Rough idle/running after start up...no codes...what's up?
 

I've got a 98 V6 and have experienced rough running (at idle in the driveway immediately after starting and driving in my neighborhood) about 5 times in the last 6 months. Most days it works flawlessly from start to finish. When this happens, it doesn't die but it feels like it's running out of gas and about to die. The problem goes away after the engine is fully warmed up (5 mins or so). I drive a 20 mile to and from work commute everyday including stop&go traffic and highway speeds and don't notice any issues after warm up. No check engine light comes on.

Any ideas? What should I be checking?

Thanks in advance.

CL

I'd clean your MAF, IAC port, and throttle body first.

Pcv valves get gumed up and may cause rough idle. A oem part around 12 dollars.

Sounds like what mine was doing prior to replacing the spark plug wires. The pulse was grounding out on the engine before it could get to the spark plug. It was especially bad when there was a lot of moisture around. Is it more likely to happen to you when it has rained? Even morning dew was causing mine to ground out.

My two cents many things can cause rough idle. It is just what your willing to deal with and how much time and expense to correct. That said first bring all your services up to date plugs, wires, pcv, air filter if they are not already there. While you have the plugs out do yourself a favor do a compression test wet and dry it takes about 30 min. Take a look at the plugs they can tell you alot.

You can rent a compression tester from the some auto part stores. Make sure you have the throttle plates open when doing the test (I gently place a large screw driver handle under the throttle plates while doing the test) After all the services are update you can look for things like vacuum leaks maybe the plug reading will show a injector problem if that's what the problem maybe.

Other causes dirty MAF sensor, Idle control valve or a front O 2 sensor. For me I had a rough idle because my alternator brushes were worn out at warm idle the engine would move up and down 25 to 50 rpm after the brushes being replaced it's rock steady now so it was a voltage issue.

Don't get me wrong if your services are up to date then great. We see so many times that the previous owner put in the wrong type spark plugs or bad pcv . If you get everything up to date as they should be then you can look for something that might be wrong. While doing the service some times you find a vac leak or a bad wire. These are well designed vehicles and really very simple compared to to 80's and current made vehicles but many times they lack there services being up to date :cowboy:

I did throttle body, MAF and maybe IAC this summer.

I haven't done plugs and wires yet, so I'll do that first. There may actually be a correlation to damp weather but it's not every time. Will also get a new PCV.

Thanks for the replies all.

Didn't mean to sound like a bu## if it came off like that. Having your servies up to date is really important in the long run it will save you heart ach. When you do the plugs do the compression test and keep the plugs in order maybe take a pic so when your doing work later on you can refer to the old plugs.

Not part of your problem don't for get about the Coolant, Belts, Filter, Trans/Transfer case and Rear end fluid. Not sure of your long term plans to keep your 4runner so it's a balance

I purchased my 2 2001 SR5s last year plan on keeping them for along time so I did all the services now I just have to keep up on them. One I put a JDM engine the other I rebuilt the engine. Good Luck:dance:

Just changed mine today to start the process of troubleshooting and that thing was beyond its time.
Changed the pcv and grommet. Was well worth the $11

love that mustang in your profile pic.

For what its worth I am chasing a rough idle stall issue. Popped up out of no where.
4runner is fairly new to me so Im not confident the service has been update.

Changed the fuel filter the other day. Beyond disgusting rust colored fluid not really fuel.

Changed it and pcv today and its running pretty smooth. The idle and stall also had no codes.

Get some of those serviceable items up to date and then you can eliminate those as possible problems.

No way. Totally agree on bringing services up to date. There was a lot done before I got it but of course no records. I'm slowly working my way through the list. Cooling system is next big one. Thanks for your input.