Today I leave the house and all of a sudden the truck starts to misfire and the service engine light comes on and starts flashing. I decide to go to Autozone to get the codes read and the following came up.

P1590, P0440, P0441, P0455, and the code for misfire on cylinder 3. I can't remember the exact code for that one.

What do you think I should check or replace? What relation does the misfiring have with the other codes?

 

1) P1590 is an ABS code. Unrelated.

2) P0440 Purge valve not sealing
P0455 and P0441 code. Both refer to evap/purge/leak problems in the fuel evap system.
First off, make sure your gas cap is securely fastened. Next make sure all the lines related to the purge valve are intact. After thy might be time to replace the purge valve. I hear positive things about running the Hyundai purge valve.

3) Check cylinder #3's plug wire.

I believe the misfire is mutually exclusive from the other codes.

 

Thanks that is just what I was reading in another website.

Any idea on what to check or replace.

 

First thing I would do after confirming the fuel cap is tight is inspecting the lines feeding the purge valve. Check for bad connections, Knicks or breaks in the tubing. This is where a smoke test would come in handy. You could try replacing the purge valve with a known used unit or pick up the Hyundai one the auto parts store. Install it clear the codes and see what happens.

 

Thanks. Is that a common culprit for the misfiring or is that something else.

 

I believe it's something else. In this case cylinder 3.

Put some zip ties on the lines feeding the purge valve. Some times the ends of those little buggers enlarge over time and leak.

 

I have had a new E C U unit fitted in my old Discovery 1998/20 00.
I now has very sluggish acceleration, not running as it should be I have had it from new/shop demo . any help with this problem would be greatly appreciated

 

Please move this to a new thread.

 

The P0455 code won't cause misfires. It's probably the purge valve. Cheap to buy and very easy to replace. I ran my truck for a few months with that code and there were no adverse effects. finally bought the new part, installed it and the code went away.

The misfiring cylinder could be plug, could be wires could be coil pack. All are easy to fix. Pull the plug out of cylinder 3 and switch it with another or just buy another one. See if you still get the code on the same cylinder.

If you do, then try a new plug wire or switching the wire with another.

If it still doesn't work then it's most likely a coil pack. There are 2 at the back of the top-end. A real bitch to get out but do-able. I did it a few months back. not much skin left on my knuckles but, problem fixed.

All of the above being said, if you have never changed the plugs, wires and coils before or haven't done it a long time then it's probably good to do it all anyway. I will not get into the #plugdebate on which to buy.

Maybe have a mechanic or shop take a look at the "spark" end of your plugs as well. you can tell a lot from that.

 

You did the coil-packs and wires without removing the plenum??