94 xlt Runs like it is missing I need Help ASAP

[welder080]

Ok guys i have been a member here for awhile just haven't made very many post. I need help. The explorer is running terrible under load and seems to have a slight miss at idle. Here is a list of what i have done since the problem has come up.

Fuel pressure test 28PSI @ idle W/regulator
36PSI @ Idle WO/Regulator
36PSI Just turning Key on In spec
New ECM
Pulled plenum Checked all intake bolts all good.
Compression test Results as follows
CYL#1= 115 PSI added oil to cylinder= 144PSI
CYL#2= 110 PSI added oil to cylinder= 142PSI
CYL#3= 150 PSI
CYL#4= 115 PSI added oil to cylinder= 160PSI
CYL#5= 105 PSI added oil to cylinder= 140PSI
CYL#6= 140 PSI

Pulled each plug wire to verify spark and all had spark and made difference in idle. Also the plugs look normal paper sack brown like they should.

I am getting no codes or CEL. I am at a loss here i need help. I know the results after adding oil to cylinders indicates worn rings or cylinders but this problem just all the sudden happened and, I don't think the cylinders just all the sudden went low. Please any ideas or help are greatly appreciated. Drive this ex alot and want to get her back on the road. Sorry so long just wanted to give as much info as i could.

 

[welder080]

Anybody? I really need your guys input. Did i post in the right section?

 

[arco777]

Check MAF, try unplugging or swapping MAF.

Verify spark plug order, note that on one side the order matches the coil, on the other side it does not.

Check for a misfire on a specific cylinder. Sometimes a hairline crack in a spark plug can cause a misfire. Test by pulling wires off at the coil, tempgun pointed at exhaust manifolds. Try a KOEO test followed by a Cylinder Balance Test.

Check fuel pressure while driving (under load) by leaving the test gauge connected.

 

[welder080]

Check MAF, try unplugging or swapping MAF.

Verify spark plug order, note that on one side the order matches the coil, on the other side it does not.

Check for a misfire on a specific cylinder. Sometimes a hairline crack in a spark plug can cause a misfire. Test by pulling wires off at the coil, tempgun pointed at exhaust manifolds. Try a KOEO test followed by a Cylinder Balance Test.

Check fuel pressure while driving (under load) by leaving the test gauge connected.

I verified plug order and it is correct. I also pulled all wires from coil one at a time and all made a noticeable difference. I dont have a temp gun here but i can bring one home. Did the KOEO test followed by Cylinder balance Test. The test just keeps cycling through. I count 5 interruptions in rpm. 3 consecutive a long pause and then two more. I assume this would be cylinder #4 not turning off or not working. I have a scanner that does this. it is an innova hand held scanner for OBD1&2 vehicles. For some reason it will not do the KOER test says it cannot get cylinder ID. I Will have to get and extension hose for the fuel pressure tester to check it while driving. I unplugged and swapped the maf. Did both individually. Neither made any difference.

 

[2000StreetRod]

low fuel pressure

. . .
Fuel pressure test 28PSI @ idle W/regulator
36PSI @ Idle WO/Regulator
36PSI Just turning Key on In spec
. . .

According to my Haynes Repair Manual your fuel pressure is slightly below spec:
Idle with vacuum hose attached 30 to 45 psi
Idle with vacuum hose detached 40 to 50 psi

Do you have more than 50K miles on the fuel filter?
Did your loss of power happen immediately after a tank fill up? Maybe you have bad fuel.

How old are the spark plugs? Has their gap wear increased beyond spec?

Why and when did you replace the PCM? Is the connector retaining bolt snug?

 

[welder080]

According to my Haynes Repair Manual your fuel pressure is slightly below spec:
Idle with vacuum hose attached 30 to 45 psi
Idle with vacuum hose detached 40 to 50 psi

Do you have more than 50K miles on the fuel filter?
Did your loss of power happen immediately after a tank fill up? Maybe you have bad fuel.

How old are the spark plugs? Has their gap wear increased beyond spec?

Why and when did you replace the PCM? Is the connector retaining bolt snug?

Just changed fuel filter when this started. Problem started before last fill up but, fuel is yellow. Noticed that when I checked fuel pressure. Smells normal though. Spark plugs were changed around 7k miles ago and look great. checked all gaps and all right at .052 As for the PCM truth be told it probably didn't need one I replaced it because nothing else is working. Probably me not properly diagnosing the problem and yes the bot is snug

 

[pauley]

im guessing the rough idle your getting is due to the lower compression on the 4 cylinders you added oil to. my 93 xlt acted the same way when I had 2 cylinders down on compression due to a leaking head gasket. the part about being down on power may or may not be another issue. to be honest judging by your compression numbers and the improvement the oil made to them your engine may just be tired/ worn out.

 

[welder080]

I agree about the compression numbers. It is just shy of 300K. It did finally act up while i was pulling plug wires for the fourth time/ Number 3 plug is suspect. Gonna replace it and see what happens. Just wanna get some more life out of her while i save to put a rebuilt engine in her. I will report back

 

[pauley]

Could just rebuild the one you have it will most likely cost less. Hope the plug works out for ya.

 

[Roadrunner777]

I might consider a weak coilpack or throttle position sensor.

 

[welder080]

Ok i would like to thank everyone for your input. I finally got it. It was the number 3 spark plug. guess it finally gave up this morning when i was pulling wires off the coils and checking for the fourth time. Looks like motorcraft plugs are in its near future. These are Bosch Platnum. I have used these plugs for a long time and had no issues from them but with a less than 10k mile failure looks like its back to OEM. I have read on here that these engines dont like anything but motor craft. Why is that? Thanks again for the help. Intermittent problems suck.

 

[2000StreetRod]

single or double platinum?

Your waste spark system fires one bank of plugs from the center electrode to the outer electrode and the other bank from the outer electrode to the center electrode. Metal is removed from one electrode depending of the direction of firing. Single platinum or single irridium plugs will only last longer than copper in one bank. For many years the factory installed different plugs in the left bank than the right bank. Also, your waste spark system fires two plugs simultaneously (one on compression stroke and it's pair on the exhaust stroke). That results in special plug requirements.

 

[welder080]

Your waste spark system fires one bank of plugs from the center electrode to the outer electrode and the other bank from the outer electrode to the center electrode. Metal is removed from one electrode depending of the direction of firing. Single platinum or single irridium plugs will only last longer than copper in one bank. For many years the factory installed different plugs in the left bank than the right bank. Also, your waste spark system fires two plugs simultaneously (one on compression stroke and it's pair on the exhaust stroke). That results in special plug requirements.

They are single platinum. I knew the waste spark system fired 2 plugs simultaneously but, did not realize that it reversed the spark on one plug. This now makes sense as to why the OEM plugs last longer as they are designed for this use. Thank you for the lesson on the subject. I will have to write that down to add to my list of notes.

 

[DonnieFB]

runs like its missing

check ignition coil pack. i had several go bad and mind missed real bad. good luck