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Just got my first rotary powered car the other day and started it yesterday. It's a 91 vert with a manual swap. The previous owner had done an emissions delete and told me I'd need an aftermarket ecu with a tune to run it. Like the title states I'll start it and it jumps right up to 6k. Is there by chance a work around I could do like maybe I'd have to adjust the throttle body or disconnect something to bring the revs down? Thanks in advance for any tips.
- Previous owner deleted the thermowax without removing the linkage, and it now jams the throttle blades open.
- Previous owner retained the thermowax but played with the adjustment screw and it now idles way too high when cold.
The thermowax is a bit of 1980s weirdness. On most EFI cars the ECU uses the idle valve to maintain a higher idle during cold starts. On the Rx7, for some reason, this is done mechanically. A device called the thermowax handles it and deleting it improperly can cause what you're experiencing. I'll describe the specifics later, but basically coolant runs through a channel with a wax piston. When the car is cold it props a linkage open to crack the throttle slightly and up the idle to about 1500rpm. When the coolant gets hot the wax melts, which extends the piston, and disengages the system so the car will idle at 750rpm.
Ways to diagnose:
- Remove throttle elbow and look down the bores. When no throttle is applied and the engine is cold, the secondary blades (the two top ones in NA cars or two bottom ones in TII cars) should be all the way closed. The primary blade (bottom one on NA cars, top one on TII cars) should be cracked slightly open if the thermowax is present. If the engine were warm, they would all be closed.
- If the previous owner deleted emissions the second set of butterflies are probably gone. If that is the case you can disregard the following. In stock cars there are two sets of blades in the secondary barrels, but the outer set is often removed. If they are present you need to push them open with your finger to see the actual throttle blades down the bores. Look up pictures online to see what I mean.
If you do the above and the throttle blades are more than a bit open, you need to find out why:
- The thermowax (if present) sits on the back side of the throttle body. There are two coolant hoses going to it, and it has a little piston pushing on a linkage. If the thermowax is present, you can turn the adjustment screw to adjust the amount it cracks the throttle open at idle. I adjust it for 1500rpm personally. Once the car gets hot the piston extends and this pushes a cam off a roller and disengages the thermowax.
- If the thermowax is not present, PO may have removed the thermowax and not the linkage it pushes on. In this case, grab the throttle linkage at the front of the throttle body with one hand and push it all the way open. Reach to the back side and feel for the thermowax linkage, and when you find it try twisting it all the way back and then slowly releasing the throttle linkage from the front. You should see the blades go all the way closed. Then you can let go of the thermowax linkage, and press the throttle once. If you hear a "springy" noise and the throttles no longer close, you know that it is the extra linkage springing into place and causing the throttle to be unable to close. The next step is to remove the throttle body and modify or remove the linkage.
I realize the above probably seems like a lot if you are new to 13Bs, but it makes a lot more sense once you have it in front of you. I suggest searching some pictures of a stock TB vs a modified TB to see the difference. Also search for emissions delete procedures and you'll see the linkage I am talking about.
Yeah I've been in a few automotive classes the past couple years trying to learn the trade so I got a decent picture painted in my head of what to do. Really excited to have found this car so cheap, I know it was cheap because it needs lots of work but it's mostly cosmetic. It was 3k I mean cmon most fc's for that price are shells lol. That whole explanation of what I could check I'd great to see l, especially if it could save me money from buying an ecu. Here's the most recent pic of my car just after I put on the bumper. A bit of a ill fit but better than just seeing nothing hehe
03-17-22, 08:18 PM
