Hello, i am a new member here in search for more information<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

So i did a tune-up with new plugs and cap+rotor and after i my truck would randomly come down in idle and stall out. <o></o>

I checked all vacuum lines and there are no leak, replaced fuel filter, checked spark the coil seemed like it could have been cutting out so i replaced that. After replacement of the coil i checked timing and set idle for 720. The coil helped but it still will randomly cut out. I removed the sensors that are known to be go bad and cleaned them. all looked good. New fuel pump also. As of now there are no codes. on the tune up i did have to pry on the pick up coil but the it doesn’t really make sense that it would run perfect but not and idle <o></o>
It will jump around from 700 to 730rpm. <o></o>

Also i changed the thermostat because the truck would not heat up over 140 and it will only get to 150 now. <o></o>

Thanks for all the help
1990 Chevy k1500 5.7L 5 speed

 

The idle is controlled by the idle air control on the pass. side of the throttle body. It may be faulty. I had the same problem with not heating up with my 90 350. I replaced the quick connecter and the hose for the heater where it goes into the intake,and it warms up now. Don't ask me to explain this as it makes no sense.

 

Thanks for the response. I have replaced the IAC and temp sensors. I also changed the o2 because i was getting a code.

The only thing i have not changed at this point is the map.

it will sit at idle then drop to 500 and sometimes it will jump up to 1000 and another it will stall out.

 

Have you looked at the EGR valve?

 

I have not looked at the EGR value, today as it stalled on me i plugged the reader in right after it came back wif the with a code that could be

Electric spark timing (EST) circiut- open or shorted to gound during engine run
OR
Direct ignition system (DIS) fault - Bypass circuit open or shored to ground
OR
Fuel cutoff replay circuit - open or shoted to ground.

i dont know why it will read one now, but im willing to guess that code would clear itself when i check tomorrow.