2G Car won’t idle when hot

[98gstJames]

Alright so after finally getting clutch in my car I took it for a drive, started great and was idling at 850, let it warm up then started driving, once the car got hot and I’d try to come to a stop then the car just dies, I can start it right back up and if I’m holding the gas then it’ll stay on but if not then it dies. I thought maybe the isc but it checks out and I’m getting good numbers across the board so I’m not really sure what it could be, could the tps be doing this? I never could get it adjusted right I just stopped fighting with it and sent it but I’ve been wanting to get that right just had bigger issue. Any ideas?

 

[dwb]

Does it idle higher than 850 on a cold start? Do you still have AC installed, and if so, does it idle up when you turn it on? How about when you turn on a bunch of electrical things at once like headlights, blower, rear defrost - does it compensate for the load?

 

[98gstJames]

Does it idle higher than 850 on a cold start? Do you still have AC installed, and if so, does it idle up when you turn it on? How about when you turn on a bunch of electrical things at once like headlights, blower, rear defrost - does it compensate for the load?

Yes when it first starts up it sits at about 1200 then drops down to 850 after about a minute or so and yes I still have the ac installed but i didn’t have the ac on when I drove it and I had the headlights on but no ac or anything like that.

 

[Justin DuBois]

Close position switch? ISC is supposed to open on close throttle signal to prevent stall.

 

[chrysler kid]

Have you done a boost leak test?

Do you have any exhaust leaks at the downpipe?

 

[98gstJames]

Have you done a boost leak test?

Do you have any exhaust leaks at the downpipe?

I have not done a boost leak test since the rebuild but before I pulled the motor and had it running I had no boost leaks then which I know doesn’t mean anything since I took everything apart but I figured that probably wasn’t my issue, but I’ll do a leak test, and as far as the downpipe, it’s brand new so I know that’s not leaking.

 

[98gstJames]

Alright did a boost leak test tonight and I have a leak on the outer tb gasket, but wouldn’t it affect my idle when the motor is cold too? Why is it different results when the car is hot? I just don’t get why it dies only when it’s hot.

 

[ILLEAGLENY]

Turn the biss screw on the throttle body 1/4 turn counter clockwise. It is very sensitive. Turn the key. If it runs adjust the idle to 950rpm (better for the alternator, i have a chart with my after market alt that says it starts charging at 1100rpm. With warmer weather it may not pull enough vacuum to keep it running tune/cams/ect... Check fuel pressure(probably 43.5), Definitely should have the throttle set as well at stock voltage. When the engine is over 205* the ecm pulls a degree of timing. So should also make sure your initial timing is correct. A boost leak will make the engine run in different places on you tune. Definitely want to fix any leaks.

 

[DSMPT]

Alright did a boost leak test tonight and I have a leak on the outer tb gasket, but wouldn’t it affect my idle when the motor is cold too? Why is it different results when the car is hot? I just don’t get why it dies only when it’s hot.

You probably need a proper throttle body adjustment. To me it sounds more like the engine is missing air rather than sucking more air through vacuum leak when the engine gets hot.
You should check if the throttle plate is slightly open as it should. If it's fully closed, this may cause engine stall more often especially when the engine coolant temp gets hotter. While the coolant temp is lower, you are having more air coming in through FIAV, so the engine stall occur less. If this is the case, just adjust the throttle body properly by following the FSM and see if it would solve the issue.

 

[Stapl3]

Above is correct. Throttle plate is not cracked open correctly. 1200 cold then dropping to target idle is too low. Adjusting the BISS all you want and letting the ISC pick up the slack is wrong. Having the engine stall out during rev-down is wrong.

I have tuned this out in the past not knowing better and it's absurd looking back on it. You need to adjust the throttle stop screw, which doubles as a sensor. Factory it's 15/16 of a full turn clockwise from the plate closed. Feel free to play from there.

 

[99dsmer4g63]

The SAS is 1 1/4 turn from making contact on a 2g car. We went over this with this guy a couple months ago. I spelled out how to properly adjust the entire TB for him. Also told him to blt multiple times in that thread as well.


-Daniel

 

[Justin DuBois]

After the engine is warm, closed loop, check the ISC position using ECM Link. Adjust the BISS until the ISC floats around 30 at the target idle.

In order for the ECU to catch your engine from stalling, the ISC and Throttle close position switch needs to be working.

Is this a MAF setup or a SD setup? On MAF - be sure your BOV isn't venting to atmosphere.

 

[98gstJames]

Above is correct. Throttle plate is not cracked open correctly. 1200 cold then dropping to target idle is too low. Adjusting the BISS all you want and letting the ISC pick up the slack is wrong. Having the engine stall out during rev-down is wrong.

I have tuned this out in the past not knowing better and it's absurd looking back on it. You need to adjust the throttle stop screw, which doubles as a sensor. Factory it's 15/16 of a full turn clockwise from the plate closed. Feel free to play from there.

Omg, I completely forgot about this… welp that would make complete sense, it’s not sitting at the right position so when it’s hot it’s not allowing the air in, thank you all I can’t believe I forgot all about that little screw, I was messing with it way back when it was idling too high and I have a feeling I turned it out too far…

 

[98gstJames]

After the engine is warm, closed loop, check the ISC position using ECM Link. Adjust the BISS until the ISC floats around 30 at the target idle.

In order for the ECU to catch your engine from stalling, the ISC and Throttle close position switch needs to be working.

Is this a MAF setup or a SD setup? On MAF - be sure your BOV isn't venting to atmosphere.

I have a maf setup and my bov is recirculated so I know that’s good and I still need to adjust my tps bc I know it’s still not adjusted right.

 

[99dsmer4g63]

There is no point in adjusting the TPS until the SAS has been set properly.

1. Adjust SAS - 1.25 turns after making contact
2. Adjust throttle cable
3. Adjust TPS. There is many threads how to do this properly.

-Daniel

 

[98gstJames]

I think I got everything adjusted good now.

I let the car get up to temp and drove it around the shop and it didn’t die when I came to a stop so think it’s all good there, although I’m not 100 percent sure because I went to go for a test drive, I started the car and when I pressed the clutch in, my brand new OEM slave cylinder broke on both ears and was just left hanging by the line, so I’m just gonna pull the seal and spring out of the new one I got and put it in the old one that came with the car. I’m assuming it came from the factory so I’m gonna try that one out.

Comparing both of the OEM ones, the new one I got is clearly made way more poorly so that’s just a shame. I tried to get a warranty done but it was a lot of BS and they wound up telling me they can’t warranty it because my title is “branded” so I’m out 100 bucks on a part that wasn’t even on the car for more than two weeks. I didn’t even use it the whole time it was on because of the throttle issues so it’s just a whole mess.

I’ll let you all know if my throttle is good once I figure out this slave cylinder ordeal. Fun stuff

 

[Stapl3]

After the engine is warm, closed loop, check the ISC position using ECM Link. Adjust the BISS until the ISC floats around 30 at the target idle.

To compound on this. The ISC has a working operation from value 0-120. The idea of getting it to 30 as a starting point is because it still has some ability to close, but more ability to open. Most of the time, it is going to open to allow more air past the plate rather than close, so you start at 25% of it's working range. When you're aiming for that 30 value, have the radio off, headlights off, AC off, etc. This is important. Then, if you then turn on the headlights, blast the radio, move the power windows, move the power seatbelt, kick on the AC, etc etc, the ISC can open to allow more air in thus bumping up the idle to compensate for the load.

Do not pull your hair out getting the value at exactly 30s. Around 30 is perfectly fine.