P0505...this is getting annoying

Alright, long story short, a few months ago i had a high idle, took it two different shops (one being toyota), and they replaced the iac, checked vaccum lines, cleaned maf,etc.. Everything and still no fix. Finally, I sent it off to MAXBORE (rip), and my problem was solved. No codes and no problems with the idle.

Today, check engine light comes on again, and its a p0505. However, truck is driving the same as it has been for the last 3 months, idling ar around 1k rpm. No problems as far as i've noticed, aside from the CEL coming on just now... Not sure what to do at this point???

In between the last 3 months i should mention that i did get a check engine light for the rear 02 sensor, which i replaced, and the code for that went away.

Any help is appreciated, cheers

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****Update on page 3, finally solved.

 

2.7 or 3.4?

 

3.4 v6, 1998, 4x4, manual

 

vacuum leak check again, paying close attention to the brake booster?

 

Your IAC valve may be getting momentarily stuck, or slow to move.
You can test it. I can post the info if needed.

I’dd first check your intake for any vacuum leaks.

 

But nothing is wrong with my idle. If there was a leak or my iac valve was getting stuck, wouldn't I notice something change with the idle?

The only thing that I noticed since MAXBORE was that the engine occasionally makes a higher pitch sound at 2900 rpm when I'm heavy on the gas pedal. I cant confirm that this started only after sending it to maxbore, it's possible it was happening before. I was going to reach out to George to ask him if he's heard of this before, but he has since passed away. Rest in Peace.

It's also worth noting that when toyota replaced my IAC (when they originally thought that it was the cause for my high idle), they replaced it with a non-oem IAC.

I do have a spare OEM IAC off a 4runner throttle body that I had purchased when I sent my originall one to MAXBORE, but I'd rather not go through the headache of replacing it, if my truck is currently idling fine?

 

P0505 is thrown when your idle air PWM cannot reach the desired RPM the ECU wants. I get this when controlling my idle with an aftermarket ECU with the factory ECU still plugged in.

Should be easy to check for a vac leak post-throttle plate since it's also post-MAF. It will not be metered so your fuel trims will be adding (positive). Otherwise, you may need to adjust the throttle plate setting to close it slightly (small screw). 1k rpm is not "running fine", that's about 30% too high

 

what do you mean by adjusting the throttle plate settings? My idle was at 2500 rpm before I sent it off to maxbore. He re-borred it, and marked all the screws with a note telling me not to change anything. When I got it back the idle lowered to 1k and has stayed that way for several months without throwing a code. If 1k idle is not "running fine" then why didnt my CEL come on earlier?

 

1000 rpm is high for a warm idle.

 

Ok so is it possible that it's an IAC issue? This is a new IAC but it's non-oem. I have a 4runner throttle body and IAC, and when I put that into my truck, the idle did lower below 1k, i would say probably around 750. But the thing is, the TB didnt fit my throttle cables, so i ended up using my stock TB that was re-borred. So i still have the spare IAC laying around. The screws have this glue/melted plastic stuff on them IIRC (perhaps to keep them from coming loose), so it seams like it may be a bitch to take it off. Is there anything i should be careful of when swapping the IAC's over?

 

Little screw in the middle.

 

hmm, okay. Are you able to put a circle around it, I don't know what I'm looking at. So I guess the question is, is this a throttle plate issue, or a IAC issue? Since Maxbore marked all the screws/bolts for me, I'm more inclined to believe it's the latter?

what do you guys think?

Relavent comment that I made earlier: "I have a 4runner throttle body and IAC, and when I put that into my truck, the idle did lower below 1k, i would say probably around 750. But the thing is, the TB didn't fit my throttle cables, so i ended up using my stock TB that was re-borred by Maxbore. So i still have the spare IAC laying around."

 

I think you're over fixating on the throttle body and IAC. A high idle can be from many different things. The throttle cable could be incorrectly adjusted- there is a sweet spot, where there isn't slop, and it's not too tight to the point of opening the throttle. Vacuum leaks would be next to check. Could be a crack in the intake box, rotten vacuum line, or even something within the brake booster. I'd also check your exhaust sensors. Bad data from there might be causing the ECU to try to let more air in to compensate. You really need the whole system to be healthy for the ECU to control the idle correctly (~750 rpm).

 

If your throttle plate is set too open by default, no amount of IAC reduction will be able to lower it to where the ECU wants it.

 

Ok, interesting. Thanks for the help guys.

Just took the truck out now for around 20min and it was idling at 1k on the dot when warm. Parked it and started it up again a few seconds later and this is where it's idling. Super weird. I cleared the CEL.

 

So I have to take the TB off and see if the butterfly flap is too open? And then if it is tighten it? Or can I do this without taking the TB off?

 

You should be able to hook up an ODBII reader when the key is in the On position and the truck is off to get a throttle position reading. Should be around 10%, but YMMV

 

Ok I have a pretty cheap OD II reader but I don't think it tells me that kind of info.

This is the one: https://www.canadiantire.ca/en/pdp/...eader-scan-tool-0251097p.0251097.html?loc=plp

 

I can't tell if it reads live data... if you want an even cheaper solution that will, check the links in my signature. You just need an android

 

Perfect, so when I scan it, lets say it's saying that it's more than 10% open... can I just adjust the screw without taking the TB off?

Going to buy a scanner for my iphone and will post the data here after I scan it