Inconsistent idle

hi. i’m a bit of a noobie to this, so i’ll try hard to fit in as much as i can

I have been trying to diagnose a rough idle problem.

I have researched and tried a few things (listed at the end) but i’m at a loss as what to try next and i’m hoping you can help.

I have a 2008 4cyl manual with 198,000miles and I adore it.

here’s the idle problem:

ambient temperature is 44 degrees on a cold engine

startup
needle bounced between 1100 and 1500 rpms
white billows from exhaust


after about 90seconds
needle will bounce between 800 and 1000

after about 3 mins
no more white billows from exhaust
temp reads at about 1/3rd up from Cold
600 and 800 sometimes 900


temp is now 1/2 way at about 4mins 30

I drive for 20mins seems ok
idle when stopped goes back to fluctuations between 600 and 900


Cab fan blower is set to off

I have checked MAF sensor and PCV valve and they seem fine.

She has a newer air filter and an even newer battery that I put in.

Any ideas on the peculiar idle?


many thanks

 

Have you cleaned the throttle body and reset the learned values by disconnecting the battery for a few min?

 

Clean the MAF and the throttle body

 

The MAF looks very clean so I didn’t spray any cleaner on it.

I haven’t cleaned the throttle body. I can probably do that. Is there a special cleaner or just brake cleaner?

thanks

 

There's actual throttle body cleaner, but WD40 or any penetrating fluid works as well. (they are solvents)

 

‘Get throttle body cleaner, some people use carb cleaner. No no no on the brake cleaner.

 

Do like others suggested. FYI when ever I do an oil change on any of my vehicles I take out the MAF and clean it. Doesn’t matter what it looks like. It does sound like a dirty throttle body.

 

thank you soooo much everyone . I will take in your expert advice.

hny

 

Oil creates blue smoke, fuel creates grey or black smoke and water (50% of coolant) creates white smoke. With coolant flow into cylinders, the smoke usually only appears at startup. Are you having to refill coolant? Seeing little air bubbles in the radiator?The cycling of rpm would point me to a sensor issue. Dirty mafs and tbs tend to change the rpm at idle as well as rich or lean conditions, but usually do not create cycling rpm. Sometimes bad data to the ecu that keeps reacting by moving the throttle plate and keeps chasing the changes leading to the cycling. Rpm data comes from the cps, so that is also on the table.

 

hi, coolant levels seem to be fine and I don’t have to refill.
The rpm ups and downs are definitely apparent at idle and depending on engine temperature it determines where the ups and downs span on the rpm range.
when the engine is warm there is a constant up and down cycle / wave from 600 rpm to 800 rpm, sometimes 600- 900rpm.
I was thinking a bad sensor also. but I don’t know which sensor would affect that symptom

 

there is a feedback sensor in the throttle body. on scanner, go to live data and view the throttle position data pid along with rpm and look for any signs that something is wrong. If TP is moving, that means the TP is bad OR the ECU keeps moving it as it is trying to compensate for a unexpected rise or drop in RPM. also look at coolant temp for fluctuations. iat sensor is also possible, so observe that too.

 

again sorry to be a newbie , there seems to be a million odb scanners from $20 to $700. Do you have a scanner brand or model you recommend that can monitor the live data like you mention. Thank you so much in advance.

 

I'd do the throttle body cleaning and see if that fixes it before you get too deep into it.

 

hi. everyone!
just a follow up.
sorry for the delay, but cleaning the MAF sensor and the Throttle Body did the trick.
Works super great now.
Thank you sooooo much for your help.
And yes the Throttle Body was quite dirty!

Wasn't too hard of a job to do either. Hardest bit seemed to be getting the Toyota Parts guy at the dealership to sell me a Throttle body gasket... ha ha.... are you sure you want this,,, ha!

 

Next time you encounter a silly catalog jockey like that, say 'Yes please. Me Jane. Just picking up what Tarzan asked for'