pendrag

I don't know if the two are related, but my 1999 2.7L is idling too low when stopped, warm, and in drive. The whole truck is shaking and it's idling around 650. I'm hearing an intermittent rattling sound from under the hood somewhere when it idles really low. There's a click-click-click I can hear with the hood down coming from the region of the PWM Vacuum switching valve or the Evap. OBD Pressure Switching Valve, I think. If I give it a little throttle, it smoothes right out.

It wasn't doing this before I put in the mini-header. I'm not saying the mini-header did it, but I wonder if I could have damaged something putting it in, or whether having that cracked exhaust manifold could have done something. These are the first real days in the 30s around here, but the truck only does this once it's warmed up. I noticed some moisture coming out of the exhaust pipe, which had a fair bit of black soot in it. O2 sensors, maybe?

I'd love to hear some thoughts. I'm moving in 2 weeks, and I really don't want more hassle with these trucks.

Geeze, is it cold out there!



ADDITIONAL INFO:

04/01/10
MAF - Cleaned. Tested with ohm meter: good.
Spark Plugs - Replaced with 4 Denso K16R-U.
Vacuum Hoses - Inspected and Replaced as needed.
Air Intake - Inspected and partially cleaned

10/18/10
Crankshaft Position Sensor - Pulled wires out of CPS sensor while replacing alternator. Removed CPS, soldered on wire to repair, and reinstalled.

11/19/10
Air Filter - changed.
Exhaust Mini-header - Replaced cracked-in-two exhaust manifold with Toyota Mini-header. Used all new Toyota studs, nuts, and gaskets all around, but cleaned and reused old manifold-to-cylinder head studs. I've been driving it around a little for a day or two, plan to retorque all the nuts very soon.

scuba

The computer could have adjusted for weird AFR's since the manifold was cracked. I'd pull the negative battery cable for a few minutes to reset the ECU and then check back after a day or two and a couple drives.

pendrag

I had the same thought. I pulled the cable a few minutes ago. I'll report back tomorrow or later tonight if we go on a food run

pendrag

Nope, when I come to a stop in drive, the idle drops down slowly to around 650 RPM.

pendrag

I dumped in a bottle of techron this afternoon on a half tank of gas. We'll see if there's any change.

scuba

I'm at a loss then. 650 isn't horribly low. Warm idle is 750, though. As you may know.

pendrag

Yes, I believe the normal idle range is 750-850, and the truck definitely smoothes out at around 800. I've love to have it idling at 850, as it seems to be the sweet spot (you might recall that I have another 4runner (my 3.4L 1999) also doing this low idle crap. I had a long thread about that some time ago.

I need to change the fuel filter on the 3.4 and 2.7 at some point, possibly that might help. I dunno.


CORRECTION: THE FSM says the idle range should be 650 to 750 for the 3RZ-FE engine, and although I've heard "750-850" quoted online for the 5VZ-FE engine, the FSM says that the range for that engine should also be 650-750.

pendrag

You know, I wonder if I screwed up my MAF when I had the intake off to do the mini-header install. I think I'll pull all that off tomorrow and clean the throttle body, IAC, MAF, all that.

pendrag

I cleaned the MAF (looked clean already) and the throttle body (fairly dirty). No real change in idle speed. I adjusted the accelerator cable as I describe in this thread. I thought it resolved the issue, but it's still idling low (not quite as bad) and it's started sputtering and coughing when I turn it off.

NwRunner

I have the same low idle and mini header as well. Ive rebuilt the whole top end of my motor and cleaned every part you can imagine to no avail. let me know what you find out here.

Run seafoam through the PCV and check for any exhaust leaks, the white smoke makes them easy to spot.

4rx

You might want try to adjust throttle cable. I took the throttle body off the intake manifold and cleaned it. Then put TB back on there and the idle was high due to error throttle cable setting. It idles normal from just adjust throttle cable.

pendrag

I tried adjusting the accelerator cable, but that caused it to splutter and cough when I cut it off, so I figured I'd be doing more harm than good. I re-loosened the cable, so that it's taut, but it's not holding the throttle plate slightly open when my foot's off the gas. Back to idling looow. Shakes the whole truck.

Can bad O2 sensors do this?

drift_king

i had a low idle problem on my 2.7 and we had to play with the little magnetic vaccum switch on the top of the engine to get to the right vaccumn to idle at about 800 i hope that helps

IanB

If the truck shakes at low idle, maybe it's not running on all cylinders? Try pulling the plugs and take a look at them, make sure they are still gapped properly, nothing weird going on, etc. Maybe a plug wire got knocked loose when you were doing the header install?

As you've stated, 650-750 is the proper idle speed when warm, so something else is going on. Where did it idle previously?

space-junk

iTrader: (1)

my truck does this too, but it idles around 650 and diesels before fully shutting off...

i have a nagging feeling your issue has to do with the fuel tho... maybe try cleaning the injectors, fuel filter, and check the fuel pump to make sure the sock is clean and the pump is working to full capacity...

pendrag

I've been in the middle of a move (and broke) for the last month or so, but I'm ready to try and knock this out, even if I have to take it somewhere and not do it myself.

I pulled all the plugs today and visually inspected the wires. The wires seemed fine, although they are quite old. No fraying on the harnesses, the contacts were clean, and they snapped on the plugs cleanly. The plugs are 10 month old Denso K16R-U. They came out a little sooty, but not too bad, and the rear ones had a little bit of 'wetness' to the soot, but again, nothing that looked too bad. The gap was 0.032 on all of them. I brushed them off with a paper towel and reinstalled the plugs and wires, and everything was the same. Still idling rough.

So I've got a couple of ideas that I wanted to run by everyone:

1) Could it be a bad crankshaft position sensor? I ripped the wires out of mine during my alternator reinstall, but I soldered it back and shrinkwrapped / taped it up pretty good. Still, I could see that eventually failing.

2) Could the rough idle come from an overly-tightened alternator belt? I wasn't sure if I overtightened it, but nothing's burned out in the last few months, so hopefully it's cool.

3) Bad O2 sensors that aren't throwing a code? Pretty sure I've still got the originals in there!!

4) I pulled out the front two fuel injector connectors while it was running, one at a time, and it immediately began to miss quite badly, so I assume they're fine. I couldn't reach the back ones to check them.

5) Vacuum hoses? I'm halfway convinced I hear a vacuum leak somewhere, but I can't for the life of me find it. Most of my vacuum hoses were replaced a 6-10 months ago, where I saw problems, but a few are originals.

6) An exhaust leak? I installed the miniheader, but I'm not 100% happy with how well the header sealed to the exhaust pipe. I think the face of the exhaust pipe may have been slightly warped. I may take this to an exhaust shop for their opinion.

7) Fuel filter? It's the original one, and I don't believe it's really a lifetime part, based on what I've been reading.

Anything else???

pendrag

I'd like to, but I now live in an apartment complex and I'm trying to go under the radar with my parking lot maintenance work.

pendrag

Since the spark plug wires were still the originals, I figured it couldn't hurt to replace them. I put in a NGK 4441 wire set. The blue is pretty, but it didn't fix anything with the rough idle. I'm pretty sure the original wires were still fine, BTW, with 170k miles on them!

I can feel all four injectors ticking when I put a screw driver up against them, but beyond that, I can't say for sure that they're working perfectly.

syth_ryan

you can atjust th idle manualy from ISC below the thruttle body ,there is too scrow ,relase them then atjust after u finshe tite them,,, i will upload photo tomorro