Newbie question, rev problem

[clement87]

Hi

Nice to meet you everyone, I am a complete newbie in rotary and just got my FD (1st gen) RX7 about a month ago. The car has been modded by previous owner, who is a friend of a circuit owner in Japan who I bought the car from, so I don\'t really know a lot about what exactly has been modded (apart from what I can see under the bonnet and the LSD which keeps locking me up all the time!)

The car seems to be mostly fine, good pulling power etc. However, since couple of days ago there is a problem with the water temp and rev. It happens suddenly once the car is warm. Normally my car stays at around 80 degrees when its warm, which I think slightly too cold for RX7? it shows 80 degrees on the Power FC and the original coolant temp gauge shows middle

When the problem comes, the rev isn\'t stable. Plus the water temperature will drop significantly for around 15 degrees (ie from 80 to 65 or sometimes even lower). When the car is idle, the rev will jump between 500 - 1200rpm. When I step on the gas pedal, the car goes but the rev still doesnt stay stable and will wobble at a range of around 500rpm (ie when I am doing 3000rpm it will jump between 2750-3250rpm). It lasts for a while... sometimes it happens only for 10 seconds, and sometimes it happens up to 3 mins (so far the longest record)

My thought is the water temp sensor is not working well and gives false signal to the Power FC, which then gives wrong management signal to the engine. But as I said I am complete newbie so I aint sure at all.

Would some experts help me out here please?

I am currently in Japan doing my year abroad, join the motor club in university and got the RX7 from a circuit owner (who has good relationship with the motor club) and he has good reputation. I love the car but it needs some bodywork TLC... most importantly, got at only around 2000pounds:Talking1

Here are some pics of the car and engine bay, hope someone can give some good advice. appreciated and thanks in advance









Here are some specs of the car which I can see from my eye:wiggle
- Big radiator (I think is trust?)
- Cusco intercooler pipe
- ARC intake box
- Cusco oil catch can
- Some uprated pulleys
- Power FC
- HKS blow off valve (VERY noisy!)
- Cusco LSD (I think is 2 way but not sure)
- Cusco Braces
- Tein HR-A (?) suspension
- Endless brake pads
- 5Zigen brake discs
- Devi water temp gauge (which is currently not connected, cant find the wire!)
- Fujita front bumper
- Amemiya Alloys (not shown in pic)
- Fujita exhaust and cat
- Amemiya steering column boost gauge
- FRP bonnet
- Mazdaspeed replica sideskirt (not in pic)
- Amemiya style big ducktail spoiler (not in pic)
- Amemiya carbon rear diffuser (in the night pic)
- Amemiya rear lights cover (which I personally don\'t like it and its off... will be for sale in Japan soon, can ship to UK or anywhere if there is good offer!)

Long list I know but these are only what I could see! Thanks for the advice!
I am also a Mazda MX5 enthusiast which got a Eunos roadster in UK, so if you need help getting JDM stuff it is worth giving me a shout:yes

[yehreally]

....search this site with \'hunting\' :WaveBye and temperature probably the sensor :rolleyes: other than that probably best to wait for more answers !

[clement87]

....search this site with \'hunting\' :WaveBye and temperature probably the sensor :rolleyes: other than that probably best to wait for more answers !

cheers for the reply

had a search on hunting and seems like hunting means a regular rev wobble at certain limit...

mine isn\'t regular, it will just keep jumping between 500-1250ish randomly, sometimes up to 750 and drop to 500 and sometimes 1250 drop to 700 and rise again. and at low rev it sounds like it is going to stall at anytime. And it will self cure after a while and water temperature usually will rise back to normal-ish 75-80 degrees C... which I still think its slightly low

when it happens, i step on the gas and go. but the rev will keep jumping whilst I am accelerating. probably not only an idling problem? The car was fine for the last 3 weeks or so... then it came up. PFC wasn\'t installed recently so I suppose probably not caused by a \'newly installed\' PFC?

:Grrr

[m1tch]

If its been modded, did the previous owner say anything about porting?

[clement87]

If its been modded, did the previous owner say anything about porting?

i have never met the real previous owner, long story and some japanese local reason which is hard to explain

but the car ran fine for the first 150km or so since I got the car... then this problem came out and seems like it is getting more and more serious, as it is happening more frequently

what problem would you suggest it would be? cheers

[Timmy]

It\'s difficult to sell a car direct to someone secondhand i think, most cars are sold through agents and auctions.
Alot of rx7s have problems getting decent idles, just start with the water temp problem could also poss be the thermostat.

[m1tch]

Might be an idea to check for air leaks in the rubber/plastic hosing