1G TB shaft seal leak bad enough to prevent setting BISS properly?

[foxfan88]

I have a leak at the TB shaft seals. When i perform a BLT its definatly a noticeable hiss, but its nothing crazy just shooting out real hard at the moment.

Ive notice that when i ground the ISC pin on the diag port (to center ISC), i cant get the idle down the 750 like it sould be, i can only get it to like 900 or so.

Would this small leak at the TB seals be getting enough air to cause this? ive ordered new seals from mach V, but i am trying to figure out if i should still be looking.

 

[LiquidX]

I'd fix all of your leaks before you try adjusting the idle. If you have a leak, it's unmetered air entering the system and altering the fuel trims which will mess your idle up.

 

[carbide]

Are you grounding that diganostic pin properly? It should be grounded right to the battery, not to the ISC plug. Sorry if you meant that differently. If it's not grounded nothing you do will change the idle.

 

[steve]

Ive notice that when i ground the ISC pin on the diag port (to center ISC), i cant get the idle down the 750 like it sould be, i can only get it to like 900 or so.

Are you grounding that diganostic pin properly? It should be grounded right to the battery, not to the ISC plug. Sorry if you meant that differently. If it's not grounded nothing you do will change the idle.

He should be grounding the Mode pin on the DLC connector along with the check timing connector under the hood to set the BISS. This steps the ISC to it's default position (not centered) for idle.

 

[foxfan88]

Yeah i mean grouding the PIN to ground not the ISC.

I wasnt aware that it wasnt centering the ISC.

I had my car apart (jumped time) i replaced the TB shaft seals.
Have done a few BLTs and i am confident its sealed good, i found a leaking PCV but i fixed that.

I do ground the timing pin near the battery. But when i ground the ISC pin under the dash, i dont really hear the idle change at all really (like the ISC didnt move.)

I then just set the BISS to that, got it to 750ish, buttoned it up and drove it. the car idled great the ISC seemed to work great. Worked and bumped the idle up a bit when turning the AC on. The BISS was almost 2 full turns CCW from the bottom.

But after a few hours the car would start idling higher, around 1200 or so, and would get the occasional surge.

I turned the BISS in some, now its idling like normal (around 750) but the BISS is only maybe 1/2 a turn CCW from the bottom. I thought it should be out more than this.

The idle still works fine from what i can tell.
Also somtimes the car will idle a few hundred rpm higher around 950-1000 for no apparent reason.

I dont know if something is amiss here or not.

FWIW when i was putting the car back together after messing with it some last week, i went to screw down the alternator eyelet, and i didnt realize the battery was still connected. i accidently touched it to the alt case, got a nice spark show for a split second. Got the car running and the seatbelts wouldnt work unless the key was on, and the door dinger sounded real scratchy.

Also the idle was too high and surging( when it was set properly before and idling fine the day before. and hadnt messed with anything.)

I found the 80 amp ALT fuse was blown on the passenger side, i fixed that and my idle went to normal and the seatbelts and dinger are fine now. The car ran performance wise just fine with the fuse blown otherwise.

Perhaps i messed up an ISC driver? (something in this circuit apparently affected it since it was honky after the fuse blew.) The ISC drivers were known to be good a month ago because steve had my ECU for repair a month ago.

i tested the ISC coils and they all test around 30ohms cold. So thats good.

Like i said the the car seems to idle correctly and work good with the AC and all. Only strange things is occasionaly it will idle a few hundred RPM higher, also the idle seems to bog down slightly when the cooling fans kick on, i am not sure if the ISC is supposed to raise the idle for the engine fans or not. And the fact i cant really hear the ISC go to default when i ground the diag pin. Had to pretty much guess at the BISS adjustment.

 

[steve]

Yeah i mean grouding the PIN to ground not the ISC.

I wasnt aware that it wasnt centering the ISC.

I had my car apart (jumped time) i replaced the TB shaft seals.
Have done a few BLTs and i am confident its sealed good, i found a leaking PCV but i fixed that.

I do ground the timing pin near the battery. But when i ground the ISC pin under the dash, i dont really hear the idle change at all really (like the ISC didnt move.)

So a couple of potential errors or misunderstandings here already.

1. Surging is caused by too much air getting past the throttle butterfly. That can be from a leak that a pressure test can identify or from problems related to touching the throttle body like during replacing the shaft seals. For example, the factory uses a sealant on the back side of the butterfly to close the gaps between the plate and the throttle bore. If you cleaned the plate spotless during process you just messed up the TB.

The Idle Position Switch on a 1G or Fixed SAS on the 2G TB sets the position/limit of the butterfly at idle. The adjustment of these is critical to getting a good idle and the FSM warns not to touch the factory settings. If you touch it and get it wrong the throttle can stick or be too far open. The difference between the two is tiny as far as the adjustment goes.

Neither of these problems would show up when checking for leaks but both can cause surging because too much air gets past the butterfly. It's also important that the throttle cable not pull the throttle open. There should be slack in the cable when the throttle is closed.

2. There is no ISC pin under the dash. Your confusing it with the mode pin on the diagnostic connector. Grounding it puts the ECU into diagnostic mode. Grounding it while the timing adjust pin in the engine bay is grounded puts the ECU into Set BISS mode. This is why you can't set the timing while a datalogger is attached because wind up in set BISS mode.

I then just set the BISS to that, got it to 750ish, buttoned it up and drove it. the car idled great the ISC seemed to work great. Worked and bumped the idle up a bit when turning the AC on. The BISS was almost 2 full turns CCW from the bottom.

But after a few hours the car would start idling higher, around 1200 or so, and would get the occasional surge.

I turned the BISS in some, now its idling like normal (around 750) but the BISS is only maybe 1/2 a turn CCW from the bottom. I thought it should be out more than this.

The idle still works fine from what i can tell.
Also somtimes the car will idle a few hundred rpm higher around 950-1000 for no apparent reason.

I dont know if something is amiss here or not.

Unless both pins were grounded you were adjusting the BISS and the ECU was moving the ISC to try and correct for the changes you were making up to the point where the ISC hit the limits of it's adjustment and then the idle would change.

This also assumes that the ECU knows that the car is idling, not just moving slowly. The IPS tells the ECU that the throttle is closed and the VSS tells it that the car isn't moving.
The IPS needs a good ground to the throttle body on a 1G (It's internal to a 2G TPS) and there is a ground strap on the top of the TB running to one of the mounting bolts into the intake manifold to ground the IPS. The IPS grounds the signal from the ECU when the throttle is closed and lets the signal float when you open the throttle a little.

FWIW when i was putting the car back together after messing with it some last week, i went to screw down the alternator eyelet, and i didnt realize the battery was still connected. i accidently touched it to the alt case, got a nice spark show for a split second. Got the car running and the seatbelts wouldnt work unless the key was on, and the door dinger sounded real scratchy.

Also the idle was too high and surging( when it was set properly before and idling fine the day before. and hadnt messed with anything.)

I found the 80 amp ALT fuse was blown on the passenger side, i fixed that and my idle went to normal and the seatbelts and dinger are fine now. The car ran performance wise just fine with the fuse blown otherwise.

Perhaps i messed up an ISC driver? (something in this circuit apparently affected it since it was honky after the fuse blew.) The ISC drivers were known to be good a month ago because steve had my ECU for repair a month ago.

i tested the ISC coils and they all test around 30ohms cold. So thats good.

Like i said the the car seems to idle correctly and work good with the AC and all. Only strange things is occasionaly it will idle a few hundred RPM higher, also the idle seems to bog down slightly when the cooling fans kick on, i am not sure if the ISC is supposed to raise the idle for the engine fans or not. And the fact i cant really hear the ISC go to default when i ground the diag pin. Had to pretty much guess at the BISS adjustment.

I suspect your BISS is misadjusted or the IPS isn't working right. If you have a logger you can look at the ISC steps and they should be around 10-20 when the car is idling at operating temps.

 

[foxfan88]

So a couple of potential errors or misunderstandings here already.

1. Surging is caused by too much air getting past the throttle butterfly. That can be from a leak that a pressure test can identify or from problems related to touching the throttle body like during replacing the shaft seals. For example, the factory uses a sealant on the back side of the butterfly to close the gaps between the plate and the throttle bore. If you cleaned the plate spotless during process you just messed up the TB.

The Idle Position Switch on a 1G or Fixed SAS on the 2G TB sets the position/limit of the butterfly at idle. The adjustment of these is critical to getting a good idle and the FSM warns not to touch the factory settings. If you touch it and get it wrong the throttle can stick or be too far open. The difference between the two is tiny as far as the adjustment goes.

Neither of these problems would show up when checking for leaks but both can cause surging because too much air gets past the butterfly. It's also important that the throttle cable not pull the throttle open. There should be slack in the cable when the throttle is closed.

2. There is no ISC pin under the dash. Your confusing it with the mode pin on the diagnostic connector. Grounding it puts the ECU into diagnostic mode. Grounding it while the timing adjust pin in the engine bay is grounded puts the ECU into Set BISS mode. This is why you can't set the timing while a datalogger is attached because wind up in set BISS mode.



Unless both pins were grounded you were adjusting the BISS and the ECU was moving the ISC to try and correct for the changes you were making up to the point where the ISC hit the limits of it's adjustment and then the idle would change.

This also assumes that the ECU knows that the car is idling, not just moving slowly. The IPS tells the ECU that the throttle is closed and the VSS tells it that the car isn't moving.
The IPS needs a good ground to the throttle body on a 1G (It's internal to a 2G TPS) and there is a ground strap on the top of the TB running to one of the mounting bolts into the intake manifold to ground the IPS. The IPS grounds the signal from the ECU when the throttle is closed and lets the signal float when you open the throttle a little.



I suspect your BISS is misadjusted or the IPS isn't working right. If you have a logger you can look at the ISC steps and they should be around 10-20 when the car is idling at operating temps.

Yeah i know what causes surge. Thats why i was confused since my BISS is almost fully turned CW to get it to idle correctly.

As for cleaning the throttle. I did wipe it off with shop towels, but i am pretty sure i didnt use any carb cleaner or similar products (didnt have any at the time.) I wasnt aware of this though, so i dont know if its messed up like you say. It definatly makes sense how too much air would get by if it was meant to seal originally.

As for the IPS i had the thottle body off when i replaced the seals, but i didnt touch the IPS or move it or anything.
I also have a ground wire coming from the small threaded hole on top of the TB straight to the firewall (same screw where the intake manifold grounds to.)I also did check the IPS with a meter checking continuity to ground with the throttle shut and it worked fine.

The throttle cable is good i am pretty sure, i do have the slight slack you speak of.

And by "ISC pin" i mean the mode pin, i didnt know what it actually was called, just that it needed to be grounded to set the BISS. Also i do ground the timing set pin near the battery before i ground the mode pin under the dash. Its just i dont hear the idle change like the ISC has moved (if it was off.) I can definatly hear the idle change when i ground the timing set pin, the idle will drop down some when the timing locks to the base timing.

I do remember hearing a change before though i am pretty sure, thats why i am wondering if i potentially screwed something up when i accidently blew that ALT fuse. It does sort of seem like the ISC work working against me. I could slowly turnt he screw the idle wouldnt really change. Perhaps when i ground the mode pin i am not grounding it good enough. What i have been doing is unscrewing one of the small ground screws behind the kick panel and tightening it down with a bare wire sandwiched in, the other end has a small alligator clip which i hook to the mode pin, I could try going straight to the battery.

I'm pretty sure the VSS is operating correctly. the car will idle up slightly if the car is moving, and drop down as soon as its completely stops.

At this point i dont have any sort of logger, this car is a just a DD at this point, not even a boost gauge yet hehe. I dont know if its worth it for me to buy a logger. If i decide to start modding more i would like to get dsmlink.

Like I said the ISC system seems to be working good, it idles up on cold starts and will raise with the AC engaging and idle up if the car moves etc etc. I dont know of what other states that i can see if the ISC is working, is it possible something like a driver is screwed up? In an earlier post i stated the engine rpms drop ever so slightly (enough to change the exhaust tone) when the coolant fans kick on, i am not too sure if the ISC is supposed to raise the idle with more load on the charging system(due to fans?) Perhaps you can elaborate on all the things the ISC works with/reacts to.

Thanks for the help.

 

[steve]

Perhaps you can elaborate on all the things the ISC works with/reacts to.

Start by reading the 1G DSM Technical Manual. http://www.dsmtuners.com/forums/fre...tions/344490-download-1g-service-manuals.html