Any ideas ?

Vacuum leak, even though you haven't found it yet. Use a water spray from spray bottle and listen for drop in idle when water is sucked in.

cannot detect a vacuum leak as yet but that is difficult to do. Not sure what to do next. Let me know if you can help.

If the engine has an EGR then that could be not shutting properly and that is a vacuum leak also.

 

Thanks for the information , cheers. Will let you know what it was when i have sorted it. Thanks

 

When you cleaned the idle air control valve, did you disassemble the electrical solenoid and clean inside the magnet housing? Often there is a buildup of gunk inside the magnet housing and it prevents the actual idle "barrel valve" from rotating freely, which is what actually controls the idle airflow. This valve is VERY precise and should have ZERO resistance to rotating. Another consideration is that the IAC body to IAC solenoid leaks air and is considered a vacuum leak (or unmetered air) into the intake manifold. Ditto on a faulty EGR valve leaking as well. If you can get your hands on an automotive smoke machine, you will see exactly where your engine is leaking air, and see it very quickly. Might be worth your time to track one down.

Here is the IAC Solenoid that was removed and cleaned to allow unabated rotation of the actual IAC valve. You can also see the black Toyota FIPG (form in place gasket) that was applied to seal a vacuum leak where the solenoid mates to the IAC aluminum body.

You can see the smoke detector smoke emanating from the top of the IAC solenoid Assy. which is "unmetered" air into the intake, otherwise known as a vacuum leak.

Here I removed the IAC solenoid to expose the valve. My smoke machine smoke is clearly seen bypassing the IAC barrel valve.

The IAC valve is cleaned of gummed residue and now rotates very easily with the tip of your finger. It rotates only a few millimeters clockwise or counterclockwise. Zero resistance to turning by finger should be the proper functioning of this valve.

FIPG applied to seal vacuum leak.

 

 

Hi Strega , thanks for all this information , i did clean the valve so it was really free but not to the extent you have shown. Also no gasket adhesive was used on the refitting as it looked intact. I will try these things and see how it goes. Thanks a lot for the information the way you explained things is awesome. Should be a Tech school teacher .Will let you know how it goes after i find the leak. Cheers

 

Hi there again , i have done the smoke test and i had only one tiny leak from the PCV valve grommet , fixed that and nothing else. Tested the inlet manifold system and exhaust system and no luck. Any ideas where to go from here? I am thinking it could be mechanical and not electrical but don't know where to start? Let me know what you think?Thanks

 

Dirty fuel filter?

 

Ok thanks , i will check that as well , cheers

 

Techron fuel injector cleaner. If you look at the fuel trims you'll know for sure. High positive LTFTR is almost always clogged injectors. After a can of Techron the fuel trim will get lower, that's your indicator that this is the problem. The engine is starving for fuel at hot idle. That's why no check engine codes. When it gets bad enough you'll get P0171 lean or P0300 cylinder misfire. A lot of varnish builds up over 20 years.

 

Ok thanks for that information , will plug in computer and check fuel trims and go from there. Thanks

 

Have you tested the throttle position sensor ?

 

I will give that a go, will read up on it and try that in the next few days. Thanks for the suggestion.

 

Looks like the only thing left is injectors. With 123,000 miles how could they not be gummed up?

 

I have been running an additive similar to Techron as i cannot find that brand in Australia . I will speak to my mechanic about injector cleaning etc. Thanks

 

Any resolution to this problem?? My car has a VERY small idle surge only easily detectable when standing behind the car listening to the exhaust. since it's so minor, I haven't troubleshot it but have done a thorough cleaning of the IAC to correct an engine dying at idle issue. It very much needed a thorough physical cleaning, not just a few shots of carb cleaner. Wheatwacked's comment about cleaning the injectors is certainly valid but I don't think it's a given that your injectors need service after 123,000 miles. Mine have never been removed at 574,000 miles and I have long since ceased to use injector cleaner. Bragging? yes, stupid lack of maintenance, probably, but still it's an interesting piece of data.

 

Hi there , no resolution yet , no vacuum leak so i am going to swap out Egr valve and Tps sensor 2nd hand items which is from a Camry running well from the wreckers and see how that goes. Will post once i find out. Mine only idle hunts/surges after 20 minutes of driving and you can notice at idle and when taking foot off the accelerator to slow down. Thanks

 

In 1985 I had a rash of clogged injectors in the 6 cylinder Olds Cutlass that happened only with customers using Exxon gas and GM let me cover it under warranty. The next year year they used a different injector part number. Look at your LTFTR..Awesome mileage.

 

What were the numbers? Especially. high long term fuel trim indicates that either low fuel pressure or clogged injectors or major vacuum leak like the brake booster. The Fuel pressure regulator tends to fail to high pressure. The TPS will not fix anything but the urge to change parts. 5 mg Lithium Orotate a day will help that. EGR if stuck open may cause lean. The deteriorated hose might be a sign of that. Your time would be better spent pulling and cleaning the injectors.
I did it on Highlander. It worked great the hardest part is sealing the carb cleaner tube to the injector. I used a rubber nipple held on the injector with a hose clamp and mini alligator clips to a 9 volt battery and poked the tube on the carb cleaner into it. You actually see the injector spray pattern improve. Use a 9 volt battery to activate the injector while spraying. You'll see the spray pattern improve. The injectors are 12 volt, so 9 volt is safe continuous for a few moments. Protect your eyes. There is a u tube video. You can get a set of fuel rail to injectors fairly cheap at RockAuto or Ebay. Change the injector to manifold seats as a set or not at all.

 

fuel rail to injectors

fuel rail to injector o-rings.

 

Check for torn or cracked hoses from the IACV to the intake manifold. There are 3 hoses and plastic tee.

 

Hi all , it turns out the EGR valve was faulty even though there was no check engine light. Changed it out for a 2nd hand one and runs great. Thanks to all for all of the ideas and information, a great help to learn for future issues as well. Cheers

 

EGR like the fuel pump and regulator are not monitored by the ECU so no code. EGR solinoid though will. Ah, it all makes sense now. Thanks for letting us know the resolution.

 

Was there a change in the LTFTR before and after the repair?

 

Please don't replace any parts without a thorough diagnosis. With the car fully warmed up and in closed loop, please post your OBD2 readings at idle, 1,500 and 2,500 rpm. Be sure to include engine coolant temperature, LTFT and STFT on both banks as well as throttle position, MAF, IAT and timing advance. Your readings should be similar to the attached. Together, there should be some clues as to what is going on.

 

Looks like your EGR may have been open enough to cause rough idle but not enough to set P0402.

Did you clean the old EGR valve and check for valve open & closure prior to replacing it?