Very specific symptoms - smoking and clunking
 

Hey all,

Here's the scoop. Whenever I am in gear and am using the pressure of the engine to slow the car down (usually down hills), I'll get one of two symptoms. When I am using an average amount of engine pressure to slow the car (2-3k RPMs down an average hill), it will make a metal on metal 'whack!... whack!... whack!.. whack whack!' sound that gets faster. Or, if I am in a high gear and going down an average hill at low RPMs, like 1500 RPMs, over time it will start to shoot enough lighter smoke out the back, so that I can easily see it in the rear view.

Earlier, I had a very helpful guy on here say piston rings. But now I know these symptoms in detail. Keep in mind, who knows if they are related. And my clutch is pretty worn. Could that be the issue?

THANKS!

The rhythmic metal pounding on deceleration is likely your timing belt tensioner clanging against its housing because it has failed. Think of it this way:

When you accelerate, the top side of the timing belt is pulled taught like the top side of your bicycle chain when you're pedaling. When you decelerate, or go down a hill, the top side of your chain would then go slack, right? The timing belt is the same way, but there is a spring-loaded tensioner mounted above it. When the top part of the belt goes slack, the spring-loaded tensioner pushes against the top of the belt, pushing against the slack and keeping the belt from slapping up and down.

What seems to be happening is that the spring in your tensioner is shot, so as you decelerate, the slack of the top of the belt is flapping up and down, bouncing the now zero-tension tensioner up and down against its metal housing. When you speed up, the top of the timing blet goes tight again, and no more tensioner-bounce clanging.

Drawing the next logical conclusion, the slack in your timing belt is causing your exhaust valves to open a little prematurely, and allowing a bit more unburnt fuel than usual to blow out the back. Hence the smoke you're seeing in the mirror.

I can tell you that your vehicle is currently on a downward spiral toward the wrecker's yard at the moment. This isn't something to mess with when you drive a car with this specific engine. Whoever replaced your thermostat may not have replaced/reinstalled the timing belt and tensioner properly. If the timing continues to deteriorate, the intake valves might still be open (and protruding into the combustion chamber) when the piston is in its upward stroke. This engine is designed to run in a VERY specific timing pattern to avoid this scenario, as it is one of the few catasrophic failures this otherwise bulletproof engine can experience.

This is kryptonite bro. Please don't mess with it.

Excellent reply. Exactly what I needed. THANK YOU.

Here's the situation. I'm a college student who can't really afford to have a timing belt, tensioner, water pump job done on this car. And while this sounds like neglect, I love this car and Audis in general, but that's just the truth. So here's my point: Is there harm being done if I go down EVERY hill in neutral unless I'm accelerating? That's how I've been driving the car since I first figured out these symptoms.

If this would allow the car to continue on without any more damage done, then in a year, when I get a real job, I'll be able to fund the surgery this awesome car wants and needs.

i dont think its going to last that long! you are lucky its still running! you should be able to do this job with a basick set of tools

(Just to clarify your guys' point...) But a timing belt and tensioner job will do the trick? The car is still worth my time, yeah? It will all be straightened out if this job is done? I don't have the expertise or confidence to do it myself. I'll need to pay someone to do all that.

Water pump, tensioner, and timing belt replacement in a shop will cost between $500-600.00. Is it worth it, yes!!!! Anyone will tell you that our cars last longer than an energizer bunny. I too am a college student. Dont you have a financial aid check coming next month for fall semester???? Might be wise to invest part of it in your car, ESPECIALLY if its your only source of transpo.... Not trying to get personal, just trying to offer suggestions:)

Based upon the (now more detailed) explanation you've given... Yes, I sincerely believe that this is your issue.

I also sincerely believe two other things:

One, I personally love my vehicle enough that I wouldn't want to tackle this work myself... and that's saying something. This is a VERY precision-required set of tasks we're talking about here. Can I do it? Yes. But, every hiccup and sputter that I feel from that point forward would scare the Hell out of me.

Look at it this way. You've made it this far without a major expenditure on this vehicle. The Teutonic Piper is now calling your account due. So, do you sell your body to some well-to-do cougar for a night of well-lubricated delectation in order to scare up some jing? I guess it depends on how much you need your own ride. Because you know as well as I do that spending $600 on a car you know is a FAR better bet than $600 on buying a car you don't know.

So, suck it up, Buttercup. Go shirtless in front of a couple of your frat-bros' Moms. Shake your money maker. You'll think of something to come up with the cash if it means that much to you.

And two, your car is dying. No foolin'. No BS. Dying... as in floating at the surface of the fishtank, right-side-up and gills still moving, but if the cat even looks at it cross-eyed from across the room, it will flip over and end up in the toilet.

Tellin' ya. Kryptonite.

Alright. This is a dicy situation for me. Just got off the phone with the mechanic who has done everything else for me on this car. He's done a lot of work on this engine on lots of B5's.

Loudgoldwing, I pretty much summarized your thoughts behind the clunking and the smoking, and he thought that the clunking tensioner was a realistic thought, but he thought that it fixing the smoking shouldn't be expected.

Here's my point. If I'm going to have to the tensioner, I might as well have him do EVERYTHING that he can reach while he's there. The bill for that will probably be around $1100 or so depending on everything else he does. Valve cover gaskets, cam tensioners, etc. (I think that's what he said).

And while I want to keep this car for years and years, the way it is driving now has been reliable. Last weekend, I just did a 700 mile round trip to a friend's wedding with NO problems.

So... I'm not questioning your judgement, but I am only trying to get to the bottom of this. Is there ANYTHING else you could think of that could cause these symptoms? Perhaps something in the drivetrain causing the clunking and something else causing the smoking? I just don't want to drop a grand and not have a problem fixed. (And yes, I know it should be done anyways, but rent comes first, and I can't exactly ask my dad for a $1200 loan from his wallet without decent assurance that everything on my car will be fixed for good.)

Thank you Loudgoldwing, bronxnativ, and crazy_russian for the replies. Cougars are in short supply during the summer, maybe there will be some who will offer a pretty penny when they come to move their daughters in here in a month or so. 8)

Timing belt tensioner... definitely.

Smoking on deceleration... I know that there is an automated system that changes the fuel/air mixture ratio on deceleration. It IS possible that whatever it is that does that is malfunctioning and blowing too richly out the back end.

Lemme do some research and get back to you.

Thanks again Loud, looking forward to your reply.

Feature of the 12V 2.8L V6 as described by 12V.org...

•Idle stabilizer with deceleration fuel cutoff

Is it possible that this guy might be having an ICV cut-off issue that would make him blow rich upon decel?

Which also, I suppose, begs the question: Coriard, when you're sitting at a stoplight, does the engine ever feel like it wants to die, and then picks back up again for a while, and then it wants to die again? If so, we might have one of your answers...

itt could be part of a problem... but the clunking....

That makes complete sense. However, the engine idles perfectly both when its cold and hot.

Nah, we already figured out the clunking. That's definitely the timing belt tensioner.

The "smoking," however, still stumps me. It's only on deceleration. That tells me that we're looking at a rich/lean issue. Not an oil issue. An oil issue is most evident after sitting for a few minutes at idle, then blowing a cloud when taking off from a stop.

This is the exact opposite. He's clean at idle, and only puffing upon deceleration. That HAS to be a weakening or failure of whatever vacuum-actuated servo or switch leans out the fuel/air mixture when you let your foot off the gas.

I just can't remember what that is, and my PC with the ELSA software on it is getting worked on.

Coriard, call your mechanic and tell him what you've read here. I am dead positive that I'm right on both counts, I'm just having difficulty with the specifics. If he's worth his salt, he'll probably be able to figure out your issue using what you have here, and a little detective work.

Good luck, and I'll check back in once I get my PC back.

The clunking... You never said if it's coming from the front of the engine or nearer to the shifter. What make, model and year is the car?

If this is a quattro car, you may have a bad support bearing for the rear drive line. That causes clunking on deceleration. Read some of the symptoms below.

http://www.blauparts.com/audi/audi_d...pair_kit.shtml

Smoking on deceleration could also be a bad fuel pressure regulator or ISV. Does the MPG computer jump up and down with normal steady driving? (Like from 20mpg to 50 or 60 and back down) This is one of the signs of a bad FPR, also hard start and smoking on start.

Coriard is in a FWD Cabriolet.

If he has a rear shaft support bearing, I'd hate to see the size of the guy whose shaft he's supporting in the rear...

{...ducks flying box of Magnums...}

No I'm not. It's a 1995 90 Sport Quattro. 12v w/ 182k miles. Love it.

dnachristen,
I wish I could tell where it is coming from, but I can't tell, even with my head out the window when it is happening. Although, the one reasonable symptom that is similar to mine from that link would be the 4th one.
Also, I don't have an MPG guage.

Loudgoldwing,
A couple little things that you reminded me of that I hadn't mentioned that might make a difference...
First, if I use the engine to slow me down a steep-ish hill at at the bottom of the hill is a red light, when I pull away from the red light, then I will spit out a light yet still very noticeable cloud. It's as if this smoking accumulates somehow and will release when I give it gas. But after a certain bit of time, it will spit out the back regardless if I give it any more gas when decelerating downhill in gear.
Secondly, at highway speeds in 5th gear, the engine check light comes on, but in 4th gear (about 300rpm faster) it never happens.
Another thing, when I am accelerating in 4th or 5th gear, EXACTLY at 2775rpm or so, the engine will whistle. It sounds cool, but I'm guessing it is from highway mileage wear? That rpm is where 5th gear puts the engine when driving 64 mph. Is any of that relevant and/or should I worry about it?

Again, thanks to everyone for the time and effort of helping.

{...scratches head...}

Wow, man. Color me A.D.D. This whole time I thought you were in a Cab. Quattro's are a whole 'nother can of beans for me.

Way out of my league for long-distance diagnostics. I've offered the best "Shade-Tree Wrenching 101" help that I can offer. Looks like I need to step back and let the pros chime in.

Geez, I'm sorry.

It really sounds like you have a bad fuel pressure regulator.

Here's a quick and easy way to tell if it's bad... If you don't know where it's located, follow the two fuel lines (Covered in silver mesh) to a little canister with a vacuum line attached to it. Run the car for about 1 minute then shut off... Pull the vacuum line off of the canister... If fuel pours out of the nipple or the vac line rubber is soaked in fuel... It's bad.

My car had really similar issues that yours has. All along it was the FPR. I replaced a whole bunch of stuff before replacing that. Nothing cured the problem, except the FPR.

What happens is the FPR gets a hole in the diaphragm, and fuel get's sucked into the vacuum system causing a rich running condition from all the extra un-metered fuel... I.E. black smoke, really rich running with coasting downhill, and usually hard starts.

Next thing, since you get a check engine light is to get a code reader. I think your car is still OBD 1 if I'm not mistaken. OBD2 came along in late 1996.

Check down in the drivers footwell for 3 little open plugs. (Grey / Black, White and blue) If you have those it's early OBD1. If you don't have the plugs, there is generally a larger kind of rectangle green or blue plug (socket) somewhere on the vehicle.

Get one of these: http://cgi.ebay.com/ebaymotors/VAG-C...motiveQ5fTools


And if your car has the 3 plugs you'll need a 2x2 adapter: http://cgi.ebay.com/ebaymotors/2x2-2...motiveQ5fTools


I got one of these and they work great! It uses the free version of scanning software from Ross-Tech. If you buy the full version you can do so much more!

Anyway, hope this helps.

Thank you dnachristen,

Using this site and method, http://12v.org/maintenance/dtc.php, the codes I pulled are "2411", which points to the EGR system. That's one system I have zero understanding of. And that's the only code there was.

I'll check the FPR as soon as I can. Also, do you agree with Loudgoldwing in regards to the tensioner being the sure-fire reason for the clunking on deceleration?

I do agree with his assessment. The 6cly engine has two hard plastic tensioner runners that wear out.
That's if the sound is coming from the front.

I have a clunk on deceleration, but mine is caused from failed transmission mounts and possibly a bad carrier bearing for the rear shaft.

Good to know.

So I will have the FPR checked out, as well as a full timing belt, tensioner, water pump (and everything else that can be reached when there) job done. It will cost a pretty penny which is hard on a college dude, but I'll make it work. Obviously, it would be an investment in this car's future.

In regards to your previous link, where it says...

"Symptom: Quattro driveshaft clanks near the hand e-brake area. This occurs on acceleration or deceleration.
Repair Solution: Make sure the vehicle is turned off and in park. Inspect the Audi center support bearing. Has the rubber that surrounds the middle of the bearing separated from the bearing bracket? If the rubber has separated from the bracket, replacement of the center support bearing in needed."

...I suppose I should have the mechanic look at this first. If that's the problem, then it is probably a cheaper solution, and I can hold off just a little longer for the timing belt job.

THANK YOU! You guys will have saved me many hundreds of dollars for having a mechanic root around to tell me what the likely causes are before they even make any progress.

On that same site, you can buy the "kit" of parts for the timing belt job. Includes the water pump, all belts, tensioners, seals and the special radiator fluid. With that kit, it will cost you 1/2 what the mechanic would charge to get the parts. And they're all German OEM parts.

http://www.blauparts.com/proddetail.asp?prod=GH21110-B

Oh, one more thing. I didn't get your guy's thoughts on the highway engine check light at 2775rpm like I described here.
What might that mean? Again, the only codes pulled was "2411".
Thanks