I feel like I'm chasing my tail with this thing

[LILCBRA]

Here's the story: The 1999 Camry (4 cylinder 5 speed, ~123k miles currently) I bought as a commuter/second vehicle has had this slightly annoying issue since I bought it that I can't seem to figure out. When I start it cold, it idles a touch high at around 1100 rpms, but RPMs increase and top off around 1800 as the engine gets warm. Then, to top that off, it has a surging idle when warm but only when coasting to a stop, either with the clutch engaged or in neutral, and it throws no codes to speak of. Here's what I've done up til now in no specific order:

Replaced Air filter, plugs, wires, oil change - basic maintenance stuff.....
I've not found any vacuum leaks
Replaced OE O2 sensors
Replaced ECT sensor
Replaced the TPS
Cleaned the throttle body and OE IAC to no avail, then replaced the IAC
Replaced timing belt, drive belts, water pump, and thermostat (thermostat was stuck open)
Found a tutorial about resetting base idle by turning the key to the "Run" position 3 times before starting the car - had no effect
Pulled the fuse for the ECM, no effect

I'm not sure what my next move should be since it's a multifaceted issue. Part of my mind is saying to check/replace the VSS but it isn't giving any other indications of having a problem. It isn't a mass air car so there's no MAF to check or clean. I've thought that maybe the ACT sensor could have some kind of problem but it seems to run fine other than the idle issue which seems to defy my belief that that's part of the problem. I've thought that maybe the MAP sensor was a problem, but I tried unplugging it and it wouldn't allow the car to start so I don't think that has much of anything to do with it. It seems to be temperature as well as speed/motion dependent - maybe one, maybe both??

I just bought and received a KingBolen S500 scan tool and tried it out last night to see if anything popped up that my CarQuest code reader didn't show. It didn't give any other codes than the CQ reader had already shown - and most were my fault anyway. The only code it's thrown is for the IAC, but something's causing it to operate like it is. I've tried unplugging it and it idles and drives better, but it presented a few minor drivability problems so I plugged it back in. I fiddled with the scanner a little and ran a live stream, nothing stood out to me but I'm by no means an expert with this tool nor all of the info it can/will give. The things I remember from last night is the MAP sensor read around 4-5 PSI at an idle speed of around 1750-1800. I think the TPS said it was something like 27% open. Coolant temp was somewhere in the 200-210 range. It did not give any info about the VSS, but I wasn't moving and I think it said it wasn't available through the ECM anyway.

Like I said, I'm at a loss as to where to look next - I'm open to suggestions from those who are smarter than I.....

 

[nickyb]

If removing the engine coolant temp. Sensor isn't too difficult if say remove it and test it.

 

[Potomus Pete]

I have owned a 99 Tacoma foyr cylinder for 23 years, and these motors don't diagnose easily. I am surprised your not getting a code because they are good about popping one. I have had to bring my truck to a mechanic a few times. There is a sensor on the very back of the motor that controls some idle. Its out of sight kind of like our PCV is. You might want to look for that

 

[LILCBRA]

If removing the engine coolant temp. Sensor isn't too difficult if say remove it and test it.

That was one of my first thoughts which is what led me to just replace it. I figured it was only about $10 so it wasn't gonna be a bad idea to just throw a new sensor in it, but it had no effect. Then yesterday the scan tool gave me what the sensor was reading and it seemed to be ok at around 200-210. I haven't thrown my voltmeter on it to see what kind of voltages it gives me though.

I have owned a 99 Tacoma foyr cylinder for 23 years, and these motors don't diagnose easily. I am surprised your not getting a code because they are good about popping one. I have had to bring my truck to a mechanic a few times. There is a sensor on the very back of the motor that controls some idle. Its out of sight kind of like our PCV is. You might want to look for that

Do you remember what sensor that is? I can only think of a couple other sensors that could contribute to this but they seem even more unlikely than what I've looked at up to this point. The crank or cam position sensor come to mind but it seems that it would run like crap at any time if one of those was out of whack.

 

[Potomus Pete]

Temp sesor that goes into ECM

 

[nickyb]

Was the ECT sensor an oem toyota part? You know them aftermarket ones are not n miss

 

[LILCBRA]

Was the ECT sensor an oem toyota part? You know them aftermarket ones are not n miss

No, it was just a cheapy.

I hooked up the scan tool again when I got home from work, here is some of the info I was able to pull. One other thing I tried on my way home - turning the AC on eliminated the surging and lowered the idle to around 1200.

I found the VSS display so it does show up. That pic is just rolling down my driveway and backing back up to where I park it.

 

[Mcmahst]

Have you put a vacuum gauge on it to see what the idle and 1500 RPM vacuum is? You said you could locate any vacuum leaks, but didn’t mention what inches it’s producing. A vacuum leak matches the symptoms.

 

[LILCBRA]

Have you put a vacuum gauge on it to see what the idle and 1500 RPM vacuum is? You said you could locate any vacuum leaks, but didn’t mention what inches it’s producing. A vacuum leak matches the symptoms.

No, I've not, and I agree it kinda feels like a vacuum leak with the exception of the surging it does when moving. I'll throw one on there but it might be tomorrow at this point.

I just come in from taking these 2 short videos.


View: https://youtu.be/LbP4H6qZBtg?si=3Nk7qgLGyn8rLKh6



View: https://youtu.be/mJSABvLgxeo?si=kleFkWoOCskXFsb4

Slightly high idle with the IAC unplugged, but it drops by a considerable amount with it disabled.

 

[LILCBRA]

Didn't have much time last night to do anything other than eat dinner. But I did have a thought - since it's ran this way since I bought it AND I changed the timing belt, I wonder if it's off a little. I didn't line it up with the little dot through the gear, I marked the gear before I removed the belt so it was easier to see when I reinstalled the belt. I'm curious as to whether the last person installed the belt wrong and I didn't correct it at all when I replaced it. I got to thinking about that because the scan tool showed that ignition timing was at -5* when the IAC was disconnected and it was idling around 1200 rpm. You can see it at around 1:15 in the second video. That number just doesn't seem right to me and that's really the only explanation I can think of. So it's kinda looking like I'll be tearing the timing cover off if I get the time this weekend.....

 

[Mcmahst]

I wonder if you can pull the cover without removing it to see if the dots align. You may be right that it’s advanced.

 

[LILCBRA]

I took a quick look the other day as I had the same thought. I don't think I can, but I'll give it a closer look, hopefully Sunday.

 

[Mcmahst]

Maybe with your phone as a camera, you can get in there? Or one of those flexible cameras on stem?

 

[manicmechanic007]

The cam and timing advance will have nothing to do with a surging idle and high idle speed hot IMO
Your Camry has an intake leak (unmetered air) causing the surge and subsequent high idle IMO
Pull the intake manifold off and inspect for a cracked gasket

 

[LILCBRA]

The cam and timing advance will have nothing to do with a surging idle and high idle speed hot IMO
Your Camry has an intake leak (unmetered air) causing the surge and subsequent high idle IMO
Pull the intake manifold off and inspect for a cracked gasket

Hoping to get out there in the next couple hours, I'll have to see what I can get done today, but I'll be sure to check that out too! Thanks!

 

[LILCBRA]

Update: it looked like the cam was one tooth off, so I I corrected it. Here is where it was when threw it back together. The mark is pretty hard to see through the little hole they designate to be used....

Got it back together and as @manicmechanic007 says it did not affect the hot idle. I sprayed carb cleaner all around the intake manifold and it had no effect, but I cannot say that there's not some kind of defect somewhere with it. But - unplugging the IAC drops the idle. So I then went ahead and started unplugging vacuum hoses to see if any of them had an effect. None did, they only caused a surging idle. Only disconnecting the IAC seemed to have a positive effect except when I unplugged the vacuum hose from the manifold that runs to the MAP sensor. If I pulled it and then put it up to the connection a d held it loosely, the idle dropped to where it sounded like it shoud be. But if I connected it properly again the idle would climb and stay high. Which leads me to this piece here - what is this? Just some kind of check valve?

After all of this, this is what a vacuum reading says. My gauge told me it was just about 20 inches while the idle was lower, but increased to about 23 as the idle climbed and leveled out around 1800 rpm after the IAC decides to ramp up the idle.....

So I guess the question is what is causing the IAC to kick on and raise the RPM by at least 700 rpm? Coolant temp is around 210 by what the scanner says and it reads about 20 degrees hotter than my infrared says.

That also has me wondering if there might be something else going on as the thermostat is supposed to be 180 - the fans kick on as they should but it still seems like it should be a little closer to 180 than this.

 

[Mcmahst]

Man, that’s a very comprehension diagnosis. I’m stumped. Hope smarter folks can help.

 

[LILCBRA]

Found someone posted in a Toyota forum that asked the same thing. It's just a filter.

https://www.toyotanation.com/threads/need-help-identifying-part-screwed-into-back-of-intake-manifold.1595378/

Found one on Amazon:

Amazon.com

Now to see if I happen to have an adapter laying around somewhere that I can pull the filter off and install in it's place to see if it'll correct the issue.....

 

[LILCBRA]

Pulled it off and it doesn't have any resistance to speak of, so I cleaned it up and put it back....

 

[LILCBRA]

Checked the MAP sensor readings and it seems to check out, so I don't have a strong suspicion that it's related. There's this sensor on the intake between the filter and throttle body. I pulled the electrical connection as well as I tried pulling the vacuum line and the second line (which has a Schrader valve?) and butted them together, that didn't have an effect either.