Spark Plug Change Now High Idle?

[lookinin]

Hi to all! This forum has been a great tool and I've learned heaps. Many thanks to all who take the time to post. Anyway, today I changed my spark plugs (NGK Iridium IX) and I also noticed that the throttle body "flap" had some grunge on the outer edge. I cleaned that bit of crud off the flap and restarted the car (it has 210,000 kms on it) but the idle won't go below 1100 RPM now. Did I do something wrong? Is the air flow different now because of the light cleaning of the flap? I don't think it's the plugs, but you never know. If anyone can tell me what to look for I'd be very grateful. And no loose lines that I can see either. Thanks.

Cheers,

Kevin

[curiousB]

A few thoughts:

1) Did the throttle plate get slightly bent and isn't closing fully? Straighten or buy new plate

2) Did all the cleaning solvent carry sludge into the hinge (pivot point) and the spring is no longer strong enough to close the plate fully? Re clean

3) Is there a chunk of sludge holding the plate open some? re clean

4) Has the engine warmed up sufficient that the warm up higher idle is completed? do nothing this is normal

[lookinin]

A few thoughts:

1) Did the throttle plate get slightly bent and isn't closing fully? Straighten or buy new plate

2) Did all the cleaning solvent carry sludge into the hinge (pivot point) and the spring is no longer strong enough to close the plate fully? Re clean

3) Is there a chunk of sludge holding the plate open some? re clean

4) Has the engine warmed up sufficient that the warm up higher idle is completed? do nothing this is normal

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I'll take a closer look, curiousB, but I can't imagine that anything is bent. The flap closes firmly and quickly, so it seems to be OK. Perhaps I should put the old spark plugs back in and work backwards from there? Very frustrating. I guess the expression, "No good deed goes unpunished" applies here. Save a buck by doing something myself and it could end up costing heaps more. Too bad - the car is a dream to drive. Thanks for the ideas, curiousB.

[curiousB]

Hard to see how spark plugs would cause this. IACV system is a closed loop feedback system. ECU monitors engine output speed and trims IACV to let just enough air pass by the throttle plate to maintain constant idle. The system can get "fooled" if air improperly bypass throttle plate such as the ideas above. Maybe your IACV is a little sticky and needs the same cleaning as the throttle plate did?

One point I forgot to mention, did any vacuum lines come undone or cracked so they are leaking? Any type of air leakage can mess us throttle speed.

[lookinin]

Hard to see how spark plugs would cause this. IACV system is a closed loop feedback system. ECU monitors engine output speed and trims IACV to let just enough air pass by the throttle plate to maintain constant idle. The system can get "fooled" if air improperly bypass throttle plate such as the ideas above. Maybe your IACV is a little sticky and needs the same cleaning as the throttle plate did?

One point I forgot to mention, did any vacuum lines come undone or cracked so they are leaking? Any type of air leakage can mess us throttle speed.

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Well, I just put the old plugs back in - no difference. More wasted time. When I push on the throttle plate (engine off, of course) it doesn't seem to fully-seated, if you know what I mean? It can be pushed to a tightly closed position with very light pressure on the throttle plate. Perhaps there is a spring that is fatigued? Where do I find the IACV? Is there a schematic diagram on this forum that I could refer to for parts? Thanks for all your suggestions, curiousB. I'm pretty sure that my vacuum lines are OK, but without diagnostic equipment it's just a guess.

[curiousB]

OK a non closing throttle plate sounds like your problem. Spring could be fatigued but I bet the pivot point has some crud in it and isn't turning freely as it should. Consequently the spring unable to pull it fully closed. I'd try cleaning it up some more with throttle body cleaner.

[lookinin]

Thanks, curiousB. My coolant is a bit low and the service guy at Toyota thinks that I've got air blockage. I had the coolant flushed and filled yesterday and I have discovered a small leak in a rad hose that connects to the throttle body. The hose is small - only 5/8" inch or so, but it's leaking. The overflow tank is low, but not empty. The dealer will "burp" the cooling system tomorrow, but I just can't imagine the bad luck whereby I clean the throttle body, change the plugs and low coolant creates a high idle. You can't make this stuff up. I'll let you know how it goes - thanks for your suggestions. By the way, do you spray the cleaner/solvent on the parts while they're on the car or do you remove it and clean it? I believe that gaskets would be required if I removed it, right?

Cheers,

Kevin

[steve2006]

I did my TB clean during a starter motor rebuild so took it off completely,it helps if you can get to both sides of the butterfly,you are correct in that you need a new gasket but they only cost a few $$$.

I used carb cleaner and an old toothbrush to do the job.

[lookinin]

OK a non closing throttle plate sounds like your problem. Spring could be fatigued but I bet the pivot point has some crud in it and isn't turning freely as it should. Consequently the spring unable to pull it fully closed. I'd try cleaning it up some more with throttle body cleaner.

Yep, curiousB, it was low-coolant and air blockage which prevented water from flowing through the TB. The sensors assumed the engine was cold and tried to rev it up accordingly. At least I'm fully versed in spark plug R&R as I took the old ones out, put new ones in, took the new ones out, put the old ones in, took the old ones out (again) and installed the new plugs, again. All for nothing. Crazy waste of time.

And I will order a gasket and remove the TB for a thorough cleaning later on this summer - if it ever gets here.

Thanks again.

Cheers,

Kevin