a couple shots in the dark here.

when i put on my exhaust there was a bung in downpipe that i plugged with a freeze plug. over time it worked itself loose and began rattling like crazy (sounded like the engine was trying to eat itself at idle), i found it by crawling under the car with a cigarette and blowing smoke around until i found a spot where the smoke was pushed back. it had never occurred to me to check that bung because i had sealed it with rtv sealant and kind of forgot it was there over time.

second point, and one i am going through right now, is that i lost a bunch of those stupid pop it fasteners from the undertray. the car rattles like crazy at odd times. it was driving me nuts till i got under there and started shaking things and noticed the tray was only being held on by the handful of remaining fasteners.

-edit-

it's also completely possible that the honeycomb inside your cat is breaking up and dropping little (or even big) pieces in there. might wanna pull the cat off the car and take a look inside at the substrate. if you need a replacement i know a guy with a spare perrin that would probably be willing to part with it.

sounds like your ***** are loose

Do you have stock or aftermarket exhaust pieces?

as a guide, we have a set set of season tickets here at work that we all pitch in for.....our regular seats are about $40 a ticket.....tickets for the winter classic based on season ticket price are $140 each...(3 rows from the top of the stadium)

have someone rev it lightly while you are down there llistening to where it is coming from

always - i mean always check your bung......


u need dzus fasteners.....i replaced those cheap plastic pos clips a long time ago with 1/4 turn dzus's - works great.

i'd rather watch it at home.....where its warm and you can actually see the game up close and in HD

Already checked that. I'm good.

I have stock down pipe and cat then a 3" bushur cat-back. There is suposed to be a hanger at the back end of the cat that was not there. I replaced it with a homemade clamp and hanger, but that didn't fix the problem.

I was thinking about that. Next chance I get, I may take the cat off to investigate. I'll keep the perrin in mind. Thanks.

Is the pipe/cat vibrating against the chassis?

Not that I can see. There a couple places where the cat-back gets close but I can't see evidence that it's hitting. I did melt the thin heat shield in a small spot on the chassis.

Do you have aftermarket exhaust hangers? I had kartboy ones on my viii They can help the tight clearences of the 3 inch pipe.

Have any of you guys on E85 notice the ethanol content creeping up? Doesn't someone in here have the content analyzer sensor in their Evo?

It seems like every few weeks it keeps getting lean. I keep rescaling my injectors to compensate and now the scaling my 1000s on E85 is getting ridiculous. I plan to pull the injectors when I get a chance to see if they are getting gunked up as I have heard happens on E85. Anything else anyone can think of? Is there anything I can do pumpwise to determine if that may be suspect?

Thanks in advance.

Well, I have a sensor in my Evo. Where are you getting your ethanol from? The E-85 in wexford at the Get-Go is steadily at the 82-83 level. It has been quite some time since I have gotten any E-85 from the Sheets in Monroeville. The car is down for a week or so with the turbo issue, but when I get it back I will go get gas from wherever you are and tell you the content, no problem.

As for the gunk issue. I was studying this right after I switched to ethanol, it was a little science project I used my lab at work here to test. The gunk is a precipitate from the detergents and cleaning agents that petrol manufacturers put in 87-93 octane to meet government standards for solvent cleaning in gasoline. Most of these solvents are harmless, but there are a select few that bind with the ethanol and react to form a gel-like substance (black gunk) that some people have found on their injector tips (these detergents were not intended for use with ethanol, but sometimes nobody under a Quality Analysis system catches the mistake and the gas owners or local refinery just uses gasoline that has been treated with these detergents already, which leads to issues such as this). See, some gas stations just get E-100 from the ethanol refinery and then mix (or self dilute) the ethanol in 87-93 octane on site with a little math and just loading both up in the storage wells at their pump station. This seems not to be the case here in PA, but it has popped up in some remote E-85 locations where support from the ethanol refineries is scarce, thus they must blend their own fuel. The gunk is completely soluble in gasoline, so most people just switch to pump gas for a tank and run it all through the system and it will burn off, others just pull the injectors and use a little toluene or other benzene derivative to just clean the crap off on a towel or something. I for one would do the second option, you don't want that crap making its way through your pistons and valvetrain, do you?

Pull one injector and see what you see, if there is a good bit of black on it then you might have a problem and you should pull the rest. It takes a good bit of gunk to totally block them, but it is possible, and I have seen pictures of it posted up on the boards here. Page 4 is where I started to explain and then eventually ran the tests, and the detergent contamination was what I found.

No, I think everything is stock with the exception of the one I put on the back of the cat.

Last night I had some free time so I put the car up on the jack stands, started it up, climbed under .... and nothing. Purred like a kitten. No bad engine noises, no exhaust noises. I'm thinking more like it's the substrate in the cat. Maybe temperature affects if it's loose or holding itself together.

Read through that thread, good work dude I can see how the additives could create problems.

I normally fill up at the Oakmont Service plaza on the turnpike, occassionally at the Sheetz in Monroeville. I suspect that the ethanol content at these two stations is higher than at Wexford or at least it was. Last time I filled up at Wexford (I believe it was in May?), the car went pig rich.

When I get a chance, I will pull my injectors, take a look, and let you know.

Thanks for the help