Damaged SOMETHING with backfiring ...

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.

The timing belt may have jumped a notch when it backfired throwing your valve timing off.

I am with Eric. There is no way a little exhaust leak at the manifold is going to cause significant power issues.

Did you do a compression test or a leak-down test on the engine? Engine is probably fine. It will have less power than stock without the exhaust attached. So attaching a GOOD exhaust should bring your power back. Your exhaust manifold leak should be fixed too and it could make a ticking sound. It the leak is not too bad it should not cause a serious power loss. JMHO

I don't know what a leak-down test is and I haven't done a compression test. Do I need to do both? Also, I can't seem to find the timing marks anywhere. I looked inside the port that is on the bell of the transmission and I didn't see any marks. I rolled the car in high gear and looked in there with a flashlight --- nothin'. Am I looking in the right place?

Also, can I use my Matco oil pressure tester guage to do a compression test?

no

Have you removed the plastic stuff from the bellhousing? You should see a pointer. If you do not see a pointer then you need to remove the plug. I remove the distributor cap. I figure out where the number 1 wire is. I put a socket on the ratchet and I turn the crankshaft pulley until I get the rotor pointing close to number 1. It is possible that someone replaced the flywheel and did not make new timing marks. I also use a screwdriver in number 1 sparkplug hole to watch the piston come up to tdc. I also do this to make sure I am not getting confused by all the marks on the flywheel. This is all covered in the Bentley manual you purchased on Ebay. The manual also has the restof the story about timing belt and camshaft. If you never replaced the timing belt you probably should. Well maybe not if you are asking how to do the job. It is again covered in the cheap Bently manual found on Ebay.

Leakdown test is answered with a google search.

when trying to locate a running problem with the engine it is a good idea to test the condition of the engine.

My definition A compression test will determine how much the engine will compress air. There are certain procedures to do this, such as disable ign system, remove plugs, open throttle, crank over engine and watch compression gauge during all strokes. The first stroke will be important also, so that needs to be watched.

A leak down test, injecting a cylinder with air and watching a gauge, will check how well the engine can hold that compression. Compressed air will leak out via piston rings, valves and possibly elsewhere. It can help determine where that leak is too. Piston needs to be at TDC in firing position.

I'm going to check timing first since it should be easiest. BUT there is no mark OR pointer. (I removed the plastic plug) I think I have found TDC on piston 1 using the techniques above, but I still don't know how I'm going to locate 6 degrees BTDC. I can put a dab of paint on the flywheel, but still, I don't which way is "before" and which is "after" or how far 6 degrees is. Also, do I need to pull the vacuum advance hose? And as for the exhaust problem ... is it possible that a piece of the gasket is stuck in the manifold? I was just wondering if I might have an exhaust clog somewhere before the catalytic converter ....

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?

PS -- 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

It is covered in the Bentley manual. See page 68. You do not have an exhaust clog. Banish that idea from your mind.

Good now you can proceed to other issues like ignition, fuel exhaust, etc since the engine passes the comp test.. Yes replace any known bad component to eliminate that as a possibility. You have identified that #2 noise as an exhaust manifold/gasket leak. Fix that if the tick is annoying or very loud.

And you think the loss of power is due to a clogged cat??? There are inexpensive "universal" cats out there or you can temporarily install a test pipe on the exhaust in place of the cat. I vote you install a bolt on cat and be done, unless you are not sure about having a bad cat. ;-)

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

Shouldn't be hollow and yeah the guts could be plugging your mufflers.

It's probably more than you wanted but could very well be time for a cat-back exhaust.

Old post to answer too. If it is completely hollow then somone probably gutted it with a screwdriver. On my cars they tended to melt down and chunks would break loose. Those chunks either rattled making a noisy car noisier or the car would not run due to a corked up exhaust.

The converter is supposed to look like a honeycomb. But the grid is a lot smaller than the honycomb you buy at the store to chew on. The holes might be .5 mm in size. Maybe it is a bit bigger but it is fairly small. You can hold a good converter up to light and see through it input to output. A failed one meaning one that has clogged or melted down will not pass light or you will see melted parts. Go to any parts store and ask to see a new one.

Do not put a new converter on until your car is running perfectly. You will just destroy a converter in short order if the car is running rich, lean, or if the camshaft or ignition timing is significantly off. I prefered to get someone to attach a sniffing probe to the sniffing port to make sure the mixture was correct before installing a new converter. The procedure is in the Bentley. Since the converter is hollow you could just exhaust sniff from the tailpipe. The challenge is finding someone with an old style exhaust analyzer that will let you work for 15 minutes.