High Idling Embarassment
 

BACKSTORY: I have a single TO4Z, Apexi PFC, FMIC, block-off plates NO ISC, etc. When I ordered the PFC I had the RX7Store do a base map setup based on the mods I had. So my PFC has a tune from the shop and has yet to be tuned by me or any professional on a dyno (YES I am going to). When I 1st installed the PFC, I went through the whole 1/2 hour idle learning process and it worked great. Idled around 850-1000. A while later I took the main cat off and put a mid-pipe in its place.

Ever since I have removed the main cat I have had nothing but high idle issues, mostly around 2,200-2,500 RPM. I put the block-off plate on the lower intake manifold where the "air pipe" from the main cat bolted to. I have played around with that block-off plate enough with new gaskets, gasket maker, to realize that I am not getting a vacuum leak from there.

I have all the throttle body idle screws backed all the way out to point they don't even touch. I have had the throttle cable adjusted all the way out, still high idle. I actually have learned that I have to tighten the throttle cable just enough to make a steady idle (which makes it 2,200) , because if its too loose the idle starts to "hunt" between 1,000 - 1,500. I have gone through the idle learning process AGAIN after the main cat has been pulled off, still high idle!

Reaching high grade frustration: I have had to assume that is must be a vacuum leak somewhere! Yet no matter what I do nothing remedies this problem. I have had the UIM off several times to see if I can find anything. Today I pulled the UIM & LIM off to see if there were some things not hooked up right. I found a vacuum cap on the LIM tore open. "Yes, this must be the problem!" I thought. The UIM and LIM have the metal gaskets and I replaced a lot of other vacuum caps for good measure. I bolted it all back together...you guessed it...high idling!!!

I am so freaking pissed off about this. It sucks being at a stop light with this high revving engine and I don't even have to hit the gas in 1st gear it accelerates on its own. I guarantee that its probably such a simple fix, yet I am out of ideas as what to do or what it might be!?!?!

I am wondering if the ISC being deleted might have anything to do with this? Does it have something to do with the PFC and the idle learning thing? Maybe there is something I am missing that a knowledgeable, more experienced 7 owner knows that I don't?

I have run out of the logical ideas:scratch: Any input you guys think is beneficial or stories that relate to this would be greatly, totally appreciated!

search pressure test

where is your throttle body idle air screw? that should only be 1/2 turn out or so if memory serves.

z

What's your lambda reading at idle? (AFR)

+1 Pressurize your intake and listen for the leak, it will be after your throttle body somewhere and probably pretty small. Take all tension off the throttle cable before you do it.

They sell the coupler for testing here http://www.siliconeintakes.com/index.php?cPath=8 but you can just hit up a hardware store and make your own for less.

..get a can of carb/brake cleaner and spray squirts around where vacuum ports are and the lim/uim etc...do this while the engine is running..if there is a leak the car should bog out a bit and try to die

That works too, i'm just not a fan of spraying that shit around hot exhaust parts...

..you have the ability to spray it exactly where you want....dont spray it on the exhaust if thats what you choose...

To each their own, i can have the filter off and the tester on and the intake track compressed in a minute, its not that big of deal.

the problem with spraying the carb cleaner on a turbo car is that the intake system is not under pressure. a lot of things won't leak at atmospheric pressure but will leak under boost. when you pressurize with an air compressor, you can spray soapy water and watch for bubbles to the same effect

..the guy says he has a high idle...that would indicate he has a leak at vacuum not boost....therefore carb cleaner will work just fine...turbo doesnt create "boost" at idle..if they did we wouldnt have this thing called turbo lag..

Darinn, I get tired of editing out the offensive/High school sections of your posts. Do me a favor and please keep your posts constructive and positive. Thanks.

+1 on that.

First thing i would do is a boost leak test just like others recommended. it's real easy to make one takes 5 min.

From my experience, when you took off the air pipe and blocked the tuning at idle needs to be set. I do a couple of things, set the idle air screw to approx 1 turn out, set the pfc to
idle at 1000rpm, turn off the idle air control setting in the commander and adjust the the throttle blades to idle at 1000rpm. Once I have done this turn back on IAC and if it stays stable, set what rpm you want and this works for me. This can vary the sugested rpm
from 1000 and maybe a little higher due to porting.

This is only my input and experience Ralph

You're right on the turn out for the screw. I have all the idle screws backed completely off, and the one your talking about on the the TB inside the compression tube, I have had it screwed 1/4 to 1/2 turn out and even tried having it screwed all the way in, with no difference.

I believe its around 12.5ish

Thanks, guys! :) I am definitely going to do this GREAT suggestion. Never thought about doing something like this. Thanks for the link too. Hopefully this will help reveal some problems.

Thanks for the cool tip! :icon_tup: As I said earlier I am still learning the PFC, so this is cool to know I can do that.

I think I will still do the pressure check though, because I think if there is a mechanical problem no matter what I set the idle to through the computer, it will still have a high idle because the computer can't control a free radical vacuum leak. If the mechanical end is fixed I can then come back and straighten out the computer side per your suggestion!

i am having the same exact problem...whats the update ?

im not violating any rules on this forum obviously....i would greatly appreciate it if you would stop editing my posts and abusing your power...its getting really old

ill leave all you "magazine mechanics" alone...enjoy spending hours of your time trying to figure something out when a simple quick brake cleaner test would solve your issue in under 30 seconds...

The brake cleaner test cannot be performed without the engine running, nor can it simulate boosted conditions by pressurizing the intake. Although it can still locate vacuum leaks, those are significant disadvantages. It also cannot be performed on the LIM runners with any precision, unlike a pressure test:

https://www.rx7club.com/attachment.p...1&d=1254637452

which is VERY correct...however if you read this users post..

"Reaching high grade frustration: I have had to assume that is must be a vacuum leak somewhere! Yet no matter what I do nothing remedies this problem. I have had the UIM off several times to see if I can find anything. Today I pulled the UIM & LIM off to see if there were some things not hooked up right. I found a vacuum cap on the LIM tore open. "Yes, this must be the problem!" I thought. The UIM and LIM have the metal gaskets and I replaced a lot of other vacuum caps for good measure. I bolted it all back together...you guessed it...high idling!!!"

brake cleaner is clearly the fastest choice to resolve this issue..not even you can disagree....what if perhaps the guy is hard of hearing?? how is he supposed to hear where the leak is doing a pressure test?? (pressure test is good for testing boost leaks...this is not the case in this thread)

Most/all vacuum leaks are boost leaks, but not all boost leaks are vacuum leaks. Many boost leaks occur due to the expansion in the system from the pressurized air. Pressure testing locates both vacuum and boost leaks.

have you ever done one of these tests? I've fixed "future" vacuum leaks with my engine on a stand using a pressure tester.

this is true..however he has a vacuum leak...like to see you disagree with that....im done here...this forum is clearly full of incoherent people

Well, I have yet to do the pressure test as my whole weekend has been consumed with my friends wedding stuff, plus I still have to fab a pressure cap up. I will update when I come up with a conclusive answer.

I haven't sprayed brake cleaner yet. I have sprayed WD40 around the UIM/LIM without any luck. No bogging of the engine or anything like that. I can try the brake cleaner. I like to start with cheap and easy fixes first!

I had the same problem. Went to lowes bought a PVC cap, drilled a hole and put a tire stem in it, pressurize and bingo LIM gasket. Prblem solve for under 3 bucks :)

Nice! I will be playing with it today to see if I can find the problem. I like the ingenuitive cheap and easy fixes.