Yesterday I changed the spark plugs with the OEM NGK #PFR5G-11 and replaced the fuel filter at the same time. I made sure all connectors and hoses were reconnected and started the vehicle and it idled great. Had my wife go out and test drive it a couple of miles with no problems. Saturday night she filled the car up at the local 7-11 with premium fuel, came home and park it until I worked on it the next morning.

My wife calls me today at lunch and says the car is idling rough when stopped and poor acceleration to boot. I picked up the car and noticed the same, got home and rechecked all connections, hoses, etc., even disconnected the negative lead to the battery thinking that would reset the ECU.

I noticed an orange light on above the check engine light, but the check engine light is not lit.

Could I have missed reconnecting something or could it be bad gas?

I would appreciate any help in this matter.

Thanks.

Your MAF (Mass Air Flow meter) could be bad, or the connection to it.

http://www.q45.org/maf.html

Prior to changing the plugs and fuel filter, the car has been running fine and has 85K miles on it.

pwflyer wrote:I noticed an orange light on above the check engine light, but the check engine light is not lit.

On my car, the engine symbol itself doesn't light up, the bar above it does. I think the orange light your seeing may be your check engine light. If you run the diagnostics, it should give you a code that will definitely make it easier to diagnose.

CoastyAV8R:

What is the process to check the code and does it require special equipment?

Do you have the service manual for your Q ? It outlines the procedure on how to do the test to check for diagnostic trouble codes. Your service manual should have been in the little storage compartment between the rear speakers- it it wasn't removed by the dealer.

Make sure the power transistors are plugged in on both cylinder heads- should be 4 plugs (2 on each transistor). When I did plugs on my Q yesterday I somehow missed the one plug on the left head that sits under the TCS and my car ran on 6 cylinders. While I was cleaning the throttle body I unplugged it and totally forgot bout it - doooh.

Another thing it could be- injectors, which require removal of the upper intake manifold to do. You should ohm them out and they should all be at around 12ohms.

If you haven't cleaned the throttlebody, be sure to clean if very thoroughly. The CEL sounds like the MAF or the MAF connector.

pwflyer wrote:Prior to changing the plugs and fuel filter, the car has been running fine and has 85K miles on it.

What year is your Q?

Heath