1990 Stalling When Cold

[4Runner Girl]

Hi, my 1990 4Runner 4x4 3.0V6 is acting up. When I first start it the idle fluctuates a little. If I don't let it run for five or ten minutes it stalls and runs rough when accelerating. When it's warm it runs fine; any ideas would be appreciated.

 

[77'911]

When's the last time it had plugs and a fuel filter? I would probably check the fuel pressures(running and rest). It might be worth checking for vacuum leaks.
regards

 

[4Runner Girl]

Thanks for the ideas! The fuel filter is new and we changed all of the vacuum hoses that looked old or cracked. Is there an easy way to check the fuel pressure?

 

[Hyde802]

Coolant temperature sensor?

 

[4Runner Girl]

I found the problem with the rough running! One of the spark plug wires installed by the previous owner was melted to the EGR valve. Changed the wire and now it runs perfect until it warms up. As soon as it warms up the idle fluctuates when you are sitting still. Any ideas?

 

[77'911]

You might check for vacuum leaks around the injectors. It is also worth noting to check the O2 sensor, coolant temp sensor, and t-stat:
1) O2 sensor- replaced our sensor around 94k, this really smoothed things out along with raising our mpg.
2) coolant temp sensor- when I pulled this, ohm-ed it out, close to the end of service life and coated with calcified coolant deposits. This helped to smooth the idle out along with MPG again.
3) t-stat- our was partially stuck open, or sticking open which caused all sorts of idle issues, as the truck could not figure out how to get out of cold run mode.
I would also test the EGR valve which can be problematic.
regards