My rough idle

[mhess19]

Ok, I'm going to document my trouble shooting for a rough idle, hopefully this helps another noob when searching for info. Going down the list one thing at a time to see what actually works/changes.

2007 4cylinder SE 40,000mi, I believe it is stock... at the time of writing this we have had the car for 2 weeks. Initial symptoms -when cold idle is fine, when warm it hunts a bita and stutters, sits at 500rpm and drops to aprox. 350 with no accessories on.

- First step, checked air filter - pristine, it looked new.

- Ran a dose of Seafoam through the fuel system. Not surprising the idle was worse for that tank of gas, did not clear up with a fresh tank.

- Checked Throttle Body gasket, was not in correctly. Removed and corrected orientation. Re-set ECU as per instructions on the forum. Idle no longer hunts, seems steady however now it is very rough when engine is cool. Still fairly rough when warm as well, not consistent sometimes worse than others.

_Next step, cleaning MAF sensor and another reset. Have to pick up a code reader!

[3CL1PS3]

you dont know if its stock...?

[mhess19]

It looks to be stock, never crossed my mind to ask about modifications. Before we found this site I had no idea what was being done to these cars. We bought it because we have always loved the look of the 4g, and the kids are still small enough to fit in back now and again.

Of course as I continue reading about the performance mods I can tell its going to be difficult not to play with it once this issue is sorted.

[mhess19]

Cleaned the MAF sensor, reset the ECU - ilde is about the same, maybe a bit better.

Code reader is on its way.

[snakeeyes]

i would get an intake.if ya cant get one right now,at least plug the hole on the intake hose to eliminate it from the engine cover.this will help some, to get more air in to help stabalize the idle so the engine isnt choking for air and do a tb bypass.

this will allso help eliminate more heat from going through the TB.may help some with idle depending on your case.check the sparkplugs as well.check pcv valve and make sure its functioning properly.simply pinch the hose with your finger and you should here a click.try running different gas from a different station.have the intake valves been adjusted ? just throwing you some ideas.

EDIT: i would get the rre pulley as well if i was you.thats all im going to say about that.

[bwilliams]

Did you check the spark plugs?

[mhess19]

Thanks for the advice, plugs are on their way. Shoe string budget so no intake or modifications at this point but the pulley is def on the short list.

I'll try the suggestions one at a time and see what happens. Don't know if the intake valves have been adjusted or not. The car is not throwing any codes so at least I can scratch that off. The idle is not as bad so at least there has been some improvement.

[MACH1219]

Remove the resonator that sits below the intake filter box, and next to the tranny pan. Opens up the breathing, and its free.

3 bolts. two of them u get from the bottom after removing splash guard

[mhess19]

Thanks Mach, I will take a look for that.

[mhess19]

Seafoamed the engine yesterday with the help of my lovely assistant then cleaned the TB and replaced the plugs. It does feel a lot better. A bit inconsistent, sometimes I can hardly feel it running then the idle kicks down the slightest bit and there it is.

Over all everything has helped. I did also check the pcv as advised and it seems fine. I'll give the other suggestions a try this weekend (air related) and TB bypass.

[MACH1219]

look for a cracked/loose vacuum hose somewhere. and pass on the seafoam, stuff does nothing

[ptr149]

Well it seems like you've checked everything that I would suggest. If your idle isn't completely fixed then I would maybe try to flush your injectors. Not that I think it is your problem, but it might help and Mitsu recommends it every 15k miles or just at 45k miles (not sure, I just remember they flushed mine at 45k).

[dejectedangle]

Do you have a ses light!!!! If so plug it in it will tell you what's wrong idk y everyone here never just plugs it in as the FIRST step.. I'm not trying to be mean but there are lots of threads with rough idol...

[mhess19]

Hey dejectedangle, I've read the rough idle threads, yes I searched (new to this forum but am active on others and know how to search) but rarely has anyone actually completed the thread with what solved the issue for them. I figured I would just track my steps and progress so when it is resolved someone else will know what has actually worked. I have checked my lines for a vacuum leak (deal with this on my bike now and then) haven't found one but its still in the back of my mind as a possibility that I'm missing and I don't have any lights or codes so I'll just continue to pick at it.

Thanks for all the advice, its been really helpful.