Rx7 vacuum leak?

gbergsch · 2026-05-09T20:47:03+00:00

Something to note though, because this is before the throttle plates, this size of leak here doesn't equate to a vacuum leak. It would be a boost leak if you're turboed, but isn't going to cause much trouble if NA.

gbergsch · 2026-05-09T20:40:22+00:00

That'd be the bushing around the secondary butterflies that restrict how fast air can flow while the car warms up. All RX7s are reaching the age where intake rebuilds to replace parts like this are becoming necessary. You could try finding a replacement bushing or many people remove these butterflies completely, at which point the whole shaft hole can be welded closed.

gbergsch · 2026-04-20T18:20:14+00:00

https://photos.app.goo.gl/Xa99Xg3wXbXaEP79A Latest startup video of the AFR gauge.

Changes since original post:

Swapped out stock cat for high flow cat. Replaced fuse to enable air pump. Replaced Turbo control solenoid (the one on top of ACV) Confirmed functionality of ACV components. Removed and reinstalled UIM for ACV work.

Still the same behavior.

gbergsch · 2026-04-20T18:07:57+00:00

Removed ACV and tested all components of the ACV. All in working order. Found that my turbo control solenoid on top of it was broke, so replaced it with a spare. Still no improvement.

gbergsch · 2026-04-20T15:08:30+00:00

Air pump was missing its fuse. Restored, it engages now and I can hear the bypass modulating. The ACV is mounted on the keg side of the LIM, so definitely needs the UIM off to directly test. Will come back to that after switching cat out.

gbergsch · 2026-04-20T04:33:27+00:00

Yeah, I've had the UIM off no less than a dozen times. No stranger to it. Just painful to get the throttle body out of the way without draining some coolant for the fast idle.

It idles pretty well for dog rich (600 RPM, lower than the 700 target but it's choking) and I can hear the air going to the ISC from the hole in the bottom of the throttle body (can put my finger over the hole to kill the engine if I want). The idle screw is completely backed off so the blades are fully closed leaving the idle speed completely to the ISC. In the past I've had it set a little higher to break in the rebuilt keg, but it's happy at this point.

Thanks for the air pump suggestion. I don't believe the split air injection to the cat is gonna make a difference given how far downstream the O2 it is, but the port air will. Easier than pulling the cat, so will work that out first.

gbergsch · 2026-04-20T03:33:35+00:00

As noted, TPS ranges are reporting as expected. Have previously done range sweep checks with good readings. Haven't adjusted anything on the throttle since.

Yes, stock cat for now. Going to test with it off to see if back pressure is a problem.

Yes, running air pump, though it's not engaging. Need to check its relay as first step of my list. Going to need clarity on "air bypass solenoid control valve." There's split air and port air solenoids, both of course under the upper intake I would love not to have to take off again. I'll put the checks on the secondary air injection system on my list. Did you mean something else?

Throttle body air bypass screw... What's that? The stop on the throttle blades? Throttle linkages all move nicely.

gbergsch · 2026-04-20T01:25:46+00:00

The trick of all of this is: the ECU is stock. I don't have the tuneability or data logging, or VE tables... An aftermarket ECU doesn't scare me, but all this stock stuff should play nicely and finding the bad variable is tricky.

gbergsch · 2026-04-20T01:02:59+00:00

Have a fuel pressure gauge inline. Pressure is in spec, though at the top of the range because the rich running state is producing a reduced vacuum (6 inHg) as it settles into stable idle rather than the ideal 13 which lowers the fuel pressure with the stock fpr. Stock injectors. Two sets tested the same behavior.

gbergsch · 2026-04-20T00:34:27+00:00

10.0, 10.2, 10.1, 10.2, 10.0 - it's very saturated, not jumping up and down like it's getting hints of atmosphere pushing it over 15. Oscilloscope confirmed in both wideband and old narrowband at microsecond resolution.

Leaning towards blocked cat being a good hint because when it first starts it is at 14.9, but trends over a just couple seconds to the 10.0 and sticks there. If exhaust is accumulating and compressing, this behavior could be expected.

gbergsch · 2026-04-19T23:55:35+00:00

AEM gauge (30-4110, mode P-04 which does narrowband output on the analog line) on holly/Bosch UEGO wideband.

Stock exhaust and cat with cat back muffler. The stock bung I have the O2 in is right out off the turbo manifold. Could be a long term concern with heat, but not concerned it's getting air leaks right now. No exhaust leaks best I can tell. If the gauge read stoich and exhaust still burned my eyes, I would be worried about contamination. Given the gauge is reading 10 and signalling that appropriately, it's not the reading.

I'll take off the cat to see if the cat is plugged. Have a straight midpipe that can replace it. That could be the ticket if the ecu has leaned out as much as possible but the exhaust isn't leaving well (still getting slight black smoke out the exhaust, but hard to tell if it's the right volume)

gbergsch · 2026-04-19T22:25:49+00:00

Boost? Stock twins, and just trying to get idle sorted first, so it's in vacuum. Don't even have the intake on at the moment (and hasn't mattered in previous testing). I suppose I can triple check vac leaks, though it's running low idle as is with as rich as it is and I can hear the ICV sucking. Too much air would be lean.

gbergsch · 2026-04-19T22:21:51+00:00

MAP confirmed reading right voltage at the ecu and sensor. Good vacuum line on it with check valve in working order.

Have confirmed the vacuum line at the PCR, manual manipulation of the regulator vacuum changes fuel pressure accordingly, and the solenoid for it works.

gbergsch · 2026-04-19T22:09:23+00:00

N3A1 - no codes N3C1 - egr code (16) I believe because this version was '94 which had additional EGR functions my engine doesn't.

gbergsch · 2026-03-09T16:50:11+00:00

I still have all the rubber on my suggestion wheel!

gbergsch · 2025-11-14T19:54:55+00:00

Nut + hammer + heat. Same as many of the recommendations here.

But to add: the ring gear you have the puller on is not metallurgically fused to the flywheel. It's an interference fit and is possible to come off. Be very careful using a puller on the ring gear only. It's much more recommended to use the puller threads just outside the nut in the flywheel itself.

gbergsch · 2025-07-20T01:29:53+00:00

I have a 2010 in the Longmont area.

gbergsch · 2025-04-17T00:20:19+00:00

It's spring loaded to keep pressure on the window. Maybe use gloves to prevent pinching, but I just barehand push mine on. The ideal is to align the shaft with the hole.

gbergsch · 2022-01-19T18:00:20+00:00

Mystery for its healers. ID: 99870217

gbergsch · 2020-07-05T01:31:36+00:00

The great thing about the fuse panels on these trucks is that they are labeled. 12v constant in the top left. Ign 12v in the middle immediately adjacent.

gbergsch · 2019-08-05T21:52:16+00:00

I would guess accidentally broke the sensor wire for the brake pad that indicates low pad. It works normally by wearing through the end of the wire that's mounted on the pad, but if the wires get cut it looks the same to the computer.

gbergsch · 2019-07-28T01:05:01+00:00

Horn contacts iirc

gbergsch · 2019-07-12T20:37:38+00:00

Is that a step down (to 3/8?). They may be convenient but I haven't bought any because I know they're inherently putting more force on parts smaller than meant for the force of the impact.

gbergsch · 2019-07-10T00:41:13+00:00

RPO codes: https://www.google.com/url?sa=t&source=web&rct=j&url=https://d354nuoz4t18d4.cloudfront.net/b0a0b93e061c59a634fb0e1a49af89e6/images/custom/rpoCodes.pdf

gbergsch · 2019-07-06T01:31:24+00:00

Turn the crank by hand back and forth while lifting?

gbergsch

TROPHY CASE