Hey Everybody,

The other day while turning left at ~ 30 mph with the A/C on, I shifted into 4th and let the clutch out. I noticed the engine coughed a bit and the MIL light started blinking. I limped another 5 miles home while watching my temp - seemed to run alright. I noticed a rich smell after I parked. I disconnected the battery, started it up and the light came back. Took the truck to get new NGK plugs, installed them, but the light was still on. I connected the OBD2, and found codes: P0300, P0301, P0302, P0303, P0304, P0305, P0306. The mid-grade gas in my car is about a week old, and ran fine for the first 100 miles on that tank. I doubt anything around the throttle body has ever been cleaned. I haven't checked the ecu for signs of moisture, but that may be the next thing I check. Any advice is greatly appreciated!

 

how long you been own this car? if you recently bought it this could cause from a bend valve. BTW why are you fill up with mid grade? use premium, car required premium will run like shit if you don't put premium.

 

I've had the car for the past 50k, a few years, has always run well. I haven't noticed a difference in MPG or performance between premium and midgrade. I usually alternate between them.

 

One other detail is that I haven't done the 105k service yet. Do you think it's possible that shifting into 4th at a lower than normal speed could have skipped a tooth on the 11 yr old timing belt?

 

only time it skip tooth is when your tensioner goes bad cause a slack in the belt. Clear the code run the car until the gas light is on then fill the car up with premium. I lend my Lexus IS300 to a friend and when he return the car, I ran around the block notice the lack of engine response give me a code of cylinder #3 miss firing sure enough he later admit forget the car need 93 so he fill with 87 instead.

 

Regular gas didn't cause the misfire. What a load of crap.

Bad gas may be the cause, but I seriously doubt it if it ran fine the first 100 miles.

I'd definitely check the ECM/PCM for signs of moisture intrusion/contamination, but I'd also be highly suspicious of a slipped TB (due to bad/leaking tensioner)... Check your timing marks.

 

What's the best way to check the timing marks? It may be time to order the 105k service items I've been meaning to get around to, and push the car in the garage till they show up. If it is the ECM, are there any issues with swapping it out with a used 2004 6mt ECM?

 

Checked the ECM for moisture. The dust and spider webs are undisturbed. No signs anything in the center console has ever been wet. Tomorrow I'll start on the timing belt and see what I find. I'll compression test each cylinder and check the valves while I'm at it. Any other ideas what could cause this or what else to check?

 

Friday, I pulled each coil pack out, and checked the resistance of each with a multimeter. They ranged from 1.79-1.85 kilo-ohms - most were close to 1.80. Since they were all fairly close, I thought they were probably okay. I spent my weekend doing the timing belt/water pump/thermostat/cleaning egr and throttle body. Everything was due and dirty, but found no smoking gun. When finished, I started the car up and it still ran poorly. At least I knew that the timing hadn't slipped. I swapped out the ECU with one I bought for $90 on ebay, and found the cylinders wouldn't fire at all. I put the old ECU back in. I went to the parts store and bought one coil pack. I did the drop test with the motor running, and found that pulling the plug on cylinder 1 had no effect. I swapped the coil pack out there, and that fixed it!

I decided to Seafoam my intake manifold, and give the car a bath to celebrate the new parts - even cleaning the windows.

It was the coil pack that measured 1.85 K ohms. Seems strange that one bad one can throw misfire codes in all the other cylinders too, while measuring fairly similar resistance. On the plus side it made time for me to do some much needed maintenance.

 

Glad to know you found and fixed the issue. Thanks for the troubleshooting details as well.