[perk]

It typically idles around 650 rpm, 2 weeks ago it idled rough and began trembling and eventually stalled while coasting into a parking lot. It was just barely warmed up at that point. I came to realize it was a matter of rpm’s dropping to 200-400 that was causing the rough/trembling idle and stall. It’s done it intermittently since than. Cold idle was off a couple times, but in the opposite direction, too fast. Cold idle has mostly been correct. During this time, when the warm idle has not dropped, its been either 650 or 800.

Acceleration has also been effected. The morning following the initial episode, it idled too high upon start up then accelerated in reverse more rapidly than normal. That was the only abnormal acceleration that’s been noticed until tonight when it started acting up for my wife. While traveling about 40 mph she said it began accelerating without gassing it, and when taking off from a stop it rapidly accelerated as soon as she took her foot off gas.

Maintenance items done over the last 8 months include new OEM plugs, wires, cap&rotor, EGR modulator, air filter, pcv valve and hoses. Throttle body was removed and cleaned. EFI sercive at dealership and a can of redline gas treatment.

Any experienced advice would be appreciated.

Thanks a lot,
Perk

[Cruiserhead05]

Perk,

I would say check the entire intake hose that goes from the air box to the throttle body. Typically they can crack and will mess up how your truck runs. My truck was doing just what you described. i got home, checked the hose and it had a 2 inch crack in the bottom that was hidden pretty well.
If not that then maybe fuel injectors?

some others should get on here and help better then i can....but thats where i'd start.

[IdahoDoug]

Crack on the bottom of the pleated section of the rubber hose that connects the air cleaner to the engine. Next time you change the filter, remove the hose clamp that holds it to the air cleaner instead of bending it upward.

DougM

[KliersLC]

As far as the unexpected acceleration, My old camry had a crack in the intake hose similar to the cracks that develop on the the cruisers. PO siliconed it, but a year later the engine sucked the silicone out of the crack and into the TB causing a very interesting driving experience. Check for something stuck in the TB-chunk of rubber, sililcon, dead mouse, etc
Good luck,
Dan

[perk]

When I replaced the air filter (about 4 months ago) I closely inspected the air hose and no cracks underneath on the pleated section. Maybe one's developed since than. There is a crack about 1" directly under the clamp at the throttle body. It was there when I changed the air filter, it may be a little worse. Is there any way that could be the culprit?

[Rich]

Regardless of whether or not the crack under the clamp is causing a problem, it does indicate that your intake tube is at end of life and should be replaced.

Unfortunate that the part was not manufactured with a more durable material. It would be interesting to explore what aftermarket tubing is available.

[perk]

Pulled the hose... no crack other than small one under the clamp thats directly over the metal of the throttle body. I'll replace it and keep my fingers crossed, but the minute amount of air, if any, that could enter there wouldn't be enough to cause these problems....would it?

Any more educated guesses would be appreciated

Perk

[Beowulf]

Originally Posted by perk

Any more educated guesses would be appreciated

Perk,

The hose is the most likely culprit.

Next would be related to:
"Throttle body was removed and cleaned. EFI sercive at dealership" ... I would double check what was done here. Maybe something with the TPS or the MAF. Check electrical connections on the tube.

If all of the above check OK, then inspect the main engine wiring harness at the EGR valve, along the firewall, and where it enters the cabin under the glove box. You're looking for frayed or cracked wires, loose connections, burnt insulation, etc.

-B-

[landtank]

check your coolant level. I had erratic idling when my coolant got a little low. I think it had something to do with the temp sensor for the ecu.

[IdahoDoug]

Rick,

That's funny - I had this also a couple weeks ago on the 97 and forgot all about it. Prolly suppressed due to embarassment at ever having low coolant (yeesh)....shaking head....

DougM

[perk]

I replaced the air hose (thanks Dan). I've driven it a few days now since I replaced the hose and there is little to no change. Intermittent idle problem is still present. Sometimes it idles correctly at about 650 but other times it will drop to 200-400 causing the engine to tremble and sometimes stall. Sometimes, but not as common, it will idle too high at 1000-1200 rpm.

I've double checked all the electrical connections including MAF and TPS, as well as the main wiring harness. No signs of frayed or burnt wires. All insulation is intact so I'm assuming the wires are OK. Coolant is full as always.

Any other ideas???

Thanks alot
Perk

[powderpig]

I would double check the TPS to see if it is adjusted properly. The computer may not see that the TPS is in the idle position and thus create you weird idle stuff. Check the wires at the back of the engine to see if the are touching the EGR pipe, if so move them away and see if the have melted any thing, Just a couple of thoughts. good luck robbie

[perk]

Thanks Robbie

Wires are ok although very close to the EGR pipe, if not slightly touching. I tried pulling the bundle away, but it seems to be fastened in it's position.

I'll check the TPS as soon as I purchase a vacuum. A couple questions about the procedure in FSM...What is the throttle valve? What does the - mean for throttle valve condition when checking VC-E2?

Thanks alot
Perk

[powderpig]

I think they are refering to the throttle plate inside the housing. This sometime get caked with oil residue thus not allowing the plate to fully closed. this is one thing that if has happended can create proplems for you. It needs to be cleaned once in a while. if there is a build up on this plate. the tps may not registar that the plate is in the idle position thus creating problems for the computer to determine where the throttle is. good luck robbie

[MoJ]

Originally Posted by powderpig

I think they are refering to the throttle plate inside the housing. This sometime get caked with oil residue thus not allowing the plate to fully closed. this is one thing that if has happended can create proplems for you. It needs to be cleaned once in a while. if there is a build up on this plate. the tps may not registar that the plate is in the idle position thus creating problems for the computer to determine where the throttle is. good luck robbie

I was having some random low idle issues over a year ago and cleaning the throttle plate cleared it up. I didn't remove the throttle body. Just removed the intake hose, held the plate open by placing something on the gas pedal, and scrubbed it with 3M throttle body cleaner. It took a little time to get both side of the plate clean. I did jack up the drivers side so that the cleaner would run back out onto some paper towels. It got the plate and surrounding area spic and span but to do it totally right I probably should of removed the throttle body and cleaned it.

[perk]

My idling issues appear to have gone away now with the new intake hose. It took about a week of driving before all misidling stopped. As I posted earlier, it continued to idle incorrectly for a few days after installing the new hose which made me think there were other issues besides the hose. Why did it need to run a while with the new hose before the problem cleared up?

Much thanks to those who drop their knowledge,
Perk

[powderpig]

Something else is up in that it does not take the later model trucks that long to learn its limits after work(even the early ones only take about 15 starts to learn the idle). I would check all the wiring at the battery for loose connections and or clean the posts well. Check the side of the intake manifold for loose grounds. I jsut do not think the hose was the true problem. Hopefully it will not come back and this misterious fix is all it needs. later robbie

[ronin-0707]

is there an "idler body" that needs to be adjusted or replaced.
my mechanic mentioned that this can be a problem with Toyotas in general.
my car has the same issue with the idle dipping to 400 feels like it going to stall then 2 min. later the idle is back to 600-650-cycles like this at a stop light-no acceleration problems, no actual stalling.
my mechanic looked at the air intake hose and throttle body-all is good-and feels it is probably the "idler body"-needle is getting stuck not letting enuf air thru
what to you guys think-a $500 replacement just for parts

[gbell210]

Curious if this issue with your Intermittent idle has been fixed for good now? I have the same problem. Seems like after highway driving (nice and hot) it idles fine (600rpm), but just around town driving it can idle around 400rpm.

I also notice it can be idling at 600 and I turn on the A/C it dips down first but then goes up like it should. But turning the A/C off drops the idle down to this 400rpm mark and doesn't come back up, until I've driven it for a while.

I've checked my intake hose, and no cracks through it, although I can see some hairline cracks starting to form on the rubber. Also, I just replaced one of my PCV hoses (one closest to the pass. side of the valve cover) as there was a crack that could let in air. Inside the throttle body opening looks clean, but I didn'g get a good look at the plate. I've had the rig for about 8 months now, and this started about 2-3 months ago (end of summer). Engine has 205k mile on it, but the previous owner said he rebuilt it at 190k. When it does idle at 600rpm, its nice and smooth, is there anything else I can check for?

[perk]

More data and surprise surprise you were right Robbie...
It's idled correctly for about the last two months/1500 miles. Than...the rough idle/rpm drop to 200 reared its ugly head again. It happened after a two hour highway drive (the only drive of any real distance during this time). RPM's started dropping down too low while stopped at the end of the off ramp. Idle problems (either too high mainly at startup or too low causing rough idle) continued for the next few days of around town driving. Following this time, there was a short period where it seemed like it was back to normal (600-700), mainly in town driving, but it began idling rough/dropping rpms again after a fairly short highway drive. There seemed to be a connection with the rough idle/low rpm problem coincinding with highway driving?? Maybe just a coincidence, not sure.
I decided to put a bottle of Redline Fuel System Cleaner (after reading positive reviews of it here) into a full tank of gas to see if it would help...it did. I put it in about a week ago and immediately drove about 1 hour on highway. When I exited the freeway the idle stayed where it should (6-700). I've driven it around town and short highway trips over the last week and have experienced no problems with dropping rpms/rough idling. It does, at times, idle at 800 rpm, but hasn't dropped below 600. Hopefully the Redline treatment fixed the problem. I'll post back if the problem returns.

Perk

[perk]

Two weeks since the Redline treatment and the problem came back....worse than ever.

Took the family down to the Living Desert in Palm Springs this weekend. After about 45 minutes of hwy driving, while going through town, the idle began going mad. It would not go below 1200 at a stop, requiring heavy brake pressure to keep it stopped, and when placed in N or P, would quickly rev to about 2200 rpm than drop back to 1000 than back up to 2200 than back down; up...down...up...down...etc.

After leaving the park and coming to the first stop sign the engine immediately stalled. After that, the engine idle continued to do the up...down thing described above.

I'm resigned to taking it to a shop as this problem seems beyond my 1-2 capabilities. More diagnosis ideas would be appreciated.

Thanks
Perk

[CJF]

I see above where you said you checked the connections to the TPS; did you ever actually do the diagnostics for testing/adjusting it? Absolutely do that if you haven't.

Curtis

[Beowulf]

Perk,

It may help us if you will summarize what was done just prior to the problem and everything that you have done in attempting to correct the problem.

Robbie gave you several TPS & MAF pointers. Were you able to eliminate those as the cause?

The main wiring harness has 2 areas that have been known to cause problems. The first is where the harness is routed close to the EGR valve. The insulation on the wires can become brittle and crack from the heat. Strange problems will be a result and there are numerous symptoms including poor idling. The second area is where the harness goes into the firewall and underneath the glove box. This is where it goes in to the main ECU. Check it carefully.

-B-

[desmocruiser]

I had a strange idle problem as well, turned out the wiring harness was compromised in both areas mentioned in the previous post. One other thing is to also check the throttle cable (thanks CDan). I did just a bit of basic testing by waiting until mine acted unusually and would press the throttle body end to be certain it was closing completely, it didn't change my trucks behavior. Could be a possibility since your's seems to change as you pull to a stop or change throttle position. I changed parts in the following order. #6 injector, TPS, fuel reg, and finally throttle cable, fuel filter wiring harness, and installed a cleaned set of injectors as the grand finale. Problem resolved after the final stage. Good Luck, certainly frustrating but with the help from this forum there will be a resolution.

[perk]

A few questions.... Is an OBD II scan tool needed to test TPS and MAF? The wires in the wiring harness are encased so if the encasing is intact can the wires be damaged? If yes, how should one go about inspecting the wires? Should the throttle cable be tight(mine isn't)? Should the IAC valve be tested?

After looking through the FSM at the troubleshooting procedures, I think I'm ready to turn at least the diagnosis over to a professional. How long should it take a shop to run the inspections/tests discussed so far? It seems like for a professional mechanic with the proper tools it would just take a few minutes. Is it necessary to go to the dealer for these types of inspections, or should I just take the FSM to an indy(they would need it wouldn't they)? I would like to avoid my local Toyota dealer as they seem to exaggerate labor time.

Thanks,
Perk

[IdahoDoug]

Throttle cable should not be tight or close to it at idle. Dunno about other stuff. No check engine light? Does this light go on for a few seconds each time you start it (along with the ABS light, airbag light, etc)?

DougM

[perk]

Yes, check engine light does come on when key is in "On" position and quickly goes off upon start-up?

[Beowulf]

Originally Posted by perk

The wires in the wiring harness are encased so if the encasing is intact can the wires be damaged? If yes, how should one go about inspecting the wires?

Yes, by the EGR valve. Unlikely under the glove box. Get yourself some high temp tape (heavy sliver stuff available at a speed shop) to reseal the harness after you open it. Some have been able to wiggle the harness in this location and change the problem (make it worse, cause it to start, make it stop, make it better...) I would think you could detect idle changes with some movement of that harness while the engine is running.

-B-

[CJF]

Originally Posted by perk

A few questions.... Is an OBD II scan tool needed to test TPS and MAF?

On a 3FE you easily test the TPS and MAF (actually I believe it's an AFM on a 3FE) with an ohmmeter. Not so on later years?

Curtis

[desmocruiser]

I was not able to get my to correct itself by just moving the wire, I could not understand why I could not. Not the most electrical saavy person around, so I can't explain why a new wiring harness fixed the problem when replaced, but couldn't get it into a position that it would solve the problem by moving it around. Maybe a slight loss of current in a very precise system made for some type of pulse or lack of signal.?.?. It was the most frustrating problem that I and several associates at the local Toyota dealer had ever experienced and I have been in the auto industry my entire life. Good luck, hopefully you will not have to replace as many parts as I did in the process. The wiring harness is a fairly serious undertaking, so I did not attempt it until I had ruled out EVERYTHING else, starting with the most obvious and the least expensive. Had to move most of the attempts from my repair file to my PM file as I continued to install with no change. Might want to do a search and reread the posts as well, I seemed to find something new with each reread. Mine was like solving a very complex (expensive) problem and it only had a ~25 rpm drop, driveable but very annoying each time you stopped and would let the truck idle.