Hey all
does anyone have any info on the cps mod to adjust the timing on a 3.9? I have heard of this but canot find the correct info on the procedure. Any info would be appreciated. Thanx

 

The CPS MOD Crank Position Sensor Modification. It is not recommended for anyone who has a stock or lightly modified motors. If done to much you can ruin you sensor and flywheel.

The purpose is to Advance the timing. The Death Flash was the main cause for some to attempt this mod.

All you do is open the mounting holes. A Drimmel bit works best. Make the slot towards the rear of the engine/truck. Then when installing the sensor slide the sensor forward towards the oil filter. Don't know the specifics on how much to open the hole. You don't want to use a larger drill bit due to you will loose your side to side location. And with only opening the correct side you can adjust and get back to stock.

Another typical talked about Modification is:

There is a TPS MOD too Throttle Position Sensor Modification. Click HERE
Again it is not recommended for stock to light modifications motors.

The purpose is to get the voltage higher, which the PCM Power Control Module/Computer will think the throttle is open more.
The bad is at WOT Wide Open Throttle the PCM goes to a preset valves and Ignores other sensors. So the TPS Mod only improves low to mid range RPM's and also will lower the range where the WOT program over runs.


All you do is drill out a larger hole in the mounting bushings. Then you can rotate the sensor. Hook up a Voltmeter and turn the sensor to get the highest valve. FSM states 1 Volt min. But not a MAX at Idle, I don't recommend any more than 1.2 volts.

 

Thanx for the info...I was looking for an easy way to gain a little more power and economy...without spending a ton of cash. I drive almost 100mls a day back and forth to work and with gas over 3.00 a gal..i need all the help I can get. My Dakota is a 4x4 and not to mention it has 215,000 mils on it...still runs pretty good but does have kind of a rough idle. I'm getting around 16mpg on the highway but think i might be able to do better. Any other ideas would be helpfull....thanx

 

Adjustable timing chain- $60

Free flow exhaust $150

Tuneup- $70

Tire pressure - $0.75

Since your only getting 16 mpg on the highway, I think you are having some internal wear showing. You have not said what your tire size is, speed driven, ect.

If your on the stock cam, then your tachometer will say what your best return power is for what RPM.

Also, advancing your timing may affect ignition ping, which would affect the type of fuel you will have to use (cost effectiveness?). All in all, a tuneup is the only cost effective manner to help mileage, sans the intake filter style, and exhaust.

 

Wondering if a chip might help the mileage as well as the running of the engine.

 

Stock 235/70/15 tires and wheels...drive 65-75mph...i do know it could use a timing chain..thats going in soon...and yea, i do realize the milage prob has alot to do with it at 215,000, just hoping to get a lil longer out of the motor...

 

I had a block with over 200k and just needed a berry hone to true the cylinders. They came out at 4.0025". Any vehicle making it to 200k should be congratulated.

 

Yea...I pat her on the dash every day! Considering I only paid $300.00 for the truck and put about 200 to 300 in it, I guess i cant expect miricals...though it is rust free and a nice looking truck..just a boatload of miles...and uses no oil! Baught it off of the original owner who did alot of highway driving for his job...I guess I'll do the timing chain and a good tune up and go from there...then exaust and aftermarket filter.

 

crazy i'd add that the pcm can relearn the min voltage (i know you can do it whe the drbIII ) so that may be just a temporary gain. and if you had the batt loose for any reason then it would learn the new min voltage.

also i'de like to add that i had a 91 ranger with 300+ on it. when i put on bigger pipes it helped. but i was not able to tell a diff when i whent to the k&n filter.
some people big gains but i never did notice one. i can't say that my mileage got any better or worse either.
im notsaying that you won't get a bit of improvement just that i wan't able to notice one.
who ever had my dak before put a stupid lil chrome edelbrock filter on it. like the ones you had in the carb days. i hate it to death. it's hurting my power and economy. all it does is suck in hot @$$ air off the exhaust sound like a hoover. so im looking to go bck to stock myself. personally i would say up and get an intake for it maybe swap the cam while your doing the chain. you'd see a lot more power from a cam then going to a better flowing filter. you'd actually notice a considerable difference with just the cam. but this is just my $0.02 worth.

 

I'll take all the .02 cents I can get! I have thought about a cam change but dont know if installing a better performence cam in a 200,000 plus mile motor would be worth it although the truck is worth putting some money into...I tryed to attach some pics of my 300.00 find...I hope they are able to be seen. Like I said, the truck is rust free...just a bunch of miles!