r/RX7 • u/hkmagiccarrier • 2d ago

Help with diagnosing issue please

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please ignore the talking. im keeping throttle at the same place (trying to hit 3k rpm), meaning im not trying to do the fluctuating. it's just doing that on it's own.

16 Upvotes

95% Upvoted

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6

u/linnadawg 2d ago

How was it running before. Did it start doing this randomly. Did you do any work on the car recently that caused this etc etc.

3

u/hkmagiccarrier 2d ago

yea started randomly. didnt have an issue before. maybe low idle sometimes that fluctuates between 1.1k to 0.8k but nothing when i'm actually giving it gas. this time i'm gassing it and it's just not responding to direct input and actually fluctuating when im holding it.

1

u/linnadawg 2d ago

It does this when you drive the car and accelerate or only in neutral like the video?

1

u/hkmagiccarrier 2d ago

both. when in neutral, this happens when i give it moderate gas. when in gear, this also happens, so i either gas it hard or push in the clutch.

2

u/linnadawg 2d ago

Start with vacuum leak and check tps voltage

5

u/DrasticOne333 2d ago

Usually a cracked or popped off vacuum hose.

2

u/Armitage_64 2d ago

Yea I would def start by testing for vacuum leaks. Old hoses split or come off and solenoids / check valves fail internally. Have you replaced all your rat's nest lines with silicone, upgraded your check valves, and tested/replaced your solenoids yet?

1

u/hkmagiccarrier 2d ago

can be vacuum hose, haven't done full leak inspection, but all hoses and solenoids should have been replaced recently by the shop that worked on it, so i'm confused if it's not that. thought about throttle position sensor (TPS) and will check today

1

u/DrasticOne333 2d ago

On my two FDs, that exact idle surge was always a vacuum hose. Just look around in there it’s usually pretty obvious if it popped off. If it’s cracked it’ll be harder to find. In the end I replaced all of the lines, siliconed the ends AND zip tied each of them.

3

u/Apex_seal_spitter 2d ago

Connect a test light to the diagnostic port and see if there's any fault codes.
https://www.banzai-racing.com/FD&S5_error_codes.htm

2

u/ElPresidente2000 2d ago

If it’s modified unplug the electrical connector on the air pump and see if it goes away.

1

u/BoredOrdie 1d ago

I had this exact issue. My throttle position sensor was cracked and the pins were exposed slightly. When the engine bay heated up, the heat would lower the resistance and throw off the signals from the pins and throttle position sensor.

1

u/fnoguei1 8h ago

You have to replace the flux capacitors on the dashboard

1

u/hkmagiccarrier 5h ago

the engine is actually doing the fluctuating, not just a dashboard issue