drcolt
20+ Year Contributor
- 76
- 12
- Jun 27, 2003
-
Toronto,
ON, Canada
I'm trying to figure out why recently my idle vac went from 14in to less than 10.
The most recent change was a rad change.
After a blt and a compression test(140s when cold, 150ish when hot.) No leaks .I figured to change the isc to a new 91 ISC which I have as spare.
Motor is 6 bolt , stock except for BC 264/272 CAMS, evo3 16g@16psi, with link v3 and 3"GM MAF AND FIC 750. After the cams were added and all bolt-ons,vac. went from 19 down to 14. My tuner said that is typical. At the time I cleaned out the tb, new shaft seals.isc and FIAV seals. But I just left the old ISC on and never messed with the FIAV. In the winter the motor revved up high during warm up until it reached warm temps, dropped in rpm and ran a bit rough and once fully hot it settled steady at the set 1000rpm.
So I removed the TB to inspect it. The fiav spring physically compresses but I can't turn the adjusting cap. I tried another TB and tried was able to crack the FIAV loose.
Could the problem be the FIAV?
I'm going to try another 90 TB ,I have spare new seals. May as well rebuild the spare TB.
Could the FIAV cause a low idle and low vacuum situation?
Also going to be checking the egr.
Motor still has emissions in place.
The most recent change was a rad change.
After a blt and a compression test(140s when cold, 150ish when hot.) No leaks .I figured to change the isc to a new 91 ISC which I have as spare.
Motor is 6 bolt , stock except for BC 264/272 CAMS, evo3 16g@16psi, with link v3 and 3"GM MAF AND FIC 750. After the cams were added and all bolt-ons,vac. went from 19 down to 14. My tuner said that is typical. At the time I cleaned out the tb, new shaft seals.isc and FIAV seals. But I just left the old ISC on and never messed with the FIAV. In the winter the motor revved up high during warm up until it reached warm temps, dropped in rpm and ran a bit rough and once fully hot it settled steady at the set 1000rpm.
So I removed the TB to inspect it. The fiav spring physically compresses but I can't turn the adjusting cap. I tried another TB and tried was able to crack the FIAV loose.
Could the problem be the FIAV?
I'm going to try another 90 TB ,I have spare new seals. May as well rebuild the spare TB.
Could the FIAV cause a low idle and low vacuum situation?
Also going to be checking the egr.
Motor still has emissions in place.
