I have a 2000 L with 73k miles on it that has recently developed a ping. I took it to a local dealer and they suggested a decarbon and plug change. I had them do the decarbon and did the plugs myself two days ago replacing the stock ones with NGK TR6IX gaped at .052. I still have a light ping when under a load at approx 1/4 - 1/2 throttle, and heavier pinging at WOT when shifting. I live in Phoenix AZ so it's nice and toasty during the summer. Any other suggestions on what else to try / check? I only have access to 91 octane fuel and have tried switching brands. Truck is stock with the exception of a K&N filter.

After having the decarbon done, I've been having problems with the idle not returning to normal when coming to a stop. It seems to hang ~1k RPM for a few seconds before dropping down. IAC? Thoughts?

Thanks in advance for any assistance / feedback.

 

I'd agree that the faulty idle is a dirty or worn IAC. Maybe the decarboning caused a piece of carbon to hold the valve open?


Can't help with the pinging


Dan

 

Dude...you shouldn't have to pay for a 'decarbon'. Any decent fuel system cleaner (all of the Hayabusa guys use Redline as 'Busas are infamous for carbon build-up on the intake valves) should do the trick after a few tanks. Another old trick is to squirt a fine mist of water into the intake tract as the water hitting the hot carbon deposits tends to make them 'shatter'.

Having lived in Phoenix I know all about the crappy 91 octane, which depending on where you bought it, may not be true 91 octane. Drivers have been know to fill tanks with the wrong grade (either accidentally or on purpose). Try getting gas from a different station or you can try an octane booster (the only one I've really seen work is the Torco Accelerator). I used it religiously in Phoenix.

You can also try cleaning the IAC with some brake cleaner and air (do a search on IAC* and cleaning and you'll find all kinds of good info) and you might want to double-check the TB's voltage (there's another good tutorial on here if you search for throttle body voltage).

Hope that helps man!

*Crap...just noticed the TR6's gapped at .052. You could try possibly shrinking that gap a tad (I'm assuming a stock truck can get away with somewhere around .035-.038).

 

First off thanks both for the reply.

I tried several tanks of Techron and STP cleaner, but that didn't do anything. I recall hearing the water trick several years back, but was afraid a large piece of carbon might break lose and cause further damage.

Not to switch subjects, but does anyone have any thoughts on putting an 8+ lb pulley on a stock motor? I have the colder plugs and was thinking about dropping the thermostat to 160. Anyone know what temp the truck goes from open to closed loop?

 

Would there be any performance difference for a smaller plug gap? I've read / heard to go with the widest gap possible w/out getting plug blow out. OEM calls for .052.

 

Have you changed your fuel filter lately?

 

I thought I read somewhere that a defective EGR valve could cause a vehicle to spark knock! Jim

 

OEM calls for .044, .054 is for a naturaly aspirated 5.4. Your gap is way to big. I would pull the intercooler and give it a a good cleaning. If it is extremly dirty, which it probably is it will contribute to higher IA2 temps and possible detnation. You also need to insure your intercooler pump is sill working. If it is not your getting no use from the IC and you will definately get detnation. I have run the 160 for 3 years no problem. If your in a warm climate it will be fine. There is alot of things it could be but I would start with these....

1. Pull plugs and regap to OEM or slightly less
2. pull intercooler and service
3. insure intercooler pump is still functioning.

 

Yes fuel filter was recently changed. That was the first thing I did. Would it be worth my time to do a pressure check on the fuel system? Anyone know what it should be?

 

The supercharger was replaced under warranty a couple of times. Would that have been flushed as well during those times?

 

Make sure you Intercooler pump is working. My L developed a ping gradually a year or so ago and it was the intercooler pump. I had it changed out and no more ping. Open up your intercooler reservoir and check to see that the fluid is moving and flowing well. If it's not moving, check the fuse for the pump and then check the pump. Good luck .

Peace

 

A Couple times?

 

The entire engine was originally replaced at 3k miles due to an oil leak. It was nothing major, but apparently SVT decided to replace it rather than tear it apart. My understanding is they like to investigate why something failed. That or the dealer was just blowing smoke up my a$$.

The supercharger was replaced due to the coating wearing off inside. They thought it was contributing to the cavitation noise. The other time they thought it to be the culprit of another noise which ended up being a bearing elsewhere.

 

A shot in the dark. I would say that many miles without the injectors being gone through could cause that issue easily, and all the cleaners in the world could possibly make the situation worse.

Yoda see's some flow testing in the future.

 

Well, I just spent about an hour trying different timing / fuel changes using the Diablo Predator. Doesn't seem to affect the lower RPM ping one bit. Changed spark advance to -3 and fuel to -1 to make it richer.

I did verify the coolant in the intercooler is circulating. It appears to have a good flow.