Low idle after start then dies

[Cowboy59]

I have searched the forum and did not find a thread with this particular problem. I have a 98 LX with stock driveline and exhaust. When I start the engine it fires up then the rpm's dip, then bounce back up. If I try to shift into gear during the dip the engine dies. If I wait to shift until after the dip the engine runs and drives fine. What could be causing the dip in rpm's? Or is this normal?

 

[marshotel]

Try cleaning the throttle body and the butterfly valve at the front of the intake manifold with a toothbrush and a can of throttle body cleaner. After that it will run rough for a few minutes and it might even stall at idle until you burn off the soot and the TB cleaner residue. But after that it will smooth right out.

While cleaning the throttle body, disconnect the battery for 30 mins to reset the ECU.

When you reconnect the battery, start the truck and let it idle in park for about 10 minutes, and then take the vehicle on a spirited drive through the countryside.

This will enable the ECU to "relearn" the fuel trim settings, and hopefully will eliminate your rough idle problems.

 

[Elijah]

How many miles on engine/cruiser?

 

[marshotel]

After thinking about this a little more, I bet it is due to a dirty throttle body.

Crap and soot in the butterfly valve prevents the valve from closing all the way at idle.

This allows too much air in the mix at idle, and the lean mixture causes the "dip" in rpms until the ECU realizes that the mix is too lean and adds fuel to compensate.

I bet if you clean your throttle body and butterfly valve really well, then the problem described in the original post will disappear, the vehicle will run more smoothly at idle, and your fuel economy will improve.

Let me know if this works---

hope this helps.

 

[Jordan345]

or it could be low coolant level if you've recently had it replaced.. toyotas are hard to 'burp' and can airlock when the temperature isn't brought high enough to open the valve, allowing coolant to circulate. if you've not opened your coolant system or haven't had it tampered and no leaks, then this probably isn't the problem. I had the same symptoms after i pulled my rad out and flushed it. took a while to burp and pressurize the system.

 

[TXLX100]

I'd clean the MAF sensor in the air intake also, there is a specific aerosol cleaner for it. If that and the TB clean doesn't fix your problem, check your battery.

 

[Bismarck]

+ 1 on the MAF and throttle body. Assuming no codes/CEL?

 

[Cowboy59]

Thanks all. 170k on the cruiser. Will try the throttle body cleaning then progress from there. Thanks a ton for the info. Will let you all know how it pans out.

 

[Lc80series]

I had a similar problem on my 80. Turned out to be the fusible links...

 

[Cowboy59]

Used throttle body cleaner and a too the brush on it today. Started, ran rough as hell then smoothed out. Let it warm up then shut her down. Upon restart the issue was not present. Gotta love the $2 fixes. Thanks a bunch guys!

 

[RyanStl]

Sorry to revive an old thread, but sometimes doing so is useful.

I experienced very similar issues yesterday morning on the way to work. My '02 Hundy with 142K miles was going great until I stopped at one of the multiple four way stops and she died. She wouldn't start back up unless I gave her gas and if I let off the gas she would die again. After sitting for a while she'll go about 3/4 miles then die just the same.

I had her towed to a local shop who said they would fit her in. Well after 15 hours they finally looked at the TLC and could not replicate. I am not happy about that. I picked her up and it happened again after about 3/4 of miles. I limped her back but goosing the gas and trying not to stop. I ended up coasting into their parking lost, so they finally saw what I was talking about. Well, the shop is so busy they can't schedule an in-depth diagnostic until Monday.

The mechanic gave me a tip that if I run the defrost it will not die when I stop. That trick worked, but it is a bandaid. Since it was rainy today this is probably why they could not replicate.

Is the Mud brain trust diagnosis still dirty throttle body?

This is what I know. There are no codes showing up and they said there are four OBD sensors ready for input or something like that. They thought that was weird, like I reset the codes myself. I did not and the battery was never disconnected. I do have a bluetooth OBDII ready which I used to scan after this incident. It showed no codes and I did not use the reset function.

Thanks all.

 

[digitalmarker]

Mud saves again! Had this same problem over last weekend after doing a bunch of other work on the truck and scratching my head about what I messed up that would cause it to stall out immediately after starting.

Ended up cleaning the MAF with the special cleaning spray, cleaned the throttle body with throttle body cleaner, and cleaned the air filter. Fired right up and idles perfectly at 1200.

Thank you!!