Idling and acceleration problems

[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]

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]

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