bd307

My car has been in a mechanic shop for the last few weeks for hesitation (during 2-3k), idle (sometimes would stall), and bad exhaust smell issues.

I got the car used last February and the car was driving all right until the car would hesitate in traffic around 2.5-3k rpm while giving little gas. The car would buck like you were learning how to drive a stick shift first time. Then it gets worst. The car would stall/almost stall when coming to a stop.

Few months ago, the gas mileage becomes very bad. From 240 miles a tank down to 180. That was why I brought the car to the mechanics.

He pulled the code and it indicates the fuel is too rich. The car maybe turbo/SC'ed by the previous owner as I was told by another mechanics, but compression and leakdowns tests were checked out fine.

The mechanics told me to change the injectors. After the change, he said he car runs much better, but still idle bad and rich.

We thought the owner could have changed/reflash the ecu, but peeps on here said this can't be as the ecu for 2005 and older models of s2k can't be reflashed. I also checked the part number for the ECU and it is confirmed to be the stock one for MY02.

The mechanics have checked all the sensors and they are all okay. He also checked the fuel pressure, and everything checks out okay.

Now we have no idea what is going on and I am sure someone would have the same problem before.

Thanks for your time and the long read. Really need some help here.

What could cause a car to run rich without ECU reflash?

negcamber

Replace the MAP. You can try the "MAP Whack", but more than likely you have the original MAP sensor.

The IAC can also cause idle problems...you can try to clean it to see if that will help, but it may also be time for it to be replaced.

Might as well replace the plugs if the car has been running rich for a while. Use OEM only...anything else is a risk.

BTW...MY00-05 ECUs cannot be reflashed.

$Piker

If the MAP doesnt fix it....You can always tune your stock ecu by plugging in an Apexi VAFC and then put it on the dyno for tune...

bd307

Thanks for the replies.

I have replaced the MAP, but it did not solve the problem.
Have also cleaned the intake manifold. It helped the idle a little better, but still not normal.

I know the previous own has intalled a VAFC or other fuel management device. He has taken it back with him when sold me the car. As confirmed, 00-05's ecu can't be reflashed, so the ecu should not be adapted to any setting from the VAFC if it is taken off.

I do not want to spend unnecessary money as I've spent some already trying to fix the problems.

Hope someone can chip in and help to solve the problem.

emdzey01

could it be a faulty o2 sensor?

that's the only thing i can think of after what you've mentioned has been done.

bd307

My mechanics is currently trying to replace the o2 sensor from another. We hope this solves everything as other parts are checked out and cleaned.

Kirpich

Yeah, do the primary O2 sensor replacement, not the secondary. Then make sure you do the ECU reset, and the engine idle learning procedure. It's been covered here on forums a thousand times, I won't go into it here.

Also, at times our Catalyctic converters (Cats) go bad and their internals fall apart, and block exhaust. Take the Cat off and look inside to see if all's good. Post a pic here, ppl will tell you if it's good or not.

bd307

Great. They are doing the O2 sensor, and I should know if this solves everything soon.

Will also check on the cat as well.

Will keep this updated.

bd307

All the problems were solved. Mechanics replaced both O2 sensors (the primary was damaged due to the car was sitting too low), radiator (engine) sensor - not sure the proper name and a valve adjustment.

The fuel is no longer rich, hesitation and idle problems were all gone!!

Hope this helps those who may have this problem later on.

iDomN8U

I bet that feels good.

too bad the CEL wasn't more helpful