About a year and a half ago I stopped driving my Evo on a regular basis, a few months back I started driving it again on a some what regular basis (after changing the battery and filling up the tank. Other than some rattling from the down pipe (which was worse, but I've had it for quite sometime) the car drove much the same I remember it. I decided to do some dataloging during normal driving to make sure everthing was running okay, which leads me to the problem.

The datalogs (using Evoscan) seemed to show some knock in the 2.5k-4k range especially at part throttle. Usually between 1-2 counts (10-20 on y axis of the graph). Occasionally I will get a 3,4 or rarely a 5 count. Like I said it's usually not at full throttle and quite often when I let off the throttle to shift or initially jump on the throttle. I'm not really expirienced with tunning, but I can't see and real pattern there. Ironically enough it seems to occur more often in lower gears, where on would think that the engine would be under lower load at a given RPM. I'm really baffled and I can figure out what the issue is. The only think I can think of is that the rattling own pipe is the culprit, and is fooling the knock sensor. I need to start driving the car so I really need to figure this out, but if it is knock I dont want to pop the motor.

Any thoughts? Could it be the rattling down pipe, or does it sound like real knock? If it is the later is that amount something to be concerned with? In the datalogs I ran before I stopped driving it I would sometimes get a 1 or 2 count, but very intermitantly and unpredictably (and the downpipe rattling was also not as bad). Any help would be much apprecieated. Mods are Megan TBE w/ test pipe, Perrin filter, MBC, ETS 4"IC with Muse UICP and LICP, dyno tune (292 on a mustang dyno) MMs, and a ACT clutch (which has been good other than the rare high RPM lockout) along with some other little stuff. I can't remeber the name of the shop that did the tune but they were located out by Dulles in VA, and the owner tuner was named Nick. I beleive they went out of business. The only thing I installed after the tune was the colder plugs and the shift bushings. Also had to reinstall the cat, but then removed it after emissions testing. At that time I started getting a CEL for the rear o2 heater (p037 i think) not sure if thats related. Thanks for the help, I can post some data logs but they are mostly part throttle stuff, as I don't want to run the car hard until I figure this out.

 

The rattle is prob the brace that goes across the exhaust. As the engine moves it is prob hitting that bar. Try taking it off and adding a washer to each side or just take it off and see if it goes away. With that it does make since to have the car have knock, being the knock sensor is prob picking it up. Try doing one of the 2 and see if it goes away. If it does then you know why the knock was there. If it doesn't then it is comming from somewhere else.

 

Is it ok to remove those tie bars? If so thats what I will have to do, as I have already tried spacing them out. I was actually thinking about outright replacing the downpipe, but that would certainly be a cheaper option to seen if that's whats causing the problem beforehand. I just didn't realize I could completely remove the tie bars safely. Thanks

 

Just wondering, why did you go to colder plugs? On the 9 there is no reason to run anything but the stock heat range

Also, try loosing the connections of the exhaust and adjust it and re tighten. It will probably help with the rattling noises.

 

Yeah you can remove them, all they are for is to pertect the downpipe and exhaust. They technically are braceing for the underside but I know plenty of people that just get rid of them.

 

I am betting it isn't a plug issue. I know my cars downpipe hits those bar things once and a while if I get on it some. Being there is only a few counts its more then likely just phantom knock and being caused by that exact thing.

 

Hi, which program did you use to log knock counts? Also, how does 10~20 equal 1~2 knock counts?

Cheers

 

I went with one step colder because at the time I though I may go to a larger turbo in the short term (didn't work out that way). You're right of course, but I figured a bit increasing the margin of error there a bit couldn't hurt even if it came at the cost of a bit of power. It's not comming from the plugs, as the rattling occured (at a smaller scale of course) long before the plugs. Also the plugs were done quite some time ago and little to none showed up when they were originally installed up to the time the car sat/was stored. The connections were all checked thoroughly upon install, I had a broken alternator cable at the time which had to be replaced as well and when we did the plugs we for got to rehook one of the coil packs. Made for an interesting "oh s%$@" moment when the car was started. Triple checked the whole iginition system after that.

I am 99% sure the rattling is coming from the downpipe, just worried that that may not be whats tripping the sensor. Haven't had time to actually work on the car as a have wierd schedule WRT hours and travel.

 

I'm using EvoScan. 1 or 2 on the readout with show up as "10" or "20" on the Y-axis of the graph. Not sure why it's done like that, I guess it makes it easier to compare to other values on the same graph without have to rescale.


If anyone would like to look at the acutal logs I can send a copy. I have a couple long part throttle with some limited 3rd full thorttle to 6k I think (was driving back from a relatives and just let it run).