aaronius

Hello all. I've been a fan of this site since I got my car almost 2 years ago. The information that I've been able to find on here has been awesome and has saved me a lot of head scratching. However, I have come to a point in my current problem that I need to seek out some help. So, now that we have the obligatory ego stroking out of the way, on to the issue.

The car is a 2002 IS300, and is about as stock as they come. Since I bought it, it has been an oil burner. Like, 1 quart in 500 miles. Otherwise, it has been an awesome driving car, with no real issues to speak of outside of typical maintenance and simple repairs (dirty throttle body, anyone?) So, recently I went ahead with rebuilding the engine to fix the oil burning and cat fouling behavior, especially since the valve seals I just did made no difference. The rebuild went just fine, and the engine went together with no issues. We got it installed back in the car, and had no parts left over. All the electrical connectors went back in place, and no vacuum lines were left hanging. However, since going back together, it refuses to idle properly. It does seem to run normally from about 1500 and up, though. This is where it gets insanely frustrating.

The spark plugs have maybe 5000 miles on them, and are NGK iridium plugs. They show no signs of fouling or anything. I had all the injectors cleaned and patterned off the car, so those are doing fine. I tried checking for vacuum leaks, and found absolutely nothing. The cam timing has been confirmed at least 5 times by myself and my dad (we are both former dealer mechanics, for what that's worth). On a whim, I put a timing light on the #1 plug wire, and it was looking like the spark was coming about 60 degrees ATDC. So that led me down a whole VVTi path. I took the gear apart and found small chunks of hard silicone inside it, preventing it from properly rotating. So I got that all cleaned up and it rotates normally again. I also just today put a new OCV in, even though there were no VVTi codes set, but knowing that they are prone to fail. However, that didn't help. It still idles like crap.

It did finally set misfire codes, for cylinders 1, 3, 4, and 6. Yes, those are paired cylinders. So I went back to the timing light trick. Now there is 0 spark at idle on the #1 wire, but the #5 wire pings away. I couldn't reach the pickup under the intake to check to see what the #4 wire was doing, but I suspect it's the same as #1. And, when the engine is revved to 1500 or more, the spark comes back and the engine smooths right out. I swapped the coil packs around, but the issue stayed on the same holes, meaning there has to be a problem either with the igniter or ECU circuit. I have removed the ECU and visually inspected it for any signs of damage, but saw nothing. I also went and opened up the wiring harness after the #2 coil connector to see if any wires got cracked or anything, but saw nothing out of the ordinary. All the wires from the igniter to the coils (both the +12v and the C1-3) show continuity, as do all the igniter-ECU wires. I have also checked continuity to the knock sensors, cam sensor, and crank sensor, and have found nothing abnormal.

At this point, I have been trying to find the problem for close to 2 weeks, and I'm completely out of ideas. I'm tired of just replacing parts and crossing my fingers. Does anyone have any insight as to where I can look next, or other tests I can try running? Thanks ahead of time.

aaronius

So I've been digging further into things. Using the DC Hz functionon my trusty Fluke 78, I was able to determine that the ecu isn't sending the igt signal to the igniter on idle, but starts during away when the throttle is opened. I was getting flustered so had to walk away, but plan on checking the corresponding injector output at the computer. I'm starting to wonder if maybe something is up with the crank sensor, maybe being too far from the trigger wheel causing low signal output. In just really grasping at straws here. Does anyone possibly have any insight?