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Stalling when decelerating. I Need help

dmj

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Joined
Feb 2, 2008
Messages
673
Location
orlando FL
Boost leak test done no leaks that I can hear . Idle control switch and pigtail checks out good. I changed the throttle shaft seals and did a fiav block off today. Car is worst than before It will start but won,t maintain the idle as it now cycles up and down constantly. I need your help.
 

ktmrider

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Sep 10, 2007
Messages
3,128
Location
Tempe, AZ
ISC check? Or just the Closed Throttle Switch?

Also what BOV/BPV configuration are you using?
 

dmj

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Feb 2, 2008
Messages
673
Location
orlando FL
Installed new isc yesterday even though old one checked out within specs. Bov is recirculated (Dejon modded)
 

dmj

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Feb 2, 2008
Messages
673
Location
orlando FL
^^You got me there /ubbthreads/images/graemlins/idea.gif I will reset it in the morning and post the results.
 

dmj

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Feb 2, 2008
Messages
673
Location
orlando FL
The car will not idle with the biss terminal grounded and the logger plugged in so I can't reset the biss. If I disconnect the ground and leave the logger connected the car idles. Note for some reason the coolant temp reading on the logger showed 158 degrees. (I am assuming celcius) while the gauge on the dash was in the midpoint. The car has a new radiator, temp sender and rad fan sensor . Before all of this the car sat for 5 months for a boat load of maintainence.
 
Last edited:

beaner

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Jun 22, 2005
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1,562
Location
b'ham, mi
Quote:

for some reason the coolant temp reading on the logger showed 158 degrees.


Bingo.
 

mikus

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Jan 11, 2007
Messages
2,763
Location
Aurora IL
KnowYourThermoHousing1G-1.jpg


Your temp gauge and temp sender are two different units. Image linked not hosted due to boat shenanigans.

Usually the problem is temp sender wiring broken and you'll read something like -40º. Sounds like you have a failing sender based on the 158º reading. 158 C would be 316 F by the way
 

dmj

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Feb 2, 2008
Messages
673
Location
orlando FL
I just tried logging the temp. and now my logger took a crap. I have a fatal alert and it won't reset.I swear this car loves jack stand balling as soon as I fix one problem 3 new ones show up /ubbthreads/images/graemlins/banghead.gif
 
Last edited:

dmj

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Feb 2, 2008
Messages
673
Location
orlando FL
Replaced the coolant temp sensor with oem unit and tested it before installation. Tested the voltage at the connector both within specs. But the car still stalls on deceleration. At this point I am going to remove the ECU and take a look at the board for any damage.
 

vtecds1

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Joined
Jan 16, 2004
Messages
1,705
Location
Las Begas
What other maintenance did you do with the car? Was it doing it before?

Check timing, TPS, check ecu(like mentioned), Idle switch and ground on the t-body. I was having the same problem for the past year and could not figure it out. Then I remembered that the needle in my speedometer was bouncing up and down. Messed around with the cable and speedo housing for a bit and finally solved my problem.
 

AWDPower

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Feb 28, 2011
Messages
107
Location
Vacaville, CA
Quote:
The car will not idle with the biss terminal grounded and the logger plugged in so I can't reset the biss.



If it won't idle with the biss terminal grounded, the biss screw may be closed too far. Open the biss screw most of the way, then ground the terminal. You will start with an idle that is too high and close the biss screw to work your way down.
 

jepherz

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Aug 8, 2004
Messages
7,877
Location
KC, Missouri
Yes, that hints that there is no more adjustment in the idle motor if the car can't idle on it's own. Remember that all the idle stepper motor is, is a pendulum essentially. When you ground the pin, the ecu sets the stepper motor in the middle of its throw. Then you set the biss screw to be at the ECU's target idle.
 

dmj

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Feb 2, 2008
Messages
673
Location
orlando FL
Ok .so I tried the suggestion above backed out the Biss, grounded out the terminals and the idle is all over the place between 600- 1800 rpms. I slowly tried to turn in the biss screw to set the idle and it did not help so I
disconnected the ground and It idles on it's own at 850-950 rpms,but every few minutes it starts cycling up and down again.I drove the car about 55 miles today and fortunately it did not stall, the idle drops under 500 rpms when coming to a stop but recovers quickly and cycles up and down at least three times before settling to about 850 rpms.
 

ktmrider

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Sep 10, 2007
Messages
3,128
Location
Tempe, AZ
I've heard of ABS issues creating idle surge issues ( mostly high idle tho ). Is your ABS intact or disabled and if off how?
 

dmj

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Joined
Feb 2, 2008
Messages
673
Location
orlando FL
Abs in good shape, no codes or lights. Pulled the Ecm today looks like there is acid on the board but I an not sure maybe someone can confirm from these pics




 

s_firestone

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Jun 27, 2002
Messages
1,610
Location
Park City, UT USA
Check your butterfly gap. Test the continuity of the CTPS again, they are notorious for sticking in one position (open or closed) when they go out. It also relies on the ground of the throttle body.
 

Terry Posten

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Dec 16, 2003
Messages
9,009
Location
Davenport, Iowa USA
That is not acid, it is flux. That board look pretty clean fom what I can tell from the pics you have.
 

dmj

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Joined
Feb 2, 2008
Messages
673
Location
orlando FL
That eliminates the ecu as the problem then.I am going to check the resistance of the wires from the ecu socket to the tps, iac,cas and the closed throttle switch. I will keep the post updated.
 

dmj

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Joined
Feb 2, 2008
Messages
673
Location
orlando FL
All wires ohmed out fine including the p/s pressure Switch. Later I will check the voltage @ The iac, cas and tps. If that checks out ok then I will replace the throttle body.
 
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