Ok so I purchased a 1980 RX7 that had been sitting for 4 years. The guy said the motor had a knock in it... so I assumed it was a tuning issue since it had a holley carb and I know they can be testy. Got the car home and replaced the fuel pump, filter, plugs, wires, and cleaned the carb/replaced gaskets. Car started and it runs really rough. The knock the guy heard sounds like detonating or backfiring, and the muffler had diarrhea all over my garage door(black sooty gas). Didn't smoke as bad as I thought it would. Can a vacuum leak cause it to run like this?

 

Yes, a vacuum leak will cause it to idle extremely rough, or not idle at all.

Check all the vacuum connections around the carb and manifold, and follow any vacuum lines in search of leaks.

Also, when you say that you cleaned the carb, did you completely disassemble the carb, and clean all the jets ect throughly? If not, you could have clogged jets and passages in the carb, which could cause the issue.

 

I did a poor mans carb cleaning. Just took it part sprayed it down with vigorous amounts of carb cleaner, replace gaskets, and put it back together. The car didn't start prior to the carb "refreshment".

 

Vacume leaks are always a suspect on a car that age. I would suggest changing all your vacume lines with new heavy wall silicone hose. It's cheap and you don't need to get the pre-formed hoses that are so freakin expensive. First hose I would suspect to be blown is the one against the firewall on the passenger side. It was designed too close to the header and blows thru in a few years. It has two sizes of openings and looks roughly like a "D". Keep engine running and carefully spray carb cleaner around the hoses and listen for idle to climb. Thats where your leak is. Check your intake manifold for leaks too!

 

Explain the diarreha. Is it only smoke or is there liquid too? Didn't see a new cap and rotor on your parts lists. Get your hands on a wideband and check your afrs, along with timing. Once you get the Holley tuned right and if the knock is still there, it may be a cracked apex seal or a bad bearing.

 

The diarreha was pretty much pure gasoline... although I have been attempting to start it several times over the past few days. I'm assuming it was gas that had accumulated in the exhaust due to my failed efforts. The smoke is pretty minimal... considering how long the car has sat. The car dies if get anywhere near WOT from Idle. There really isn't a knock.. it's just pinging, popping, and doesn't have any power.

 

Just checked the plugs, and they have a nice dry black coating on them.

 

Yowza.... rear rotor plugs are clean as a whistle. Would assume blown coolant o-ring, but no bubbling with radiator cap off and very minimal smoke. Hmmm... checked cap and all of the points look nice and clean.

 

make sure you have spark at all the plugs.

 

I couldn't hear it during all of the pinging and popping that it was doing, but sure enough it's knocking. The speed of the knock is consistent with the rpm. It's not very loud, so I am thinking it's a bearing or a stuck seal. Theres nothing in the oil that would indicate that a bearing has gone bad. Going to try the ole Sea Foam, and hope it unsticks.... what I hope is a stuck seal. Any other suggestions(aside from rebuilding it).

 

G'day, just one quick thing. Before you spend anymore money do a compression test(if you havn't already). It's cheap an it tells you alot about the engines seals and pretty much if the engines still good.

 

Thats the next step. I did the listening for compression test and it sound pretty even, but I am hearing a tapping now that I got all that popping/pinging fuss squared away. I'm suspecting a stuck apex seal or spun bearing. Bugger!

 

If it's pinging and popping, then fix your damn timing! Also, make sure that your spark plug wires are hooked up to the right plugs, and that your leading coil is actually firing your leading plugs....

 

I just fixed an 86 that had a bit of ping and knock to it......a trailing plug and leading plug wire were reversed.

Also,have you determined if the exhaust is restricted?
The reactor or heat exchanger could have collapsed,which could be rattling around internally and causing the noise......not to mention the lack of power,as it chokes the engine to death.