1988 Dodge pickup issue

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Thanks for reading.

1988 Dodge D150(2wd) 318/5.2L manual transmission, 175k.

Starts/runs fine...except after getting it nice and hot, it will not idle without feathering the gas pedal, and runs rich, as evidenced by black and wet tailpipe, smell of gasoline. It will stall when you stop, and before it gets to the point of stalling, it runs rough. Plugs, cap and rotor have been replaced fairly recently.

Temperature gauge shows normal operating temp.

This is the TBI, or "injector carburetor" setup. As mentioned, it runs flawlessly when cold, starts immediately without pushing the gas. When hot, you have to give it some gas to get it to start.

I am thinking it may not be getting out of the startup rich loop and may be flooding (?) but wanted to check with everyone here. Thanks for your comments.
 
He is running rich for some reason.Try to unplug lambda sensor and see if it improves.Second that came to my mind is TP sensor.When TPS die car will run erratic,rich and stall.
 
Originally Posted By: Chris142
Originally Posted By: yvon_la
Oxygen sensor
or coolant temp sensor


O2 sensor is lazy. I would replace both o2 and coolant temp sensors. 1988 is a ways back there.
 
Could be a bad MAP sensor or a hole in the vacuum line going to the MAP sensor as well.

I would do an oil change as soon as you get this straighted out since that extra fuel is likely finding its way into the crankcase.
 
Last edited:
Originally Posted By: dnastrau
Could be a bad MAP sensor or a hole in the vacuum line going to the MAP sensor as well.


I was thinking this too. With the old Chrysler 2.2/2.5 TBI engines you could just unplug the MAP sensor as a test. On those engines stalling and poor idle was almost always a bad MAP sensor. You could even swap in some of the GM MAP sensors, the connector was the same.
 
Sometimes you can have a failing IAC motor cause this, or sometimes the passages between the IAC and the engine get dirty.

How old is your PCV valve? Really old ones make the engine behave like it has a vacuum leak. Even if your PCV valve still passes the shake test, you don't know if the spring is still good. Good thing PCV valves only cost a few dollars.

All the other things mentioned by previous posters are possible.
 
The 2 wire coolant temp sensor is for the engine computer, the one wire one is for the gauge.

Do the Key dance, pull the computer's stored diagnostic code

If you do replace the o2 sensor, use NTK. Do not use Bosch.
 
I like the TPS idea and here's why:

It uses the TPS to decide if the driver is in control of the idle (greater than .1% throttle) or if the computer should do it. The "scratchy pot" in the TPS goes bad near idle, where it spends most of its duty cycle. The truck doesn't want to control the idle, so it goes below the design minimum, probably 600-650 RPM on a V8. The cam makes less vacuum here so the MAP enriches things and you see smoke.

I wonder, I'd get flamed, what would happen if you bumped up the base idle.
laugh.gif
Just for diagnostic purposes, keep track of how mnay turns so you can put it back. Though a similar trick would be to unplug the TPS, should get a perky high-ish idle.
 
Thanks everyone; as soon as I get the time I'll report back....
 
Originally Posted By: FlyNavyP3
What was the issue?


As noted in 1st post...would not idle once fully warmed up, O2 sensor had been replaced.
 
Originally Posted By: Kuato
Originally Posted By: FlyNavyP3
What was the issue?


As noted in 1st post...would not idle once fully warmed up, O2 sensor had been replaced.


I think he was asking what fixed it, but if I read it correctly you sold it without resolving it.
 
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