2000 Caravan W/3.3 Reg misfiring at all "normal" RPM ranges usages, also backfires during heavy, not WOT, acceleration...at high WOT high RPM it's seemingly smooth.

I've changed the coil which seemed to help for a while...but it has gotten worse.

I'm suspecting the computer. I can get one from the junk yard for $65. instead of dumping $55 for a diagnostic test...

Does anyone have any suggestions?
Thanks!

 

Long shot but condensation in the fuel will cause this condition, buy a can of HEET, Dry GAS, Water Out and dump in the fuel tank. may not work, but it is a heap try.

 

Check the simple things first,

Do you have a check engine light on?

Check your spark plug wires that they're tight and not frayed.

Check the battery terminals for corrosion and tightness.

Check the condition of the spark plugs ( oily? broken tips?, correct gap? )

Backfire-

Check for vacuum leaks

Check for lean condition, correct fuel pressure/supply.

 

Yes, I've done this...thanks for your reply!

 

Sorry for the previous reply, I couldn't delete it...

My "simple tests" preformed.
I used lucas injector cleaner, a tank with Heat...light would come on, then off...did find code I think it was POP303 #3 misfiring.

The major indicator was when I put a timing light on all three front cylinders, that spark flow stopped at each hesitation...what is telling the coil what to do? I'm thinking it's the computer.

Right now I'm not going to try to pull the #3 plug that's in back of the motor when the front plugs are misfiring also.

I was told when the crank sensor goes bad, it just stops working...no intermediate on/off situation.

I did replace the coil, which seemed to help for some time, then went back.

My limited understanding, the computer is always checking vehicle running conditions..transmission included...to make changes for better performance, efficiency etc. This may be the why the coil "fixed" the problem for a short period of time.

I like the vacuum check idea!

If I was loaded with $'s I would have the dealer fix it. This is why I'm here, thinking you guys would know this motor & van.

Any suggestion/info is appreciated.

 

Have you made sure all the spark plug wires are going to the correct cylinders and in the correct order on the distributor? Also, ive used heet on my truck when mine was sputtering and it would feel as if it were gonna stall. It fixed the problem and now i use it everyother fill up. And have you tried installing a new throttle position sensor? If you believe everythings good with the plugs and wires, as well as the cap and rotor, you can start looking for small vacuum leaks and start checking sensors.

 

If you are getting an intermittent signal look at the fuel injector wiring harness connector.

This connector sometimes comes loose or if you've had work done on the van it may not have been connected tightly and the little red tab may not have been pushed all the way to lock the harness connector properly.

This will cause misfire and hesitation and engine dying.

Happened to me when i had a local mechanic install an intake manifold, the wiring harness connector was not in tight and caused poor starting and misfiring.

It may be your pcm, however check the grounds to the wiring harness to the coils.

I don't know how to test the pcm itself but others may chime in this.

Hope this helps.