Backfires damaged SOMETHING ....

Well, I finally got my 83 GTI up and running (it needed a new hall sender). But it seems that the numerous backfires have taken their toll. I actually noticed this new problem just after one of the last backfires so I'm pretty certain it was the cause. The car now makes a pretty loud clanging noise roughly once per revolution (guessing). At first I thought it might be a hole in the exhaust pipes or something, but that's not the case. The car also has much less power. What should I look for here? Thanks and happy 4th!!!! Fred

Reply to
Fred Mann
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if it gets louder when rpms are increased then it is a catastropic failure. if it gets quieter at higher rpms then its something simple.

Reply to
boxing

It DOES get louder. What does that mean?

Reply to
Fred Mann

Your catalytic converter may be damaged internally.

Reply to
Madesio

You need to distinquish between backfire and afterfire. They sound about the same. But a true backfire is firing back into the intake. Check for damage in air cleaner, choke or whatever is in the induction system.

An afterfire may damage muffler, air injector system components or converter.

Reply to
Don Stauffer in Minnesota

I always thought the definition of 'backfire' was a 'fire' on the back side of a cylinder valve, any valve.

So it can 'backfire' out the exhaust or 'backfire' out the carb or intake.

Mike

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Reply to
Mike Romain

Exciting new data!:

Well, I pulled each plug wire with the engine running, and found that the noise comes from cylinder #2. The noise occurrs with each spark (I checked with a timing gun). Where does this leave me? Sounds expensive. Again, the problem occurred during a particularly violent series of backfires, so that was *probably* the cause.

Reply to
Fred Mann

If the noise subsides when you pull #2 wire, and it is a mechanical type noise, then a moving part is broken or hitting another part. Perhaps a crack in the piston pin boss area, a failed big end rod bearing, a very worn piston skirt, etc. To rephrase, something that is so worn or broken that the explosion force of a firing event makes it slam against something else, yet makes little to no noise without a firing event. I have seen worn pistons do this, and worn rod bearings too many times to count.

It wouldn't hurt to give engine data when asking about your engine. What is this, a VW Rabbit or something?

Toyota MDT in MO

Reply to
Comboverfish

Thanks. Yes, this is an '83 Rabbit GTI -- 1.8 liter. I'm a learn-as-you-go "mechanic", so I know little about checking for internal engine problems. Are there any steps I can take to better diagnose this problem? I'm not 100% certain that it's a mechanical noise. I don't have an ear trained for this type of thing, but it is somewhat "metallic" sounding. Could a backfire problem cause this type of thing?

Reply to
Fred Mann

Also, I can feel some pulsing air when I put my hand around the back side of the engine, so maybe this noise is some exhaust leak? But then why would I have a loss of power and why would it be isolated to #2 piston? Hmmmmm.....

Reply to
Fred Mann

You *could* be hearing an exaust leak from the area of cyl #2 only. The exaust manifold could be warped, bolts could be missing, loose, pulled out, etc. Still, I would tend to think that a metallic noise, even one detailed by a self-professed non-car repair expert, would be from metal objects hitting other metal objects.

You really won't get much help (it's near impossible) via text discussion of engine noises. Grab an experienced friend or coworker and let him name that sound for a beer.

Toyota MDT in MO

Reply to
Comboverfish

You're probably right. But just one basic question.... Would I experience a loss of power if it was an *exhaust* leak?

Reply to
Fred Mann

You still haven't said if your "backfires" were bangs out the exhaust pipe or sneezes through the intake. People use the term interchangeably.

I'm going to take a SWAG and say you were talking about tailpipe bangs, and further guess that the bang blew out the exhaust manifold gasket by cylinder #2. A leaky exhaust manifold gasket right by the exhaust port makes a sound very much like a clacking valve. If that's the case, no big deal.

Reply to
Steve

Ugh. I'm having nightmare flashbacks to a VW-block '78 Horizon my Dad once owned.

You sure you're not looking for an excuse to crush that thing? :-)

That could EASILY be an exhaust manifold leak right next to the #2 exhaust port.

If it was "backfiring" out the exhaust and not a true backfire, which is burning in the intake manifold.

What was the cause of your "backfiring" problem?

Reply to
Steve

Yes, these were tailpipe explosions. I blew up the muffler several times. The cause was a faulty hall sender -- i.e. intermittent spark. The thing that concerns and mystifies me most is .... why would I have a loss of power. I didn't think this could be a symptom of an exhaust leak....

Reply to
Fred Mann

Reply to
sdlomi2

I'll answer that: Yes, absolutely. Citing an old example, years back I was driving a v-8 Buick when the catalytic convertor and exhaust pipe fell off. I tied it up to the frame with some wire I found in trunk, and it would run only about 30-40 mph for the 6 miles or so back to the shop. Note this was only a *big* exhaust leak! Please see my suggestion below for an easy check needing doing. s

Reply to
sdlomi2

blown exaust gasket can really hurt the power. 2.8 firechicken went from a nice 160km/h highway cruise to a 90km/h noisy ass hour trip home in a matter of seconds

Reply to
stockblackxj

In my younger days, I had a problem like this after a backfire problem in a Volvo. Everything was hunky dorry until the power suddenly dropped after one humongous backfire. A compression check found #3 cylinder dead. A rather larger hole was found in #3 piston. Since then, I do not ignore backfires of any sort until I know they are harmless. They usually mean tuning problems that should be worked out.

Lugnut

Reply to
lugnut

Probably the catalyst is also damaged, that would definitely cause a power loss. Catalysts are a ceramic "honeycomb," and tailpipe backfiring can wreck them- especially since a bad hall sender would mean constant intermittent misfires which would severely overheat the cat even when its NOT banging audibly.

Reply to
Steve

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