jaav

Hi all, I'll try to make this short if i can. I've read post after post similar to mine but can't find any solution to my problems.

Here is a brief history of the problem. Car ran fine for years then all the sudden my idle rpm would randomly jump between 800 to 1500. I neglected the issue for years by adjusting my idle screw for smog checks. Now I'll be due for another smog check but with the idle screw all the way in, i'm still sitting at 1000 rpm. Not only that but along with the high idle, my mileage has gone down to 200 miles per tank (all highway) and it takes for ever to hit 70mph flooring the throttle.

Here is what I've done.

Truck has new plugs, wires, water pump, thermostat, radiator and battery.

Majority of small air hoses that i can access has been replaced.

Thinking it was the iac valve, i thoroughly cleaned the throttle body and both water lines/hoses to and from it. No change.

Put in new TPS adjusted within spec. No change.

New coolent temp sensor was replaced. No change.

For some trouble shooting, I tried blocking the idle screw hole and iac valve hole in front of throttle body and it wouldn't start. With just the iac valve hole blocked, the vehicle idle came down and i was able to adjust the idle back up, but for a test drive, still no acceleration power. I've check the iac valve but I'm not sure if the valve is suppose to be fully air tight closed or not. I ran boiling water thorugh the water line and the valve closed but i was still able to wobble the valve. Because i can adjust the idle with the screw, if iac valve hole is cover, i am thinking that iac valve should be air tight but it's just my guess.

I've tested the AFM and the only reading not in spec is from e2 - tha (lower than it's suppose to be). Could that be telling the ecu to send more gas because temp is too low?

Also took out catalytic converter and honey comb still looks good. I fully open the egr valve but my car still doesn't die like it used to. Could air passage to the valve be restricted somehow?

I also read somewher that the knock sensor might be the cause because when I jump te1 - e1, the engine is suppose to retard but it doesn't. the engine light does flash meaning te1 - e1 is jumped. no codes found.

Last thing i did was run seafoam and it help the engine smooth out but that is all it did.

Some helpful suggestions/solution would be appreciated. I want to try all i can before taking to dealership for diagnostic just to be told try this and that part (only parts left to try will cost me around 200 bucks each). This issue seem to have many causes based on what i've read on these posts.

nickmak

Might be a long shot, but any vacuum leaks? From one of the gaskets as you've already replaced some vacuum hoses. The reason I ask is because I've had pretty much the same problem but on some domestic cars. Or I would have said TPS as I had sort of the same problem until a few days ago!

jaav

nickmak

i have a new tps installed already and adjusted within spec.
i believe if i have a vacuum leak, my car would idle low. correct me if i am wrong.
you mention you had this same problem until a few days ago? how did you fix it?

Arkman

Im not for shur on any of this but i had the same problem and replaced my tps and all and it in fact turned out to be my vafm. Got a good used one off ebay for $60 with shipping and it ran just like it used to dont hold me too it though lol

nickmak

Hmm.. I've seen cars with vacuum leaks that can't find a place to idle (goes up and down) as well as idles quite high. Not sure about 4runners though. I should look more into that. Anyway, my problem was:

Idle would go up and down - it was very slight, but noticeable. It wouldn't idle in the same spot everytime I'd stop at a light either, sometimes it would be 500rpm up to 1000rpm, it was never constistantly 800rpm everytime I'd stop or pull over. So I guess it would idle high you could say, but only sometimes.

Hesitation when accelerating - started noticing it when the engine was cold, then it started to do it when the engine was warmed up too.

Wouldn't pass our emissions test - I used a sniffer at work just for ˟˟˟˟s to see where my truck was at with the new engine (bored at work), and it was WAY off. Can't remember what was off, but that's how I figured something was wrong.

So here's why I thought your problem could be TPS related, but I would think it's something else if you've already replaced it, I'm probably way off.

When you jump the diag. connector, the timing (and idle speed) doesn't change. Mine did that too, for some reason I was at 20 degrees jumped or not! Crazy. I set it to 8 and drove it home, no power and sucked on gas. I adjusted the TPS, adjusted the idle and timing again, everything was fixed. No more hesitation, idle's steady, drives better than it did when I first got it running. It would be good to know what's wrong with your truck once you figure it out in case I ever run into the same problem! Good luck

BlueJerseyDevil

I have the exact problem many new parts I do however need to replace my knock sensor. But money is stopping that for now due to the fact that I replaced every thing else. Let me know what you find out and I'll do the same.