98 SS Rich at Idle but not with A/C on
08-19-2019, 07:52 AM
#1
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98 SS Rich at Idle but not with A/C on It's a 1998 SS with 65k miles. Turbo @ 10 lbs. Supporting fuel mods and meth injection, but no internal engine mods. Dyno tuned to ~500 rwhp.
It runs excellent and has the whole time I've owned it, just gets a little stinky at idle. The wideband shows 14.5 - 15.1 while cruising, light throttle to coasting; and 10.6 - 11.1 at WOT.
At idle it seems to stick around 12.2 - 12.7:1. At idle with the A/C on it comes back up to 14.6 - 14.9:1. Turn the A/C off and it dips back down.
The guy I bought the car from said they were having trouble with the AFR's on the dyno and ended up dumping the maf and using a map/speed density tune. It was tuned in 2005 by a very small (now defunct) shop in Midland, MI before the car was stored for 10+ years.
I love the car and it's a blast, this is just a nuisance issue more than anything. Thanks for any input.
Ferg
It runs excellent and has the whole time I've owned it, just gets a little stinky at idle. The wideband shows 14.5 - 15.1 while cruising, light throttle to coasting; and 10.6 - 11.1 at WOT.
At idle it seems to stick around 12.2 - 12.7:1. At idle with the A/C on it comes back up to 14.6 - 14.9:1. Turn the A/C off and it dips back down.
The guy I bought the car from said they were having trouble with the AFR's on the dyno and ended up dumping the maf and using a map/speed density tune. It was tuned in 2005 by a very small (now defunct) shop in Midland, MI before the car was stored for 10+ years.
I love the car and it's a blast, this is just a nuisance issue more than anything. Thanks for any input.
Ferg
08-19-2019, 08:31 AM
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also, it has 60 lb. injectors. I've read on the sticky here that a richness issue can result when the minimum transient pulsewidth table is not added or something like that. Do I just need to take it to a tuner?
08-30-2019, 08:15 AM
#3
My first guess is that when the AC is switched on the engine gets more load on it, and the map cell changes. When this happens, that cell is probably setup a little differently causing the idle afr to change.
Is this a SD tune do you know for sure? Any local tuner should be able to fix that pretty easily.
Is this a SD tune do you know for sure? Any local tuner should be able to fix that pretty easily.
09-01-2019, 12:35 AM
#5
My first guess is that when the AC is switched on the engine gets more load on it, and the map cell changes. When this happens, that cell is probably setup a little differently causing the idle afr to change.
Is this a SD tune do you know for sure? Any local tuner should be able to fix that pretty easily.
Is this a SD tune do you know for sure? Any local tuner should be able to fix that pretty easily.