Piston Slap: Ain’t Got No Problem with Coke!

Brian writes: Hi Sajeev, I have a 1999 Nissan Frontier. 207k miles, 2.4L four cylinder. I have a Service Engine light which comes on AFTER driving for 30 minutes, parking it and letting it sit for 30 minutes. When I come back and start the truck I get the vibration and Service Engine light. The code is a P0303, i.e. cylinder #3 misfire. I replace the plugs, wires, distributor cap and rotor. Made no difference, still have the same problem.This repeats just exactly the same each day. Occasionally the cylinder will start functioning again as I drive and vibration will go away but the light stays on. Had the injectors flushed, no difference. Nissan seems to think it's carbon in the intake (EGR Port). I doubt that, but maybe the injector or the wire harness? Seem to have the problem after the engine gets warmed up and then parked for 15 to 30 minutes. Because it doesn't do it when the engine is started cold at the first start of the day. I haven't tried it yet but I'll bet at the first start of the day I could drive it indefinitely and it wouldn't have a problem as long as I did not shut it off and let it sit, and then restart it. Sajeev answers: Why do you doubt what the Nissan mechanic said? Oh yeah, the completely valid, long-standing mistrust between vehicle owners and the people who work on them. Which is fair…but after all your previous (and good) repairs…you can't casually dismiss an EGR problem like that! It is, more than likely, the heart of your problem, even though it is hard to tell at this mileage. You probably have multiple problems and everything you've done so far is money well spent in my book. Sadly, obviously, the next wear item, the EGR system needs attention. EGR systems can do some bizarre shit to your ride. Put another way, this guy on this Honda Prelude forum said, "you'd be surprised wat codes your ecu will throw all because of egr problems."  Tru dat. It's time to clean or replace the EGR valve.  And clean the (intake manifold) ports that feed the EGR its precious exhaust gases.  At this mileage you could have severely coked up/blocked up EGR ports, and the valve could be well past it.  My advice is the same as the Nissan Tech, clean the valve and the ports (carb cleaner and a toothbrush, a wire brush or a screwdriver for the real bad stuff, WEAR GLOVES) and if the problem continues, replace the EGR valve. Best of luck!   Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you're in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice. from The Truth About Cars http://www.thetruthaboutcars.com

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