2002 Sequoia Mystery Idle, any ideas would be GREAT =)

2002 Sequoia mystery idle issue

Sorry for the length, but this way the details are there.

Hello, thanks for looking at this. I’m trying to troubleshoot an issue with an '02 Sequoia (268,000 miles) that I started maintaining earlier this year for a family that’s friends of mine. They don’t know much about its history, as the dad/husband took care of the maintenance, and he died in February. What I’ve been able to find out is that it hasn’t ever had (or needed) any major repair, and it has “had some oxygen sensors replaced last year.”

So, here’s what’s going on. In February, the lights were left on for an hour or so, the battery was old, and so they had to get a jump start. After the jump start, when you’d let off the gas, the engine would usually quit, but if you coaxed it, you could sometimes get it to run a low rough idle. (Additionally, the check engine , VSC, and Trac lights stayed on. The check engine light had always been on, and I’m told the VSC and Trac may have gone one and off.) So, they took it to the Toyota dealer, who replaced the battery and “reset the computer” (they didn’t know that’s a matter of disconnecting the battery) and said that it should be fine. Well, as you might assume, nothing changed. So, I offered to work on it for them, and so I cleaned the throttle body (REALLY needed it), and changed the air filter, and reset computer. Problem solved, it ran like NEW, the VSC and Trac lights have been off, and its been perfect since then until July, I changed the oil (Mobil 1 extended) and changed the transmission filter (never been done), cleaned the pan, new gasket, and added new fluid (I did not flush the transmission or mess with anything in any way. For the sake of the following, I did not disconnect the battery (so no reset).

Here’s where the problem starts. For the first 20 minutes or so, it ran and shifted perfectly (I was driving it this day). Then, while accelerating onto the interstate, it started “bucking” so I backed off the pedal a little and all seemed well, except the VSC and Trac light were on. Once off the interstate and in stop and go, I noticed the engine was idling rough and at low speeds when I’d let off the gas (say 25 mph, letting off to slow to stop) you could hear a sort of (somewhat slow rhythmic) clanking sound from the engine compartment and sometimes at idle, as well.

OK, so since then, I’ve driven it a good bit, and know the actual symptoms better (and they stay the same, not worse, not better)…
-Starting cold, it initially seems smooth. Then as rpm slows, the roughness appears.
-For a short period after a battery disconnect, that clanking sound as mentioned above will happen at idle. It turns out to be the butterfly valve clanking open-shut-open-shut). After awhile, this clears, and unless the battery is disconnected again, it doesn’t do it anymore, except sometimes when decelerating you can hear it).
-Once engine is warm, it always idles rough (unless a/c compressor on, then smooths somewhat).
-Warm starts go like this… First try: engine always pops off quickly, then immediately quits. Second try: engine pops off quickly and keeps running (happens this way most of the time, occasionally first try will keep running, second try always keeps running). (Cold starts always keep running).
-VSC and Trac lights stay on, always (as well as check engine, but I don’t think it is related, as it has been for years).
-When slowly giving gas from idle (like pulling out of stop sign), it’s slightly rough at first, but once it has maybe 1200 or so rpm, it smooths out.
-ANY TIME the engine hits 3,000 rpm when accelerating, it bucks fairly heavily. Letting off gas slightly (to under 3k) smooths it out.
-I’m not sure whether to add that I think the exhaust smells a little rich when idles, as I’m not sure how it smelled before this, so I can’t really compare it.

I did go by the auto parts store and have them tell me the codes it’s giving. Basically, it says all of the oxygen sensors and the mass airflow sensor, but they said those codes had been there for a long time (and apparently some have been replaced w/in the last year). I don’t think it’s the mass airflow sensor, as I ran it briefly with it disconnected and there was no change.

Anyway, sorry for the length, but I wanted to be thorough. I really want to help them, but I’m not sure what the problem is. I feel it’s associated with idle air mixture, but I don’t know what. I’m not sure how that explains the bucking at 3,000, but I wonder if that’s something to do with the traction control being confused (because it feels sort of like a rev limiter). So, any thoughts would be REALLY appreciated. Thanks!

gt2av8 writes —

<font color=“Blue face=“Times”>”… In February, the lights were left on for an hour or so, the battery was old, and so they had to get a jump start. After the jump start, when you’d let off the gas, the engine would usually quit, but if you coaxed it, you could sometimes get it to run a low rough idle. … So, they took it to the Toyota dealer, who replaced the battery and “reset the computer” (they didn’t know that’s a matter of disconnecting the battery) and said that it should be fine."

In jump starting the car, the computer code in the electronic control module may have been corrupted. The dealer, rather than simply disconnecting/reconnecting the battery, may have reflashed the computer. (The dealer usually charges for re-downloading the code, anywhere from $100 to $300.) If the dealer did not reflash the control module, you may be running with a corrupted electronic control unit.

268K miles. Any chance the spark plugs need to be changed?

As mechaniker hinted, disconnecting the battery may seem to “reset” it, but if there’s something wrong in the code, the flash would have been required. A “reset” of the type you would use by disconnecting the battery may cause more problems than it solves, as Tester and this site will tell you: http://www.aa1car.com/library/battery_disconnect_problems.htm

A decent diagnostic for the rough idle will surely point to something specific. What the codes actually are (PXXXX, and not " all of the oxygen sensors and the mass airflow sensor") may assist. Often one thing can set off more than one code.

Thanks Mechaniker and chaissos… I’m pretty sure the dealer didn’t (based on their receipt/print out) re-download the code. So, that’s an interesting thought, though it was since it was at the dealer (and had no change whatsoever from their work) that I cleaned the throttle body, at which time I disconnected the battery, and then in ran like new from then (beggining March) until July. So, that leads me to think it’s not corrupted. Also, the spark plugs were changed (so I’m told for the first time) in the 250,000s. So, next step, I’ll try to get the specific codes. Thanks!

What were the EXACT codes that were pulled from the computer? The format is “P1234” - vague notes about O2 sensors and MAFs don’t say anything. Codes also don’t tell you that parts are bad - so having changed some sensor or something referenced in a code doesn’t mean anything. So get the codes and post them.

Check the coolant temp sensor and fuel pressure.

Someone will need to scan it for codes re: the VSC/Trac lights (probably requires different equipment from the auto parts store’s OBDII reader). If you get them, write down the codes and post them.

Thanks everyone for your replies. So, today I was able to get some helpful information.

The codes it was reporting today were…
P0100 - mass or volume air flow circuit fault
P0101 - mass or volume ar flow circuit range/performance
P0110 - intake air temperature circuit fault
P0135 - O2 sensor heater circuit malfunction (bank #1 sensor #1)
P0141 - O2 sensor heater circuit malfunction (bank #1 sensor #2)
P0155 - O2 sensor heater circuit malfunction (bank #2 sensor #1)
P0161 - O2 sensor heater circuit malfunction (bank #2 sensor #2)
So, I cleared the codes, and P0100 came back immediately.

Additionally, I found the service record from the time it was serviced at the dealer that I mentioned in the first post. At that time it reported these codes…
P0125 - insufficient coolant temperature for closed loop fuel control
P0155 - O2 sensor heater circuit malfunction (bank #2 sensor #1)
P0161 - O2 sensor heater circuit malfunction (bank #2 sensor #2)
C1203 - not sure… possibly communication fault between skid control computer and ECM, or I also found, engine control system communication circuit malfunction.
C1363 - not sure, but best I could find is "brake booster pedal force switch"
B1242 - wireless door lock tuner circuit malfunction
So, they cleared the codes (that’s the only “reset” that was done, now seeing the record), replaced the spark plugs, and the battery ($50 just in labor for replacing the battery!! ugh). On the sheet it said that per the owner, 4 oxygen sensors were replaced in October, 2010 (at another shop). So, after they got it back, it wasn’t any better, and that’s when I came along and started with it… TB cleaning which cleared the issue and ran great till the current problem.

My thoughts…
First I thought, seems like MAF sensor because of symptoms, and 100,101, and 110. I’m still HOPING that seems somewhat logical, as it’s inexpensive. But, what I don’t understand is that, if all of the oxygen sensors were so recently replaced, obviously they can’t all be malfunctioning (specifically with the same problem reported with each). C1203 and 1363 I’m not sure if is in there or not today, as I doubt the store’s reader would show. Same with B1242, but this vehicle doesn’t even have keyless.

I’m beginning to worry that it’s more than a simple MAF sensor, that it could be an ECM problem? That would be… not good.

I also want to point out that what stands out to me the most, symptom wise, is warm starts first try usually starts and immediately quits, second try is always flawless; rough idle; and (it seems like this one might be a clue to something) when low speed decelerating (say in traffic, in a parking lot, or for a turn) roughness and I can hear the butterfly valve in the TB clicking slightly open and shut repeatedly.

What are everyone’s thoughts? Thanks SO much everyone!

First, note that none of those codes tell you anything about parts. Note the word circuit in each and every one. A code - such as “P0135” doesn’t say that the O2 sensor is bad - only that the PCM is getting out of spec electrical signals. All of the sensors have to send/receive electrical signals/power. The sensor are part of the circuits, so if the sensor do go bad they’ll throw codes like this. But the problems can easily lie elsewhere - as in the wiring. Or yes, even the PCM.

Anyway, that is quite a pile of codes. I would actually take a look at a wiring diagram and find out if all of those things might share the same ground or something before I spent much time on everything else.

But if that was all good I would move on to the MAF - but that doesn’t mean just replacing it. Clean & test & check. A scantool and someone who can use it at this point would be your good friend. But even just a visual inspection of the wiring & a simple multimeter can get you quite a ways.