Running rich, hissing sound, and more!

[Starlite528]

Well it is most definitely running rich. As I stand behind the car I can smell unburned gas, and it's running poorly. Listening to the engine I can hear what sounds like hissing, or a vacuum leak. I can't tell where it might be coming from, but it's on the firewall side.

A guess would be the rocker arm cover. The PCV is on there isn't it? I know the bolts worked their way loose on the rear end before, and I still need to get the manifold off to replace those rocker arm gaskets with the neoprene ones I bought.

The exhaust is making a 'poofy' kind of sound if it revs up a bit. My buddy tells me it's missing.

Maybe I'll get my mic and poke it around in there and get a recording for you guys to listen to.

[Mach10]

Well it is most definitely running rich. As I stand behind the car I can smell unburned gas, and it's running poorly. Listening to the engine I can hear what sounds like hissing, or a vacuum leak. I can't tell where it might be coming from, but it's on the firewall side.

V6?

There's a few things that will hiss on that car:

1) EGR pipe. It's almost definitely cracked, which basically means huge air leak--especially if the valve isn't sealing right (like most 20yo EGR valves)

2) Exhaust manifold cracked. Depending where the crack is, this will be a clicking noise, or a reasonably steady hiss. Add to the problem a plugged (even slightly) catalytic converter, and you get a hiss, AND a mixture burning problem. If the sound gets louder when you load the engine (if auto, put in gear, brake hard, and give ti some gas) this is almost definitely the problem.

3) leak in the the brake vacuum line. This one is a big vacuum line, and makes a big racket if defective.

4) Rusty Catalytic converter; pinhole leaks make nifty whistling and/or hissing noises that are a bitch to find without burning yourself. Pick up the car, let it get ice-cold, then start it. QUICKLY go over the whole exhaust system with a thick, clean COTTON (not synthetic) rag. If the hissing suddenly quiets when the cloth is over a joint/rust spot, then you've found your leak. Do this VERY quickly, an dbe careful; the exhaust will heat up quickly. If the rag starts smoking, it's too hot. Stop, cool off, pick up where you left off. MY estimate is that you have 45s to a minute before the exhaust starts to become a fire hazard.

The PCV won't hiss unless it's completely toasted(pull it off and shake it; if it rattles freely, it's fine) And even then, it's not likely to hiss because the "vacuum leak" would be inside the pcv hose itself, so you wouldn't actually hear it unless you disconnected it and had a listen for yourself.

[Boscolingus]

If it's a V6 - pull off the black intake tube on the TB and stick your finger over the IAC inlet on the bottom of the throat inside the TB - if the motor continues to run at ANY RPM, you sir have a vacuum leak

[Starlite528]

I'll give those suggestions a try, but for now, I'm not hugely concerned about it unless it relates to my new (as of last night) problem.

The hissing sound is barely audible, and I'm not even sure it's a hissing.

IT DID PASS SMOG this time, turns out the SPARK PLUG WIRES had gone bad on me.

Current problem: for no apparent reason, the engine will lose 50 to 200 rpms when I'm going on any kind of an uphill incline. It happens about once or twice a minute, and only last for a second or less. It's irritating the hell out of me![/u]

[Mach10]

:scratch:

Does it shudder or surge at all on flat land at cruise?

That's weird, dude...

Are you sure it's the incline, and not just the load on the engine?

Pick the car up off the ground (4 wheels) and jack the front higher than the rear. Start the car and idle it with your foot on the brake, and bring the gas up a little (wheels aren't turning, not at full stall on the converter) and see if it does the same thing

Then repease the test with car level, then the nose down.

Honestly, "uphill" doesn't mean much; as far as the fluids/mechanical bits in the car are concerned, "uphill" is the same thing as "steady acceleration."

I'm willing to bet it's a load issue; where the car is missing when under low throttle, moderate load. This is usually a timing issue, or else a vacuum leak issue (more accurately, leak in the EGR system.)

[Starlite528]

:scratch:

Does it shudder or surge at all on flat land at cruise?

Are you sure it's the incline, and not just the load on the engine?

I'm willing to bet it's a load issue; where the car is missing when under low throttle, moderate load. This is usually a timing issue, or else a vacuum leak issue (more accurately, leak in the EGR system.)

flat land on cruise, yes. 65mph @ ~3000 RPM's. It feels the same as if I take my foot off the gas a tiny bit for half a second, and then it recovers.

By incline, I did mean there's more of a load on the engine than normal. I thought it might be an EGR problem, but I'm not sure yet. I didn't notice it when driving through the city today, but if get on the freeway I'm sure I'll get it some more.

To get it to pass smog, I replaced the O2 sensor (don't know if I needed to now) and the wires, after I got zapped by them. I haven't adjusted the timing since I replaced the engine, but I have taken the cap off for inspection (looks all right afaik). The EGR tube is a PILE OF CRAP! I think I've posted pics of it, looks like some hack job done to seal it after it cracked the first time. I want to get the new one from the fiero store, but I've got to try to save my moneh too.

[Mach10]

Cracked egr tube explains pretty much all of your symptoms;

Miss at cruise, stumble under load, uneven idle...

If the leak's small enough, it'll stumble the engine but not toss a code.

Been there, done that, smacked head against wall for 4 days coming up with a solution since most junkyard Fieros are in as bad/worse shape, and the OEM replacement (if it's even available) is freakishly expensive.

I believe I ended up canibalizing one from a Camaro and just welding the ends of the Fiero unit onto it, and re-bending to fit.

Hint: Leave the heat cover OFF, since it will soak up water and corrode the shit out of the "new" tube.

[Starlite528]

I guess I'll have to spread more orange RTV on it.

[Mach10]

That won't work so good. Half the time, the tube is under pressure when the EGR is closed, and then it's under vacuum when it opens.

I remember someone doing a writeup a long time ago about using a braided steel teflon-lined hose as a direct replacement...

That always sounded to me like a fantastic idea. Maybe not on the cheap end of things, but still nowhere near what the OEM tube costs...

[Starlite528]

That won't work so good. Half the time, the tube is under pressure when the EGR is closed, and then it's under vacuum when it opens.

I remember someone doing a writeup a long time ago about using a braided steel teflon-lined hose as a direct replacement...

That always sounded to me like a fantastic idea. Maybe not on the cheap end of things, but still nowhere near what the OEM tube costs...

Isn't that what the Fiero Store has for sale for a hundred bucks?

[Mach10]

Yep.

$100 for a 6" peice of corrugated mild steel tubing?

Sorry, someone has to buy me dinner, a movie, and a rufi-colada before I'd consent to that kind of buggery.

[Fastback86]

Yep.

$100 for a 6" peice of corrugated mild steel tubing?

Sorry, someone has to buy me dinner, a movie, and a rufi-colada before I'd consent to that kind of buggery.

With flanges! :thumbleft:

[Mach10]

Just because you get kissed first doesn't mean you aren't being fucked

If you have the coin to spare, then it's certainly a minimal effort fix...