d_illman

Ladies and Gents,
Hoping someone could aid me in some technical advice
I recentley picked up a 1999' Trans Am with an LS1.
The car is completely stock except for Ram air has been added with a K & N kit.

Car has a major hesistation when accelerating, mostly betweeen 2-3rpm.
It also seems to be a lot worse on a hot day and runs way better on a cool evening.

Smog pump is siezed i think (ordered new one) and will be replacing it. Would the smog pump not working bring these codes up ?

here are the codes the car is bringing up (bare with me)
P0137 - 02 Sensor low volt bank 1
PO157 - 02 sensor low volt bank 2
po410 - secondary air injection
po412 - secondary air injection switch
po418 - secondary air injection system control circut
Po507 - idle air control system RPM higher then expected
P1415 manufacture specific


Car can not break loose the back tires even if you try to brake torque.
Very slow and no power in the bottem. ANY HELP would be greatly apprecaited.

RPM WS6

iTrader: (3)

The AIR system stuff can be deleted if you don't need it to pass emissions. I don't know what the requirements are in Canada though. The air pump really shouldn't be causing driveability issues, unless maybe it was running constantly and thus causing overly lean O2 readings once in CL (closed loop). If it's not running at all, then I don't see how it could do any harm.

The P0507 means that something is preventing the PCM from keeping control of idle speed. PCM commanded idle rpm is achieved via constant adjustments of the IAC (idle air control) motor. If the motor is clogged, not responding properly to PCM inputs, etc., then it won't be able to deliver proper air flow (could be too much OR too little) for commanded idle speed. But the IAC is not always the problem, sometimes it will be working fine but some other outside source of air will cause idle speed to increase beyond the limit for which the IAC can compensate. This would be some sort of vacuum leak, possibly in the PCV system, intake gaskets, EGR or EVAP, etc. You'd need a scanner to see the IAC pintle position (0 is closed), and if it is 0 but the idle is still too high then you have a vacuum leak somewhere. Elevated LTFT (long term fuel trims) can also be an indicator of a vacuum leak, but not a guaranty.

You mentioned some hesitation in the 2-3k rpm range. This can often be due to a dirty MAF, something which is common when a K&N-type filter is used (filter oil gums up the MAF sensor wires causing poor reporting of air flow). But, this hesitation could also be due to (or made worse by) poor fuel trims based on that possible vacuum leak.

The O2 codes probably won't tell you much about the issue because they are for the rear sensors which only monitor the cats. You can delete them entirely and the engine will still run fine (many people do this when they add headers and delete the cats). Front sensors, on the other hand, are extremely important and can cause several driveability issues if they are not reporting correctly or are receiving corrupted readings themselves (such as an exhaust leak near or before the sensor, or if the AIR pump was running constantly during closed loop as mentioned above).

To sum things up, I'd start by cleaning the MAF since it's easy and might help a great deal with your hesitation issues (my method is to remove it from the car, disassemble it via the four torx screws, and then clean the sensor wires using Q-tips and rubbing alcohol - be very careful with these wires and don't use any real pressure on them, just glide along the surface until clean). For the high idle issue, you'll likely need access to a comprehensive OBD scanner to look at fuel trims and IAC position, otherwise you're just shooting in the dark. What you do with the AIR system will have to depend on what sort of emissions tests you need to pass (if any)

1 FMF

iTrader: (1)

being that the car is 14 years old, and you didn't mention the mileage nor what kind of life the car had.... if it were me i would do a compression test on as many cylinders as possible to see where you stand... might not be worth it throwing parts at it if the motor is weak. if compression checks out then i would look at doing maintenance things,
- consider replacing your front O2 sensors
- pull your maf and throttle body and clean both, check for oil behind throttle body which can indicate a pcv problem
- the pcv rubber hose that connects to the throttle body... my 2002 is a summer only car with 70k miles and i ended up replacing that little bit of hose because it dry rotted and cracked. check all your pcv hoses and replace as necessary, that can be the source of your vacuum leak.
- didn't the 1999 model year have EGR? if so consider ripping that bad boy out and cleaning and replacing the EGR pintle doodad. all EGR is notorious for carbon'ing up over time and causing problems.

garygnu

like said ^^^ ,clean IAC solenoid & MAF .delete back O2 ,replace front O2 .delete & remove if possible ,or replace with used 1 from the used parts section.how many miles on the car ? replace or delete cats .look at you PCV system ,get a new PCV valve and check for any cracked tubing .

d_illman

RPM WS6, 1fmf, Garygnu
thanks all for the excellent tips.
I will do a compression test we are sitting at 100 000 miles. Car seems tight overall and clean which compression didn't cause me an issue but I will do a check tomorrow.
clean MAF once but I will get it done again. I have a 6 hour drive on Friday and wouldn't mind taking the T/A.
RPM Ws6, I will do a some trouble shooting and hopefully i can get this car ready for next friday!

Thanks Gents