need help! (1 Viewer)

[selk78]

i've looked in FAQ but can't find anything.

i have a 1992 pickup with a 3.0 , it's in the shop now and there having a problem tracking down a a fix.

It runs good for a truck with 211,000 mile , but when i'm driving and I need to stop for a traffic light or i'm in stop and go traffic, when I put in the clutch pedal the motor starts to sputter and idle's really low (400 to 500 rpms) and then bounces back up to its normal idel speed of 1000 or so rpms only when I come to a full stop or I blip the throttle , now my truck is stock except for a k&n cold air intake, they tryed replacing the mass airflow meter and they said it runs worse so they put the old one back on, I told to try the tps sensor yesterday and when they scoped the truck it told them to look at the air mass sensor, so now there looking to the tps sensor.
so my question is has anyone experienced the same idle sputter and if so how did you fix it ? or is it just better to live with it, like I said the truck run's good but it's just annoying.

 

[ms018kmf]

You've covered the TPS, good start.

Does this happen when it's warmed up or just all the time?

There's some kind of thermal valve in the throttle body that can fail and cause idle issues. If this only happens when warmed up this could be a culprit. It is part of the TB and is not replaceable by itself.

Also check for vacuum leaks from the rat's nest of hoses and leaks between the TB and upper intake plenum (bad gasket).

One last thing, I'd check the connections at the ignition coil. I had running issues with randomly dropping the idle and then completely dying. The connections at the coil had bad seals, the terminals were completely filled with water. Good luck!

 

[Hilux]

Me thinks...


https://forum.ih8mud.com/79-95-toyota-truck-tech/155085-idle-dips-when-brake-pressed.html

https://forum.ih8mud.com/79-95-toyota-truck-tech/283933-idle-question.html

 

[egil1963]

thermal valve

there is a thermal valve behind the plenum, close to the fire wall that is hard to see, I had a similar problem, one of the connections broke, thus a vacuum leak, and for some reason it effects the idle. I second the idea of checking the coil. Only other thought would be to check your brake booster vacuum line, if its worn or cracked may need to replace.

 

[selk78]

it happens all the time, not just when it's warmed up, they were gunna check something called the thermal bottle senor or bottle valve, it's just behind the tps sensor, it might be what you guy are talking about ?!?! and so far no vac leaks were found BUT that doesn't mean there are any that they've found, if they haven't found it by today i'll ask them to check the connections at the ignition coil like you suggested...

 

[Rix86]

Time to take it to a different shop.


Unplug the vacuum line to the EGR and cap it, see if it stops.
clean the throttle body with some sort of intake cleaner/carb cleaner crap.
check vacuum line routing/condition.

 

[Crawdad]

x2 on check your vacuum lines. My Egr vacuum was plugged with rust when I went to change the rubber, had to drill out the blockage and the idle came back to normal with some new tube and cleaned out plugs.