[bjd]

hi

this problem has been going on for about a month. i have a 1998 frontier 2WD 4 cylinder manual transmission with 99k miles on it. when i start the engine it seems like it is idling really rough, shaking the entire vehicle, and now the service engine light has come on. i have noticed that this problem is definitely worse when it is raining and the humidity is high. it seems like once the engine warms up it tends to go away, but i definitely want to fix the problem. I changed the fuel filter, tried injector cleaner, and all the fluid levels are ok.

it does this when in neutral and when clutch is engaged, so i don't think it's the clutch going. it is probably due for new spark plugs at this mileage, but i don't really want to do things that aren't going to fix the problem. i guess the 4 cylinder engine has a timing chain instead of a belt, so i don't think that's it either.

any ideas?

thanks.

 

[Bounce]

Try and give the air mass sensor a spray with some carb cleaner. This is located in the tube that comes into the engine bay that feeds the air filter. You will have to remove the air filter box to be able to see it. If the sensor is either dirty or broken it will be sending false signals to the ecu causing this. Worth a try.

 

[bjd]

Thanks for the reply. I didn't check out the MAF sensor yet because when i was reading about how to do it, i discoverred you can get the PCM self-diagnosis codes to display through the check engine light. However, when i tried to turn the PCM to self-diagnosis mode, i was unable to find the screw to do this. It is allegedly located in a hole in the side of the PCM, but i couldn't find the screw inside the hole. Then, the truck wouldn't start until i poked around the PCM again with a screwdriver. I am afraid of buggering-up the circuitry of the PCM. Do you have any experience with this?

Thanks.

 

[Bounce]

Ive not had anything to do with it on my nav as yet but when it happened on my skyline, same symptoms. Really rough idle, barely ticking over sometimes just stopped altogether, cleaned the sensors (twin turbo one for each) worked fine. Problem never came back. Was just the first thing I thought of. They are delicate little things hence not really touching them just a quick spray with carb cleaner as it cleans then evaporates.