Idle surge

Ok, let me introduce my self. I am new to the board and my current truck is a 2001 2.7 4x4. Just picked her up about two weeks ago for a good deal.
She has 164000 miles and runs strong, no leaks either.

When I bought the truck it had a check engine light (P0410, catalytic) if I remember correctly. And the idle would creep up, a quick rev would bring it back down.

I narrowed it down to the IAC valve for the idle and thought I would replace both o2 sensors for the CEL.

Replaced both o2 sensors with denso factory units and the CEL went off but now I have this idle surge along with the creeping up idle.

Today I replaced the IAC valve, cleaned the throttle body and installed new gaskets along with a new TPS since the TB was on the bench. I also checked the MAF sensor and cleaned it also disconnected battery and drove for about 20 miles for the computer to re learn.

No creeping idle( IAC fixed that) no CEL but the idle surges bad. 500-1100 rpm every 2 seconds. Checked all vacuum lines and verified no leaks.

I am officially LOST on what to check. I keep thinking put the old o2 sensors back in and see if it still does it? Any ideas?

Thanks
TJF

 

Some one has to have some recommendations.

 

IIRC the IAC is vacuum powered on the 3rz. Did you stick something in the vac port for the IAC to verify that it isn't clogged with gunk? I would try that. It probably wouldn't be able to control idle well with a restricted port.

 

I do.

Did you disconnect your battery so that the ECU can relearn the operating parameters of the new sensors? If you haven't, unbolt the negative cable and leave it off for about 15 minutes or so. Then put it back on. It will take a few cold start cycles for the computer to relearn the parameters.

Greg

 

Unfortunately he already did that

It still sounds like a vacuum leak to me. I'd double double check everything, making sure there aren't any hoses that were moved and developed cracks.

Vacuum-powered IACV? Who reinvented the wheel on that one? lol it's just a controlled air leak, all you need is a plunger valve controlled by pulse-width-modulated current through a solenoid

 

I cleaned all ports on the throttle body, it looks new. You say the IACV is vacuum controlled? Mine has a harness that plugs into it. (2001)

Today I cleaned all electrical connections, TPS, IAC , Coolant sensor and replaced the coolant sensor and thermostat. Also double checked all vacuum hoses and sprayed carb cleaner all over them and throttle body. No difference in rpm.

I also put the old o2 sensors back in. No difference.

Tomorrow I am going to replace the vacuum lines one by one and put the new o2 sensors back in since I know that is not the problem. I will probably remove the throttle body once again and double check everything.

Do you think it's worth it to pull the whole intake manifold off and clean the crap out of it? I have new gaskets for it as we'll.

I am pretty damn mechanical and this thing is kicking my butt!!!!

Oh my ultra gauge also shows up tomorrow! Maybe that will help.

 

My bad, my 99 3rz used a vacuum diaphragm for the IAC. Didn't mean to lead you astray. I think pulling the plenum would be unnecessary. I think you'll be on the right track with replacing the vacuum lines. One probably has a leak you can't see. A leak at the intake manifold gasket may cause the symptoms. But your MAP sensor should "see" it. So I wouldn't go this route quite yet.

 

There's gotta be something we're not thinking of.

This thread reminded me... I ran into something like this on my dad's '93 F-150 5.0L. Stupid thing wouldn't idle right. It surged from 700 to 1500 rpm about every 2-3 seconds. Turns out it was a problem Ford knew about. New gaskets, IACV, and EGR wouldn't always fix it. If not then they'd sell you a plate to bolt onto the IM with a pair of tiny adjustment screws in it and you could create your own custom tailored vacuum leak to smooth it up. Typical Ford fix. Kinda like the cruise control on that truck that was recalled due to fires. Dealer would unplug it pending a fix that never happened, i.e. no more cruise control, ever.

 

That behavior sounds like the ECU is still hunting for the right idle speed.

 

Never had that happen on any truck I've reset the ecu on.

OP, do you have repair history on the truck? Have the valves ever been adjusted?
I wouldn't rule out an out of spec valve and a cracked head because of it.
Not trying to scare you, but the 2.7's are known for that.

 

I ran a car fax and everything came back clear when I bought it. I was thinking ECU too. I don't think it's a cracked head. The truck has plenty of power,(I can go 90 MPH easy on freeway and up hills)no smoke, drives fine, get 20 MPG, Oil is always clean like honey.

I wonder what a plugged catalyic converter does? Never had one plug on so me so I don't know

 

Shouldn't be a clogged cat. With that, it runs best at idle and worst under power because it's more apparent with more airflow.

It could be an out of spec valve. When I set the lash on my Fit, the first time I set to the tight end of spec (since I checked them annually on my Hondas, and it was good for a tiny bit of top end) and after doing the reset the bugger loped like a drag car for about 5 minutes then smoothed up for the most part. A few months later I set to the loose end of spec and after reset was as smooth as a sewing machine, and it was an easy +2 mpg.

Kinda sucks Toyotas aren't that easy to adjust

What bothers me is that it didn't surge before the old IACV came out. Does it have a new one or a junkyard part?

 

My 2012 Tacoma and 2012 Yaris both routinely do that when the battery is disconnected. But only if the previous modification in operating parameters is great enough like a different throttle body, different exhaust, etc.

 

It is a new IACV from rock auto. I cleaned up the original real good ( it was bad full of crap) I might try swapping that one back in today along with putting the original TPS back in.

I get the whole battery thing. I put about 60 miles on it and it still did it.

I am pretty mechanicaly inclined and have great troubleshooting and diagnostic skills but this is kicking my butt. I know its something simple. I will keep digging. It is not going to the dealer, I do all my own work.

 

One more thing I forgot to mention. It only does it when the engine temp reaches operating temp. When its cold it idles around 1200. Which should be normal.

 

Just to kick it out there, have you pulled the spark plugs since you bought it? I've had a bad o2 sensor foul them up before. It would be more apparent with low rpm and may not trip a misfire CEL.

 

I once replaced an ECM, an IACV, a MAF, and a fuel pump and my truck never had a loping or surging idle. High, yes. Loping, no.

PS, my dick is bigger than yours.

 

Ok last night I bought a haynes manual. Checked egr system and it's good, checked ohms on MAF, TPS, both o2 sensor, coolant sensor and IACV , all good. I also received my ultra gauge and got it all setup.

The open, loop indicator on the ultra gauge shows open when the idle lopes, and closed when it doesn't lope or under normal driving. This tells me its a sensor somewhere. I checked and replaced all spark plugs with NGK about 2 weeks ago. They were worn and showing all lean.

Today I am doing a compression check to rule out head gasket issues
( I hope) I am not loosing coolant and oil level is clean and good and no smoke or power lost so I doubt its a head gasket. Other than that I am going to drive the shit out of and see if the computer just needs more time since I changed and cleaned so much on all the sensors.

Last night I noticed it wasnt loping as bad.900-1400 rpm. And I also noticed my tach is not right, compared to the ultra gauge.

 

Almost forgot, I read somewhere that if you put your hand over the intake tube by the air filter and starve the engine of air it should die, if it stays running you are leaking air somewhere. I did this and it did die. But if I cover the tube partially with my hand it idles fine. Like its getting to much air. So can a MAF ohm out good but still be faulty?

 

ok so I have had the flu and haven't had a chance to check the compression in the cylinders. I will do that this weekend. But a cracked manifold is essentially a vacuum leak on the motor and I am curious if that could be the problem. Never heard of cracked exhaust manifold causing a idle lope before but I will check that too this weekend.

Also I have been studying the open loop/closed loop system for sensors and I have noticed on my Ultra Gauge that when the lope occurs I am showing a open loop. From what I have been reading this usually indicates a MAF sensor or O2 sensor. But what I cannot figure out is the O2 is brand new DENSO unit and the MAF has ohmed good. Not throwing any codes either??

Put roughly 125 miles on it since battery was last disconnected.

Any other ideas?

Oh and I almost forgot. When I was getting gas on Monday this week a 93 toy 4x4 pulled up on the pump next to mine and his idle was loping too!! that guy ran inside and I never had a chance to ask him but thought that was odd.