Mr Mufakka

I've got a 2001 4Runner with around 130k miles. I recently (a few weeks ago) changed the plugs (along with the regular oil and air filter change). I noticed last night with moderate acceleration, the truck seemed to stutter a bit, almost like it was shifting and then shifted back down and then up again. It was very mild and then seemed to be fine.

This morning, it did the same. However, by the time I got to work, it had progress into a rough running engine. It hasn't stalled however the RPMs have dipped below 500 a few times at a stop. Acceleration is pretty rough.

One issue is, it's not throwing any check engine lights. Any idea where I should start? A friend mention a coil could be bad. Is there a way to test the coils?

scottishb

Take one off and see if it changes? Take off the bad one and it shouldn't run any worse. Am I right?

gdutch

If there's no CEL it probably isn't a misfire. I've had misfires before, and when they start to happen the CEL will usually start flashing, then stay on.

As far as the stutter, this happened to me when my rear axle seal was leaking. The diff fluid was running down the axle and got onto my rear brake, causing it to sometimes stay engaged after I had let off the brake pedal at a stop. It would make the truck seem to stutter, as you say, but would eventually break lose after a couple of seconds. Not sure if that describes your symptoms exactly, but it could be what you're experiencing. If it's not throwing a but feels sluggish under acceleration, I would recommend you try using some Seafoam. I put some in after changing my plugs, and my 4Runner has been running smoother since, even though it wasn't bad before.

Mr Mufakka

Update. On the way home from work, a CEL finally came on. I checked the codes and it said cyl 3 & 6 had a misfire. I went ahead and bought a new coil. I believe I read on here somewhere that each coil operates (2) cylinders? I'm going to research now to see if cyl 3 & 6 share the same coil. If so, I think that's my culprit.

Waiting on the truck to cool down a bit before I start work on it.

Update 2: Appears that the same coil DOES infact service the #3 & #6 cylinders. (middle cylinder on pass side, last cylinder on driver's side). Fingers crossed that simply replacing the coil will do me right.

brian2sun

Yes, 3 & 6 are on the same coil and you're diagnosis is good. Replacing it should do the trick. BTW, sometimes the engine has to miss several times from the CEL to come on. I've heard 40.

Mr Mufakka

Yeah. It was about midway on my ride home, which is about 15 miles or so. At one point it started flashing, which made me a bit nervous, lol.

Mr Mufakka

Put the new coil in. Seemed to be better but it's not. CEL is back on.

brian2sun

You changed the middle coil on the passenger side right? And ran the wire to the last hole on the driver side (nearest to windshield)? If so, pull the codes again and see if they changed.

Mr Mufakka

Misfire but only cyl 3 now.

Mr Mufakka

Yeah, changed the middle coil on the passenger side. I plug it into the stock wire though so I didn't do anything on the driver's side.

One note, when I installed the coil, it didn't feel like it made a good seat on the top of the plug. I went to pull it out but I could tell it was connected to the plug so i left it. The coil sat about 1/2" about the top of the valve cover. I could push it down but it would just spring back up. The bolt of course tightened it against the valve cover.

brian2sun

Take it back off, put a little dielectric grease in the boot and make sure it pops on. .5" is too much space.

Mr Mufakka

Took it back off and reinstalled it. Still getting the misfire. I also notice that I had previously left a vacuum line off and was hoping that would help out. Unfortunately no.

I've purchased a set of plug wires however, after thinking about it, I don't believe that can be it. The plug wire has nothing to do with #3 as the coil plugs directly into it.

I'm at a bit of a standstill now.

brian2sun

My guess now would be the plug in hole 3 got fouled from missing, pull it and see. Maybe the boot on the new coil is bad, but unlikely.

coops2k

I just went through this with my wife's 02 supercharged Tacoma, 169K miles. never got a code, but with a Toyota scanner, it would show misfires at different times. First replaced a coil pack to correct a misfire, and found out the transmission was going bad. After having the transmission rebuild, after about 5k miles the misfire came back and to correct the problem, we had to replace all the coil packs and wires. I also replace the injectors (LCE match set) since the truck had so many miles, now it runs great. Just got back from a 3000 mile trip to NM and avg 19mpg over all, low was 15.5mpg doing 80mph in west Texas, high was 22mpg.

TheDurk

I'd start to suspect the plugs, as the problem started after a plug change. An overgapped plug can screw up its twin, too, since it is a series circuit. Plus, either might be fouled if there was a coil problem. Did you gap them before putting them in? (I know, some say you don't need to--but I do and I have seen many that needed gapping over the 11 years I have been changing plugs on my '99).

Shot in the dark: What plugs did you put in? Many have had problems with Bosch plugs.

Mr Mufakka

Autolites gapped to .044 if I remember correctly. I removed the #3. Didn't looked fouled. Picture below. What's up with the black "burn" marks on the side?



If Picasa doesn't allow direct image linking > http://lh6.ggpht.com/_e7QofmFtmbk/TE...2016.00.11.jpg

kball

Hopefully you don't get too much for that pic. Only use dual ground plugs in these.

akaphilly

i've been chasing a cyl 3 misfire for 1.5 years now. i got new plugs, wires, coils. all that junk. after failing inspection i decided on trying seafoam. i added that in the gas, oil, and directly in the intake. took a highway run shortly after and the CEL has been gone for 3 months. i found out that after clearing the CEL if i let the car idle for 5 minutes the light would go back on. seafoam solved it

Mr Mufakka

Cheers to you! Switched out all (6) plugs of OE Denso ones. Truck is running great!

TheDurk

HEY! I told you to suspect the plugs....