Thread: Codes

Replaced the boost bypass solenoid and now runs fine. A little sluggish almost like converter is getting plugged =/

Could be since it was eating plugs and likely just dumping raw unburnt fuel into the exhaust.

Thats my guess, running lean was more than likely because it couldn't measure the right amount of boost and apply the correct amount of fuel, and when those plugs would burn up, it would dump 1 to 2 cylinders worth of raw fuel/air mixture into the cat without being burnt. I am kinda considering straight piping the cat out, just concerned of SES lights coming on and reading the wrong amount of back pressure/temps/oxygen levels leaving the engine. That happened to me when I replaced the cat on my '02 Grand Prix SE and it would trip a cat code which would eat my gas mileage a bit =/

IIRC, you can get a rear 02 sensor sim and install it on the 99's and not set a light. I have one in my 00 GT and no issues. Since the upstream 02 does all of the work it shouldn't be affected since it is before the cat. The rear one just reports on the condition/efficiency of the cat from what I recall.

Backpressure isn't really any concern on these modern cars.

So I can replace the cat and put a sim in the rear 02 sensor slot and not trip a code?

After some additional looking it appears you can. Anything that is 01+ will have fueling issues using this sim. Here is a copy of the info on the 02 sim from ZZP:

OBDII cars have two oxygen sensors to measure the amount of oxygen contained in the exhaust gas. The first sensor is located on the manifold or header and measures O2 content of the exhaust as it escapes from the cylinders. This sensor is used by the PCM to calculate fuel trims and look for combustion problems.



The second oxygen sensor is located after the catalytic converter and is used only to detect the performance of the converter. The PCM does NOT use any data from the secondary O2 sensor for engine management. The PCM will set an SES (service engine soon) light (for P0140, P0141 and/or P0420) if the catalytic converter is removed, the sensor is removed, or the sensor goes bad.



The Easy Performance O2 emulator is a plug-in replacement for the secondary O2 sensor that will provide the PCM with a signal that emulates a healthy cat. An extremely compact circuit board is molded into the end of the connector to provide the most compact and water resistant simulator on the market.



Installs in less than 10 minutes and does not require any tools. The EP O2 emulator is standalone and as such does not need to be located anywhere near the exhaust system. It is further recommended that the harness connecting to the o2 simulator be coiled up and cable tied (with included cable tie) in the engine compartment away from the hot exhaust that could damage the casing of the simulator if it comes in contact with it. It also prevents obstacles in the road from catching on the harness wire if left unchecked. Some vehicles such as F-bodies with front dual exhaust have four oxygen sensors and require two simulators per vehicle.



NOTE: The Easy Performance O2 Emulator is for Off-Road or closed track use ONLY. - using this product on a street vehicle to violate emissions is illegal and we will not provide tech support to anyone we feel is doing so.



APPLICATIONS:

• 1997-2003 Grand Prix

So it's bad to run plus fuel in these cars?

I think it's 89. Not sure though I live in pa. The dude I bought the car off of told me to put 83 or 89 in it. I was like no.. are you stupid it takes premium. I don't want to mix fuels though.. that's bad.

Originally Posted by ssiebor14

So it's bad to run plus fuel in these cars?

Um, no. You need to run 91 or higher octane fuel in the GTP's. What I meant was any GP from 2001 or newer will have fueling issues using the 02 sim (meaning the ECU will not be able to calculate the proper air/fuel ratio). Not sure where you got the idea that running premium is bad

I didn't say it was bad.. mixing fuels is.

So far so good with plug issue. I'm really considering getting a u-bend delete and removing the cat and getting that 02 sim. Since I live in Michigan, no emissions testing. Once I get these issues taken care of, I want to start looking into dropping to like a 3.5" supercharger pulley. I'm not in any rush as this is my daily driver and I want to make sure I do it all in the right order and have everything working properly on the car to begin with.

Hop on zzp to get the emulator it's about 45 dollars online

Anyone done the ZZP Downpipe? I'm thinking about doing the catted 3". Should I go with the 3" or 2.5" catted down pipe? I plan on maybe one day lowering to a 3.5" or 3.4" pulley, so probably not ever going to build over 350hp. Because of that I am thinking probably the PLOG and the 2.5" catted down pipe. Thoughts?

Do a 3.5 and 3" exhaust is real loud

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So a 2.5" catted downpipe, PLOG for the front manifold, the 02 emulator for rear 02, then 3.5" pulley. I think those are what I'm going to start doing