misfire and wierdness

rob1 · 01-27-2008, 11:02 AM

wife comes home and says car is missing and check engine light is on. Code is misfire on 2 and 3 and multiple random misfires. New plugs, no change. Wires should be good. Switched coil packs no change in message. All injectors firing. Vacuum good. Fuel filter changed, no change. Fuel pressure was weak so changed fuel pump. You can tell car is happier with new pump but misfire still present. Only clear thing not right is fuel pump does not power up when key is on but performs normally when engine is started. Did this on old and new pump. Relay good. Fuse good. Kia tech said he hoped problem would all get better with new pump. If not, his only suggestion after that was to check all the grounds. Had injectors super cleaned with high power 3 step system, again seems slightly better but still with misfire if pushed. I was going to buy ECM from recycler and see if problem fixed but dealer says the ECM is VIN specific and it will not function properly. After checking grounds I am left with injectors, coil packs and ECM replacement. Coil resistance checks are normal. I don't want to start throwing money at good parts. Possibly fuse box? But if that's bad, pump should not run when engine is on. Everyone, including KIA support line cannot figure out why fuel pump does not run in key on position but does run when engine started. Problem getting slightly better with each fuel system improvement makes me think injectors but the investigation leads towards that fuel pump pwer up problem. No other codes have been thrown but random misfires. I'm open to just about any guesses at this point including current planetary alignments. Any one ever hear of this particular failure with the fuel pump? Thanks...rob

1fastkia · 01-27-2008, 11:19 AM

If a misfire is detected its the wires if you replaced plugs and coils. Nothing else will make a misfire. This is a VERY common problem in sephias.
You say wires should be fine. How do you come up with that assumption? I do hope your not making that assumption by just mearly looking at them...
Anyways, replace those wires.

ron1004 · 01-27-2008, 06:55 PM

In addition to the wires and coils there is another possible one, and that is what spark plugs are you using and what gap. The Kia's for some reason do not like plugs other than the original NGK and these should be gapped to 0.75mm (0.03").

The ECM controls the fuel pump relay, and it monitors the engine ignition pulses and if not present then turns off the pump. If the engine has been off for some time, then when you first turn on the ignition it will power up the fuel pump, but if the engine is not started within a few seconds will then turn the pump off - It does not sound like you have any problems in this area.

rob1 · 01-27-2008, 08:13 PM

Thanks 1 fast kia and ron 1004
wires are less than 1 year old(high performance wires)....watching them in total darkness shows no obvious current leaks. In any event, the wires only go to #1 and #3 and the coil packs fire #2 and #4. Bad wires would not give an error code of multiple random misfires. I did not replace the coil packs but switched them to see if there was any change in the error message and there was none. Resistance checks on the coil packs were within specs. As for the fuel pump...it is supposed to pressurize the fuel system at the key on position and it does not. Zero pressure in the fuel system at key "on" but at engine start the fuel pump does power up and run normally as long as the engine is actually running. I appreciate you all giving it a try though. I can replace wires and coil packs but I am pretty sure that will be 200 dollar waste of time. Oh, by the way, forgot to say it is a 2001. Once again, thanks, I'll post any changes as they happen...rob

ron1004 · 01-27-2008, 08:59 PM

Rob,

The waste spark system and "one coil feeds two plugs" is vulnerable to imbalances in the resistance to each of the two plugs, for this reason the selection of the wires used should be in the same range as the originals. The physical location of the coils makes them go through large temperature cycles which that type of electrical device does not enjoy.
Using a multimeter to check the coils and wires is not too reliable - the use of a Megger would be more suited and then measure not only the resistance of the coils but also the condition of the insulation between the primary and secondary, and between the Pri & Sec to ground.

I'm not advocating that you just go out and buy new coils and wires, but just mentioning a few pointers.

What plugs and gaps are you using?

rob1 · 01-28-2008, 01:54 PM

Thanks again,
My only meter is the multi. I had NGK's when the problem started and I put the new Bosch no gap spark plugs in when I changed them. The problem got a little better when I did so. In fact, everything I have done makes it a little better at each step. The Haynes manual says to check the resistance with a multi meter but I was wondering if they could check okay there, and still be bad. 162,000 miles and these are the original coil packs so it couldn't hurt to go ahead and change them with new wires. That would be one step cheaper than replacing all four injectors. Again, I appreciate the tips...rob

ron1004 · 01-28-2008, 07:30 PM

Rob, I'd advise doing a forum search on the use of those Bosch plugs and the phenomenon of the Kia only being happy with the original NGK plugs, and I'm sure you'll find a overwhelming amount on the subject.
The Bosch plugs have a relatively larger spark gap and possibly a higher internal resistance and this makes the standard ignition coils and HT wires insulation more vulnerable to break-down. I think you need to upgrade your coils and HT wires to use these spark plugs.
The only thing known to work is the original NGK's and these need to be gapped at 0.75mm (0.03").

Checking the resistance of conductor in the high voltage wires with a multimeter can only assess "continuity" but tells you nothing about the state of the insulation, which is more of an issue when dealing with high voltage.
Viewing the ingition coils and HT wires in the dark with the engine running often reveals sparks tracking to ground indicating insulation resistance breakdown, which you'd not detect with a multimeter continuity check.

For the relatively low cost of the plugs, I'd start by installing correctly gapped NGK's before digging into my pocket for coils and possibly later injectors at $100 a piece.

rob1 · 01-29-2008, 01:03 PM

Thanks again.
Will go step by step with your advice. Wires first, then plugs then coils. I hope cleaning and refastening the grounds cures my fuel pump anomoly. That will come after the misfire is cured. thanks again ron 1004. It will be a few days but I'll post back and let you know if anything worked. I wish they had a generic ecm you could borrow or let the dealer put on to see if that cured the problems. Oh well. one step at a time. Thanks again. It's pouring rain here in east Tennesse today and tomorrow.

rob1 · 02-01-2008, 02:43 PM

Half of the final answer...got some salvaged coil packs and wires and that cured the major misfire problem. So I'm happy I didn't have to spend alot to guess. The fuel pump still does not run unless the engine is actually running(which isn't right) and I've also discovered that the head lights don't come on unless the engine is running (which also ain't right). However the car runs and I hopefully will have time to track down the other problems. Let's hope for loose wires, and grounds and not PCM. Thanks to all for their help. ron 1004 and 1fast kia get to say "I told you so"..thanks rob