Idle surge needs help

Recently the car has have some idle surge problems for a long time and I don't know what going wrong with it. I have been replacing the ISC (used) and one of the IC that used to control the ISC motor couple years ago, the idle worked properly at that time,but for some reason,now it is idling around 1500~2000rpm, the idling gets lower when the temp is reaching to normal range around 1100~1400rpm but sometimes it would get higher when it stops at the traffic lights.I've just adjusted the BISS, but no luck, need help!!! the following was all the log data, please let me know what is going wrong out there according to the log data.Thanks!!

RPM : 1500~2000 (START UP) 875~906(NORMAL TEMP.) 875 (A/C ON)
KNOK : 0
BAROMETER: 98
ISC: 0 STEP 0 STEP (NORMAL TEMP) 30 STEP (A/C ON)
FUEL TRIM HI 99%
FUEL TRIM MID 99%
FUEL TRIM LOW 139%
TIMING 16~17 DEG. 11~14 DEG.(NORMAL TEMP)
O2: 0.20~0.53 VOLTS 0.21~0.61 VOLTS (NORMAL TEMP)
AIR FLOW: 56 HZ. 44 HZ. (NORMAL TEMP)
AIR VOLUME: 0
AIR TEMP: 68 DEG.
THROTTLE POS. : 12%
COOLING TEMP : 177 DEG. 199 DEG. (NORMAL TEMP)
ACCEL ENRICH: 0 %
O2 TRIM: 99% 119 % (NORMAL TEMP)

 

[turbofonz]

Is the idle switch working properly? The 1 wire sensor on the T/B.

And an obvious one, but any boost leaks?

 

[rgeier11]

You need to test the ISC for resistance per the vfaq.com method. If that checks out bad, it may have burned ISC board on your ECU, which means both need to be replaced/fixed.

That would be my first and most obvious guess.

 

The idle switch was function good when I checked with my palm logger,I would take a boost leaks test ASAP.
Thanks.

 

the isc might going bad but the ecu I already checked have no problem.

 

[toybreaker]

Quote:
ISC: 0 STEP 0 STEP (NORMAL TEMP) 30 STEP (A/C ON)



Are you saying the iac is zero'd out cold and hot?

That's a sign there's something seriously amiss in the command/control area of life, as when you key it up, it should show a count of 120.

Right after it you start the engine, teh ecu will cut it back, contigent on ect and iat, to a number it's happy with. (Usually 1100 to a 1500k fasty idle, but sometimes as high as 1750)

If you get things up to operating temp, are still idling above the target idle speed (~850rpm), and the iac count is zero, it's time to start looking for extra air entering the system.

The Fast Idle Air Valve is a common problem, as are leaks around the throttle body seals.

The t.b leaks will show in a boost leak test, as will any cracked/deteriorated/un connected vacuum lines. Be sure to spray soapy water around the injector seals, as they are another area that can be problematical

Issues with the fiav will not show up in a boost leak test, so bear that in mind.

Quote:
THROTTLE POS. : 12%



Your tps % is a little high.

After making sure there is plenty of slack in the throttle cable, it's time to investigate why.

Can you shoot a pic of where it is in the adjustment range?

Also, please shoot a pic of the closed idle switch, showing where it is in it's adjustment range as well.

With those two pics, we can determine how much, if any, the position of the tps, (or throttle plate), needs to be adjusted to get things to the sweet spot.

Once the throttle plate is centered, and the tps is adjusted correctly, you can adjust the base timing/set idle speed (with the correct procedure as found in the vfaq's)

This will help insure that everything is centered up in it's adjustment range, before fiddling with the biss screw.

Bodging around with the biss without having everything else centered up in their adjustment range will just have you chasing your tail, and your car idle hopping at embarrasing times. (like when you're at a drive thru /ubbthreads/images/graemlins/rofl.gif )

After it's all said and done, you will probably show a small positive iac count at a warm curb idle of around 850rpm.

Turning the steering wheel slightly, and the iac count will yump ~15 or so, and the idle should remain solid. Click on the a/c, and it should jump a bunch, and then stabilise.

Done deal. /ubbthreads/images/graemlins/smile.gif

 

Thanks for all the information. I will check them all step by step and take some pics;for sure the isc was in the 0 Deg. position when I start it up and even the temp. reached normal and it only changed position when I turned on the A/C.

 

today I took some pics for idle switch and throttle cable, hope those pics can help you guys to find out the adjustment range and position that will fix the problems,for sure I still need to do the boost leak test and check the throttle plate , fast idle valve,isc!!!!!!!!

 

[toybreaker]

Thanks for the pics, shows you're serious about fixing this. /ubbthreads/images/graemlins/smile.gif

I can't quite see what I need on the closed throttle switch though... We need to see how many threads are sticking out. Can you shoot one from the same general area, just from lower, pointing up? That's probably the best angle to show the extension of the switch thru the body.

I must apologise for not asking you for a pic of the tps from the side. We need to see where it is indexed in it's adjustment range.

With that info, we can help you get started figuring out what might be out of range.

Since your car was in a shop for an extended time and the problem wasn't fixed, a slightly different approach than usual may save you time and aggravation in the long run. Many times, frustrated techs will just start bodging around, twisting this, fondling that, and the next thing you know, it's all fubar.

Covering the basics thoroughly now ensures the adjustments you'll be making later will be the right ones.

Good luck, and keep us posted!

 

[turbowop]

Although it's not connected in the pic, the idle switch is usually connected, right?

 

I unplug the wire just for took a pic and the switch was worked properly when I used the palm logger to check it,I will post the side view pics tomorrow when get back from work.

 

[turbowop]

Sounds good, just making sure. /ubbthreads/images/graemlins/smile.gif

 

sounds like a vacuum leak to me... spray around all vacuum lines and intake manifold with car cleaner.. if the idle changes, locate the leak and fix it... also check youre bov isnt leaking too much at idle..

 

I will do the boost leak check later when I get the tool done,I took some pics today with the good view angle ,hope that work,if need more let me know.

 

[ktmrider]

Have you tried adding an extra ground to the TB? Lots of folks have had issues with poor grounds causing weird sensor readings.
Still looks to be a vac leak but for $5 and 10 minutes extra grounds can't hurt...

 

I need to check the grounding wire later,I relocated the battery to the trunk,couple years ago,when I modified the turbo intake, maybe is the time to check everything up