Hello all, I am in need of some advice/guidance. My daughter has a 99 Dakota sport 3.9 4x4 we bought her as her first vehicle about 15 years ago. The truck has over 250K on it, however all of the major assemblies have been replaced to include the engine which is a crate replacement done about 5 years ago.

Recently (about 4 months ago) it began to experience issues starting, basically at times it seemed to struggle to start (meaning it sounds like it isn't spinning freely or as normal), it fires but will show ~1000 rpm and then dies unless you apply the gas pedal it and get it to about 2000 rpm and hold it for a little while. More recently it started to periodically die when the gas pedal was released like when coming to a stop sign/light (which completely freaks out a 28 y/o female who has never driven a vehicle w/o PS and PB).

I have read this and many other forums and YouTube and applied the majority of suggested solutions, however given the recent dying deal I decided to apply a holistic repair approach and 2 days ago and did the following;

- checked fuel pressure; steady at 50 psi
- removed the TB, cleaned it and replaced the IAC, TPS and MAP
- replaced the O2 sensor
- removed the plenum and replaced the bottom gasket
- replaced the thermostat, water pump by pass hose, serpentine belt
- installed new spark plugs
- replaced the valve cover gaskets (was leaking)
- replaced the temp sending unit
- changed the oil
- checked the alternator output (14.3V); the battery is about 1.5 year old
- reset the ECU

It was good for a day, this morning she told me it was struggling to start again and she had to "rev" it up to get it to run. I am about out of ideas, I am open to about everything. It has been a really good truck but this issue has proved illusive.

 

Getting any codes?

What brand IAC? If it ain't Mopar, that may be a big part of the problem.....

Slow crank may be the starter on its way out.

 

No codes.
I have tried 3 O'Reillys brand IAC's and 1 Standard brand.
The slow cranking seems to only happen when it isn't going to start correctly which has me thinking is an indication of an electrical issue; in other words I am thinking that either the alternator isn't fully charging the battery (due either it being bad or poor connections) or the battery itself has become weak.

I appreciate the response, again I am seriously confused by this or more so my inability to fix it.

 

Have the battery, and alternator tested. (preferably separately.) Verify they are both good. Or not.....

Get a real Mopar IAC. You can find them online for less than what the dealer wants for one.......

Slow crank is either low voltage, (weak battery, bad connection....) or failing starter. Doing a starter draw test when it is cranking slow might tell the tale.

 

Going to test the battery and alternator tomorrow, ordered a new Mopar IAC and will get it Friday. I really don't think the starter is weak as this only occurs in the morning after the truck has sat overnight. Not completely ruling it out but putting down the list for now.

 

sounds like the battery is keeping a surface charge between starts, but draining low overnight

 

I believe I found at least part of problem, While checking the battery and alternator I discovered that there was an issue with the ground cable. Subsequently I cleaned and tightened all of the grounds as well making a change to the negative cable end which was poorly assembled. We also ordered a new Mopar brand IAC, but so far so good.

The battery is 6 months old.

 

So far so good, my daughter says the truck is doing very well so it seems that the ground cable was at least a contributing factor.

 

That would make sense too. I would expect it to be more consistent and less random in that case, but hey, you never know.

 

I think it was making "just enough" contact to act like something else.