Backfires damaged SOMETHING ....

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.)

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

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

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.

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.

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.

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

Yeah, I've turned a couple of pairs of oval mufflers into round mufflers that way, too :-p

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

Nope, definitely not.

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.

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.

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.

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.