2G RX-7: Help with Idle!

[Silkworm]

Hey guys,

Welp, the RX-7 is now officially a running motor. However, I can't get the bastard to idle. Tach doesn't work, not sure what the RPMs are at, but just a hair bit of pressure on the throttle and the engine will remain steady at that RPM, but if I back all the way out of the gas, it's dead. I've removed the thermowax and fast idle cam as well as the dashpot (which is going back on), adjusted the TPS to read correctly at fully closed throttle (1K Ohms), and set the timing (well, kinda.. It wants to run around 25 degrees BTDC with the jumper installed, backing that down, and it gets real real rough.

Help?! 88 RX-7 electronics (89 block)

PaulC


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[TURN9]

Sorry I can't help you at this point, but Congrats on getting the thing going. You have obviously learned what to do and what NOT to do, and that can help out others in the process. So, when you build your next one...

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Corey L. Clough
Ex-1st Gen, Pre-2nd Gen
[email protected]

[BrianB]

Sounds like a vacuum leak to me. Did you plug the opening in the intake pipe just before the throttle body that was connected to the BAC? Otherwise, I'd try setting the timing back to factory , Put the fast idle cam and thermowax back along with the dash pot,and try again.But it sounds like a vacuum leak to me, If there is a big leak the Air flow meter will not open at idle speed and cut the fuel!Is the AFM in a new position with the flapper fighting gravity or whatever?
Good luck,BB

[Silkworm]

Thanks Corey I don't plan to build a second one, I learned my lesson the first time around..

Welp, as far as I can see, everything is plugged. doesn't mean I haven't missed something though. I went and picked up a junkyard TB, I'll swap that in and see if that fixes the issue first.

Any other ideas??

PaulC

[BrianB]

Paul,
You probably removed the two front throttle plates from your TB. There is a potential for a leak where the shaft bores are. Otherwise, without the fast idle linkage, maybe the throttle plates just completely close with your foot off the gas.Will the engine rev up?Stalls at what RPM?
BB

[eprodrx7]

Paul,
The biggest problem on these cars is the TPS switch. As the cars warm up they go out of adjustment. Signs are fast idel or a fluctuating idel or no idel like your car. Even after you think its right just slightly out and the car will fall on its face or sputter around 6300 rpm. When you go to adjust it you need to heat soak the manifold to get it right.
John

[Silkworm]

I did remove the two throttle plates, and sealed the holes with JB weld. I'll hit that area with starting fluid and see if I hear RPM changes for vac leaks. I'm going to go thru the who intake next week looking for a leak.

I adjusted the TPS, and the engine was relatively hot at that time. Didn't change the idle behavior however. First things first, I'm going to swap in the junkyard TB and see how that goes.

PaulC

[BrianB]

Paul,
Check your timing!
Brian

[xr4racer]

I am having the same problem. I cannot get the newly rebuilt motor to idle and the initial set connector does not seem to do anything when jumpered. What is everyone setting their timing to? I have the Maza comp pulley. Thanks I cannot get the idle low enough.

[Silkworm]

Well, I can only offer what I have gone thru, I haven't solved my problem yet. Now that I have an exhaust, I'll be going at this problem full bore again

Look for vacuum leaks
get your timing set (5 ATDC leading)
Check the TPS (1K ohm at full idle, progressing to 5K ohm at full throttle)

Now, looking at my TB after removing the secondary plates and thermowax, the throttle plates are fully shut, no clearance what so ever. So if I just can't figure this out, I'm going to bump up the throttle stop to get it to idle. (shrug)

me, I'm more worried that I can't get the engine to run right at factory timing spec. It definitely wants to run 20* advanced.. Retarding it back to stock spec, it just starts running real rough. I'm going to reseat the CAS for the 10th time, but I don't think it's wrong...

G'luck.

PaulC

[BrianB]

Paul,
You could try setting your throttle plates to idle clearance(wookshop manual)making sure that the fast idle,thermowax( if they are there) isn't influencing the plates. Then reinstall the TB and set the TPS with a light( you can make one with a brake light bulb) or volt meter following the workshop manual procedure.On my racing beat pulley, 5 degrees ATDC(leading) is approximately 3/16" to the left(as you face the pulley) of the middle mark at idle.You might also check the AFM flapper for sticking as well as the resistance values for possible meter problems. If all else fails, try swapping another computer in.
good luck! BB