boncing idle
Thread Starter
Rotary Turbo
Joined: Aug 2007
Posts: 422
Likes: 1
From: A-Town, IL
boncing idle
when my 86 na is turned on it goes to 3k rpm then goes at 1500 after 15 sec or so and at 1500 it bounces (1400-1600). and in the back of the exhaust i fell liquid drops im thinking raw fuel because of the smell, what coud cause the problem and how could i fix it?
Senior Member
Joined: Sep 2002
Posts: 408
Likes: 0
From: WDC
1 : Fix fuel / vacuum leaks (likely a vacuum leak is causing the problem) The best way I can tell you to fix them is to get a high quality silicone hose kit (with the thick hoses that wont collapse, 3mm) and replace *ALL* of the vacuum lines, including the 'spider' ones. [Dont forget the brake booster line]
2: Replace fuel lines. Those lines get dry rot quickly from the heat.
3: Replace Pulsation Dampner
4: Adjust timing
5: Adjust TPS and Thermowax .
Hopefully thats all you will have to take care of.
2: Replace fuel lines. Those lines get dry rot quickly from the heat.
3: Replace Pulsation Dampner
4: Adjust timing
5: Adjust TPS and Thermowax .
Hopefully thats all you will have to take care of.
Last edited by Dcrasta; Sep 6, 2007 at 09:18 PM. Reason: forgot something...
check that your throttle plates are fully closing, maybe the fast idle cam isn't fully releasing and your getting messed up by the gap between the throttle stop. Check this out:
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/video-still-crappy-idle-no-response-idle-adjustment-657023/
I had the same thing but we fixed it. The link above has videos of my car and the idle stuff.
oh yeah, SEARCH sometimes, it helps everyone.
Goodluck. let us know what happens.
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/video-still-crappy-idle-no-response-idle-adjustment-657023/
I had the same thing but we fixed it. The link above has videos of my car and the idle stuff.
oh yeah, SEARCH sometimes, it helps everyone.
Goodluck. let us know what happens.
this is from that thread above, Scrip and Hailers really came through and we have vids of the whole process:
I would have never guessed "township". I guess I learned something new today. Man that's quite a commute for ya! I guess you drive your Volvo to work or the GXL?
Ok. I duplicated the hunting idle on a '88 TII that I have at work. I manually held the throttle at 1100-1200 rpm and watched the timing. It advanced 6 degrees from base timing and back and forth until I released the throttle. So basically, anything holding the idle that high will cause the bouncing, whether it be thermowax, vacuum leak, tight cable, dashpot, BAC screw, or whatever. It doesn't have to be strictly a bad tps as so many on here have suggested.
Bottom line is: The idle speed must be kept at or under 1000 rpm with the tps set correctly to prevent the bouncy idle. So, in my opinion, when other people have a bouncy idle complaint, the diagnostics should start with:
(1) A visual inspection of the throttle lever to insure that it contacts the stop screw (by using a mirror and flashlight or temporary removal of the intercooler)
(2) If a gap is found between the throttle lever and stop screw, inspect thermowax and fast idle cam position adjustment, dashpot function and adjustment, and throttle cable slack.
(3) With the throttle lever against the stop screw, perform vacuum leak test using the propane method or compressed air method and make associated repairs.
(4) Set timing to spec with engine below 1000 rpm.
(5) Adjust A/F mixture screw (if equipped) to obtain smoothest idle
(6) Adjust BAC screw (if equipped) to obtain 750 rpm idle (or your preferred speed at 1000 rpm or less) and re-adjust A/F mixture screw if required.
(7) Adjust TPS per FSM and re-adjust idle speed if necessary.
Ok. I duplicated the hunting idle on a '88 TII that I have at work. I manually held the throttle at 1100-1200 rpm and watched the timing. It advanced 6 degrees from base timing and back and forth until I released the throttle. So basically, anything holding the idle that high will cause the bouncing, whether it be thermowax, vacuum leak, tight cable, dashpot, BAC screw, or whatever. It doesn't have to be strictly a bad tps as so many on here have suggested.
Bottom line is: The idle speed must be kept at or under 1000 rpm with the tps set correctly to prevent the bouncy idle. So, in my opinion, when other people have a bouncy idle complaint, the diagnostics should start with:
(1) A visual inspection of the throttle lever to insure that it contacts the stop screw (by using a mirror and flashlight or temporary removal of the intercooler)
(2) If a gap is found between the throttle lever and stop screw, inspect thermowax and fast idle cam position adjustment, dashpot function and adjustment, and throttle cable slack.
(3) With the throttle lever against the stop screw, perform vacuum leak test using the propane method or compressed air method and make associated repairs.
(4) Set timing to spec with engine below 1000 rpm.
(5) Adjust A/F mixture screw (if equipped) to obtain smoothest idle
(6) Adjust BAC screw (if equipped) to obtain 750 rpm idle (or your preferred speed at 1000 rpm or less) and re-adjust A/F mixture screw if required.
(7) Adjust TPS per FSM and re-adjust idle speed if necessary.
Thread
Thread Starter
Forum
Replies
Last Post
LongDuck
1st Generation Specific (1979-1985)
12
Oct 7, 2015 08:12 PM