Rough idle

[acg72]

I posted a while back about my gn having a rough idle that was progressive until it eventually would not idle at all and would miss very bad under throttle. Advise I received was to check maf sensor. I installed a new maf sensor and the car would idle but not much change and still missed real bad. I checked the plugs and they where very black. Replaced plugs with UR5's. Car started and ran smoothe but after a few day's and starts it is starting to idle rough again except after it runs for a few minutes or increasing the throttle it smoothens out. I also noticed an almost fresh smell of gas while running( no leaks).. so im thinking a spark issue. Seems it's not burning the fuel correctly.. Coil pack Maybe.. Any suggestions... I don't have a scan tool(need one bad)... Thanks

 

[mikestertwo]

What MAF sensor did you replace the old one with? Stock, reman, lt1+translator? Sounds like you are running rich. Definitley need a scan tool. What is your fuel pressure set at?

 

[acg72]

replaced with stock maf and fuel pressure is set 37 or 38 with vacuum off.

 

[TurboBuRick]

Sound like possible bad injector. Any of the plugs look different then the others?

 

[speedskills]

Smeel of eggs? Do u still have a converter on your car? The list goes on and on for a rough idle. At the least you need a scanmaster to tune, but for now a cheap way to go is replace all your vaccuum hoses with windshield washer hoses and zip tie them. It helped mine. Don't do too much till you have a scanmaster or something might go chitty chitty bang bang.

 

[acg72]

Injectors, chip, and turbo are all new ( of course that doesnt mean theres no bad injectors ) . Off the top of my head I can't remember if the plugs looked diff. I think one or a couple looked black and kinda burnt. I have replaced most of the vacuum lines with clamps or ties but have not done windshield wiper lines yet.

 

[speedskills]

You misread. I wasn't saying replace wiper hoses, I was saying use those for vac lines as a cheap alternative. Most auto parts stores carry spools of different sizes. Good luck. Sounds like your on the right track.

 

[mikestertwo]

Sound like possible bad injector. Any of the plugs look different that the others?

Rick maybe on to something. You may not have a bad injector but you could have a shorted injector harness. Does the fuel rail hold pressure after you shut the motor off? Check the harness around the plugs on the injectors. Did the car have this problem before you changed the injectors? When did this problem start?

 

[acg72]

It does hold pressure and it did not have this problem prior to changing injectors. Changed injectors and matching chip same time.

 

[mikestertwo]

It does hold pressure and it did not have this problem prior to changing injectors. Changed injectors and matching chip same time.

Check the injector harness. If it holds pressure after you shut it down most likely the injectors are good but you could have a short on the low side (computer side) of the injector.

 

[acg72]

Thanks for info guys.. I'll check the pressure in the fuel rail this weekend and then move on to the harness if need be.

 

[TurboBuRick]

It's important to pay attention to the plug when removed.

If one is severely darker than the others, the condition is only on that cylinder.

With this information, a direction can be taken.