[Hpr] John Kulp's truck

Jonathan Kulp jonlancekulp at gmail.com
Fri Jul 29 09:24:18 PDT 2016


On July 29, 2016 8:45:22 AM EDT, Patrick Dailey <pdailey03 at gmail.com> wrote:
>John,
>If your rough idle symptoms persist, it may be a stuck EGR valve, the
>Idle
>Air Control (IAC) valve, or a coolant temp sensor (CTS). Cleaning, or
>replacing the EGR may do the trick. There may be a way to test the IAC
>and
>the CTS with a scan tool. Often the parts stores have those to lend
>out.
>I'm not sure if the Bluetooth OBD2 testers can perform diagnostic
>tests,
>but its worth a shot if you have one. If its none of those things, then
>it
>may be a vacuum leak, or worn out plug wires. A vacuum leak can be
>found by
>listening for a hiss, and then spraying the area with your throttle
>body
>cleaner. If the idle smothes out while you're spraying, then you've
>found a
>leak. Just don't spray too much at once. Its highly flammable, and
>engines
>are hot. Stay away from the exhaust with it. Vacuum leaks can come from
>cracked, or disconnected vacuum hoses. Don't mess with the Mass air
>flow
>sensor, except as a last resort. They are very sensitive, and often
>fragile
>devices.
>
>Because it happens after driving for a while, I'd start with the EGR
>valve,
>and the Coolant temp sensor. Some cars have EGRs that just get dirty,
>and
>stick open, and cleaning them fixes the problem. Other cars have EGRs
>with
>weak solenoids, and need to be replaced. A little research will
>probably
>tell you which is more likely for you.
>
>The throttle body cleaning was a good start, and you probably did a
>good
>enough job to eliminate it. The butterfly, and the side passages are
>the
>most important. If those got cleaned, then you're done there. Dirty
>plenum
>walls are relatively unimportant. You may wish to pull the IAT, and
>clean
>it, and its passages.
>
>You could also look to see if there is an adjustment procedure for your
>Throttle Position Sensor.
>
>Bad plug wires can be diagnosed by misting them with water from a
>spritzer
>bottle in a darkened garage, or in the evening. If you see little blue
>sparks, then its time to change wires. Be sure to do them one at a time
>so
>that you don't mix them up. If you change wires, do plugs, cap and
>rotor
>(if you have them) too.
>
>The last thing that I can think of is dirty fuel injectors that are not
>atomizing fuel properly. Sadly I don't know of a cheap DIY remedy for
>that
>(or diagnosis for that matter). Black smoke (even very faint) from the
>tailpipe as the car dies would hint at injectors, the IAC, or a faulty
>coolant temp sensor.
>
>Best of luck. Let us know how it turns out.
>
>
>------------------------------------------------------------------------
>
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Patrick, thanks so much for this detailed feedback! I'm going to save this for future reference. Great to get this analysis from someone with your level of experience. I'm glad to report that the truck has been doing just fine since the throttle body cleaning so I'm going to consider it solved for the moment. 

Jon 
-- 
Jonathan Kulp 
http://jonathankulp.org 
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