1985 Bog when revving in open loop
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
1985 Bog when revving in open loop
Hey guys, I have a 1985 corvette with quite a few mods, but when it was stock it had this problem too. The car will bog down when you rev it while it is cold in open loop. When you drive it during open loop it is very annoying because the car bogs during acceleration and you have to give it more gas to go.
Any ideas as to why this is happening? I guess let's think of some items that are active during open loop! Thanks for any help!
Any ideas as to why this is happening? I guess let's think of some items that are active during open loop! Thanks for any help!
Race Director
Joined: Apr 2003
Posts: 17,699
Likes: 1,667
From: moraga ca
If you have a wideband or a scanner, you can tell if you are running too rich or lean. You could try getting an adjustable fuel pressure regulator and increasing the fuel pressure to see if that helps. It sounds like you are running lean. A tune might put you in the ballpark.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
If you have a wideband or a scanner, you can tell if you are running too rich or lean. You could try getting an adjustable fuel pressure regulator and increasing the fuel pressure to see if that helps. It sounds like you are running lean. A tune might put you in the ballpark.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Good idea! The car is at my father's shop right now so I will check tomorrow, and I'm assuming probably a lean reading. I have a video too of it.
https://db.tt/nxslbxmx
It may be kind of hard to tell in this video, but it does not respond right away.
https://db.tt/nxslbxmx
It may be kind of hard to tell in this video, but it does not respond right away.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
And really? No one else has ever commented on the idle rpm and I always thought it was fine. It used to idle at 900 - 1000 RPMs because the previous owner messed with the throttle adjustment screw. After I drew the screw all the way back it idled like garbage until I reset the tps.
Also, my timing is set at 12 degrees BTDC. Checked many many times.
The tune is also set for 12 degrees. My tuner says he doesn't see anything in the data logs that would cause that. And it can't be something I did with the mods because it was like that when it was stock.
Safety Car
Joined: Sep 2001
Posts: 4,153
Likes: 553
From: Glenbeulah Wi
You need to lool at your WB when it bogs, it is either lean or rich, I suppect lean. Your tuner needs to add more acceleration fuel (assuming it is lean) to eliminate the bog. (I am assuming you do not have a mechanical problem like low fuel pressure or failed throttle position sensor)
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Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
You need to lool at your WB when it bogs, it is either lean or rich, I suppect lean. Your tuner needs to add more acceleration fuel (assuming it is lean) to eliminate the bog. (I am assuming you do not have a mechanical problem like low fuel pressure or failed throttle position sensor)
Safety Car
Joined: Sep 2001
Posts: 4,153
Likes: 553
From: Glenbeulah Wi
It sounds to me like your tuner needs to spend more time figuring out the problem and either fixing the mechanical issue or programing it out. (All this takes time and money)
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Okay so I revved it this morning, and it went very lean to the max reading of 22.4:1. It also like backfired and stalled once. Also I should add that some times it takes two tries to start it when it is cold.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Okay, well I set the timing down to 10 degrees BTDC instead of 12, and I got rid of my idle surging for now.
Hopefully this will affect the cold starting problem.
And, the AFR readings at WOT were low 13s, since I did the timing change, the power is similar, but at WOT the readings are mid to high 13s now.
I called TPIS and they said that 12.5:1 is the best.
Hopefully this will affect the cold starting problem.
And, the AFR readings at WOT were low 13s, since I did the timing change, the power is similar, but at WOT the readings are mid to high 13s now.
I called TPIS and they said that 12.5:1 is the best.
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
what is your temp sensor telling the ecm what the temp is reading? These reading need to be real close to what the engine temp really is or you will have lean and rich conditions also
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
The temp sensor is new and the system is functioning properly. I tested it when after I did the engine mods in the beginning because the car was over heating because the computer was going into limp mode. The place that soldered my adapter messed up but they fix it for free. Free shipping too. 