Blind Freddie

Hi, ive just bought an FC series V 13B turbo as a japanese import... and i have a few little gremlins that i need to take care of.. Few things you might need to know is the car sounds like it could have a mild port.. the ECU has been re-tuned or chipped by Panspeed in Japan and it has 3inch mandrel bent exhaust from the turbo back and seemingly a blitz sequestion boost controller although i cannot find the hand controller for this unit. While driving the car boosts well and boost peaks at 0.6 bar according to the HKS boost guage.

Firstly... Every now and then at idle the car fluctuates about 500 rpm. Doesnt sound like its bout to stall just goes up and down ranging from around 1K to 1.5k strangest thing is it almost always happens when the lights are off and when you them on it rectifies this problem... although it does sometimes happen when the lights are on and stops when the lights are turned off. Another way to correct it is to rev and hold the revs at bout 2K for a second and it usually stops the fluctuation for bout 10 secs then starts again. sometime s the problem isnt there or just goes away on its own.

Secondly... Upto about 3K rpm.. you cannot accelerate slowly rpm fluctuates by bout 100 rpm. could this be a product of the porting that could be done to this engine...?

Finally... strange clunking noise is there sometimes but goes away when u put the clutch in... prehaps thruster bearing?

Any help would be greatly appreciated.. cant wait to get the car running perfect so i can take some photos and post em up!

thanx a lot Daniel

Molotovman

iTrader: (49)

Clunking are bad tranny or diff mounts, you should replace them because they are at least 16 years old if they have not been replaced. Get a new OEM mazda thermostat for your car, it was the culprit of my hunting idle (the jump from 1-1.5k ). If you have the cold start system(resovior in the back left of engine bay) make sure it is full. Thats if you have that. If that does not work, try adjusting or resetting the Throttle position sensor and adjusting the Idle speed.

Hope that helps, and nice find, You're lucky to have that car.

Blind Freddie

Thanks for your help... a few other things i'd like to know... is there anyway i could tell (without pulling the engine apart) if its ported? whenever i take the car up my driveway, which is a little steep, or under a hard launch when the clutch bites i get a screeching sound until i've totally lifted the clutch and driving also this only happens from a stationary start ill replace the thermostat tomorrow and then let you know how i go... thanx a lot for your help... Daniel

Molotovman

iTrader: (49)

make sure you get the right mazda OEM thermostat for it.

Blind Freddie

Just curious, what's the OEM stand for?
something engine management?
What if my local auto place has a thermostat for the car, but it's not the actual original mazda one??

Daniel.

turboii87rx7

oem just means a stock replacement.... its like original equipment manufacturer or something

sa22c_Drifter

very informative, i have that clunkin sound too, so i better buy some mounts

Blind Freddie

in terms of being the thermostat?? why would having the lights on/off alter this problem im having with the fluctuation of the revs... i was thinking it was more of an electical fault thanx Daniel.

SonicRaT

iTrader: (6)

Check the bypass air control valve.

Blind Freddie

y would the bypass air control valve have anything to do with this?? im not very experience with rotors although i cant really see the reasoning behind this... anyways thanx for ur help daniel.

SonicRaT

iTrader: (6)

Simply because it controls the ammount of air entering your engine at idle, adjusting when a higher electrical load is placed on the engine. If this is sticking, it explains why it'll idle better when there's a higher load. Typical problem on rotary cars

Blind Freddie

Hey,
Alright cool i'll look this up. In terms of the mounts, i don't think that's them, i didn't really express myself properly, it's not really a clunking, it's kind of like a whirring too, like something spinning, that's why we thought it would be the bearing.

Well, today i'll check out this air bypass valve if i get a chance in the Haynes book, see if it's got a way of determining if it's faulty. Are replacements expensive?

Also, does anyone know a way of determining if my car would be ported (Extend or mild ported, maybe even j ported) without ripping the engine apart? It sure sounds like it to me, but i've got nowhere near the experience in rotors to tell, it has an odd on and off sort of burble at low idle. Could the unsteady acceleration up to 3k rpm be the porting?? Because i'm a little worried about that, how up to 3k rpm the accelration is not smooth, you can't make it smooth, no matter how slowly you accelerate, the rpms go up and down by about 100-200 rpms. Could this be something serious?

Thanks heaps everyone, Daniel.

P.S - got my webspace working, will post up some pics soon.

evileagle

iTrader: (1)

OEM == Original Equipment Manufacture

Blind Freddie

k cool.
What about all the other stuff i asked?
porting?
erratic acceleration up till 3k rpm?
I'm pretty worried about it. Sounds like there's a grinding noise from the gearbox too, goes with that screeching when the clutch bites on a steep angle, or something even just taking off.

Molotovman

iTrader: (49)

The whirring, is it coming from the transmission, and does it happen in every gear except for fourth?
COuld you please describe the erratic acceleration too, what does the car do?

Blind Freddie

Ok the whining - it's there mainly when you're sitting in idle, you put the clutch down, it virtually disappears, it's very quiet, same for when it's in gears, you can barely hear it, or not at all. It's only when ur sitting there in idol, and can be quite loud sometimes. It sounds like it's coming from the transmission, but you can hear it from the engine bay too, but pretty sure it's loudest from the tranny area of the car. I'm not sure if the gearbox is ok, there sounds like there is a grinding, but it feels beautiful, slips into first perfectly, never slips gears or anything. Feels great through every gear. We think it's got an aftermarket clutch too, it's very heavy, and grips very tightly. The importer felt it and straight away is convinced it has an aftermarket clutch.

Ok now the acceleration, which i'm mostly worried about atm. Sitting there idling, not driving it, you rev the car, until you get to 3k rpms, the rev's don't stay steady even though you're holding the accelerator in one place. After 3k rpm it's fine, but before that, the revs fluctuate by about 100-200 rpms. You can even hear the BOV blowing off a little with each fluctuation. Could this be something serious? Also, could it be a side effect of porting, if it has indeed been ported? After 3k rpm, it sits perfectly and increases and decreases perfectly, before that, it fluctuates. Thanks heaps btw for all the advice, i'm going to test the air bypass valve tomorrow if all goes to plan, using the Haynes tech manual to test it out.

Dan.

SureShot

Tranny gear/bearing noise? - I'd start by draining & refilling the tranny with synthetic gear oil.

The no load uneven revs is a non-issue unless it also happens while driving. As was said above cleaning the BAC may help. It's supposed to be closed above idle speed, but could be leaking.

Blind Freddie

Hey,
Alright thanks man. I was thinking of replacing the gear box oil, it's just after i've done the full service, bought the haynes manual, detailing crap im flat broke for a while, was hoping it could be one valve i could replace Anyways, thanks again for all the help, i'll let yous know how the idle fluctuation (not the revs fluctuation) goes after testing the bypass air valve

catchas, Dan.