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Surge With biss in

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01QuadDak

15+ Year Contributor
157
0
Jan 6, 2004
Glenolden, Pennsylvania
Okay, heres the scenario--
Idle surge(yaaayyy another noob post)
But heres the kicker-
Disconnect the throttle switch, and the idle goes to 1500 RPM, but the biss screw is ALL THE WAY IN!
If i turn the biss out, the idle increases, but i cannot get it any lower than 1500 RPM.
New ISC, coils all test okay.
FIAV blocked off with a plate, however I have holes drilled in it to allow air for the ISC to work. ****Possible problem****
No noticable vaccuum leaks, i sprayed the engine down with 2+2/starter fluid with it running and the RPMS stay rock solid(with the idle switch disconnected).
Fuel pressure is at 40 at idle, new injectors, and a fresh engine.
I am thinking that one of my ports inside the throttle body is leaking, where the blockoff plate meets the two halves, and thats is giving me my problem.
Any takers on this theory?
 
Plug those holes you drilled for a little to see if that's the problem. If not, do an actual boost leak test.
 
Are you jumping the ISC correctly? You can't just turn it while its running like that, unless your MAF is unplugged.
The Ecu fights your biss adjustment.
So either
Unplug the MAF.
Or jump the ISC (Find out how on vfaq.com)
I hope this helped :)
Best of luck.
 
Make sure you are adjusting the BISS correctly...it is incorrect if you are just turning it in and out. You have to tell the ECU to leave your ISC alone while you adjust it. It's simple, you ground to things and your ISC will center itself. Check this out if you think it will help:

:laser: 1G BISS Adjustment
 
I tried using my dsmlink to adjust the idle, using the ground diagnostic and ground timing features, but it was surging during that process. Perhaps the link doesn't mesh with the 90 ecu as well as the later ones, or mebbe my o2 sensor is bad.
 
I tried using my dsmlink to adjust the idle, using the ground diagnostic and ground timing features, but it was surging during that process. Perhaps the link doesn't mesh with the 90 ecu as well as the later ones, or mebbe my o2 sensor is bad.

Yeah, adjust it the old standard way, let us know what happens.
 
Oh yeah, it will still surge with the ISC disconnected.

Of course it will.
It sends the ECU into loop back mode. Did you fully read this link
1G BISS Adjustment
Read that, and do exactly what it says.
It seems that you aren't understanding what to properly do, you do not unplug the ISC to adjust the BISS.
 
I wasn't adjusting the biss like that, i was just going through the motions of figuring out what was wrong. I haven't had the chance to get to the car since friday night, I was just posting up all the information that i had found while going over the car.
 
It still surges with the diag and the timing terminals grounded.
It stopped surging when i hooked up the timing ground, then started surging again with the diag hooked up.
The ISC position on dsmlink was around 4-9 counts, should be around 30, so the isc is trying to stay closed, I'm gonna have to pull off the throttle body and check the gasket inside of it, I dunno where else it could be leaking from.
RTV on the intake manifold,
MAFT with silicone couplers throughout, so its a pretty short run between maft and TB.
MAFT zeroed out.
 
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