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Interesting idle surging - only when coasting in neutral, stops when parked


derekmw
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Galant VR-4 org Post #: 973710 posted 03/02/11 10:23 AM     Remind Me!  Send Private Message   Edit Post      
I initially had an issue with low idle/stalling and checked the ohms on the ISC and found it to be bad. So I bought a new one which fixed the issue. But now another interesting small issue developed but I want to correct. I have idle searching ONLY when coasting in neutral. It will idle between 1500-2000 until I come to a stop and drops back down to 800.

Anyone know why I would get idle searching only at cruising? What could be the culprit?

Car is not showing signs of vacuum leaks or boost leaks either.


Edited by derekmw (03/02/11 11:08 AM)

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Red_Bird
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Galant VR-4 org Post #: 973713 posted 03/02/11 10:47 AM     Remind Me!  Send Private Message   Edit Post      
Check your FIAV, EGR (if you still have it), BISS screw, make sure your TB is closing all the way, and also check your o2 sensor.

There are not many other things after what I listed that will cause it.

Do go ahaed and check you vacuum lines, pop one off while idling and cover the hole with your thumb. If it gets better you fixed it.

One last thing, it's called idle surge, not search.

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derekmw
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Galant VR-4 org Post #: 973716 posted 03/02/11 11:10 AM     Remind Me!  Send Private Message   Edit Post      
Thanks for the reply. Lol, I changed the title, thanks, I think I was searching so much I switched the words.

For the vacuum leak, I did already check that, and as I expected, no issues. It idles smooth when parked.

I'll have to check the FIAV, EGR and TB being closed. BISS doesn't look like it's ever been touched and from what I read, there is no need to adjust these correct?

For o2 sensor, other than getting an error code, how can you check them?

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Red_Bird
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Galant VR-4 org Post #: 973719 posted 03/02/11 11:20 AM     Remind Me!  Send Private Message   Edit Post      
That depends, your car is 20 years old so things might need to be tweaked and tuned to get it running well.

What I listed are really the only things that can cause bad idle.

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alansupra94
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Galant VR-4 org Post #: 973743 posted 03/02/11 12:59 PM     Remind Me!  Send Private Message   Edit Post      
I noticed that I have this issue as well. It usually stays at around 1500rpm and varies a little. I personally believe it has to do with my Ostrich 2.0 as I have set my BISS 100% correctly, no vaccum leaks, IAC is fine and the EGR is removed. I don't really mind as it helps bump the alternator which I sure isn't performing to its peak ability.



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Red_Bird
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Galant VR-4 org Post #: 973764 posted 03/02/11 02:12 PM     Remind Me!  Send Private Message   Edit Post      
If you are coasting and in nuetral your car should idle higher than if you were stopped. It's like that in most vehicles. It does not drop the RPMs all the way down to 750 when you let off because that can cause the car to stall. It is all written on vfaq in plain english.

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derekmw
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Galant VR-4 org Post #: 973767 posted 03/02/11 02:33 PM     Remind Me!  Send Private Message   Edit Post      
Yeah, staying at a higher rpm (and varying slightly) is different than what I posted this topic about. In my case, there is a huge surge (1500-2000) while coasting. This occurs whether cold or warmed up.

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ktmrider
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Galant VR-4 org Post #: 973772 posted 03/02/11 03:25 PM     Remind Me!  Send Private Message   Edit Post      
Did you check your ECU before replacing the ISC? Many times a bad ISC will take out the ECU driver boards(s) and cause that kind of issue.

Also check the Closed Throttle switch, it can cause similar issues.



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Red_Bird
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Galant VR-4 org Post #: 973791 posted 03/02/11 04:20 PM     Remind Me!  Send Private Message   Edit Post      
Be sure your throttle cable isn't too tight.

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PreskitVR4
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Galant VR-4 org Post #: 973915 posted 03/02/11 10:58 PM     Remind Me!  Send Private Message   Edit Post      
501 has this identical problem. to the T.



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Edited by PreskitVR4 (03/02/11 11:03 PM)

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Lonewolf64
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Galant VR-4 org Post #: 973950 posted 03/03/11 01:04 AM     Remind Me!  Send Private Message   Edit Post      
Have you unplugged the ABS computer situated in the trunk? If you have eliminated ABS but it is still plugged in it will cause this exact problem.



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alansupra94
Excuse the retarded question.
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Galant VR-4 org Post #: 973997 posted 03/03/11 08:28 AM     Remind Me!  Send Private Message   Edit Post      
Quoting Red_Bird:

If you are coasting and in nuetral your car should idle higher than if you were stopped. It's like that in most vehicles. It does not drop the RPMs all the way down to 750 when you let off because that can cause the car to stall. It is all written on vfaq in plain english.




Figured that this was the case just had no proof and didn't really see the need to go searching for it.



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derekmw
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Galant VR-4 org Post #: 974020 posted 03/03/11 09:47 AM     Remind Me!  Send Private Message   Edit Post      
Thanks for all the replies. I still have ABS (car is completely stock) and throttle cable is fine.

How does one go about 'checking' the ecu? Previous owner just changed it out with a new one (new from Mitsubishi...he actually went to dealership and bought it from them and had them install it).

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Red_Bird
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Galant VR-4 org Post #: 974066 posted 03/03/11 11:29 AM     Remind Me!  Send Private Message   Edit Post      
hmmmm, does he have documentation that he did that. To buy an ECU new from mitsu and have them install it, I would think that you would need a second mortagae for that.

Make sure it's "new." Take it out and open it up, you can easily tell if something bad happened in there.

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derekmw
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Galant VR-4 org Post #: 974086 posted 03/03/11 12:08 PM     Remind Me!  Send Private Message   Edit Post      
Yeah, I have the receipt as well, if I recall correctly, for $1200 or $1500 something. He wasn't a regular here and this was his spare car (drives an M3 for daily driving) so although I am sure he was shocked at the price, he just let Mitsubishi handle and fix the car.

But I will def check it when I go home as even a dealership can cheat people. If they happened to have a working used unit, I can see them just swapping that in there instead of purchasing a new one and make more money.


Edited by derekmw (03/03/11 12:11 PM)

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grocery_getter
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Galant VR-4 org Post #: 974108 posted 03/03/11 12:55 PM     Remind Me!  Send Private Message   Edit Post      
All the other type of idle surging failure with the isc, fiav, throttle body plate not closing all the way, misadjusted biss will show up the same whether you are at a stop idling or you are at coasting with no throttle and in neutral. So those are not it. You said that it idles at a stop perfectly fine.

The problem happens in neutral no throttle coasting right? The only difference between resting at a stop idling with 0 speed and the condition that you are experiencing is that the car is not moving in one scenario and the other scenario the car is coasting in neutral? I would check speed sensor. In our case it is the reed switch in the back of the instrument panel. It is easier to switch out the instrument panel with another one with known working condition and see if that made a difference.

Or try using your cruise control for a good 2-3 minutes or more if you can. A good reed switch is critical to the cruise control function in our car. So if your cruise control still works perfectly then its not the reed switch.



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derekmw
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Galant VR-4 org Post #: 974111 posted 03/03/11 01:02 PM     Remind Me!  Send Private Message   Edit Post      
Exactly, only while coasting (like coming to a stop light) in neutral does it surge. Once I stop, it continues surging for a second or two, then drops down to 800 rpm or so and stays steady.

Because of this, I too thought it was probably something speed sensor related, but the gauges work fine, and cruise control works great. I can cruise at a constant speed for hours (Just did a drive to Phoenix - 6 hour drive and had many long stretches where it was on cruise control).


BTW andre, great to see you still posting here. Not sure if you remember a chat we had a while back, but I have known you from back when I was into Hondas and you made the most beautiful 3" exhaust ever. I still remember your VR4 from back then and always wanted one since


Edited by derekmw (03/03/11 01:05 PM)

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iceman69510 Galant VR4.org Moderator
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Galant VR-4 org Post #: 974116 posted 03/03/11 01:13 PM     Remind Me!  Send Private Message   Edit Post      
I may have missed this if already mentioned, but maybe closed throttle switch?



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OMFGeofffff
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Galant VR-4 org Post #: 974369 posted 03/04/11 12:52 AM     Remind Me!  Send Private Message   Edit Post      
I have this same exact problem. I'm not really sure why it's speed related.



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1990ggsxnj
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Galant VR-4 org Post #: 974415 posted 03/04/11 08:12 AM     Remind Me!  Send Private Message   Edit Post      
I have this same issue with FIAV blockoff in two cars. Idle is solid and smooth but coasting in neutral gets a surge. I've been thinking of disabling the reed switch and seeing if the car can handle not stalling while coming to a stop. My thinking is it will be ok since the ISC is still functional.



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belize1334
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Galant VR-4 org Post #: 974452 posted 03/04/11 11:35 AM     Remind Me!  Send Private Message   Edit Post      
The speed sensor is a binary detector that just blinks every time the cable turns. If the symptoms change when the vehicle is rolling then I'd say the speed sensor is working or else the car wouldn't "sense" the rolling condition and there'd be no difference.

When the car is rolling the ECU will keep the rpms up at about 1100 in anticipation that you may reapply the gas or else depress the brakes. It's basically anticipating either dip-in or load and it doesn't want the rpms to be too low when that happens. It's possible that your BISS is adjusted too far in so that the ISC is all the way open just maintaining the 800rpm idle and that asking it to maintain an 1100rpm idle is just asking too much. It can't lift the engine up that high so it starts wigging out.

Go through the procedure for setting your idle correctly. And I HIGHLY recommend getting a block-off-plate to disable the FIAV while leaving the ISC in-tact. The ISC is more than capable of handling cold-start situations and you'll appreciate the simplification of the coolant system when you don't have coolant lines running to the TB. Once done, the ISC is the only game in town so diagnosing the surge becomes alot seasier.



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moidsm1
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Galant VR-4 org Post #: 974937 posted 03/07/11 01:01 AM     Remind Me!  Send Private Message   Edit Post      
I had this problem too. I did the un-preffered method. I cut the reed switch wire at the ECU. So now the ECU never knows when the car is rolling. Im not sure if this was the best thing to do but it cured the surge while rolling in nuetral.

Also with my Hyundai Excel 4G63t swap, and an older Mighty Max Swap I never connected the reed switch. The Cars seemed to run just fine



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PreskitVR4
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Galant VR-4 org Post #: 975180 posted 03/08/11 12:19 AM     Remind Me!  Send Private Message   Edit Post      
Quoting Lonewolf64:

Have you unplugged the ABS computer situated in the trunk? If you have eliminated ABS but it is still plugged in it will cause this exact problem.



That gold box in front of the fuelpump access panel? Damn! My abs is so gone, it looks OE



"Hey your the guy with the.....the B13 Sentra?"


Edited by PreskitVR4 (03/08/11 12:24 AM)

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Lonewolf64
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Galant VR-4 org Post #: 975219 posted 03/08/11 07:40 AM     Remind Me!  Send Private Message   Edit Post      
That's the correct box. Upon unplugging that the issue was solved in the case of 116 and 889.



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derekmw
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Galant VR-4 org Post #: 975243 posted 03/08/11 09:43 AM     Remind Me!  Send Private Message   Edit Post   
My car is completely stock. I haven't had any chances to troubleshoot it further but I think it may actually be surging when driving partial throttle as well.

Although faint, you can feel the car jerking a little when driving at partial throttle. So this would seem to be more throttle body /tps related to me, what do you think?

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