Quiet down my taco!

So I have this 1996 Taco (2.7L) that is idling higher than it should. At least it sounds like it is and since Toyota decided that there was no need for a Tachometer even though this is a 5 speed manual tranny I really can't measure the exact RPM.

I did however attempt to adjust this bolt but there isn't much play. A little adjustment either resulted in a very high idle or the engine stalling after it starts.



I've let the truck run for a while and the idle doesn't seem to subside once the truck gets to operating temps.

Can anyone tell me what else I can try to get the idle a bit lower. Where is the Idle Air Control Valve? Would cleaning the throttle body help at all?

Thanks in advance!

 

One piece of advice, DO NOT TURN ANY BOLTS ON THROTTLE BODY THAT YOU DON"T KNOW WHAT THEY DO.
There are some adjustments from factory if you turn them you will never get proper number back.

1. cleaning throttle body is always good.
2. Get some tool that measures the RPM. Most scanguage things will read that out of OBD II port.
3. I am pretty sure 96 already had IAC valve that's controlled by ECT (Engine Coolant Temp) sensor, test ECT - check if it is grounded or value at given temp is wrong.
Good luck

 

@BlueT
Thanks for the tips man! I plan on cleaning the TB and have an OBDII but not sure if it will measure RPM's.

This may be a stupid question, but how do I check if the ECT is grounded? Wouldn't it throw a CEL if it wasn't working properly?

THanks Again!

 

On older trucks grounded ECT will not throw code. The way to check it is... you need multimeter and check ohms between body of ECT and any of two prones coming out.

To check if thermal piece is working correctly you need to warm up ect in glass of water then check ohmage between the prones. In FSM there is table showing what ohmage needs to be at every temp.

But if you never replaced ECT and you have some good mileage on the truck, I would say $10 for new ECT is steal. they should have them in NAPA or Autozone. Thermal piece tends to loose its reading with time so those things needs to be replaced sooner or later.

 

I hooked up an obdII scanner while I drove to and from work. The idle starts at around 1100 rpm and then continues to climb and maxes out around 1500. According to the FSM, the idle should be between 700-800 RPM's.

This is my plan of attack for this weekend.
- Seafoam
- Remove and Clean Throttle Body
- Clean Idle Air Control Valve
- Clean MAF
- Check Engine Coolant Temp Sensor.
- Disconnect battery to reset ecm
- Drive about 50 miles

Any other suggestions?

 

The IAC(idle air controller) is on the side od the throttle body. It has a passage from one side of the throttle plate to the other. The IAC and the throttle plate can stick partially open from carbon build-up and cause idle problems. Throttle body cleaner is the solution for the throttle. IAC will probably need replaced. They wear out.
IAC is probably your issue.

 

loud like this

http://www.youtube.com/watch?v=VK7_KQRzQzU&feature=mfu_in_order&list=UL

 

I'm waiting on some gaskets before I take the TB and IAC off. Nobody seems to stock them so I had to order from Advanced Auto Parts. There were only 4 bucks total for both gaskets.

I seafoamed the engine via the brake booster vacuum hose this weekend and the it did help the rough idle a bit but it is still idling high.

I'll report the results after inspecting the IAC and giving the TB a good cleaning.

Thanks!

 

If RPM's climb I think its more likely to be ECT but yeah cleanup throttle body, I would replace ECT at the same time as well since you will be disconnecting coolant lines anyway. ECT is cheap enough to just throw new one to rule out the issue.

 

I finally had a chance to remove and clean the Throttle Body last night, and boy was it dirty! (See attached pics)

Unfortunately, the screws that attached the IAC were amazingly tight so I couldn't remove it to clean. I didn't want to strip the screws so does anyone have any suggestions for getting these off? (Aside from hitting the gym )

I shined up the TB and put it all back together but to my dismay the idle is still hovering around 1800-2200 now!

Another question - What is the best way to adjust the throttle cable to eliminate this as a potential cause of the idling? I don't think it will completely resolve my issue but when I tug on the throttle while the engine is running the idle drops (audibly so).
@BlueT mentioned that this shouldn't be adjusted but wouldn't this be necessary over time as the cable deteriorates or expands?

My next step is to test the ECT. I will report my results.

Thanks for your help so far. I hope to avoid taking it to the dealer

 

Well you definetely get award for "most dirty" TB , holy crap what are you feeding that truck with? peanut oil ?

1. If TB is that dirty you definetely need to clean up IAC valve. If you affraid of stripping the bolts, try this. There should be washers under the bolts. Find very thin metal blade and try to cut them of (atleast notch them) but not all way to bolt. Just enough to stick flat screwdriver and brake washer a part. You may have to notch them on both sides. Once you remove those stupid phillips screws go to hardware store and replace them with hex screws so next time it is easier to take them off

2. Don't adjust anything yet. Throttle may be sticking from being dirty. BTW make sure you replace gasket under throttle body. You goign have to remove that again to clean up IAC passages.

3. Definetely check the ECT sensor. Do you have table from FSM to check resistance at given temp?
When I get home and I find my old ECT I will snap photo how to check for ground in it.

4. Since your TB looks like crap when was last time you replaced PCV valve?

FYI: Its a simple system there so going to dealer is probably last item to do but lets try fixing this.

 

Agreed but i'm a newbie. Thanks again for your help!

 

TB looks like no maintenance was really done to the truck so you can expect other things having issues.

1. Yep cut those washers off get new ones to replace with hex bolts instead of phillips (thats what I did ) you will never again have problems removing IAC. What you can do to try is use phillips bit (instead of screwdriver) find one that fits perfectly, then tap it with small hammer (sort of to press into phillips screw) then use rachet with socket to press on the bit and take the philips screw out.

2. If you loosen any screws that you should not then you going have to adjust them, look into FSM for procedure but I would do that after you check ECT, Clean/test IAC, Check PCV. You don't want to adjust them on bad parts or dirty parts.
Yes thats the gaskets. Make sure you keep them clean and nice. If you planning to remove them what you can do is buy teflon spray (one safe for o-rings) and spray them before you put them o nthe truck. let them dry first. It will keep rubber protected from air and scratches when you bolting things up.

3. I believe ECT is somewhere on driver side, sorry its been too long since I sold my 2.7 so memory is not so good.

4. PCV, you need to check PCV itself. This is one of the maintenance items and expected to be replaced, There should be rubber grommet that needs probably replacing too. May as well get new grommet, be careful removing old one, rubber gets brittle and hardened so it will most likely fall a part.

Your Welcome, glad can help
Its karma I help you, somebody helps me , you help somebody else

 

Thanks to your advice, I was able to get the IAC off the TB. Lowes didn't have hex screws that could replace so I picked up new phillips srews and mini crush washers. Should be easier to get off next time. It was pretty dirty and cleaned up ok. Bits of corrosion or rust here and there but the airways functioned fine. I didn't test the sensor, didn't have a multimeter. I cleaned it with some carb cleaner making sure not to spray or slurry up the connector. The gasket was in good shape and I gave that a wipe. Then put everthing back together and checked out the

- PCV Valve. Was a b!tch to get out. I was anticipating being able to just pop it out by hand. I couldn't get the grommet out. I wiped down the PCV valve and it tested it by blowing on either end and it did all air through. I pulled the hose off while the engine ran and car stalls so I assume the valve is doing its job.

- Replaced the ECT with a brand new one, but the connector is missing the tab to completely secure the the male end but still plugs in tightly and doesn't slide out on its own. Could it be the female connector that is faulty? Wiring was in good shape.

After all this, I started the truck up and it idled noticeably quieter for a little bit and the OBD showed 1634Rpms but still increased to over 2K RPMs at idle within 10 minutes. However, the acceleration is definitely more responsive and it sounds better when in gear. Probably due to cleaning the IAC (or just my imagination) and I also, forgot to mention I drained the radiator and ended up with about 1.5 gallons of coolant. Mixed up a new 50/50 mix of coolant and distilled water and refilled the radiator. When I shift into the gear the idle will stay around 1000 RPM's while in 1st gear and standing still (this is how the Korean military trains to drive a manual tran according to my dad) but when in neutral the idle sounds much higher, again hovering around 2K RPMs.

I feel pretty close to getting this thing cracked. I'm loving the way the truck feels when in gear, but it is way loud in neutral like an airplane jet preparing to launch.

I'm guessing that I might need a new IAC and the PCV is cheap enough that I might as well replace that too. What do you think? I should mention that I do have a check engine light - P0336 which is a Crankshaft Positioning Sensor error (sensor A). This sensor has been replaced in an attempt to clear the code but persists. Could this in any way have an influence on the engine idling so high?

Any more ideas bud?

 

Here is some anecdotal testing.

1. Turned on AC full blast. RPM's go from 2025 to 1900

2. Pulled the hose off the Resonator that goes to the IAC Valve and cover the hole just slightly. I feel a vacuum pressure pulling air in. I can vary the amount of air that goes in and can get the idle to drop to 695-900 rpms. I'm thinking this is once again pointing to a defunc'd IAC valve.

Back to that damn throttle cable. I don't think that has much to do with the idling. It seems that when the engine is running the ECM tells the throttle to close completely. I noticed while I was cleaning the TB that the spring doesn't completely close the butterfly while the spring is at rest but does so via the ecm at idle.

Hopefully this will help add some insight to the idling issue. I'm in search of an IAC valve for a good price. Toyotapartszone has it for 200 bucks but I found one on ebay for 90 after shipping.

 

Idle is controlled via the IAC. The throttle is controlled by your foot, not the ECM.

 

Hopefully this is the culplrit since I just bought a new IAC Valve. Should arrive in 3-4 days, I'll report the outcome once I swap it in.

Thanks!

 

I got the new IAC Valve installed along with the new gasket.

The truck is still idling at around 1900 RPM's.

So far none of the following fixes have resolved this:
- new Engine Coolant Temperature sensor.
- Coolant drain / flush
- new IAC valve
- Throttle body cleaning

Any ideas?

 

I've managed to get the idle down to 845-955 RPM and it sounds so much quieter.

The solution:
I tinkered with the set screw which was preventing the throttle from closing any further. This made a huge difference.

Thanks for all who helped me out.