1997 2.5 DOHC with Flashing MIL and Code P0303 (misfire)

[dsurls@newenergyassoc.com]

Hey Guys,
I've been doing my best to research the potential solutions to my problem, but I haven't come up with anything, yet.

Here's the situation: I've got a flashing MIL with code P0303 (Cylinder 3 misfiring), and a pretty rough idle. I took the vehicle to my mechanic who diagnosed the problem to be bad plugs or wires. He recommended a tuneup for $380, so I decided to try and do it myself.

I first swapped the plugs between cylinder 3 and 4 to rule out a bad plug, but I continued to get the misfire in cylinder 3. So, I checked the resistance in a couple of the wires and I decided to go ahead and change the plugs, wires, rotor, and distributor cap, thinking I was probably overdue for all those anyway. The plugs were not fouled, and the wires, rotor and cap didn't seem unusually worn. Unfortunately, that didn't fix the problem. Still got a pretty rough idle, and code P0303 keeps getting triggered after I reset the codes with the scanner.

So, I read in a Millenia service manual (1996 version from MilleniaTech) that I should check the resistance on the primary and secondary coil winding on the distributor. The primary is supposed to be in the range of 0.49-0.73 Ohms, but mine was registering 0.9-1.0. The secondary was supposed to be 20k-31k Ohms, and mine seemed to be fine at 26.6k.

So, my questions are:

1. Is the resistance on the primary coil winding far enough out of whack to be the problem? And would it only be affecting cylinder 3???
2. If the coil is bad per #1, can I just replace the coil in the distributor, or do I have to replace the whole distributor? The manual indicates I should change the whole distributor, but AutoZone sells the coil itself for about $85, whereas a remanufactured distributor costs north of $300.
3. Am I missing something -- could it be something else that is only affecting cylinder 3? For instance, could it be a bad injector?
4. Could it be the problem mentioned in the TSB 01-027/02 which describes using a "top engine cleaner" (something like Seafoam??) sucked in through the intake manifold to clean out carbon deposits?
5. Anything else?

I would really appreciate any advice or suggestions. I'm trying to keep this thing for a few more months before we sell it, so I'm trying to spend as little as possible on it and do most of the work myself, if possible.


Thanks in advance for the help!!

[dsurls@newenergyassoc.com]

Well, I checked the resistance on electrical terminal for the rear fuel rail, and sure enough, the terminal posts for cylinder 3 (a-d posts in the terminal) had no resistance at all. The other two cylinders each read about 13-14 ohms.

So, I guess I need to try and replace that injector? Any suggestions or advice, or thoughts otherwise that might help?

Thanks, guys!!

[darrell]

I had this problem recently with my Lexus GS. I got the exact same code P0303. It ended up being the injector just like you mentioned. I have driven it a few hundred miles since the repair and it is running great.

[dsurls@newenergyassoc.com]

Thanks for the reply, Darrell. Yes, it was the injector.

It was a bit of a bear to replace the injector, because I had to remove both fuel delivery rails in order to get to the one injector -- the tight was too fit to remove only one rail. It was also a bit of a challenge to disconnect/reconnect the fuel line return, since it was running beneath the intake manifold and very hard to reach. Finally, I also dropped a couple of the injector insulator spacers down into the engine while I was trying to remove the rails -- what a pain, but I finally found them and retrieved them with a coat hangar!!

But the problem is fixed and the car is running much better now -- no codes, no CEL, and smooth idle. All in all, thankful for the internet and the online manuals and forums for all the help, and fairly proud of myself for pulling off this job. It literally saved me hundreds of dollars!