New fun thing to do. Idle bounces between 1k and 1.5k Rpms cruising to a stop in neutral for a bit then leveled out at 800 900 Rpms. Then when I start driving on a green light, the car stumbles forward then catches itself and goes.

 

I took the time to adjust the idle screw below the throttle body because of the posts I've read about making adjustments twice a year for spring and winter. Though I live in Florida and skeptical about our yearly weather. I went back to DCs PFC idle adjustment pdf on banzai's racing site and turned it 3/8ths of a turn. Then I adjusted the screw on top towards the front of the throttle body to dial in 840-870 Rpms on the PFC commander. I did so without the fans on because when the kicked in, the idle dropped about 60 Rpms. So I waited until they turned off.

 

Check your cruise control clutch switch. If the contacts are bad, or the spring is broken it will mess up your idle:

https://www.rx7club.com/3rd-gen-arch...switch-495391/

 

Okay I'll do that this afternoon. Thanks for the guidance.

Just wanted to clarify it bounces between 1300-1500 Rpms when I coast to a stop in neutral and then slowly settles into 850-900ish Rpms

 

what mods are done to the engine?

 

Mine does something similar however this is only before a full warm up and on the stock ECU. I figured there was just some skewed logic in the ECU when it's crossing over from the throttle held open via the coolant valve and the ISC taking command of the idle. I've read about a lot of funky idle situations with the PFC so I'm in for the fix when I get one myself.

Matt

 

PFC, hks downpipe, stock midpipe, racingbeat catback, 99 twins, stock intercooler, k&n intake filters, deleted airpump, deleted egr, deleted choke.

 

Btw when the vacuum line with the check valve between the throttle body and firewall is disconnected, the issue is fixed.

 

Exactly which vacuum line? What is it connected to on the firewall?

 

There shouldn't be any vacuum lines with check valves there unless you're referring to the MAP sensor hose. If that's the case that is a filter and not a check valve (regardless of the arrow on it). A vacuum leak can cause a high idle depending on the severity. When the MAP sensor is disconnected, it runs like total butt toots. Is your issue with the double throttle? The double throttle is a second set of throttle plates in the UIM that limit the throttle during warm up. With vacuum applied, the throttle plates are closed, and with no vacuum (hose disconnected) the plates should be open.

Matt

 

Untitled by Gerald Mugar, on Flickr






Should I reset the PFC?

 

That hose is for Solenoid Valve C which is the secondary air switching valve. This valve controls the Air Control Valve and whether or not it provides port air or not. With the Air Pump deleted, the Air Control Valve should also be deleted. With that disconnected from the manifold like that, you are effectively creating a vacuum leak.

Matt

 

Untitled by Gerald Mugar, on Flickr

 

Untitled by Gerald Mugar, on Flickr


Untitled by Gerald Mugar, on Flickr


Untitled by Gerald Mugar, on Flickr


Untitled by Gerald Mugar, on Flickr

 

Your dashpot is bad. It should be touching like so.

Your TAS doesn't look like mine. Odd.




When you clean the throttle plates and areas where they close, I bet you'll have to readjust the secondary plates closed. I had to on mine.

Matt

 

How do you readjust the plates? In a simpler form? I'm going to order a new dash pot Monday and hopefully have it Tuesday or Wednesday morning.

I was reading some threads and was afraid my dash pot was bad. I measured it and it's 1/8 inch instead a 1/4 inch like it should be.

 

The way I adjusted them was as follows:

Clean the throttle plates and bores as thoroughly as possible. Take the TAS (big screw in my pic above) and back it all the way off so that it no longer holds the throttle plates open. This should be done while separating the coolant valve cam. You can just hold this down and out of the way. This will simulate the throttle body as "warmed up". Take the air adjust screw (the one at the bottom of the throttle body adjusted with a flat head) and screw it all the way in. Once the throttle body is installed, I ran the engine and made sure my coolant valve cam separated at the proper temperatures per FSM F-79. After a full warm up, my idle was still high. From there I took the secondary plate stop and closed the plates until the engine was stalling (like 600 RPM) and used the Air Adjust screw (the one under the throttle body. The flat head one) and set my idle to 720rpm from there. This all must be done with the ten and gnd jumpers at the diagnostic box.

My idle has never been so behaved since I've done this. I'm sure yours will need additional work with the idle learn procedure on the PFC, but I believe this is a good starting point.

Matt

 

I ordered a new dash pot. It'll be here Tuesday.

Though I know it won't fix the entire issue

 

See this thread, it discusses these issues in detail https://www.rx7club.com/3rd-generati...needed-841706/

 

Okay I'm reading it now. I also have a new tps sensor coming in. I had the voltage tested on the full range and it was almost a volt less then the manual says the appropriate range is. I'm getting 3.8 when it should be 4.2 at the bottom range of the fully open. All other parameters were meet and adjusted.

 

I get about 4 to 5 surges and it settles down to desired idle. Once I get the new TPS in, I'm sure it'll work itself out. For now, new pcv and dash pot.


I love shiny new parts


Looks like the dash pot took a Viagra pill


Untitled by Gerald Mugar, on Flickr


Untitled by Gerald Mugar, on Flickr

 

Please install the brand new parts and tell us if that solved the problem as i also have the same isue.

I have a power fc and although i have tried the screws to fix the issu, my idles still surges for a few seconds before it setles

 

+1. This seems to be a common problem with the PFC.

Love the MS oil cap BTW

 

After installing the dash pot, it seems to me that it is working. I can roll into a stop with the gear engaged and clutch pressed and not have it bounce around. I also adjusted the tps but I had low voltage full open range but .5-.8 volts. So I'm replacing the sensor and adjusting the tps once more.

What also seem to help was resettling the PFC and having it learn my idle once again.


I did notice that if I am driving and through the gear in Neutral, the car dies.

 

Thanks tom, I have a matching thermostat too. Just didn't show it in the picture. I'm currently at the cabins of Nanathala Village for Deals gap. I met with my friend on the way up here. His name is boost Leak and he decided to appear on the stock oem exhaust side intercooler hose. So I'm going to see if I can find a cheap replacement at the shop tonight