Hello all,

I may need the assistance of a TBI expert.

I have recently purchased a 1988 First Gen Ram with the 318. It’s a been beautifully preserved. However, it runs insanely rich. Rolling coal that would make the Cummins guys jealous.

The previous owner replaced the EGR, the throttle position sensor (TPS), the idle air temperature (IAT) sensor, the engine control temperature (ECT), the idle air control (IAC) valve, manifold absolute pressure (MAP) sensor, fuel pressure regulator the fuel filter, and the injectors.

When I got it, I capped the lines to the smog pump and tried a myriad of unplugging various sensors, one at a time to see if it affected how it idled. It did not. I also looked underneath the truck to make sure the fuel lines were not crushed at any point along the way. They were not.

The voltage measured at the new ECT is around 5 volts when unplugged from the sensor. Which, according to other forms is what it should be measuring at operating temp. This does not cause it to run any leaner though.

It should be noted that every once in a while, it will start up and run beautifully for a few minutes before going back to chugging and smoking straight fuel

What are the chances that my PCM/ECM is bad? Is there anyway I could verify this?

Is there anything else that I may have overlooked?

Any knowledge on the subject would be greatly appreciated! Thank you for your time.

 

Try unplugging the front O2 sensor, (you may only have the one....) see if it runs any better.

 

I forgot to mention, I did try that to no avail, there is only one o2 sensor, it is on the driver side underneath the header.

I just went out and fired up the truck and it barely runs now it’s just puffing black smoke but now it sounds like it only runs on a few cylinders. I guess it’s time for another round of spark plugs.

 

Disable EGR altogether. See what happens.

 

i would likely start by installing a new set of plugs. i would assume if it is running as rich as you claim you will have likely had a few fail. have you tested the o2 sensor?

 

Any codes?
https://www.allpar.com/threads/the-1...ost-1085223107

 

pulling codes will likely be useless since he likely triggered a bunch while troubleshooting and takes quite a few key cycles to clear them and most people don't have the tools needed to clear the codes without disconnecting the battery

 

No current codes unless I unplug sensors but those codes go away if I turn the truck off and back on once i plug them back in.

Currently at work. Ill put plugs in it Friday and keep diagnosing then.

The egr also seemed to to be functioning correctly because when a vaccum is applied to the input line the engine will spit more and eventually stall. I will see if can cap it on Friday and see if it runs better.

 

the codes usually stay stored in the computer for 50 key cycles or till you reset the computer. the check engine light may have gone off when you rehooked up the sensor but the code should be still store in the computer.