Help with 3.4l Rough Idle Diag (1 Viewer)

[YotaFun]

Looking for a fresh idea gents. I am aware most here are familiar with only the powertrains in the LC but I am kind of stumped...

My Step fathers 2002 Toyota 4Runner Auto 3.4l V6 with 316k miles on it has had a rough idle for some time and a code for knock sensors.
Today I went ahead and did the knock sensors, the wire for the sensors, new gaskets for the upper and lower intake, new valve cover gaskets (they were leaking, and for 316k it looks good underneath), and a new throttle body (suspected to be bad due to pink milk shake long ago, could never get cold start idle right).
Timing belt done 50k ago and looks good still, Also did a seafoam treatment through the intake tonight. Took it out for a test drive and it seems to have improved.

Parked it in the drive way and thought "Swing! It's Good" and then a second after saying that the idle starts to stumble a bit again...

No pending codes, runs great while going down the road. No smoke of any kind, No fluids mixing anywhere, sprayed down to check for vacuum leak, all good. I'm stumped.

I know I will here plenty say its just time to let it go, and honestly I do agree even though this is the truck that started this addiction lol. I am just curious. I want to say I got it right before it finds permanent resident in a Junkyard.

Just looking for some fresh Ideas...

 

[dci blair]

Other than spraying it down what have you done for diag? Comp test? Leak down? Smoke test for vac leaks? With that kind of milage I’d be looking at mechanical. Not to sate the obvious here but my usual process is start with the basics and rule them out one by one. Spark, air, fuel, squish. Pick one, do all the tests to cross it off the list and move onto the next one.

 

[TunaKing]

Did you replace the idle air motor under the throttle body? I have good luck cleaning them if you did not replace it with the throttle body. I would check timing marks for the timing belt or do compression test and if one bank is off then go after timing marks and such.

 

[YotaFun]

Other than spraying it down what have you done for diag? Comp test? Leak down? Smoke test for vac leaks? With that kind of milage I’d be looking at mechanical. Not to sate the obvious here but my usual process is start with the basics and rule them out one by one. Spark, air, fuel, squish. Pick one, do all the tests to cross it off the list and move onto the next one.

I haven't done a compression test yet, I have to get a new line for mine. I am doing this all from my home garage, I don't have many of the tools I am used to having.

I did the tune up because it was over due, hoping that that would be the issue but no go. I'll try to get the compression test done. What boggles me is just off idle its peachy keen.

The throttle body has the iac built in on this generation of the 3.4l so I'm unable to replace separate parts on it. With the newer throttle body I put on, I got my cold start idle back, before it would start and settle right back down to 700 rpm...

Timing Mark's check out, belt still good and hasn't jumped since I put it on 50k ago.

 

[TunaKing]

Did you ever disconnect both battery cables and touch them together for a min or two to clear the computer idle memory. If it was a used throttle body make sure the throttle plate is nice and clean.

 

[YotaFun]

New development, and I think my answer, my stepdad has been mentioning transmission issue as far as now reverse when cold, I didn't take notice till today that the truck lugs when coming to a stop, he said it threw the knock sensor code when he had to brake hard...

So I changed my focus and started paying attention to that aspect more, when I was coming to a stop I would shift the teuck ro neutral, no more lugging and idle was perfect, auto transmissions have not always been my friend, and the one in the truck had to be rebuilt at 100k for a destroyed overdrive gear set.

 

[jamarquardt22]

I've got the solution to all your problems. I know what your thinking too. Oh boy this should be good. But it is. You've got a 4runner with a auto that is begging to have a 5spd swapped into it. This fixes step dad's problem. And clears out space in your garage.

It's not like you don't already have most of the parts.

 

[YotaFun]

I've got the solution to all your problems. I know what your thinking too. Oh boy this should be good. But it is. You've got a 4runner with a auto that is begging to have a 5spd swapped into it. This fixes step dad's problem. And clears out space in your garage.

It's not like you don't already have most of the parts.

Just took the truck that was going to get the 5spd swap off the road...

 

[jamarquardt22]

Just took the truck that was going to get the 5spd swap off the road...

I just don't buy how hard it is to swap it in the 01, that's where I'm getting the tranny for step dad's from. I mean manual gear box and t case and wire it so it thinks it's in park or netural.

 

[Pacer]

 

[dci blair]

Sounds like the torque converter is staying locked up.

 

[YotaFun]

Might as well put the popcorn down, ran out of time. The work I did was a vast improvement. A fellow tech who is more familiar with transmissions doesn't feel the problem is trans based. He feels it may be a weak valve spring issue.

I was unable to get a new hose to do a compression test in time. The vehicle performs great. It helped if you shifted the trans to neutral at stops. Even when the idle would lug at stop it was in normal parameters per the fsm.

Only other possible item I can think of are failing injectors. But without the ECU catch the miss and not having a oscilloscope or voltmeter to check I can't confirm.

I gave him a heads up, while I'd does feel better to prepare and drive it till it blows, I have a feeling the transmission will go first. And with the frame starting to rot it's time.

I appreciate everyones input. Now time to move to other projects that have to be done before winter...

 

[YotaFun]

Holy thread revival Batman!
Nothing exciting, but some news since the 4Runner landed itself back in my garage.

Stepdad was smelling some fuel past couple of weeks, and I could not see any fuel leak, then again I could only see 4 of the 6 injectors due to the plenum.

So I went ahead and order some injector o-ring kit's for all 6 injectors ($27 shipped from rock auto to cover all the o-rings 3 per injector).

Brought it into the garage today, pulled the plenum and found a few things, 1, somehow one of the upper plenum metal gaskets got a wrinkle in it, not sure how since its flat, my guess the size was a hair off when made and bent when putting the plenum on, and two, s number 6 injector all the way in the very back corner, soaked in fuel.

Replaced the gasket and all the o-rings, and the idle is almost perfect, I'll take it since it's a 16 year old truck with some hard miles on it.

If the test drive back to my parents place goes well, I might recommend we put a new manifold back exhaust system on it (cat has a whole in it and the job minake did, well makes my diff repair look good) and maybe patch the frame and get it through PA inspection!

In case anyone was wondering it seems to have been a gasket and some o-rings, I am not sure how I missed the gasket since I sprayed the intake down to verify no leaks...

 

[Pacer]

Nice update!

 

[jamarquardt22]

16 years and 300k+ miles to see a vac leak? I think it was the bad O rings

 

[Crusha]

Bet that was a relief!