I have a '98 Econoline with the 4.2. I had a bunch of codes that I was able to clear up. I had P0303, P0302, P0305, and I think these were based on the P1538 code I also had.

Misfires detected are related to the P030x, and x = cylinder number.

The P1538 code is Intake Manifold Runner Control error.

I found on the passenger side of block (Cylinders 1-3), the IMRC was rusted(bearing entering manifold was rusted/seized), and would not move, so I took my time and got it moving, and it works fine now on with the vacuum actuated controller.

I replaced all the plugs, and found the passenger side plugs were showing a little more carbon build-up compared to the driver side.

After new plugs and a healthy dose of injector cleaner run thru the system on a tank of gas, I am now experiencing the following behavior:

Let engine warm up at idle. Head out on road, with an empty truck (no excessive load).
Reset any CEL or codes in system.
When driving the truck casually around town with stop and go, and light on the pedal for typical daily driving, I notice a little rough going in the engine when accelerating from a stop. Once the RPM is above 2000, it smooths out.
After doing this 2~3 times with light acceleration at lights, I get a P0303 code. I was able to reproduce this 5 times in about 20 minutes of driving.
BUT....
If I am driving the truck like I was going for best lap time, with hard accelleration and a high RPMs on the engine, I can drive 25 miles with no CEL.

So summary: It appears that the cylinder closest to the IMRC control (#3, back of engine passenger side) is throwing CEL after new plugs, and now a functioning operating IMRC.

What else can I be looking for that could throw a misfire P0303. Could this be possible EGR problem based on IMRC failure for a while? Could this be a faulty distributor?

Any input on testing (and how to test these items) further to determine what is going on would be great help!!!

Thanks in advance.

-DD

 

I hesitated to reply as I'm here looking for tips from those who know but I see you are getting no help so I'll chime in.

My e250 4.2 has a coil pack, so is distributer less. The coil pack has three sets of coils, two cylinders on each; 'paired cylinders'. If the coil pack was not generating the proper charge I think you'd see the misfire for the pair. #EDIT - it seems possible, but improbable, that one terminal of a paired cylinder set on the coil might be bad. Like from moisture through a crack or physical failure inside the housing. So if the trouble does not follow a plug wire you might find the trouble by testing each terminal on the coil pack for resistance with a multimeter#

I'd swap the plug wires and see if the misfire follows the wire. Also, the connection for your number three might be bad. Try cleaning the plug wire connectors and the coil pack where the number three wire plugs in. You will need to go easy on scraping, abrasives, and even the solvent you choose to clean with. A lint free cloth with a little engine cleaner or wd40 might be good. But you should be sure to wipe that clean and use contact cleaner to insure the solvent is not left behind to attack the plug wire and coil pack terminal.

Also; your number three fuel injector should be checked out. If this is a batch fired system you can swap connectors from the injector harness that reach. A multimeter and NOID light should be utilized if you have them. Your number three injector may be clogged beyond the point an additive solvent will clear up the trouble. An expedient injector cleaner can be assembled from easy to obtain items; air compressor, line dryer/filter, hoses, clamps, wire, injector connector, wire, switch, 12v battery....

Please let me know if you find this helpful.

 

Thanks- I will check these things out this week, and try to post what I have learned!

-D