Topic: 3.0 idle issues

[BLACKDOG]

My "new" motor is having idle issues.  Aside from the idling, it runs great, so I'm not sure what the deal is.  The motor pulls strong, and sounds great.   My only issue is sometimes it idles at 900, then it'll idle at 1100 at the next light.  Then it'll settle at 1500 at the next light, jump up to 1800, them back down to 1300, all while sitting at the same light.  Then, at the next light, it'll be back at 1100 and while there, jump up to 1400 back to 1300 up to 1600 back to 1200 ad. nasueum. 

My question is essentially, whats the deal.  I've got 3 theories, non of which I have tried yet, but I need to   I just wanted some outside imput

1. I have a small exhaust leak where the downtube on the driver's side manifold hits the pipe going back to the cat.  This is upstream of the O2 sensor, wondering if that has anything to do with it.
2. I just need to burp the cooling system (doubtful) I've been runnning it for 3 months, at different elevations, and thought I did a decent job when I first put the coolant in.
3.  TPS is bad


Temp and oil pressure are good.  In fact, if I didn't have a tach, I probably wouldn't notice the issue much, if at all.  The motor runs good and strong, and the exhaust is the normal color.

[BLACKDOG [OP]]

ttt 

  Truck is getting good gas mileage, no loss of power, so I'm really at a loss as to what the deal is.  No codes being thrown either

[Matt_BC]

might be IAC related ? Or vacuum leak? Idle adjustment screw lose ?

Matt

[reklund5]

Check your throttle cable.  The 3.0's are notorious for sticky throttle cables.  Also, check the movement of the butterfly plate linkage at the throttle body.  It's rare...but the IAC could be full of junk and need cleaning.  You'll have to remove the throttle body and overhaul the IAC motor, but it's do-able.

Ryan

[BLACKDOG [OP]]

Check your throttle cable.  The 3.0's are notorious for sticky throttle cables.  Also, check the movement of the butterfly plate linkage at the throttle body.  It's rare...but the IAC could be full of junk and need cleaning.  You'll have to remove the throttle body and overhaul the IAC motor, but it's do-able.

Ryan

I was thinking it may be the throttle cabel today actually.  That is the first thing I'm going to check tommorow.  The pedal seemed kinda resistant to coming back up, so that could very well be it.

Thanks guys

[BigMike]

It will not be from an exhaust leak. An engine can idle without the O2 sensor.

1) Check for air in the cooling sys
2) Check for vacumm leaks
3) Check throttle cable

When it is idling, pop the hood, and using like a 3/8" drive extension, lightly tap on the TPS. If the idle changes as you are tapping on the TPS, then it is just barely out of adjustment and its not reporting an "idle" condition to the ecu.

Has the motor overheated since you built it? Like really overheated? Maybe while you had it running at first, you didnt have enough coolant and the temp quickly spiked?

Have you retorqued the head gaskets? How many miles are on the engine now? Did you also do a valve job?

[BLACKDOG [OP]]

Mike,

I didn't do anything to this motor, I pulled it out of the '88 runner that it was in, and stuck it in my truck.  I'll try tapping on the TPS as well, I "burped the cooling system yesterday, so thats good.

The motor got hot when I first started it up (not enough coolant, like you said) but I caught it before it got too hot. ( I think) 

Engine has 195,000 give or take, no valve job, no retorquing of the heads.  I just tossed it in and went.  needless to say, it runs better than either of my other two engines, except for this one issue.  Gas milage is good, temp and oil pressure are good, pulls fine, seems a tad more powerful than my old one even

I'll check the TPS, vacuum leaks, and the cable tommorow, hopefully I can pin it down 

[BigMike]

Good luck mang

[Plowking]

How is the gas milage? Waht is it?