2G eradic idle help me not have to take my car to satan

[Rustic gst]

ok guys so my car has a bad idle with no check engine light on. i have replaced coils, wires, plugs, as well as the iac and blocked off my egr. i did a boost leak test with my homemade tester and bike foot pump. i found leaks at the biss screw and injector insulators, so i replaced both and am no longer leaking from those areas. whats happening is that when my car is warming up it seems to idle pretty steady around 1300rpms untill it warms up to operating temp and surges between 300 and 600 rpms. if i take it for a drive and do a few wot pulls and my car will start idling around 1500 rpms or 2000 with little surging. i also noticed that if my rpms are low and im in neutral, my brakes only work for the first pump, after that i have to push them really hard to get the car to stop, can i be leaking boost through the vacuum booster? ive been at it for about 3 months and one shop couldnt help. im thinking about taking it to satan aka mitsubishi if i cant figure it out

 

[Vegas Smith]

13rpms? What is this? A bicycle? Anyways, you probably still have leaks (and even if you don't, the idle is always tough to perfect on these cars). You really need to get yourself a compressor and get the psi up to about 30 to make sure you're system is perfect. Also, look into the idle position switch adjustment and biss screw adjustment. There so many threads about idle issues that there is no excuse for not finding them on google.

 

[Rustic gst]

my bad ment to put 1300 haha. and i have, ive tried adjusting my biss screw i dont have dsm link so im not to sure if its set properly. ive tested my iac its one of the newer black ones, tested at 42 ohms at the coils. i havnt messed with the idle position switch, where is that? ive read that sometimes the ecus capacitors for the iac can go bad? if so i may pull my ecu and take a look at it, can you see the burnt capacitors just from a visual inspection? i dont think i have a bad boost leak cause i can get to red line at wot no problem. i just notice when im at a constant speed and low rpms again, and i keep the throttle steady, i can feel slight power surges like my car is trying to compensate for the added load of going uphill. is my iac not responsable for adjusting air flow under load? also if i turn my ac on when im parked it will bog the car down so bad that it has died on me several times.

 

[Vegas Smith]

The ips is on your throttle body. If it isn't connected or adjusted properly then you can get fuel issues at idle. Your isc sounds good, and yes you can get damaged isc drivers in your ecu. I actually just fixed my drivers a few months ago. You can often see little bumps on the drivers where it burned up. Your isc is responsible for adjusting but everything else has to be set perfectly for it to all work. You need to look into setting your biss screw while grounding your timing pin. This will get your isc close to where it needs to be. Once again, all this stuff is easily found by searching google (not that I don't mind helping, but there is a lot more info that you can find).

 

[Rustic gst]

i was under the impression that you could only adjust the biss correctly with ecm link and a scan tool. what pin should i ground to set the biss screw. the screw has to be adjusted cause i took it all the way out to put the new o ring on it. i just screwed it all the way in and backed it out 2 turns? ive done a lot of searching and only came up with the dsm link way. all your help is much appreciated and in the event that the biss adjustment doesnt work i remove my ecu and the isc drivers are bad how did you fix them?

 

[Vegas Smith]

There is a plug on the back firewall that you connect to ground and that stabilizes your timing so the idle doesn't fluctuate. Then, you set your idle via the biss screw. ECMLink just makes it easier for you.

If your drivers are bad, then you send your ecu to ECMLink and they will fix it for ~$50.

 

[Rustic gst]

can you by chance show me a pic of this plug? i cant find it, i was looking at the fire wall near the battery and the brake booster.

 

[Vegas Smith]

You must be logged in to view this image or video.

 

[Rustic gst]

thanks. so i ground the pin start the car and adjust the screw till it idles around 750rpms and then remove the plugs ground and thats it?

 

[Vegas Smith]

Correct. You can also increase your idle if the car doesn't like 750

 

[Rustic gst]

ok thanks man, im eating with the gf now so after im done ill ground that sucker and see if that wont clear up some of the issues

 

[91talonts1]

What year is your car? The 2g timing ground plug is different than the 1g, and it's only on the 95-96 if I'm not mistaken. 97-99s I don't think have one at all.
http://www.ecmtuning.com/wiki/idlesurge
This is a good place to start with idle problems. It definitely sounds like you still have leaks though, and yes there is a diaphragm inside the booster that can cause a vacuum leak.

 

[Rustic gst]

mycar is a 95 talon tsi awd i couldnt find that plug, what is it located close too?

 

[91talonts1]

It's on the passenger side firewall behind the TB. IIRC it's tan, has a cap over it and is located next to a blue plug which is the fuel pump test connection.

A search of this site or Google will find you a picture I'm sure.

 

[Rustic gst]

i think i found it. it looks different from the above post, but i found a blue connector and a black one right behind the throttle body. im gonna ground the black one and adjust the biss. if that doesnt resolve some issues ill move on the doing a boost leak test with a compressor instead of a foot pump

 

[91talonts1]

Adjusting the biss should be done after verifying you have no vacuum leaks. I think you're going to need a logger of some sort, no way to adjust the biss correctly without being able to see ISC position.

But as for the adjustment itself, I get much better results without following the factory procedure grounding timing and the diagnostics. It takes forever for the ecu to react to changes this way, it was recommended to me by the guys at ecmtuning to just adjust the iscpos to hover around 30 at normal operating temp idle.

 

[91talonts1]

The black plug is the fuel pump test connector, the blue plug is engine speed detection connector, brown is the timing ground. Check the very last post in this thread.
http://www.dsmtuners.com/threads/2g-engine-bay-electrical-connections.298047/

 

[Rustic gst]

i didnt find that brown plug, should it be next to the black and blue one? that is all i found. and i got a compressor and tried running 20 psi through my system. only leak i found was a small one at the throttle body gasket, but most of the air was escaping past my plastic stock bov its set to open up around 12 psi right? once my bov closed i held pressure for a long time

 

[91talonts1]

Yes all three should be right there together. Again, if you will click the link I posted, there's a picture of the three together in the last post.

Yeah I think the stock 2g bov starts to leak around 12-15 psi but it leaking boost probably isn't gonna cause an erratic idle. I'd replace those TB gaskets, it doesn't take a big leak to mess with the idle speed.

 

[Tyeler18]

Correct. You can also increase your idle if the car doesn't like 750

This isn't true. If the base idle in the computer is set at 750rpms (assuming non adjustable, no link) the computer will forever try and pull the idle down to 750 until it either gets to 750 or it bottoms the ISC out and can no longer adjust down. This is the sole reason so many ISC drivers are blown out on these cars. People trying to turn the idle up without having a computer capable of turning it up. As long as the computer is programmed for a 750rpm idle, there's no way around raising the idle without disconnecting the ISC and leaving it disconnected.

Fix your leaking gaskets and go from there. Your brakes becoming hard is a good sign that you have a vacuum leak. Next time you take it out for a spin, use some vice grips to pinch off the brake boost vacuum line before going for a drive. If the booster is in fact leaking this will isolate the booster, with the line pinched you shouldn't have a leak there. Also, is your FIAV blocked off? Not just removing the coolant lines, but actually blocked? It sounds to me like that is your problem. The valves are partially open from the factory, hence your 1300rpm cold idle. Since no coolant is circulating and closing the valve, it'll stay open even when warm creating a vacuum leak you won't see on a boost leak test.

 

[Vegas Smith]

How can you tell if you have a blockoff or bypass if it's already on the car?

 

[91talonts1]

How can you tell if you have a blockoff or bypass if it's already on the car?

If it has the sandwich plate, you'll be able to see it between the TB and the ISC housing. But the fiav can also be bypassed just by screwing it all the way in.

 

[Vegas Smith]

I'm asking because I have a throttle body that came with the car with unhooked coolant lines. I could not for the life of me unbolt the tb to check if the fiav was blocked or bypassed. Sometimes I wonder if it's giving me issues. So if I unbolted the isc I should see a plate behind it? Thanks for the help.

 

[Tyeler18]

You'll see the plate between the lower half of the TB and the actual upper half. It's a ~1/4" thick aluminum plate.

To block the FIAV the easy way (better way IMO), remove the throttle body, then remove the core plug on the manifold side of the lower half. There's a small valve in there with 4 bolt holes spaced evenly apart. Spin the valve in clockwise with a needle nose pliers until it bottoms out. That blocks the valve off completely.

Edit: Half way down you'll see the plug.

http://www.dsmtuners.com/threads/free-fiav-block.391977/

 

[Rustic gst]

i havnt messed with my fast idle valve. i have a old throttle body that i blocked the fiav on by twisting it in clockwise, but its not on the car. when my gasket comes in tomorrow ill switch them out and see if that doesnt change anything. as for the brake booster line, if i pinch that line and take it for a cruise wont i have weak brakes cause the line is pinched from the manifold to the booster? and i just found the brown plug, it was taped up behind the harness. i ground the metal connector, not the green one in the plug right?