Hello, I am having a horrible time with this little truck of mine. For about three months now I cannot find the problem as it comes and goes and sometimes is more severe than other times. The truck is a 1995 dakota with the 3.9l v6 engine. auto. trans. The ignition timing is running severely ritarded by the computer system. I use a timing light on cyl. one and the its running around 6 or 7 degrees ritarded (depends on the day). The truck has had a new timing chain set put on it 10,000 miles ago. I have replaced the distributor cam sensor, crank sensor, redid the wire splice under the relay box. new cap rotor plugs and wires about 20,000 miles ago. One main symptom that I cannot figure out is that after the truck is warmed up, If I shut it off and restart it and then quickly check the timing, it will be dead on. Then after 30 seconds or so, the idle goes slightly up momentarily and then the timing will drop back down to being badly ritarded and jumpy. This leads me to believe after replacing those sensors, that the computer may be bad or need reprogramming. Thanks for any input as I love this truck and just want to get it running right again. Most of the time it has really bad power loss because of this and it shakes and has completely random misfires. Its got 226,000 miles on the original motor and trans. and is has never had a single major problem and still shifts perfect like new.

 

First of all the ignition is 100% controlled by the PCM. The only thing that you can do is verify at TDC the rotor #1 Cly is pointing at the mark. Make as dead on as you can. If it is to far off then the PCM can't properly adjust the timing.

Next if your getting a miss something else is wrong, bad plugs wires injectors ect. Do you have any check engine codes?

 

Yes I have read in the book that the pcm controlls the spark timing completely. I have set the timing pysically to tdc and lined up the rotor to the cyl. 1 mark. I was told that a timing light can be used to verify that the computer is contolling the spark properly. Please tell me if this is an incorrect method. but like I said before, the timing light will show cyl 1 firing perfectly on tdc for about 30 seconds and then the timing will back off and fire jumpy and way ritarded. So would this indicate a bad pcm? or is the timing light useless on these trucks?

 

oh sorry forgot to add. No check engine codes just 12 and 55

 

I have a timing light, but never tried using it on anything newer than my 57 E-Bird.
I'll put it on my Dakota tomorrow and see what it does. I do know from reading other posts, when my timing was off, I replaced the 2-wire coolant sensor and it solved the problem, as well as a 27 code.

 

Thanks. Coolant sensor was gonna be my next try. The thermostat is a little sticky and am going to replace both together. Where is the coolant temp sensor? The Haynes book sucks. I found the 1 wire one for the guage but not the two wire one.

 

The coolant temperature sensor is the 2-wire plug to the right of the thermostat. The sender is near the ignition coil. You'll need a thin wall deep 13mm or 1/2" socket to get the new one in.
When you go to buy the sensor, there's usually two listed; one for the $10.00 range that had 1-wire and one for the $17.00 range that had 2-wire connections. You want the $17.00 one with the 2-wire connection that runs through the PCM. The 1-wire is the sender but usually listed as a sensor.

When pulling the wiring harness off of the sensor, don't pull directly on the harness, make a small L shaped loop on the end of a wire coat hanger and hook it under the connector and pull up on it, that way it doesn't damage the harness. It just plugs in without any sort of locking tab.

 

I found it finally. Its tucked behind the AC compressor under part of the harness. Looks like ill have to take off the compressor to get to it

 

I used an inductive timing light on my Dakota, but I couldn't even see any timing marks on the pulley after the truck warmed up (they were visible at a cold start), so that's either normal, or both our trucks have problems, or my timing light is broken (almost a month old and Made in China, so that's possible)..mine purrs like a kitten though.

 

Ok. I will change the coolant temp sensor hopefully tomorrow and see what that does. I just read in the FAQ that it says to stay away from Bosch multiple electrode plugs. I have the platinum 4's in there. Could that be a cause for this kindof problem? I wouldn't think so because they've been fine for about a year so far