99 EX 4.0 SOHC missing on cylinders 2 and 4

[shanes76]

my 99 explorer just all of a sudden started missing on these 2 cylinders, new plugs a few months ago, new wires, it seems to miss under a load, slight load, can sit and idle fine almost(slight up and down sometimes in tach) will also miss in park if you rev it up. codes showed missing on cylinders 2 and 4 and thats all that came up. No problems before that, have pulled out the plugs to check them and they look fine, seems to be firing ok. Does the coil pack throw a hotter spark when more gas is given? Got a slight egg smell from the exhaust, think maybe one of the converters is getting plugged?

 

[2000StreetRod]

doubt coil pack

Cylinder #2 uses a different coil in the coil pack than cylinder #4. Since your Explorer has a waste spark system if two sections of the coil were bad then there should be four cylinders misfiring: 2 & 6, 4 & 3.

The firing order is 1-4-2-5-3-6 so you have two cylinders misfiring in succession. My guess would be plug wires or plugs. A remote possibility is the crankshaft position sensor.

The following thread may give you more ideas: Engine misfire procedure

 

[shanes76]

hmm, wouldnt the crankshaft sensor throw a code?

 

[shanes76]

I also had a vacum leak in the evaporative system as well, but it has been there for a long time and I narrowed it down to the gas cap(code says small leak in evap system)

 

[shanes76]

*UPDATE* Well I found out that plugs in the 2 and 4 cylinders werent gapped right, although we gapped them when we installed them a few months ago. What would cause this? I believe i am running autolite platinum plugs, the guy working on it for me said it still shakes a little so the other 4 may need regapped, is this common on these plugs? I used AP103 plugs

 

[2000StreetRod]

single platinum plugs

Autolite AP103 plugs have a platinum center electrode tip and a nickel alloy side electrode tip. In a waste spark system one coil simultaneously fires two spark plugs (one on the compression stroke and one on the exhaust stroke). The way the coil and associated plugs are wired results in current going from center electrode to side electrode on one plug and side electrode to center electrode on the other plug. Electrode wear (metal transfer) depends on direction of current flow. The factory used to install one type of plug on the left engine bank and another on the right bank to increase longevity. I suggest purchasing double electrode material plugs (i.e. double copper, double platinum or double irridium).

 

[shanes76]

ok, I was looking at the double platinum plugs, think they run about 4.50 each, has there been alot of issues with the AP103 plugs, I mean, others have trouble with them as well that you would know of? I want to say thank you for the help you have given me, you have been very helpful.

 

[2000StreetRod]

Bosch platinum

There have been posts on this forum regarding rapid failure of Bosch platinum plugs. I don't know about Autolite. Many members only use Motorcraft. You might try a search of the forum. I'm considering the Champion Truck Plug for my next replacement. They're double copper but I only drive about 3,000 miles a year.

I just checked online and the Champion Truck Plugs apparently are no longer available.

 

[shanes76]

oh, I used autolite in mine, I drive about 600 miles a week, and the plugs would have around 12000 miles on them if I figured correctly. the plugs on cylinders were gapped at 45 instead of 55, but we gapped them before we installed them at 55, i was wrong on the miles, guessin they was installed about almost 6 months ago, so that would put alot more miles on them

 

[shanes76]

so should I reset the codes after installing new plugs to clear the computer? this all happened on a rainy day, and alot of times when its raining and Im driving the battery light will come on, but only when its raining out and cant figure that out

 

[2000StreetRod]

reset the codes

If you have a code reader then you should reset the codes. If you don't have a code reader then you can clear the codes by disconnecting the battery terminal.

My 2000 Explorer Owner's Guide specifies a spark plug gap of 0.052 to 0.056 inches.

Most people drive with their headlights on when it's raining. Headlights plus windshield wipers plus defroster means more load on the alternator. I suggest cleaning your battery posts and cable terminals.

 

[shanes76]

it comes on when I start it, then after about 15 or 20 seconds it goes out, but only in damp conditions,