1998 Explorer

newb81 · June 7, 2010

Hey guys, I just bought a 1998 4.0L Explorer... and for dirt cheap. The problem is that it won't pass inspection for a couple of reasons... only one that I am concerned with.

There was a mechanic that took a look at it, and said one of the 6 pistons was not firing off. I took a look at it myself to see which one, by taking the cap off the spark plugs one by one.

If you are looking at the engine from the front of the vehicle, the back left cylinder will fire off sometimes, but not all the times. The middle right will not fire at all, though there is a spark.

Where might I go from here to continue to diagnose the problem?

If you need any pictures or more information please feel free to ask. Oh, and hi all this is my first post here.

safn1949 · June 7, 2010

Sounds like it's time for a compression check just to rule that horror story out...I hope.If it has good compression and spark I would say it's a fuel injector quit or a harness wiring problem.I hope for your sake it's just an injector crapped out.

BobWiersema · June 7, 2010

Are you saying that you dont always get spark?

If so, I would change the coil pack, and wires.
Coil pack, wire set and a set of plugs should be less then $100. Cheap place to start.

Coil Pack

newb81 · June 10, 2010

I checked the compression and here is the results. I tried to turn the engine over the 5 times for each cylinder.

Cylnder psi
1 150
2 160
3 160
4 140
5 160
6 155

Anything, anybody? Thanks for ya'lls help!!!

BobWiersema · June 10, 2010

newb81 said:
I checked the compression and here is the results. I tried to turn the engine over the 5 times for each cylinder.

Cylnder psi
1 150
2 160
3 160
4 140
5 160
6 155

Anything, anybody? Thanks for ya'lls help!!!

Did you check or replace the coil pack?

Did you read my post?

Bob

safn1949 · June 11, 2010

newb81 said:
I checked the compression and here is the results. I tried to turn the engine over the 5 times for each cylinder.

Cylnder psi
1 150
2 160
3 160
4 140
5 160
6 155

Anything, anybody? Thanks for ya'lls help!!!

Well at least that is good,so I would get a spark checker and see if you have spark,I dislike throwing parts at a problem until you narrow it down.The spark checker will look like a spark plug minus the center electrode,as such it will have a huge gap and if it can jump that you have good spark,if not then a coil pack.
I will get a FSM for my 2000 in a week or so,I don't know how to check the coil pack but if it's as cheap as Bob has said in his previous post I guess replace it if no spark.Might as well put a set of plugs and wires on it now,that's just good maintenance.

newb81 · June 16, 2010

Thanks so much guys, ya'll are a great help to me. I changed all the plugs and the engine is running great now. I also got a computer readout...cyl. 3 & 6 misfire, o2 sensor, EGI valve, and 2 system leans. I cleared the comp. and the check engine light came back on, so i am gonna go have another diagnostic done. (orileys does it for free) We'll see what happens. Thanks again for ya'lls help!!!

2000StreetRod · June 16, 2010

check plug wire connections

engine
rear
3 6
2 5
1 4
front

coil
rear
3 4
2 6
1 5
front

Many people incorrectly connect 5 & 6 on the coil pack

newb81 · June 16, 2010

I checked the obd and i am getting one code...egr issuficient flow. what now?

2000StreetRod · June 16, 2010

EGR System O&T

newb81 said:
I checked the obd and i am getting one code...egr issuficient flow. what now?

EGR System O&T

BobWiersema · June 17, 2010

2000StreetRod said:
engine
rear
3 6
2 5
1 4
front

coil
rear
3 4
2 6
1 5
front

Many people incorrectly connect 5 & 6 on the coil pack

Dale,
This little picture always seams to help people. And you are correct, people get it wrong.

For the EGR low flow, thats from the DPFE, I have a quick test for that I'll look up.

Bob

BobWiersema · June 17, 2010

EGR flow test.

newb81 said:
I checked the obd and i am getting one code...egr issuficient flow. what now?

This is how you can test for a bad DPFE Sensor (EGR Pressure Feedback Sensor)

First locate the DPFE, its located on the left side valve cover.
I borrowed this picture from Dale to illustrate.

Remove both tubes connected to the sensor and plug them (two golf tees and some electric tape will work for now).
Inspect the sensor for any signs of heat damage, if it looks like it melted stop here and post back.

Next, locate the EGR valve, easy to find on the left front of the engine. Once again Im borrowing a picture from Dale.

Now remove that vacuum line from the EGR valve and connect it to the REF port on the DPFE sensor. The REF (reference) port is the one on the left as you face the sensor.
This picture is borrowed from RockAuto.

Now if you have a Scan Tool, reset the ECU, if not disconnect the battery for 15 minutes. That will clear the error and the EGR system will begin a new system check. It could take up to 100 miles for the system to complete all the tests. I have software on my laptop to watch the process, but basically if the light comes back on, check the error code. If you still get low EGR flow you have a bad DPFE. If the check engine light never comes back on, you have a different problem, and you could just leave the thing in bypass. (not legal in most states).

This test procedure is 100% accurate.

Try it and post back. If you have any questions about how to do this just ask.

Bob

gtyates · June 17, 2010

The testing procedure of the DPFE sounds great, but I would be willing ot bet that the sensor is bad as they have a history of going bad on our Ex's. If you can find a Motorcraft branded one pay the little bit extra and get it vs. the parts store brand. Basically the DPFE gets moisture in it (from normal combustion) and over time this builds up and causes the sensor to fail.

2000StreetRod · June 17, 2010

Ohv v6?

Based on the compression test results, I assume that newb81 has an OHV V6 and not an SOHC V6.

Bob,
That's a clever way to test the DPFE sensor for max flow. Ambient pressure is on the high side and vacuum is on the Ref (low) side. The PCM should report an excess flow error code at idle because the DPFE sensor output will indicate max flow when the EGR valve should be closed (no flow). The same error should also be reported at WOT when the EGR valve should be closed.

BobWiersema · June 17, 2010

2000StreetRod said:
Based on the compression test results, I assume that newb81 has an OHV V6 and not an SOHC V6.

Bob,
That's a clever way to test the DPFE sensor for max flow. Ambient pressure is on the high side and vacuum is on the Ref (low) side. The PCM should report an excess flow error code at idle because the DPFE sensor output will indicate max flow when the EGR valve should be closed (no flow). The same error should also be reported at WOT when the EGR valve should be closed.

Dale,
On my engine this produces no error. Because you use the vacuum signal from the EGR valve it should only have vacuum during deceleration while the system is calling to open the valve. The DPFE will see that flow and report back that all is well. The way I understand it, if you get a high flow error while performing this test, that would indicate that the PCM or something is calling for open EGR when it shouldn't. Because I have only performed this on my SOHC engine, I dont know for a fact what other engines will do.

On mine with the EGR system bypassed like this and the PCM reset, the truck will complete all emission tests without any errors. I have been running it like this since they put in a new engine and I had to replace the intake manifolds because of all the carbon build up. The mechanic that did the work over at Ford said I most likely end up trashing the Cat's running it like this but with over 100K on the converters, I dont much care about them.

Although you now have me curious, I think Ill go hook up the laptop latter on today and see if there is any pending codes. I haven't checked it since I replace that bad O2 sensor.

Ill grab some screen shots and post them back.

Bob

newb81 · June 17, 2010

BobWiersema said:
This is how you can test for a bad DPFE Sensor (EGR Pressure Feedback Sensor)

First locate the DPFE, its located on the left side valve cover.
I borrowed this picture from Dale to illustrate.

Remove both tubes connected to the sensor and plug them (two golf tees and some electric tape will work for now).
Inspect the sensor for any signs of heat damage, if it looks like it melted stop here and post back.

Next, locate the EGR valve, easy to find on the left front of the engine. Once again Im borrowing a picture from Dale.

Now remove that vacuum line from the EGR valve and connect it to the REF port on the DPFE sensor. The REF (reference) port is the one on the left as you face the sensor.
This picture is borrowed from RockAuto.

Now if you have a Scan Tool, reset the ECU, if not disconnect the battery for 15 minutes. That will clear the error and the EGR system will begin a new system check. It could take up to 100 miles for the system to complete all the tests. I have software on my laptop to watch the process, but basically if the light comes back on, check the error code. If you still get low EGR flow you have a bad DPFE. If the check engine light never comes back on, you have a different problem, and you could just leave the thing in bypass. (not legal in most states).

This test procedure is 100% accurate.

Try it and post back. If you have any questions about how to do this just ask.

Bob

I did as you said. Plugged the 2 lines, and connected the EGR vacuum hose line to the REF port on the DPFE sensor. Reset computer. Will post any findings along the way, and after 100mi have been had.

newb81 · June 19, 2010

Bob,
After running the test the check engine light came back on and i replaced the DPFE sensor thinking that it was bad. After reseting the computer, the check engine light came back on and is reading egr insuf. again. Could this mean that the original DPFE could be fine? If so what should I do next. Any suggestions to get this figured out? Thanks for your help.
newb

BobWiersema · June 20, 2010

newb81 said:
Bob,
After running the test the check engine light came back on and i replaced the DPFE sensor thinking that it was bad. After reseting the computer, the check engine light came back on and is reading egr insuf. again. Could this mean that the original DPFE could be fine? If so what should I do next. Any suggestions to get this figured out? Thanks for your help.
newb

After you replaced it did you keep it in bypass or put it back? What was the exact code? Dale thought that engine may though a high flow code in bypass.
Your engine may have another vacuum controller before the egr vacuum port, Ill check. Is that a SHOC or no.

Bob

2000StreetRod · June 20, 2010

Test the EGR valve

I suggest that you test the EGR valve: EGRS exhaust gas flow O&T (cont)

newb81 · September 17, 2010

hey, i have been gone for a while and ran out of cash too, but i am back on it now with old and new problems. besides still getting an egr insufficient after getting a new DPFE and taking it out of bypass, now i can't even start it.
what happens is when i try to start the truck a bunch of lights flash on the instrument cluster and...nothing. After that, I can not turn on the dome lights, headlights, or unlock the doors (power locks) without dissconecting the + battery cable and reconnecting it.
HELP!!! I don't know if this has anything to do with anything, but there is some kind of anti-theft (very small) switch and tiny button mounted by the drivers door. Before this started happening, sometimes I would have to hold the button in to start the vehicle. Thanks to all ya'll help-giving folks out there!!!
Ben

1998 Explorer

New Member

Well-Known Member

Explorer Addict

New Member

Explorer Addict

Well-Known Member

New Member

New Member

Explorer Addict

Explorer Addict

Well-Known Member

Explorer Addict

New Member

New Member

Explorer Addict

New Member

Explorer Features

Explorer Features

Similar threads