I bought a 1990 Ram about 2 weeks ago and I am having some engine problems. It has a 3.9L V6 with TBI and is stock. I have replaced the air filter, valve cover breather, spark plugs, and checked the timing. After driving the truck for about 15 miles, I loose all power above 10% throttle. I can push the throttle down a little, but after that it looses all power and drops down to 1000 rpmor so. I have checked the codes and I have 12 battery or computer recently disconnected, 33 A/C clutch relay circuit open or shorted, 17 engine stays cool too long - bad thermostat or coolant sensor (thermostat on order), 15 no speed/distance sensor signal detected. The timing was at 3 ATC, but apparently was supposed to be at 10 BTC. I adjusted it to 10 BTC and it ran terribly, so I then adjusted it to 4 BTC and it is running a little better. I checked this website for the codes http://www.allpar.com/fix/80s-codes.html. I think that I may be in "power limited" mode, but how do I get out of this? Replace the thermostat or coolant sensor? Any other ideas?

 

Replace speed sensor would help, battery disconnect is normal, never seen the A/C clutch relay open, would check A/C clutch relay to fix that, but that wouldn't make the run bad or i don't think it would.

 

replacing the speed sensor will remove the "power limited" mode? Even though that code came up, the speedomoter seems to work fine although the odometer doesn't work at all.

 

Speed sensor will rid it of the speed sensor code. My speedometer was giving me fits and my odometer wasn't working, replaced SS and speed but odo doesn't still.

 

my speedomoter works fine, the odometer doesn't work, but either way I want the truck to run better. I am not worried about the speedomoter or odometer. Have you heard anything about this "power limited mode"?

 

Researched mode and can't find anything about it, let me find chilton's and i'll check that and my hayne's i not sure about that mode though where did you get the mode info from and my truck did this but it would almost die when you got in it. The O2 sensor was bad. The fuel pump or injectors might be going bad too.

 

http://www.allpar.com/fix/80s-codes.html/This is the website that I got all of my information from. Look down a few paragraphs and you will find this: "* Activates Power Limited/Check Engine light on some models." The asterik refers to the corresponding code. None of the codes that I pulled had an asterik next to them, but when driving the truck it feels like the computer is limiting the throttle. What do you think?

 

I just pulled the CEL codes again to see if I had them wrong or to see if they have changed since I have been tuning the truck. Now I have 12 and 33......battery or comp recently disconnected (no prob), and A/C clutch relay circuit open or shorted (no A/C, no prob). So, I have solved my important CEL problems, but I am still having my main engine problem with losing power. Any suggestions?

 

You don't have A/C, if the truck never came with it then that code should not appear because it shouldn't register in the computer.

 

If the truckwas never factory equipped with A/C then there will be NO relay installed. Since the computer looks for a voltage change when the relay activates it will set a Code 33. Nothing to worry about. I would consider replacing the Coolant Temperature sensor and the thermostat. There are 2 temp sensors...one for the dash gauge and one for the computer...you want to replace the one for the computer with 2 wires running to it.