AJatx

After changing my timing belt two times over and checking it for the third time, I believe the crank and camshafts are all aligned correctly. I kept thinking I was a spline off, but looking at the next spline on either side of the marked one shows that it would be really off and probably wouldn't hold idle.

Anyhow, the truck gets worse over load, heat, and time (in order of relevance). I've replaced all 6 sparkplugs with Toyota OEM plugs and sparkplug wire set (from Toyota as well). New water pumps and belts.

At idle, it wasn't real noticeable. After driving in low rpm in low gear, you'll notice a little jerkiness or studder. If I hit the overdrive gear and I'm around 50mph, it starts to jerk bad like it was misfiring on a couple of cylinders.
If I unplug the negative terminal on the battery overnight, the truck runs fine for a few miles and then the symptoms start to return (that's where I started to believe my timing belt install is fine).
I let it sit in my driveway for a couple of days (w/ battery power) and it starts up with the same symptoms.

After reading a few posts on the forum in my search, I cleaned the MAF with deflux spray in my lab. It might be too caustic for the MAF, but we use it on our motherboards after re-work. The symptoms are still the same. However, at idle, it studders a lot more frequent and the jerkiness or studdering is throughout all the gears and rpm range. I noticed that under light throttle around 30mph in Drive gear, the engine sounds like it's missing, but every so often, it'll sound like it's normal and then miss again.

I took it to Autozone and the guy pulled the following codes:
P0100 MAF malfunction
P0110 IAT malfunction
P0300 Random misfire
P0302 Misfire on Cylinder 2
I thought I heard the guy call out Cylinder 4 as well.

I didn't see P0171 nor anything indicating lean.
My fuel consumption is real bad now too.

So, I replaced the coil packs for Cylinder 1 and 3, but the problem is still on my truck.

I'm going to ohm out the MAF, but I'm running out of ideas for things to check. I thought that maybe the MAF and IAT error could've come from a long time ago when I was deep in water offroading one day. My truck lost idle and it took a few minutes before it started again. Is there a way to check the timestamp on these error codes?

I bought the same type sparkplugs and belts (from Toyota dealer) and had no issues after my 60k mile tune-up.

I'm going to return the coils as it didn't fix my problem. The plugs looked fine when I pulled them. The spark wireset is connected properly.

J

AJatx

Found out the root cause.

A friend suggested taking out the spark plugs and taking a look again. Instead of the electrode, inspect the insulation body.

Spark plugs 2 and 4 had hairline cracks and a few hot spots where it was arcing.

Replaced those two spark plugs and my truck is running great.

I took pics, but the lighting was poor so it's hard to see the cracks.

J

Unhappy99

Smart friend you've got there. Its pretty rare to have a plug being defective from the factory. What brand were they?

MTL_4runner

Did you put the plugs in or did the dealer?

They are quite easy to crack so you have to be very careful not to damage the ceramic or the electrode on install. That was certainly a strange set of codes it threw out when all this happened. I usually don't do anything else when I change the belt so as to limit the potential for problems when troubleshooting a misbehaving engine.

AJatx

I put the plugs in. It's the Denso plugs straight from the dealership. I had no trouble last two times I replaced the plugs, but this time, I did it after my first timing belt replacement in the evening. So, it was dark.

I never thought twice about checking the condition of the plugs from the dealer as I assume they are good since it's new. However, I also had a spark issue on my RX-7 and last night, I was sick of having ignition issues with my vehicles. So, it was time to review EVERYTHING I touched during the timing belt replacement.

MTL, I believe the plugs were damaged before the install. On the odd cylinders, I lost the rubber grommet for my plug socket and those plugs were treated a little worse than the even cylinders.

Strange codes indeed. It makes sense for the random misfire (P0300) for cylinders #2 and #4 since those plugs were cracked. However, the IAT and MAF malfunction errors were probably from my first time in deep muddy waters where I stalled the truck after I crossed (fortunate!) over.

One lesson I should've stuck with on the timing belt replacement was to replace one thing at a time (except for water pump and timing belt since it's easier to do both at once). I kept thinking it was the cams that were off or something else like the crank sensor. However, the symptoms were very intermittent so I had doubts about the cams being off, but again, being my first time, I questioned everything I replaced.

J

MTL_4runner

A little trick..... after you get the old plug out, use a piece of rubber hose and shove it over the ceramic of the new plug (needs to fit pretty tight). Then use the hose to get the threads started on the plug and finally pull out the hose and finish tightening with a plug socket and ratchet. This make sure you don't damage the ceramic, electrode or the threads during the install.