bubbasweet

1998 Tacoma 4 x 4 V6 Automatic;

Hello guys. I took my truck into have an inspection and plugs changed and to get my frame coated as it was part of the frame recall. When I got it back I noticed that my idle started fluctuating. It normally idles at about 500 rpm. I started noticing every now and then at drive-throughs and when stopped at lites that it would once in a while surge forward and go from 500 rpm up to between 1200 - 1800RPM. This somtimes lasts for about 5 minutes and then goes back down buy itself. Somtimes it goes back down right away. I definatly cannot kick it down so I do not think it is a stuck throddle cable or anything. Somtimes when it is in the high idle state and I turn it off say to go into a store I know it is going to be hard to start when I come out and I usally smell gas while restarting, but it finally starts. I guess it is flooding. So obviously a gas related sensor or somthing? I am a tech but not a mechanic as you can likely tell. When I took it back to Toyota they found the main large hose to the charcoal cannister off and flapping around in my engine but Toyota maintains they think this is unrelated to the work they have done on my truck and put the hose and clamp back on. They say it could be a sensor but there are many and I just do not want to spend a fortune while a guy who cannot remember to put a hose back on tries one sensor at a time on my dime. Any specific ideas specifically what could cause this intermittant fluctuation and how to economically trouble shoot it?

THANX

Bubba.

Kiroshu

Sounds like Air flow issue.... just guessing. Any codes, Engine light? Possible Tps issues. Is it only at idle? Does it have probs during driving range?

toyota4x4907

3rzfes and 5vzfes idle is controlled by coolant like the older engines, are they not? If so, do you have enough coolant?

bubbasweet

No eng light at all even when charcoal cannister hose was off.. Problem is only at idle.

What Codes are you referring to? Not sure what is TPS?

Coolant? You mean antifreeze?

brian2sun

I also think this is the best place to start. I know that coolant circulates through the Idle Air Control valve (screwed to the bottom side of the throttle body). I believe the coolant controls the opening/closing of the IAC by how hot it is. I'll bet if the coolant is low, the temp might not be getting hot enough to close the valve. That could make the idle do weird things like surge.

Check the coolant, make sure it's full and it's not rusty or dirty. You could try cleaning your IAC and TB too since it's easy and your truck will love you for it. There are a lot of write-ups here on YT on how to do it.

brian2sun

Coolant = Antifreeze

bubbasweet

Thanx guys the coolant and all fluid levels are good, full and in good condition. Will see if I can figure out how to clean that other stuff.

brian2sun

TPS - Throttle Position Sensor.

What did the dealership have to do in order to coat the frame? How long did you have the truck back from the dealership before you noticed the problem?

bubbasweet

When I look back, I noticed it right away. But I did not report it for 1 month because I was not aware of exactly what was happening right away. Then when I could almost not start it in a parking lot one day and I could smell gas I realised what was happening.

They had my Truck for 2 or 3 days to coat the frame which they said was is great shape with no rust but they did it anyway. I think they just taped it with paper and applied this black messy goopy stuff.

You think it is the TPS? Can I change it? Anyonehave a link on how to do this? Or does it have to be replaced by Toyota? That sounds most logical of the replies.

THANX

brian2sun

It's possible it's the TPS, but first I would check all your wiring/elect. connections throughout the truck and hoses too since it sounds like Toyota probably disconnected a lot of stuff to coat the frame. Maybe the charcoal canister hose wasn't the only thing they forgot to hook back up.

If you can't find anything wrong, I would take it to a shop, have them put it on the computer and check for codes (they don't always set off the eng. light but still might help in figuring out the problem). Then they can also test the sensors that are in question- much cheaper than replacing them.

bubbasweet

OK NOW, finally, "check engine" light is on. Went to get groceries and idle took off about 1200 but did not come back down. Also got the hesitation or jerking when first putting it in drive. Is it OK to rive like this. Other than high idle I don't see anything else wrong. I cannot take it in until day after tomorrow and I need to drive it to work tomorrow?

brian2sun

Don't know what state you're in but most Autozones will hook it up to a computer for free so you can see what code it's throwing. Not in Cali though. Some are open till midnight.

Kiroshu

Autozone has a crappy scanner and does not pickup much don't count on that for 100% but you can try. I would take it to toyota to get it scanned for codes and then come back and let us know its kinda hard to tell you whats wrong. It could as simple as a vaccum leak? Do you knoe how to check for this? Look around for broken vac lines and listen for hissing. Air flow meter faulty. TPS Faulty. Theres alot it could be...

brian2sun

Autozone's scanners definitely aren't as good as Toyota's, but if he wants to know if it's something serious or not before he goes to work, it's free so it can't hurt. I would tell them to not clear the codes though so you can take it to Toyota later.

bubbasweet

I got it scanned at Toyota. The guy was nice to help me out. He said it was a coolant temperature Sensor code...

He cleared it and said it may be because it has been really hot here mid 30's. It did not come back on and I guess I am no closer to fixing this idle thing which did not happen today when I drove my truck. But I know it will be back. I usually happens once every few drives.

I was hoping it would be the IPS code

bubbasweet

I just wanted to say that the problem was in the cooling circuit like someone posted not the TPS as many guessed. After finally getting some codes it was the thermister in the cooling circuit that was bad, causing the symptoms in my initial post. Replaced it and my idle now is perfect and solid...

MaK92-4RnR

Mine had the same issue. you're not alone.