 you can scope injectors?
I did this work for 35 years until some yay-who ran a stop sign....and I learned long ago to not throw parts and money at something until you have a clue.
I could yank it all apart and replace all six injectors, but this vehicle has me gun-shy, as every thing we do fixes it for one day. Then it's all back.


Shake? Geez, you think the motors is gonna rip out of the mounts sometimes. Wife has to wear a neck brace when she drives it.

I can't remember if you have done a compression or leakdown test on #4? Valve issue maybe? Has that valve cover been off recently for any reason?

It would be nice to nail down that #4 is actually an issue.

I've never experienced a misfire that could be described as violent, which is why I was thinking more toward driveline.

Nissan Technician

yeah...almost feels like a "death wobble" in a front end, except you can do it loaded in the driveway usually.
Valve covers need changing, but not sure how to get the left one out from under the EGR tube into the intake plenum.

I need to do a compression test. Limited energy and mobility. And cash. But, riddle me this:

Flood Clear Crank, no dead holes. Vacuum gauge good and steady.
Valve would certainly show up there, and NOT be so inconsistent?

I don't think the down stream o2 is used for fuel trim as much as it is to verify the catalytic converter is doing its job.

if you had one cylinder running lean it would be averaged by the other cylinders that are running properly so it might not be a drastic signal to the o2.

I think you mentioned a wire to injector #4 was nibbled by mice.

the death rattle is puzzling, I wonder if a faulty injector signal could mess up the timing/backfiring on #4 and cause lean?

I would not suggest replacing the injector without evidence but would love to see the signals to #4 during the death rattle.

did you say they scoped the injector and found a miss on #4?

compression test is not a bad idea but the way it starts and stops so abruptly I would not start there. I think you said it's hard to access. on my generators I check compression every year but they are so easy to access and there is only two.

I can't wait for the fix. it's a great puzzle.
cheers
sandy


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The scope was ignition for sure. I'll ask them about the injector scope.
I would hear a backfire i the exhaust or plenum, and nothing like that.
I have no way to dynamically test the crank position sensor. Possible, but I hate throwing parts at a problem.
Fuel trims are up + a bit on B2, where #4 resides, but not real bad.
If I can't find it, gonna have to yank all six injectors and have the injector shop test them all. But if it's intermittent....then what.

im thinking electrical so I would be slow to replace injectors.

the scope signal will show if the injector is moving and what kind of message the computer is sending. I would start wdith that.

I agree, don't throw parts at it. what happens when you throw a part at it and the new part is defective? I had that with an oil pressure switch and I told my friend to take it to a real mechanic. the mechanic scoped the switch and could see it was defective.


by the way, I'm an electrician that does generators and have always enjoyed fixing my own cars. I am not a mechanic that works on ford explorers every day. that experience can sometimes be the best.

im assuming you have spoken to someone that has worked on these cars for a living and there is nothing obvious we are overlooking.

back to the puzzle, if the down stream sensor (b2s2)? is reading high this would indicate elevated hydrocarbons in the cat that could destroy the cat. the computer might begin shutting down bank 2. I would expect a trouble code.

if the shop does not have a way to prove combustion gas it might be worth replacing o2 or swapping.

I still want to see what the computer is hearing and saying.
cheers



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tomorrow I'm checking timing chain for slack. This is starting to look something like stretched and worn timing chains I have had in shops in the past.
I'll post results!