Spark Plugs

[jbish1572]

I have a 2000 Ford Explorer OHV.
I keep having to replace the sparks ever few months.
I keep getting misfires and it usually starts on the same cylinders.
I have used NKG, Ford Motor Craft, Autolite, They all seem to last about the same amount of time. I have also change the wires thinking that maybe that had something to do with it. But still it did not help.

When I take the plugs out, they look clean, they don't look like there getting hot, there is no oil on them. They actually look pretty good.

Also I notice when I hook my scanner up to it and check the maf sensor while it is running, it is reading 133 hz when it should be reading about 154 hz. So I have replaced it and it still is reading the same.

I was thinking that it could be the intake gasket leaking but am not sure.
Any ideas?

 

[marragtop]

Are you using double platinum plugs and are you checking the gap before installing them?

 

[jbish1572]

Yes, I always verify the gap. I use Platinum.

 

[96eb96]

Also I notice when I hook my scanner up to it and check the maf sensor while it is running, it is reading 133 hz when it should be reading about 154 hz. So I have replaced it and it still is reading the same.

Did you do at least 3 near wot accelerations when you checked the new MAF?

 

[jbish1572]

When I installed the new one, disconnected the battery to reset the stored numbers. I did the WOT test. I thought that maybe I got a bad MAF sensor so I took it back and got a refund and bought another from a different store and followed the same procedure. It did the same. When I reset it and hook the scanner up it does start out at the 154 and then it slowly starts dropping and before I finish the test drive it is back down to 133.

I get about 10 MPG so I was thinking that maybe the maf sensor problem could be causing the spark plug problem.

 

[96eb96]

When I installed the new one, disconnected the battery to reset the stored numbers. I did the WOT test. I thought that maybe I got a bad MAF sensor so I took it back and got a refund and bought another from a different store and followed the same procedure. It did the same. When I reset it and hook the scanner up it does start out at the 154 and then it slowly starts dropping and before I finish the test drive it is back down to 133.

I get about 10 MPG so I was thinking that maybe the maf sensor problem could be causing the spark plug problem.

What are your long and short term fuel trims at idle AND at 2500 RPM?

 

[96eb96]

Also, that BARO reading you are getting is strange, with two MAF units. That should only depend on the air flow(MAF) and the air intake/coolant temperature. Check that those sensors work properly. I have the actual source code for the PCM.

 

[jbish1572]

I read on the internet a while back that if it is getting unmetered air that it could cause the maf sensor to read low. Which was leading to believe that it is the intake gasket.
I know that it can't be a bad maf sensor, I have ruled that out. As for the coolant temperature sensor, I changed that sensor, when when I read it from the scanner, it looks normal. As for the intake temperature sensor, I am not sure about that one. I never changed it.

I am going to run a diagnostic and post it here.

 

[Carguy3J]

I have a 2000 Ford Explorer OHV.
I keep having to replace the sparks ever few months.
I keep getting misfires and it usually starts on the same cylinders.I have used NKG, Ford Motor Craft, Autolite, They all seem to last about the same amount of time. I have also change the wires thinking that maybe that had something to do with it. But still it did not help.

When I take the plugs out, they look clean, they don't look like there getting hot, there is no oil on them. They actually look pretty good.

Also I notice when I hook my scanner up to it and check the maf sensor while it is running, it is reading 133 hz when it should be reading about 154 hz. So I have replaced it and it still is reading the same.

I was thinking that it could be the intake gasket leaking but am not sure.
Any ideas?

I think that might be an important clue.
I would focus on things that would/could cause a problem on a single cylinder.
A bad MAF would affect every cylinder. And the fact that you are getting the same readings from an old one, and 2 new ones is a pretty good sign that that is not the problem.

Clearly 10mpg is an indication of a fuel/air/spark problem of some sort.
1.) do a compression check on all cylinders. See if they are all "good" and close to each other.
2.) You might be on to something with the intake leak. Pursue that as well.
3.) Perhaps a bad coil? If you look around, you can find the electrical specs for a good coil. Be sure to check it both cold and hot.
3.) Check for exhaust leaks, especially at the head/manifold interface. I spent a month chasing a misfire on a Neon. Turned out the exhaust manifold had been installed wiht no gasket, and the bolts were barely finger tight. Installed gasket, and seafoamed. Ran like new.
If you put a scanner on it, and watch both upstream O2 sensors, this might give you an indication if a particular side of the motor apears lean. Keep in mind, a misfire will actually read lean, contrary to popular belief and what would appear to common sense.
4.) Bad/incorrect Temp sensor data (coolant or air) could definitely cause misfires/driveability issues. But it wouldn't be confined to one cylinder.

 

[jbish1572]

It is not always confined to one cylinder. It usually starts at 1 but they all eventually start misfiring. Sometimes it starts at cylinder 3. It has started several times on cylinder 4. I can drive it and it seems to drive fine. but months later bam! Misfires.

I have 2 excel files that show some of the sensors readings(Ones I thought needed to be monitored), for a 2 mile drive without cruise control and I did 3 WOT and also 2 miles drive back with cruise control on.
I don't have permission to post attachments, so I put them on a website.
http://jbish1572.tripod.com/

 

[Carguy3J]

It is not always confined to one cylinder. It usually starts at 1 but they all eventually start misfiring. Sometimes it starts at cylinder 3. It has started several times on cylinder 4. I can drive it and it seems to drive fine. but months later bam! Misfires.

I have 2 excel files that show some of the sensors readings(Ones I thought needed to be monitored), for a 2 mile drive without cruise control and I did 3 WOT and also 2 miles drive back with cruise control on.
I don't have permission to post attachments, so I put them on a website.
http://jbish1572.tripod.com/

Well, first of all, something is going on with your downstream o2's one reads constant lean, and the other is constant rich. Was the truck fully warmed up, and running in closed-loop? If so, then there is something wrong here. Some combination of bad cat(s), bad rear o2's, and/or and exhaust leak. They should be doing a lot of "switching" back and forth from rich-to-lean-to-rich,etc..., like the upstream ones, just not as much.

On your upstream o2's Bank 2 showed 57 "lean" cells, and Bank 1 showed 49 "lean" cells. Bank 2 appears to be trending leaner, whic could be a sign of misfire, or not. Your log was all over the place, as far as throttle position though, so that could skew the results.

Your second log, still shows the "fixed" downstream sensors (no switching), and the trend on the upstream continues to hold true. 85 "lean" cells on bank 2, and 68 on bank 1.

It's very hard (if not impossible) to diagnose an intermittent problem like yours over the internet. It's kind of a look, listen, touch, feel kinda thing. Try doing the tests I mentioned before (compression,coil,etc..) Also, try to do a log with very steady throttle position at cruise, like on an empty highway. Delete column b (trans temp), c (closed throttle V), and Y (batt volt) and add actual voltage from the o2 sensors.
Although I'm not sure it's related, there is also something going on w/ those rear o2's. Make sure the vehicle is fully warmed up, and in closed loop before recording the log.
Also, when the vehicle has cold soaked overnight, put a scanner on it and monitor the coolant and intake temp sensors IMMEDIATELY, and watch them as the vehicle warms up. Make sure they make sense. For example, the coolant temp should read ambient outside air temp (or close)when first started, if it's been sitting overnight. So should the intake air temp, as nothing should be heat soaked yet. Also follow them to make sure they follow the actual vehicle warmup.
You might want to also check your TPS for a nice smooth linear voltage increase. Put the scanner on it, with the key on, engine off, monitor the tps voltage while you slowly and smoothly open the throttle and close it. Make sure the tps voltage follows along, and that there are no "dead" spots or "jerky" readings.

 

[jbish1572]

It was warmed up. It was in closed loop state. Also I replaced the rear o2 sensor with a new one and it did not change the reading.
The scanner shows 4 O2 sensors, but I can only find 3. One on each side of the engine and one after the catalytic converter. Maybe the other one is not real. The rear one is reading 0V but the heater is reading 450ma of current pull. Which is what the old 02 was reading as well. There are no DTC codes being generated. So I think the 4th o2 maybe just a dummy in the program.

I monitor the TP voltage and it does smoothly change as the pedal is push down and released.

Going to test the compression on the cylinders and the resistances on the coils.

 

[jbish1572]

I took a picture of the spark plug that I changed. I also recorded vehicle starting up from setting overnight. it is about 23 degrees outside and the coolant showed 20 degrees the intake show 31 degrees. Then I started the engine and the intake dropped to 28 degrees. The o2 sensors are heated ones and I did another look and I really believe there are only 3 o2 sensors.
I uploaded the recorded log along with the picture to the website.

http://jbish1572.tripod.com

 

[StangsandMavs]

Speaking of Neons... I was working on one a couple years back with a horrible miss. I replaced the ignition components and it didn't help... I cleaned out the throttle body and EGR, and it didn't help...

I ended up trying some Valvoline complete fuel system cleaner and within 30 miles, the problem was solved. By the way the Neon was acting, and the way it resolved itself with the cleaner, I'd have to say that there was a carbon buildup on the valve that was keeping it stuck open...

If none of that (including that EGR) are possibilities... I'd be thinking coil or perhaps even an intake leak. You would think that you would have some codes, though.

 

[jbish1572]

I am now sure that there are only 3 o2 sensors. When I went into mode 1 it shows the available o2 sensors and it display s1b1, s1b2, s2b1,
What is happening is when I go into the menu on the scanner to choose what sensors to monitor, it has all the senors available for all vehicles on a model.
So I uploaded a new log file with the o2 voltages.