Low idle at start up

azTony · 10-29-09, 07:03 AM

I had just relocated my washer bottle (2nd battery has been there a long time) and replaced the positive battery terminal on the drivers side. While I was replacing the battery terminal I broke the black terminal box that connects to the positive side so I rigged it until the new piece comes in. Every time I start it, it has always had idled high (a little too high) and now when I start it, it is a normal idle which makes it idle rough in the cold mornings in Arizona (if there is such a thing). I just got to work and experienced this and have not looked under the hood but before I closed the hood after my work I checked the vacuum hoses in the area around the charcoal canister but not every where. I rerouted some wires that were not secured around the back of the firewall so I was kind of all over.

What controls the idle when you first start it? Any ideas what I should look for when the sun comes up and I can see?

Thanks

Tony

RedTacoma · 10-29-09, 07:56 AM

Quote:

Originally Posted by azTony

I had just relocated my washer bottle (2nd battery has been there a long time) and replaced the positive battery terminal on the drivers side. While I was replacing the battery terminal I broke the black terminal box that connects to the positive side so I rigged it until the new piece comes in. Every time I start it, it has always had idled high (a little too high) and now when I start it, it is a normal idle which makes it idle rough in the cold mornings in Arizona (if there is such a thing). I just got to work and experienced this and have not looked under the hood but before I closed the hood after my work I checked the vacuum hoses in the area around the charcoal canister but not every where. I rerouted some wires that were not secured around the back of the firewall so I was kind of all over.

What controls the idle when you first start it? Any ideas what I should look for when the sun comes up and I can see?

Thanks

Tony

If you just did the work, then wait computer needs to learn settings again. I get the same thing after disconnecting battery.

80t0ylc · 10-29-09, 09:17 AM

Quote:

Originally Posted by RedTacoma

If you just did the work, then wait computer needs to learn settings again. I get the same thing after disconnecting battery.

Agreed. My '94 takes 8 - 10 engine on - engine off cycles to relearn. Don't try to shortcut by doing them all at once. You'll wear out your starter unnecessarily and it won't work. You need time on each 'engine on' cycle. Patience is your friend - it'll come around.

agomez · 10-29-09, 11:41 AM

you may need to clean the throttle body also check for cracks in the big rubber hose from the air cleaner to the throttle body on the bottom.

CaptainKirk · 11-05-09, 06:46 AM

Agomez - have you performed the off-the-truck throttle body clean up on your 94? I have a perpetual low idle on my '94 I am now fed up with. It hovers around 580 RPM, just low enough to cause the engine to be rough - when I use my foot to raide it to its once normal level of 650+ RPM, it smooths right out. I have had it suggested in the last couple of weeks since I have started looking for threads that I need to remove the throttle body and clean the heck out of it. If I understand correctly, the "step motor" controls the idle and it might be dirty, etc, etc, etc. Whatcha know about this? With 238K Miles, I am contemplating things like replacing O2 sensors and injectorsa but I don't know what the life span of those parts really are and I don't really want to do a blind parts replacement program if it's not necessary. Thoughts anyone?

80t0ylc · 11-05-09, 08:57 AM

Yeah, what shape is the hose between air cleaner and throttle body? Cracks or holes in this will affect your idle speed in additon to causing other problems.

CaptainKirk · 11-05-09, 10:05 AM

You are the second person to mention that. You are talking about the big 3" diameter (approx.) tube right? From appearances sake, it appears to be fine. Last night I sprayed starter fluid around all of the hoses and could only get a rise in idle speed when I sprayted into the inner fender where the intake opening is. That said, tonight I will remove it and inspect it carefully as well as spray cleaner into the throttle body (I know this is not likely to solve it without removal cleaning it comprenhensively). I had all of the hoses replaced two yuears ago, but the tube feeding the motor was not replaced. Might just replace it for S & G's. Do you know of a thread thatv supports the FSM for throttle body removal?

80t0ylc · 11-05-09, 10:54 AM

Yes, CaptainKirk, that corrugated plastic hose could be the culprit. Interesting that starter fluid brought your idle speed up when sprayed into fender intake. One could conclude that your intake system is intact from leaks. But, I'd check it anyway. It couldn't hurt and might prevent problems down the road, especially if it's old and brittle.

hawaiicruz · 11-05-09, 11:04 AM

Quote:

Originally Posted by 80t0ylc

Agreed. My '94 takes 8 - 10 engine on - engine off cycles to relearn. Don't try to shortcut by doing them all at once. You'll wear out your starter unnecessarily and it won't work. You need time on each 'engine on' cycle. Patience is your friend - it'll come around.

X3 on that one, mine usually takes 20 or so miles until the "roar" comes back

CaptainKirk · 11-05-09, 11:55 AM

80t0ylc - I notice you have two batteries - why? Also, have you replaced any of your O2 sensors yet? Do you know how many there are - aren't there 4 of them? I am contemplating replaceing all of them if I don't find a problem tonight with the intake tube. Also, I didn't mention that on a hot re-start, I get a very pronounced rough idle(so bad that one would think it had bad gas or bad plugs, bad wires and bad gas) that will sometime cause a CEL that both go away a bit later after dirving. Then the eternal minor rough idle returns. Am I making sense?

80t0ylc · 11-05-09, 03:37 PM

Quote:

Originally Posted by CaptainKirk

80t0ylc - I notice you have two batteries - why?.....

The 2nd battery is dedicated to my winch.

Quote:

Originally Posted by CaptainKirk

.....Also, have you replaced any of your O2 sensors yet? Do you know how many there are - aren't there 4 of them? I am contemplating replacing all of them if I don't find a problem tonight with the intake tube......

No, I haven't replaced any yet. I get intermittent (02 sensor) CELs. According to my ohmmeter, I got 1 right on the borderline of being bad.

Before you replace any 02 sensors visit your local Toyota service center. There was a recall on '93 & '94 02 sensors. They can run your VIN and see if you qualify - might save you some $ and aggravation.

Quote:

Originally Posted by CaptainKirk

..... Also, I didn't mention that on a hot re-start, I get a very pronounced rough idle(so bad that one would think it had bad gas or bad plugs, bad wires and bad gas) that will sometime cause a CEL that both go away a bit later after dirving. Then the eternal minor rough idle returns. Am I making sense?

You need to get the code for that CEL. '94s are OBD1 so you need the procedure and a paperclip:
Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical
I printed this procedure out for reference. I recommend you do it. Hopefully that'll be a good starting point for you.
EDIT: The illustration for the test plug is wrong. Orient the firewall to the left side of the illustration and that will give you the correct pins to jumper with paperclip.