Hey guys, check this out:

4g63 with a rough idle (sounds like it has cams), with roughness anywhere up to 3000 rpms, and above 3000 rpms runs smooth.

Sounds like the typical "spark plugs/plug wires/fuel filter" scenario, right?

Well, plugs were changed first. Idle slightly improves. A day or so later, begins idling even worse and throws a CEL (P0304 -cylinder 4 misfire).

Next, change to new spark plug wires. No improvement.

Take out the new plug, here is what it looks like:

old plugs are on the left, new plugs 3 and 4 are on right. As you can see, plug 4 is very fouled up (approximately 100 miles on new plug, per the driver of the car) SORRY at the pic size, I thought I had my cam set for VGA resolution

So my thinking at this point is, perhaps the old 4th plug wire was bad, so it fouled the old plug, and now fouled up the new plug, and that's the reason the new wires didn't help. So I put one of the old non-fouled plugs into cylinder 4. no improvement, car still sounds like it has cams.

I disconnected wire 4 frome the plug to see if she would idle the same horrible way. There is wicked arcing from the ignition coil where the plug inserts - don't know if this is normal or not (never seen my 420a do that). Every wire does the same thing if unplugged from the spark plug.

I don't think it's a plugged fuel injector, because that would mean that the cylinder would get less fuel/no fuel, and hence the plug would not be black. correct?

Unfortunately, I don't have my ohmmeter on me to check the coils at the moment. anyone have ideas? if it's not the plugs, and not the wires, then it's the coil pack. I'm gonna kill this car if it ends up being some freakish thing like a CAS or something.

I'm thinking it maybe the coilpack. Have a datalogger? Hows the fuel consumption on the 4g63?

confirmed by Dino - stuck open / leaking / failed injector

will replace and update this thread later

If you find another place besides ebay and Satan that sell 450cc injectors please let me know!

what's the best 450 to get and what should I avoid - I see a bunch of "blue top" ones on ebay for the 4g63 I'm calling all around and nobody has the injector on hand. Well one Kragen nearby has a "Nihap" brand for 119.99. wtf is nihap

another weird thing. I followed chilton's instructions to first decrease fuel pressure in the lines, by unplugging the fuel pump, and then letting the car idle until it dies of fuel starvation. sounded weird - but I gave it a shot. and the car doesn't die! it just idles and idles. I gave up after a few minutes. when I took off the fuel line, there wasn't any pressure in it anyway. hmpf

I don't know which injectors are better, I'm just as lost. My injectors, 1995 GST, are green.

If you're trying to depressurize the fuel system unplug the fuel pump harness and the "other" harness. This "other" harness is located at the center of the back seat, under a protective metal plate. I had the same problem with relieving fuel pressure and this worked for me.

FYI: Incase you have not removed the fuel injectors before. This would also be a good time to replace the injector seals or insulators. http://www.extremepsi.com/store/customer/product.php?productid=17787&cat=863&page=1

I disconnected the "other harness" that is under the seat - that IS the fuel pump harness, per chilton's. that's the only harness they said to disconnect.

I checked the coils today-

secondary coil: (ref range is 11.3-15.3 kOhm)
- 4&1 terminals 13.6 kOhm
- 2&3 terminals 13.2 kOhm

primary coil: (ref range is 0.7-0.86 kOhm)
- 2&3 terminals 1.2 Ohms
- 1&3 terminals 1.2 Ohms


So the secondary coil checks out OK. The primary coil is higher than the reference range - at least the ref range mentioned in chiltons. Significantly coil-replacing higher???? I don't know.

I checked the resistance of the suspected faulty injector #4, and the other 3 injectors. They all checked out at 2.8ohms. Didn't have a 9V battery with enough juice to determine if the injector would click on and off

well, put in another injector from a local DSMer, and the problem is still there. idles like it's on 3 cylinders, but is relatively smooth on the higher rpms. I say "relatively" b/c the car has always felt different since his timing belt ordeal (the guy had the balancer belt off by one tooth, and that was fixed later)

At this point, have new plugs, new wires, another injector which should be good in cylinder 4. What could still be causing a cylinder 4 misfire? Will a bad sensor cause only one cylinder to continually misfire, while the other 3 are okay?

I wonder if that primary ignition coil is the issue.

Is there still arcing from the plug or coil? That is not supposed to happen. Try a new coil.

What plugs are you using?

I thought I posted this earlier, but maybe not. :rolleyes

Your plugs suck. Iridium shit is terrible. Try a single electrode copper core plug. NGK BPR6ES gapped .035

NGK says their OEM plug is actually BPR6EKN gapped .032 which is a dual electrode plug. I never had much luck with that set though.

Also what brand of wires are you using? I had this experience with two sets of brand new 4g63 Magnecores:

how much are new coil packs?

Just wanted to end the story.

turns out, the timing belt skipped 3 teeth. the guy who did the timing belt change didn't put enough tension on it. no damage to engine. I suspected that 4g63s may be non-interference b/c they are low comp. or maybe 3 teeth is not enough to cause engine damage.

I sure had fun changing the fuel filter on that SOB 4g63 though! yay mitsu engineers! you guys are the best!

Originally posted by ez
I suspected that 4g63s may be non-interference b/c they are low comp.

Heh. Nope.

Originally posted by DarkOne

Originally posted by ez I suspected that 4g63s may be non-interference b/c they are low comp.

Heh. Nope.

wishful thinking

new 1g coilpacks are like 150 bucks.

3 teeth probly isnt enough to smash the valves as you have found out. i know my belt skipped and i have a great seal on my valves. dont know how far it skipped, but it was making an aweful racket.

Originally posted by ez
Just wanted to end the story. turns out, the timing belt skipped 3 teeth. the guy who did the timing belt change didn't put enough tension on it. no damage to engine. I suspected that 4g63s may be non-interference b/c they are low comp. or maybe 3 teeth is not enough to cause engine damage. I sure had fun changing the fuel filter on that SOB 4g63 though! yay mitsu engineers! you guys are the best!

did you take it to satan?

does this require to redo the timing belt?

?

sorry! I didn't see your post until now. Yea, my dad took it into satan. the timing belt has to be redone - AKA retensioned. runs awesome now.