I have read lots of the threads, and the DIY section - just looking for more ideas - where to look..

So - on start up engine races to 2K rpm, then comes down to 1500, then steps down till it gets to 500 rpm, then shoots back up to 2k and usually walks down and stalls

During driving while the rpm is bouncing the D jerks trying to hold speed @ 60 mph
After 8 miles of driving the bouncing RPM stops

What I have already done... (2000 D 4x4 4.7l 218K with a 80K engine)

1) cleaned TB so you could eat off of it
2) replaced TPS
3) replaced IAC
4) reset comp by disconnecting battery for 30 min

During RPM bounce I will get a cyl #8 misfire code, but once the bounce goes away so does the code.
Once the rpm bounce is gone - this is a great running engine - smooth quite and decent power - I just want this startup BS cleared up.

Thanks all for your help in advance...

On edit - I bought this car a week ago
My battery is only 4 months old - it is an interstate I-34 (540 CCA and 675 CA), looking at their website I should have a 27 series with 810 CCA and 1000 CA

I have a huge Deep Cycle Marine battery with similar CCA and CA as the series 27 - will give that a try...

 

The large - known good battery failed to make any changes in the way the D acts on start up...

So now I am open to all suggestions as I am not sure if this condition will become worse and make this an unreliable vehicle.

 

Does it do it every startup or just cold starts? Possibly a small vacuum leak that goes away when the intake (or w/e) expands? I'm just grabbin straws here. Honestly the first thing i thought of was map sensor but maybe someone who knows more can say. I'm just bouncing ideas.


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Only occurs on cold starts...

once I get 8 miles on her - she is good and ready, runs and starts great the rest of the day.

I have not yet replaced the MAP sensor

 

Anyone else with an idea on this?

All 2 cents are being welcomed

This issue seems to be growing worse as the D now has started to stall while cold at stop signs and red lights... not really fun - need to get this found and fixed..

Thanks for the feedback guys...

 

I have an intrepid that does the same thing, i pull out the map sensor and spray it with carb cleaner, and inside the small hole a little with a q-tip and it runs good for about a Week. Not sure if carb cleaner will hurt your sensor but I don't really care much about this car which is the only reason i do it. That and i know for a fact that's what's wrong with it. No intentions on buying parts for a car we are going to junk before to long. Know what i mean.


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ok an update

Replaced the MAP sensor (yes I reset the comp after the sensor swap)

No change what so ever

I don't like throwing parts at it - but nothing leads me to proper troubleshooting on this thing...

No codes

Still looking for help on this one...

As this D has 218K on it - IO am thinking to re-power it with something different - just dont have the cash to do it right now.

I need this D to run

THanks

 

Here is an update:

I kept getting a crank sensor code - so I replaced that, seemed to make no change at all.
In fact I think the issue is degrading at a rapid rate - as I slowed for a corner she stalled, as I stop at stop sign or red lights she stalls....

I even went as far as replacing the coolant sensor thinking there may be a bad reading for a cold start cycle... I have bled and burped the cooling system several times.

This should not be this hard... there are no codes at all...
Recap:
1) Throttle body cleaned
2) TPS replaced
3) IAC replaced
4) Crank sensor replaced
5) Battery tested - good under load
6) Coolant sensor replaced
7) Computer reset with each sensor replacement
8) Replaced MAP

So still need some help on this issue... It used to run fine after getting warmed up - but not so much now, there appears to be a miss or something as I am getting shuddering while at speed...

I seem to be losing some water as well, what symptoms does a blown head gasket display?

Maybe runs like crap till heads get hot and seal that sucker up, then under power it leaks causing the shudders...

Looking for ideas - as I am ready to pull this engine call it a boat anchor and go with something else... (just wish I had the money to do it

 

I'm taking a wild guess (admittedly), I know you cleaned. You could try running a can of Seafoam combustion cleaner throught it also. That will blow a lot of crap out.

How are your temps? Check your oil, see if it looks milky.

 

A quick compression check will let you know that you may have a bad headgasket. As mentioned in the subsequent post, your oil will have a milky appearance. Pull the dip stick to check.