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jazzmaster
jazzmaster, ASE Certified Tech
Category: Dodge
Satisfied Customers: 2951
Experience:  ase certified--32 yrs experience
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I have a 1987 Dodge Dakota 3.9L v6 that runs great until it

Customer Question

I have a 1987 Dodge Dakota 3.9L v6 that runs great until it is shut off and then restarted before it cools down. For example, if it is driven a few miles to a store, shut off, and then restarted within a half hour or so, it will run very crappy. It idles
rough, does not accelerate well, has severe "pinging", and shakes if given full throttle. It will drive fine down the highway unless I try to accelerate, then all of the above occur. It is less severe on mild acceleration, most severe if given full throttle.
This problem does not occur unless shut off and restarted before it cools down. I can drive it for miles without a problem, but if shut down and restarted before it cools down it runs terrible. Once it gets in this "mode" it does not "recover" until allowed
to cool down. I can't think of where to start looking on this one. It is frustrating that it runs so good, and then runs so crappy. It has stock ignition and carburetor.
Submitted: 1 year ago.
Category: Dodge
Expert:  jazzmaster replied 1 year ago.

Hi,l did you check the spark to each spark plug .?

this may be an issue with either the coil ,or crank sensor .

please check the spark at each spark plug and make sure the the coil bracket has a good ground at it.that is clean the spot where the coil bracket mounts to the motor ..jazzmaster ..

Customer: replied 1 year ago.
Your answer makes no sense to me. Why would the spark be there if started cold, but not be there if started warm. What would be different regarding the coil if started warm versus if started cold? What would be different regarding the crank sensor if started cold versus starting warm? Does the engine not use the crank sensor if started cold but use it if started warm? It does not appear to be a warm problem because if not shut off and restarted when warm, it will run fine for miles and miles. The problem only occurs if started when warm, and will not go away until shut down and allowed to cool.
Expert:  jazzmaster replied 1 year ago.

the issue you have is in the starting procedure or process when warm .

certain parts can fail when this happens .

.one being the ignition coil

also, the pick up assembly in the distributor .

and the crank sensor .

if you are not getting a check engine light then I would suspect the coil or pick up .

So, you need to check the spark output at each spark plug when it does run bad ..please ..

these did have a higher than average issue with the coil .

by , allowing it to cool down points to that .please bear with me on this..

and please check the spark when it does run bad and let me know ..thank you .

Customer: replied 1 year ago.
Coil was replaced when it quit running when warm. The engine does not have a crank sensor. It has Hall effect pickup located in the distributor that supplies rpm and timing data to the SCC. Both the coil and the Hall effect pickup have been replaced. Both failures caused the engine to intermittently quit running completely when warm, not the current issue with rough running after a warm start. This vehicle does not have a check engine light. Are you familiar with the 1987 dodge Dakotas with the 3.9L engine?
Expert:  jazzmaster replied 1 year ago.

yes , am very familar with this vehicle .I aslo, had an 88" with the 3.9 L.

when I was referring about the crank sensor that is what I meant .you didnt say that you had relaced the

coil ,SORRY I meant to say also, the crank sensor -as that is what it is also called .

you have an electronic vacuum advance on the ecm ,dosconnect the vacuum and see if that changes anything ,

I saw a lot of those fail and cause the same problems as you have ..