Inconsistent Idle

[FarNorthDSMer]

So after hours of searching forums, and clicking on more google links than I can count, I have still yet to find an answer. If anyone knows of a link to an appropriate thread or site, I do apologize for not being able to find it, and adding to what seems to be a never ending list of "previously solved topics".


Now the problem. I've got a '94 with 6-bolt swap. All 6-bolt, components. I had a leak coming from the TB shaft seals, and did the O-ring fix off VFAQ to get by. In the meantime, I ordered another TB from Steve at Throttlebodys.com, and purchased a new 1G TB with a 63mm bore, the Uber shaft seals, Max shaft, and half shaft mod, alond with the FIAV pass-through plate. I installed it all this morning, along with a new set of NGK wires, and BPR7ES's. I started it up, adjusted the idle switch to where it activates and deactivates at the proper points, and adjusted the BISS out 2 turns, which, from what I've read is an appropriate starting point. I had a high idle, around 1800, got it calmed down to around 1100 but can't seem to get it back down to 850 where I had it before. I checked the ISC terminals, and all the coils read in at 34 +-1 ohms. More importantly, when I sit at idle, it intermittently wants to cycle back and forth between closed loop and open loop. Any advice?

 

[Brandon Mau]

You may have adjusted your idle switch to much leaving the throttle plate open a little bit. Which you adjusted the BISS screw but you can't fully adjust due to the unwanted air coming through. And I see you have link which is good. Just log your idle switch you don't have to have the car running to read when it hits 1. If your reading 0 then you are not on but you said you have watched the demos on link so I'm not gonna say anymore.
Was your car warm when you set you ISC position to 30 and did you have the diagnostic terminal grounded through link so you can set your ISC properly? Just asking because not everyone knows.

 

[FarNorthDSMer]

You may have adjusted your idle switch to much leaving the throttle plate open a little bit. Which you adjusted the BISS screw but you can't fully adjust due to the unwanted air coming through. And I see you have link which is good. Just log your idle switch you don't have to have the car running to read when it hits 1. If your reading 0 then you are not on but you said you have watched the demos on link so I'm not gonna say anymore.
Was your car warm when you set you ISC position to 30 and did you have the diagnostic terminal grounded through link so you can set your ISC properly? Just asking because not everyone knows.

The throttle plate is closed completely, with slack in the cable. I checked that a couple times. But I also noticed the Idle Switch doesn't like to read "1" if I slowly release the throttle, like on decel. I adjusted it probably 5 times and took it for test drives trying to get it to work. I sat there watching it in link, I have it logging at that stuff.

The diagnostic terminal is grounded through the datalogging cable isn't it? You may be referring to the Ignition Timing Adjustment plug also? As that one needs to be grounded to properly set the ISC.


And to be honest, I don't think I had that grounded come to think of it. Would the ISC not being set correctly cause it to cycle through Closed loop and Open loop?

 

[92AWDHX40]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

 

[FarNorthDSMer]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

Been through all that time and time again. I grounded everything through Link to properly set the sensors, and that made it better. My ISC is sitting at 28 I believe, so closer to the 30 mark. My Idle Switch is screwed in correctly now. It runs a lot smoother, but my idle is still above where it should be. However, I'm wondering if with the bored out TB, if his custom throttle plate just isn't closing as tightly as an OEM, and it's allowing extra air to pull through. But that still wouldn't explain why it's also still cycling between closed loop and open loop, however it's only doing it 3-4 times before settling down and idling properly.


Edit: I attached a short clip from the log to show the cycling at idle.

 

[Brandon Mau]

According to the log you gave us you are driving the car at low speeds. We need an idle log and it could be that the custom throttle body plate is just not closing all of the way but I do not think that is the problem because you bought from a known good source. You have to ground the diagnostic pin to ECU for ISC not the timing connector that is for setting the ignition timing which have you done that with a timing light to double check? You need to go to the fuel tab in link and set Coasting FC offset to roughly 90 because you are going higher than the 750 stock Idle RPM. Your Idle switch could be going bad have you tried using the simulate Idle Switch in link yet?
Now that I think of it I believe you need to adjust your MAF Comp page because you have a bigger bore throttle body now thus allowing some more airflow. Adjust your sliders at you idle range and get your airflow per rev down to .25 grams a min. Then show us another log when you do what I have suggested.

 

[FarNorthDSMer]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

According to the log you gave us you are driving the car at low speeds. We need an idle log and it could be that the custom throttle body plate is just not closing all of the way but I do not think that is the problem because you bought from a known good source. You have to ground the diagnostic pin to ECU for ISC not the timing connector that is for setting the ignition timing which have you done that with a timing light to double check? You need to go to the fuel tab in link and set Coasting FC offset to roughly 90 because you are going higher than the 750 stock Idle RPM. Your Idle switch could be going bad have you tried using the simulate Idle Switch in link yet?
Now that I think of it I believe you need to adjust your MAF Comp page because you have a bigger bore throttle body now thus allowing some more airflow. Adjust your sliders at you idle range and get your airflow per rev down to .25 grams a min. Then show us another log when you do what I have suggested.

That was an idle log immediately following a 35 mile or so drive. And Link has an option to simulate grounding to the timing connector, and the diagnostic cable per the service manual, which requires both being grounded. My Maf Comp table had already been adjusted. After I reset everything, the car was idling perfectly right around 850, with the gm/min at .25 and the combinedFT at right around 0%. It wasn't until during and following that initial drive that I started to have problems. I'm going to go through and reset it all first thing in the morning. The Idle Switch came on the TB that Steve sent me, so I might switch it out with the one off my original since I know that it works properly. Though, I checked the continuity of the sensor when it becomes grounded, and the reading appears to be correct. I just got the full service manual saved, so I'll do it based off that, implementing the specs I already know, plus the offsets you recommended. It just seems weird to me that it is only acting funny and cycling between OL and CL at idle, or when the clutch is fully engaged, which based on my Idle Switch not being based on movement, is the same.


Does it require ACTUALLY grounding the two pins, versus simulating them through the Link "Devices and Diagnostics" section?

Thanks again for the advice and reccomendations.

 

[Brandon Mau]

You don't need to ground the timing connector through link just ground the diagnostic pin through link.

 

[vl4bad]

This is a great thread! I wish i could help but I'm having problems also,
I have the wire to connect to my computer to tune the car next to my passenger seat, not even sure what management system i even have...And I am not too familiar with tuning..so I'm in the shitter

My idle is horrible also, but it could be from a couple of things, I think...

1. Rebuilt Engine so it has to be broken in?
2. Rebuilt engine so it needs a tune..
3. My FPR is running really lean! So Im not sure what to do about that...
4. Something is wrong that I don't know about...
5. my personal opinion, the car may need a better tune and to be properly broken in...

help?!