Red Hot Exhaust

Hollywood · Post by **Hollywood** » Tue May 01, 2007 2:06 am

Alright, got the fiero running today and the both exhaust manifolds became red hot in a matter of minutes! So far i have heard possibly a clogged cat. Im going to unhook the exhaust and see if the problem persist. If it does then i know its not the cat if it doesnt does any one have any other suggestions as to what it could be or what i could try :scratch: I am more than open to ideals and advice at this point.

befarrer · Post by **befarrer** » Tue May 01, 2007 2:10 am

Running lean, got any vac leaksies, cracked manifold, etc....

Hollywood · Post by **Hollywood** » Tue May 01, 2007 2:19 am

befarrer wrote:Running lean, got any vac leaksies, cracked manifold, etc....

How do i check if im running lean? If so how do i correct this problem... Same goes for the vac leaks? :scratch:

Dirty Sanchez · Post by **Dirty Sanchez** » Tue May 01, 2007 8:55 am

If you have a vacuum leak this will cause the engine to run lean and the idle will be high. The most commong vaccum leak in the Fiero is caused by a cracked or broken EGR tube.

Hollywood · Post by **Hollywood** » Tue May 01, 2007 11:36 am

Egr tube huh? Let me check that one out. Car hasnt been started and ran for a long time. Can the cat convt be the problem or am i wasting my time there?

fieronews · Post by **fieronews** » Tue May 01, 2007 10:13 pm

I had the same thing. It was the egr tube like stated above. Changed it and all is well.

Shaun41178(2) · Post by **Shaun41178(2)** » Wed May 02, 2007 12:14 am

you have a vacuum leak. What is your idle at when warm? It shouldnt' be over 1000 rpm when hot and over 1800 when cold. If it idles at 2500 when cold then you have a vacuum leak which is causing your hot exh.

I highly doubt its a clogged cat.

Mach10 · Post by **Mach10** » Wed May 02, 2007 2:46 pm

You'll know if you have a plugged cat. The car will be quiet, it'll sound labored as hell at idle, and it will have ZERO balls.

I've NEVER seen it happen. It's almost always an EGR or vacuum line problem. :salute:

The Dark Side of Will · Wed May 02, 2007 3:02 pm

My cat disintegrated. It was on a long trip and by the time I got where I was going it would barely do 5 mph in 1st gear.

Mach10 · Post by **Mach10** » Wed May 02, 2007 3:22 pm

That's a neat question: How much back pressure does there have to be before the exhaust starts flowing back into the combustion chamber enough to stall the motor?

Hollywood · Post by **Hollywood** » Thu May 03, 2007 2:57 am

Thanks for the help guys, Im having EGR plates made as we speak to just block it off. Hopefully this helps. I will keep you updated.

The Dark Side of Will · Thu May 03, 2007 7:18 am

Mach10 wrote:That's a neat question: How much back pressure does there have to be before the exhaust starts flowing back into the combustion chamber enough to stall the motor?

Dunno exactly, but if the exhaust pressure is greater than ambient, you'll get reversion during the valve overlap period. The greater the pressure, the more reversion. Eventually the engine just won't have enough momentum to push the exhaust out without stalling.

Mach10 · Post by **Mach10** » Thu May 03, 2007 9:52 am

Hollywood wrote:Thanks for the help guys, Im having EGR plates made as we speak to just block it off. Hopefully this helps. I will keep you updated.

Alternatively, you COULD fix the problem.

Removing the EGR without the corresponding ECM programming will start causing problems of it's own...

Hollywood · Post by **Hollywood** » Thu May 03, 2007 1:43 pm

DOH!!! I was told egr plates would be fine! Humm... Anyone have a spare EGR tube?.. :dontknow:

Mach10 · Post by **Mach10** » Thu May 03, 2007 2:37 pm

No, but I don't recommend trying garden hose

:thumbleft:

Get something custom done up in this shizzat:

http://www.hosexpress.com/metal/316stainless.htm

The Dark Side of Will · Thu May 03, 2007 2:58 pm

Replacement EGR tubes are ~$100 from the Fiero Store.

Basically, blocking the EGR passage will cause your MIL to light on the highway when the computer realizes that the EGR is not working.

Mach10 · Post by **Mach10** » Thu May 03, 2007 3:46 pm

I was under the impression that killing the EGR will also make you burn lean at cruise as well? I know for a fact that that's not too god for your valves or your pistons... :salute:

Confirm/deny?

The Dark Side of Will · Thu May 03, 2007 4:25 pm

Deny.

When the ECM activates EGR, it advances timing and commands slightly leaner AFR. When it realizes that the EGR isn't working, it lights the MIL and goes back to normal operation.

EGR does, however, slightly improve gas mileage by slightly reducing pumping losses and slightly increasing manifold pressure, which in turn increases exhaust expansion ratio, improving thermal efficiency.

I've never known my 2.8 to audibly ping since I blocked off the EGR.

HOWEVER, the Gen II 3.1 in the Goose does ping with disabled EGR.

Mach10 · Post by **Mach10** » Thu May 03, 2007 4:58 pm

Curious: How does the ECM know that the EGR isn't working, as long as the EGR solenoid responds normally (which it will do assuming only the exhaust port is blocked off)?

Shaun41178(2) · Post by **Shaun41178(2)** » Thu May 03, 2007 6:05 pm

Make plates for the intake to block off the egr. I have never had any problems with pinging. Sure the CEL came on but big deal. it doesnt' affect the driveability of the car.

If it bothers you, then have a chip made for $40 with the egr code deleted. SInister Fiero on here can do that for you.