Bbauer

Finally after years of wanting an RX i finally got an 8! Obviously, I (probably with many others) I wanted a 7 FD but that's way out of my price range. When i bought the car, it came with an extra engine and 6 speed and coilovers. <- Racelands. but coilovers non-the-less, also not installed
So anyways I bought my car out of state and the owner said it had low compression. when i got the car unloaded it would run fine. No hot hard starts nothing. i found a vacuum line on the back side of the intake air box unhooked that went to some cylinder? LTFT was about +15 and after hooking it up its been about +5. I've been driving it for about a week, almost 2, and it runs fine. I do have a few issues that I'm not 100% sure on... which is why I'm here.
A little back story on me, I'm a FCA/Stelantis mater tech and i use to work for GM also. not quite a master tech but yeah. Also, I am/was a big VW fan, I've had a FEW lol. so, I know my way around a vehicle. obviously rotary engines are slightly different
The main issue I'm having is when the A/C is on it bogs the vehicle down a ton and makes it difficult to start from a stop, like a stop sign or light. when i do get it going it bucks pretty bad. Is that kind of normal? I've talked to some people, and they tell me it is and others are saying no its a compression issue<wtf?
Also, sometimes randomly at idle (with or without a/c on) the engine will start shaking like bad engine mounts. but when i pry on the mounts they seem to be ok and there is no twisting of the engine like a bad mount. again, this may be an issue with rotary engines I'm not sure on. It has a thrown out bearing noise which I just order parts for.

Any help will be greatly appreciated
Thanks

Meat Head

Engine mounts failing can show up as notchy shifting (2nd gear for me). They looked fine but, made a significant difference to shift feel when replaced. Exhaust side is exposed to a lot of heat.

Might as well replace the clutch when you’re doing the throw out bearing. Stock clutch is good. I read somewhere on the forum about aftermarket clutch catastrophic failures so careful about those (I can’t remember the brand). I just did the clutch in my car this spring and found out about the bad clutch brand prior to buying.

Loki

iTrader: (1)

Best way to know for sure is to do a compression test. You'll know where you stand.
I would read rx8help.com to get started. Unhooked vacuum hoses are never fun on a MAF system.
Ignition coils are a wear item and will cause all kinds of problems if left to deteriorate. If older than 30k miles or unknown, replace preemptively.

Bbauer

yeah I'm going to do a clutch kit. Not may choices for these vehicles. I did see XTD sells a kit which my buddy runs in his drag Honda and swears by them. So im going to give that a shot. I was going to do a lightweight flywheel too but I saw you need the auto rear counterweight or something like that plus with stock only weighting 18 lbs. that's not bad, so I scratched that idea. I'm going to buy a compression tester but honestly this thing runs great! I have no issues as of now. But yes, I would still like to know plus I'm building another 13B for when this one finally needs this. Any recommendations for coils and plugs? the guy I bought it from put NKG plugs and Mazda coils in I don't know when, but the boxes were in the trunk when I bought it with the old parts.

Bbauer

never mind about the xtd clutch kit. i now see clutchmasters make a kit and that is the route i will go.
I've used them in pretty much all my previous Volkswagen builds and never had an issue with them

Loki

iTrader: (1)

You'll find that for many parts on this car, like clutches, intakes, minor other stuff, OEM is best. Clutchmasters is probably fine, I don't know much about it, but ebay brands like XTD and even Exedy are a downgrade in longevity/reliability for no gain otherwise.
If the coil boxes are still in the car, that's probably a good sign. You can always put a HEI tester on each one to confirm (note, at startup only 2 of the 4 coils fire). Would also be a good time to confirm the correct coil is wired to the correct spark plug. Relatively easy to mix them up.

Back to your bogging issue, what are the fuel trims and airflow g/sec on a warm idle? You should be around 5-6 g/sec and +/- 5 long-term trim or less. Vacuum leaks tend to manifest as something like what you're describing. If it has an aftermarket intake, figure out which one and return to stock if you can.

Bbauer

Ok I'll give that a shot one of these days. And idk what my MAF is reading but i know when I bought the car the LTFT was about +15% and i found a vacuum leak. I checked the other day and found that it is sitting around +5%
It seems to bog only when the A/C is on there's no conditions other than that. I'll stop at a light and it'll be fine, then the next stop it'll shake and sound like it's going to stall. Turn a/c off goes away and runs perfect!
I mean I get a/c systems pull some power but wow.

Loki

iTrader: (1)

Maybe the ac compressor is on its way to seizing, but it might just be pushing an already precarious idle over the edge. That's why I'm asking about idle fuel trims and intake configuration.

_JB_

Exedy is OEM.