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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / July 2007Backfires 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 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. > 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. It DOES get louder. What does that mean? > > 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. > > It DOES get louder. What does that mean? It means that something is bent or cracked and is in imminent danger of breaking completely and destroying the engine. If you are going to risk starting it again, rig up a homemade stethoscope (a piece of garden hose held up to your ear) and try to localize the noise. That might give you some idea of what is broken. But if you can't tear the engine down yourself, tow it to a mechanic and have them diagnose it with the few minutes of running time it may have left.  SignaturePaul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ c (velocity of light in a vacuum) = 1.8x10^12 furlongs per fortnight >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 [quoted text clipped - 4 lines] >something, but that's not the case. The car also has much less power. What >should I look for here? Your catalytic converter may be damaged internally. > 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 [quoted text clipped - 6 lines] > Thanks and happy 4th!!!! > Fred 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. >> 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 [quoted text clipped - 14 lines] > An afterfire may damage muffler, air injector system components or > converter. 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 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) 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. > Exciting new data!: > [quoted text clipped - 4 lines] > Again, the problem occurred during a particularly violent series of > backfires, so that was *probably* the cause. 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 > > Exciting new data!: > > [quoted text clipped - 18 lines] > > Toyota MDT in MO 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? >>>Exciting new data!: >>> [quoted text clipped - 23 lines] > > Thanks. Yes, this is an '83 Rabbit GTI -- 1.8 liter. 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? :-) > 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. That could EASILY be an exhaust manifold leak right next to the #2 exhaust port. > Could a backfire problem cause this type of thing? 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? 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..... > 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..... 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 > > 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 [quoted text clipped - 11 lines] > > Toyota MDT in MO You're probably right. But just one basic question.... Would I experience a loss of power if it was an *exhaust* leak? >> > Also, I can feel some pulsing air when I put my hand around the back > side of [quoted text clipped - 18 lines] > You're probably right. But just one basic question.... > Would I experience a loss of power if it was an *exhaust* leak? 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 blown exaust gasket can really hurt the power. 2.8 firechicken went from a nice 160km/h highway cruise to a 90km/h noisy a.s hour trip home in a matter of seconds Signaturestockblackxj http://www.automotiveforums.com > Exciting new data!: > [quoted text clipped - 4 lines] > Again, the problem occurred during a particularly violent series of > backfires, so that was *probably* the cause. 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. > > Exciting new data!: > > [quoted text clipped - 13 lines] > makes a sound very much like a clacking valve. If that's the case, no > big deal. 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.... >> > Exciting new data!: >> > [quoted text clipped - 26 lines] > where similar symptoms caused a carbon deposit to be broken loose and > caused a noise as the piston compresses. Hope you are this lucky! s >>>Exciting new data!: >>> [quoted text clipped - 21 lines] > 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.... 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. Well, I got up under the car with the engine running. There is definitely a leak/hole around the exhaust manifold between the #1 and #2 "tubes". This probably explains all the noise (right?), and since it coincided with the loss of power, it should explain that as well (right?). So this is where I'm going to begin.... Now the question is, is this job doable for a non mechanic? All the bolts are heavily rusted and I can already see myself crying under the car with rust dust in my eyes. (Again, this is an '83 Rabbit GTI) > Now the question is, is this job doable for a non mechanic? All the bolts > are heavily rusted and I can already see myself crying under the car with > rust dust in my eyes. (Again, this is an '83 Rabbit GTI) I do nearly all the work that I can handle. One thing I don't fight with any more is exhaust systems. I had my '89 Grand Marquis done a couple of weeks ago for not terribly much more money than what the parts would have cost me. (But then again, they didn't have to touch either manifold.) SignaturePostulate a group whose intent is to destroy the United States from within via anarchy and bankruptcy. The actions of the United States Congress are completely consistent with the actions one would predict from such a group. >Exciting new data!: > [quoted text clipped - 4 lines] >Again, the problem occurred during a particularly violent series of >backfires, so that was *probably* the cause. 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 Well, I tested the car with the converter off. It still lacks power. I suppose there could be a fragment of gasket in the manifold, or perhaps the leak around #2 piston manifold connection is causing some turbulence which is disturbing the flow? This seems a little far fetched to me, though. Any ideas on what my next best move should be? I'd hate to replace the manifold only to find that there's a fatal engine problem. Any help/ideas/ruminations would be MUCH appreciated. Fred PS -- I have zero experience working with valves, pistons, etc. Back in the early 1970s, I owned a 1962 six cylinder manual shift Ford Falcon car.I replaced that engine with another six cylinder Ford engine.Before I got around to hooking up the exhaust pipe, I drove the car around for a couple of weeks.I used to rev up that engine and cut the ignition.POW! It was fun for a while.I ought to buy one of those exhaust cut out valves from J.C.Whitney for my old van. cuhulin On Mon, 09 Jul 2007 17:59:31 -0500, cuhulin wrote: > Back in the early 1970s, I owned a 1962 six cylinder manual shift Ford > Falcon car.I replaced that engine with another six cylinder Ford > engine.Before I got around to hooking up the exhaust pipe, I drove the car > around for a couple of weeks.I used to rev up that engine and cut the > ignition.POW! It was fun for a while.I ought to buy one of those exhaust > cut out valves from J.C.Whitney for my old van. cuhulin LOL! We used to do that with a gasoline powered Coca~Cola truck back in the 70's. It let out such a boom that I thought we gave one poor girl a heart attack! (She jumped, literally, 2 feet in the air!) Get an empty glass Coca Cola bottle. (or similar bottle) Find an inside unpainted concrete block corner in a building.Bet somebody you can hang the bottle the bottle in the corner.Rub the bottle up agains't the corner pretty hard a few times and let go of the bottle.If you do it right, the bottle will hang in the corner for a long while. cuhulin > Back in the early 1970s, I owned a 1962 six cylinder manual shift Ford > Falcon car.I replaced that engine with another six cylinder Ford > engine.Before I got around to hooking up the exhaust pipe, I drove the car > around for a couple of weeks.I used to rev up that engine and cut the > ignition.POW! It was fun for a while.I ought to buy one of those exhaust > cut out valves from J.C.Whitney for my old van. cuhulin You brought back some memories with that one! In high school I had a '68 falcon station wagon (I was the antidote for cool). We would see someone walking beside the road, cut the ignition, then turn it back on when we were right beside them. I don't know why the muffler never blew up! I don't think I have heard anything that loud to this day. OK... it isn't quite as funny today (I lied, yes it is) but back then that was the height of fun on a Saturday night in a podunk TN town. To the OP.. I would be willing to eat a small bug of my choice if a manifold leak turned out to be your problem. Exhaust leaks make noise but they don't hurt engine power enough to be noticeable. I would replace the plugs and check the wires to start with. Do a compression test on all cylinders and let us know what the numbers are. You want to resolve or at least diagnosis your no power issue before you waste your time and money on a leaky exhaust manifold. Steve B. >>Back in the early 1970s, I owned a 1962 six cylinder manual shift Ford >>Falcon car.I replaced that engine with another six cylinder Ford [quoted text clipped - 11 lines] > then that was the height of fun on a Saturday night in a podunk TN > town. In the 60's when i was in Junior high, i took public transit to school. back then they were using old 50's Fageol busses. They ran on propane. The bus driver used to wait to get under a bridge cut the ignition, then turn it back on and got a bang out of it. We always sat up front and asked him to do it. Never blew the bus up, but it was cool at the time. With that raw propane in the muffler it must have been pretty sturdy to keep from blowing up. http://americanhistory.si.edu/ONTHEMOVE/collection/object_200.html Bob Compression test results: I removed all plugs, put the pedal to the metal and cranked the engine. The results were nearly identical for each cylinder. First crank was roughly 95-100 PSI for each cyl. After about 5 cranks, the guage leveled out around 175-180 PSI. I doubt there was more than 5 PSI difference at any stage across the board. I'm assuming this means my engine is okay. At least by this measure. However, I am still operating with the rear half of the exhaust system removed (catalytic converter and tailpipe disconnected). As is, I have seen some smoke when I rev up the engine. Is this a sign of another problem, or is this to be expected when the converter is removed? I have not replaced the plugs, but I have replaced cap, rotor and wires. One of the towers on my newish rotor already had some damage -- pretty heavy carbon deposits, and what appear to be a slightly displaced inner metal sleeve. > Compression test results: > I removed all plugs, put the pedal to the metal and cranked the engine. [quoted text clipped - 6 lines] > However, I am still operating with the rear half of the exhaust system > removed (catalytic converter and tailpipe disconnected). >SNIP< > Would I experience a loss of power if it was an *exhaust* leak? Yes, absolutely. Had a catalytic convertor and exhaust pipe fall off a Buick. I tied it up to the 'frame' with some wire from the trunk; it'd run only about 30-40 mph for the 6 miles or so back to the shop. Re-attached/secured it and power jumped right back up. Note this was simply a *big* exhaust leak! Also, on SOME newer Chevy pickups we have replaced their stock muffler with low-restriction Flowmasters and dual tailpipes to create extra-low-restriction dual exhaust systems. SOME of them LOST power and got LESS gas mileage. Apparently they were designed/engineered to run with a certain amount of back-pressure; and if that pressure is reduced, it loses both performance AND efficiency. In these newer times, cars respond differently : back then, when we lowered the back-pressure we increased power, and often gas mileage increased as an added bonus. HTH, s One time when I was a kid, one of us kids got some big pliers and we squeezed the tail end of a neighbor's car tail pipe almost shut.When the neighbor cranked her car up, it made kind of a whistling noise. cuhulin Well, I finally got my catalytic converter all the way off. I had to cut the screws off with a dremel. Anyway, it's completely hollow. I'm not sure if it's supposed to be like that. My concern is that the backfires blew some of the "guts" of the CC down the pipe and possibly cause a clog there or in the muffler. Any thoughts? Also, when I replaced the hall sender, I used an old one from my other rabbit. I assume it's working fine since the car runs without cutting out now (unlike before I replaced it). As far as I know, hall senders just send a signal to the coil and it either works or it doesn't. That is, it can't send a "weak" signal. But I just wanted to make sure that I didn't overlook something or use an inferior part. Again, any thoughts would be greatly appreciated!!! Fred > Well, I finally got my catalytic converter all the way off. I had to cut the > screws off with a dremel. Anyway, it's completely hollow. I'm not sure if > it's supposed to be like that. Nope, definitely not. > My concern is that the backfires blew some of > the "guts" of the CC down the pipe and possibly cause a clog there or in the > muffler. > Any thoughts? A reasonable suspicion that would be worth following up on. Most cats are one of two types: A honeycomb like structure, or a bunch of "beads". The honeycomb is much more common. The bead type is more likely to just "blow right through" the muffler, but it's possible for the beads to clog things up. The honeycomb type is more likely to outright plug something if it "escapes" from the cat. I can EASILY see a honeycomb style cat that spewed its guts due to a backfire causing blockage further downstream. > Also, when I replaced the hall sender, I used an old one from my other > rabbit. I assume it's working fine since the car runs without cutting out [quoted text clipped - 3 lines] > something or use an inferior part. Again, any thoughts would be greatly > appreciated!!! To the best of my knowledge, there is no "sorta sends" failure mode for a hall sensor. It senses the signal point and says so, or it fails to sense, and says nothing - It's "pure binary" that way - Either it works, or it doesn't. SignatureDon Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info > On Mon, 09 Jul 2007 17:59:31 -0500, cuhulin wrote: > [quoted text clipped - 7 lines] > LOL! We used to do that with a gasoline powered Coca~Cola truck back in > the 70's. Yeah, I've turned a couple of pairs of oval mufflers into round mufflers that way, too :-p Well, it appears that timing was the main issue, so I adjusted it by trial and error since there are no marks on the wheel or a pointer in the timing hole. Anyway, I'm at about 85% full-power now. The engine still seems to miss a little bit, but it's not regular. I "fixed" the exhaust leak wih JB Weld and it worked fine for my trip downtown. The leak was limited to a small piece of missing gasket. The exhaust is a little smoky (sometimes not visible) and it kinda stinks. I'd guess this could be due to my timing being a little off? Also, would the converter help the smell. I'm certain that the fuel mixture has been adjusted, so it's probably off as well. Is there any way to test for proper amount of vacuum at the vacuum advance? I don't see this particular test in either of the manuals (I have a Haynes for this car and a Bentley for the older 79 Rabbit). If so, what should the reading be? I hooked up a meter and it moved, but it may be beyond the sensitivity of the guage. It read maybe 1 or 2 inches of vacuum when I revved it up. Just for the record, the car did not run as well with the catalytic converter removed. Besides being obviously loud as hell, there was probably an additional 10% power loss. I don't think I imagined it. So I guess a certain amount of backpressure is necessary? Moot point I guess. And here in NC, my car doesn't need to pass emission inspections, so I might put off buying a new converter ... I would like to formally thank everyone for their input. I read everything and I really appreciate it. Danke schoen. |
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