Hey all,

A few weeks ago, I posted about my V6 1998 Dakota with Idle and richness issues. Well, it so far has been a multi-part repair scenario. The idle is rough and surges a little.Exhaust sometimes smells rich, etc. Only 105K and in near-mint condition truck.
1. I replaced the fuel injectors (refurbished on ebay). The closed loop idle went from 550 to 675. No more worry of stalling.
2. ran a BT scanner in real time, and the TPS has varying rest point. When it is resting above 25% the idle surges, if I kick the throttle, and it rests at 14%, no more surging, but still a little rough.
3. BT scan tool shows real time timing advance at idle from 12-24 degrees. It constantly fluctuates. I am beginning to think this is a crank pos. sensor, since that is what regulates ignition. No misfires, and starts enthusiastically every time. ( I plan to add washers to PCM cover screws, as I have read, for good measure.)

Anything other suggestions?
New plugs, cap. rotor, wires, IAC, Oxy sensors (Denso) and replaced rattling CAT. I tested all vacuum accessories. I also plugged off all vacuum ports, checked crankcase pressure for leak-down...no leaks.

Thanks for reading and let me brainstorm on here,

 

Fix the TPS problem. That may convince the timing to settle down as well. (PCM thinks you can't make up your mind what you want to do with the throttle......)

 

I thought that too, but even when the throttle is stationary at 14% for long periods of time, the timing still jumps around. Or the timing issue may be the PCM screws? Anyhow, I will switch out the TPS first. It has a new aftermarket on there (from prior owner). Is the Delphi the same as OEM?

 

Delphi is likely better than the dorman the last guy put on there.

Wonder if you have some timing chain slop......

 

I was thinking that too,but....100K mi and very meticulously kept.Seems unlikely, but I suppose anything is possible. I also thought about the distributor being the culprit, but again, there is no slop, and the pickup coil is strictly for EFI sequence. Is this a correct assessment?

 

It's a morse-style chain, so, rather prone to stretching. Could be worn bushings in the distributor too. (or a combination thereof.)

 

I hope not...😖

 

ok, I couldn't see the timing marks on the front of the engine, but I strobed a timing light at a stain on the dampener. There was no dancing. The reference signal for the timing must be skewed. Could that be the Crank sensor? If not, which component actually measures the timing? I really don't believe its the mechanical gearing of the distributor.

 

Have you looked at the condition of your plugs? Also, what brand are they?

 

Champions. With the spec on the emmisions label. Had autolites when I bought it. They looked really healthy. Still ran the same