90 Cutlass fast idle poor gas mileage

[cambeco1]

1990 Cutlass Ciera 3300 --I have unpluged the MAS nothing happens runs fine so I can't tell if thats bad. I have disconected the the battery tried to check the codes but the check engine light just stays on. The idle seems to be stuck at 1500 rpms. Can anyone HELP

[Rayzor32]

whats a mas? maf sensor? it could be the IAC is stuck, try cleaning it out w/ solvent and if that doesnt work grab a couple from the boneyard. Also make sure the idle screw isnt all the way up

the way you check the codes is to jump a and b terminals on the aldl port with a paperclip w/ the ignition "ON" it should flash a code 12 3 times then any codes that are stored

[cambeco1]

First thank for the reply. I’m sorry I meant Mass Air Flow. I did just that using a paper clip shorting pins A & B and the service engine light stays on and never goes out. This 90 Cutlass has 6 fuel injectors it has no idle screw that I can find. I will try cleaning the IAC this thing is getting about 5 miles to the gal. I had an 89 Chevy truck throttle body that had a problem with the check engine light and ran bad. After I changing about everything I replaced the computer and it fixed everything.
Thanks again.

[Rayzor32]

the throttle plate rests on the idle screw, youll see it if u move the throttle up. Were you testing the codes with the car running? Cos the key is sposta be in the the on position u know the spot before you turn it again to start cranking. That is some really poor gas mileage wow, you check other basic stuff like plugs, wires, air cleaner, etc. Might throw some fuel injector cleaner in there but thats not gonna fix your problem but i usually do it anyway.

But my bet is a bad IAC. Or even possibly a bad TPS also, id check that too. I'd also clean the maf sensor too, youre probably going to need penatrating oil and needle nose vice grips to get the screws off on most of the sensors or at least i did

[cambeco1]

Yes, with engine off short a&b turn key to on, (not start) light comes on and stays on.
That’s one puzzle. With engine running I unplugged the MAF nothing happens. I’m thinking it should run ruff or stall, I’m not sure. TPS throttle positioning switch ?

[Rayzor32]

yeah tps throttle position sensor. No if u unplug the maf it should either run the same or the idle should increase.

Is the check engine light on when the car is running? Have u tried unplugging the battery to reset it?

I would test the tps, throw a voltmeter on the a and b leads of the tps with ignition on, it should between .4-.7volts at idle and read 4.5+V at WOT. You should notice an improvement with the clean IAC, if it doesnt fix it youll probably need a new one (junkyard=free). Thats my guess, how/when did the problem with the idle start happening? cos IAC controls the idle and its probably stuck in the closed position. but try all that and see what that does.

[cambeco1]

Ok, yes the check engine light is on when the car is running I reset several times by disconnecting the negative battery terminal but the light stays on. About two month ago it wouldn’t start it was like it was flooded waited and hour and it started rite up but it idled
fast 1500rpm and stays there.
FYI (this car only has 53k miles on it and my son uses it for work)
it’s got new plug ,wires air filter, clean oil runs great but it's just drinking gas.
I will try what you have suggested and go from there

[xeroinfinity]

The idle is not adjustable on these , if you mess with the screw thats coverd up you will only make problems worse. Idle is controled by the Ecu and the IAC. Cleaning sometimes helps, a new one only costs about $10-12.

Fast idle coule also be a vacum leak either a small hose or the intake.

Poor mileage.....how many miles on this 3.3L, 53k !?!
You sure that's not 153,000 ??

If you havent given it a tune up, plugs & wires and replace your O2 sensor, that should help MPG and idle issues.

and Welcome to AF cambeco1.

[Rayzor32]

i got 6 digit odomoter on my 91. you can adjust the idle screw all it is is a stop, MAF sensor will detect any air coming in, IAC, TPS will all read the adjustments. you have to move the screw when u adjust for minimum idle air.

[cambeco1]

actual 53k actualy owned by an old lady