won't keep idle

ThunderDave

Registered User
After getting my 89 SC running, I found out it had ported heads. With the other mods I had, it was running out of gas at WOT. I couldn't afford to upgrade fuel pump and injectors or get a tune, so to keep from having a lean condition, I decided to put the stock throttle body and mafs back on to cut down on the amounbt of air intake and correct the problem, until I can afford to do those upgrades.

Now when I crank it up, the idle drops and will stall if I don't keep my foot on the gas a little. Is it possible that I got the TPS on the throttle body wrong or could it be a vacuum leak or maybe even something with the mafs?

Haven't had time to check it out yet, but thought if I could get some ideas on what it most likely could be.

Thanks!
 
Did you disconnect the battery to let the computer do the re-learn process? If not, it may be trying to control the fuel/air like it still had the larger components installed. If you did disconnect the battery, it is not unusual for the idle to stumble some during the re-learn.
 
Larry, I didn't disconnect the battery. I had a 70mm throttle body and 73mm mafs. I'll try that and see if that does it. Thanks! BTW, driving it to work last night, it didn't seem to be dying out at WOT, so I guess the changes helped some.
 
David -
Due to the change in MAF and TB, try disconnecting the battery for 10 minutes to wipe out codes and allow the EEC to reset. Let the EEC relearn the start settings and see what happens. You may need to adjust the screw at the IAC on the TB to smooth out the idle.

Mark
'93 SC auto
'95 SC 5spd
 
I disconnected the battery like Larry suggested and when it cranked back up, it was perfect idle. Thanks Larry. :) I'm wondering though if it would have been ok to leave the 70mm tb on it and not have the lean condition, since the mafs meters the airflow, the bigger tb would have just allowed the air to flow better, right?
 
Not sure...

I don't think you would have any problems having the larger TB on the car, but I don't think there would be any advantage either. You are only going to get the volume of air to the TB that can be passed through the MAF, so unless the stock TB has a smaller diameter opening than the MAF, I wouldn't go through the trouble of swapping them out. (all of this is based on my reading other posts from folks trying to use bigger MAF's and TB's...)
 
Larry, the stock mafs is 70mm and the stock throttle body is 60mm. It's a good bit smaller in diameter. Seems like if both were 70mm, it would work out nicely. It doesn't have the dying at WOT now, like it did with the other parts on there, so I might see how it does with the bigger throttle body just to see. I had the throttle body for sale, but seems no one wanted it.

Oh well. Thanks for the info and help.
 
the stock mafs is 70mm and the stock throttle body is 60mm

I think it would be worthwhile to use the larger TB. It would seem to me that having them as close to the same size as possible would be more efficient. But, like I said, I'm no expert in this area (or any other area for that matter)...
 
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