[Doggins]

Hey yall,

So i'm having a little some trouble hunting down this throttle problem. The car is acting strange at idle in that it will go up and down between like 200-800 rpms getting worse and worse until it stalls on the low side. Also, at low amounts of throttle the car is hanging and when i drop my foot past what i imagine is WOT the car suddenly lurches and gets all its power back...weird haha...when its decelerating with the car in gear i hear like a sucking sound from like 2200 rpms to 1300. wtf.

I've already replaced the TPS and the IAC. I've searched for a vacuum leak from the throttle body hoses but cant seem to find one. Any ideas?

I have an SCT scanner so i can run a data log, only problem is i have no idea what i would be looking for as i just bought the thing and am still trying to understand all the parameters.

Heres a list of mods just in case:
Full pi swap to include the intake.
Heads were ported prior to the swap
Reground pi cams
BBK shorty headers
All the bolt ons (accufab plenum, 70mm PP TB, JLT cai, udp, etc.)

[1996 GT]

o2 sensors will cause that, ask me how i know.

[OptionalStang]

id say mafs is dirty or shot..

[Doggins]

is there any way to test these before replacing them, especially o2 sensors, they are a bit pricey i think?

[1996 GT]

Showing a check engine light? If so get your self a code reader.

[Doggins]

no check engine light haha

[bigjohnstud4200]

Originally Posted by Doggins is there any way to test these before replacing them, especially o2 sensors, they are a bit pricey i think?

O2 Sensors are about $40 a piece on rockauto for motorcraft. How many miles?

[Doggins]

not sure if they are original, but if they are around 130,000

[1996 GT]

Originally Posted by bigjohnstud4200 O2 Sensors are about $40 a piece on rockauto for motorcraft. How many miles?

^This, i did two up stream ones to my door for 86$ taxes in.

[OptionalStang]

try atleast cleaning your mafs with mafs spray..its 7 bucks at any autoparts store..

[sharkbait]

Well aftermarket cams can cause a rough idle and for it to stall.

Have you had a custom tune made yet?

[drakkhen20]

vacum leak. check your hoses and intake tube. the up and down idle is called "searching". that means the MAF sensor is going back and forth searching for the right efficient reading to idle steady. go clean it as suggested and see what happens and check your hoses. also consider the two up-stream o2s. its the very first o2s the are before the cats closest to the exhaust manifold/header. is the engine completely stock ? what after market parts do you have installed or recently installed?

[Doggins]

Will clean maf tomorrow...is there anyway to tell via the sct datalogger if the o2s or the maf are bad? As for mods I listed the major ones in the first post....no recently installed as of this problem.

[OptionalStang]

usually if an o2 sensor is bad or going bad it throws a engine code..just my experiance..just get that mafs spray cleaner and clean the mafs as well as you iac, its only 2 bolts to remove the iac, make shur to clean that spring very well in it, i even used grease cutter to bust through that shit in it.

[drakkhen20]

you might need a tune man. or a new tune. trace your vacum lines, you might have one on backwards. your idle air control vavle might be a calprit to consider also.

[Doggins]

Cleaned the maf today...no change. The IAC and the TPS are brand new as of last week. the car is hesitating as i bring the pedal down and then when it hits WOT it surges forward. Then when i come to a stop the idle starts pacing and bottoms out stalling the car....no check engine lights either....lol im lost

[1996 GT]

Originally Posted by OptionalStang usually if an o2 sensor is bad or going bad it throws a engine code..just my experiance..just get that mafs spray cleaner and clean the mafs as well as you iac, its only 2 bolts to remove the iac, make shur to clean that spring very well in it, i even used grease cutter to bust through that shit in it.

This^

Although check behind the dash, for all you know your CEL bulb may be burnt out or removed due to the person owning before you getting sick of looking at the light.

[Doggins]

IAC is brand new so its clean...also i have an sct code reader and im not showing any new codes, i am showing lean on bank 2 and rich on bank 2 though not sure if they are old or new codes..if it was a bad o2 sensor its a different code right?

[1996 GT]

Thats an o2 sensor code bud.

[Doggins]

I thought those codes were base don the trim being out of whack...i.e. i need a new tune, no that the o2 sensors have crapped out. This problem with the idle surge at WOT and stalling out when stopped is fairly new. Ill try replacing the o2s either tommorow or some time next week.