Rough idle on 03 4Runner SR5

Howdy all,

First and foremost, thank you. I am new to the site, but have used some of the exceptionally helpful information found in previous threads to keep my 03 4Runner going through the years.

I am hopeful that the kind people of this forum could help me get to the bottom of this once again.

On startup, my 03 4runner is having an intermittent jerking motion when idling. The thing is, as soon as I give it some gas, the intermittent jerking stops. After the initial jerking at idle, it does not recur on subsequent idles (at a stop light for example). A better way to describe it, is that it feels as though I am running over a small bump, even when sitting still. No codes have been thrown.

I recently replaced the spark plugs and ignition coils (I was throwing a code), air filters, the water pump, several pulleys and the serpentine belt within the last 6 months.

I have always performed my own maintenance, but am concerned this may be more out of my league. Things I have seen on other threads that may be promising (as I have not recently changed them/investigated) are as follows:

• vaccuum leak
• fuel pump issue
• TPS sensor
• Dirty throttle body
• Fuel filter.

If anyone can help me rule out anything on the previous list, or has other suggestions to try before taking it to the mechanic it would be greatly appreciated.

Thanks in advance!

 

Clean your MAF? Check your gas tank sending unit for voltages/continuity?

 

Thanks, I will give it a try and check back

 

Ok!

Tried cleaning the MAF and throttle body (after waiting the appropriate amount of time to reassemble for complete drying) and I received the following OBD codes:

P2135
P0121
P0123

Which all seem to point at the throttle position sensor.

I think it is suspicious that the codes only appeared after cleaning the MAF and throttle body. Both were very dirty (didnt clean after the last air filter change), so I get it. The vehicle is still doing the same rough idle as before, if that makes a difference.

My question at this point is, could it be a voltage difference now that the throttle body and MAF are clean? Is it something that the "brains" of the car will adjust to, or am I better off replacing the TPS?


Thank you for all your help!

UPDATE: I'm an idiot and did not re-connect the TPS sensor before trying it out. Now that I have (and cleared the codes) it seems to be running more smoothly.

The idle does seem unreasonably high, will that correct? (It's around 20-25mph)

 

Your idle RPMs are high like how high? I mean they should start a little higher on average when you start up from cold, maybe 800-1000 rpms or so... but then should settle towards maybe 600-800. Youre outside of that range?

 

Updating because I think we have isolated the issue, and I want to help anyone else who comes across this problem.

Description:
On startup, my 03 4runner is having an intermittent jerking motion at a low idle in drive or moving slowly in reverse. The thing is, as soon as I give it some gas, the intermittent jerking stops. The acceleration lags when I give it gas quickly (recently the check engine light flashed when I put the pedal to the floor). The VSC sensor

(Eventually) The check engine light came on and was showing the following codes:
- P0156 – Oxygen Sensor Bank 2 Sensor 2 – Replaced, no more code
- P0300 – Random, Multiple Misfire Detected

Repair timeline (not necessarily related to the issue):
- Oct 2022 – Water pump, Serpentine belt, tensioner pully, radiator, radiator hoses and cap.
- Nov 2022 – Oil change and filter
- Apr 2023 – All spark plugs and coil packs (6) – replaced with manufacturer recommended iridium plugs
- June 2023 – Cleaned MAF and throttle body
- June 2023 - Replaced transmission fluid
- July 2023 – Replaced oxygen sensor bank 2 sensor 2 (drivers side downstream)

Even after the relevant changes, the vehicle is still doing the rough idle and having trouble accelerating.


UPDATE: The mechanic isolated the issue to a single ignition coil (yes, even though they were only 3 months old). I replaced the coil and now the 4Runner is running smoothly again! The ignition coil was a 6 pack of Duralast coils, so to have a single one be faulty is frustrating, but at least we are up and running again.

Thank you everyone for your help.

 

Always use Denso or OEM (also Denso) for all replacement sensors and/or various electronic components under the hood and throughout the vehicle. Your whole situation could have likely been avoided with using Denso replacement coils as they would not have been bad or at least highly unlikely they would have been bad. It can be a little more expensive but you are much less likely to have this kind of issue.

I replaced all 8 of the coils on my 03 with Denso replacements from RockAuto and have not had a single issue with them.

Glad you got it fixed and posted the update so others can learn from this.

 

Yes sir, learned my lesson here. The Denso parts would have only cost and extra $100 or so. Only Denso from here on out!