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Instructor jp
Instructor jp, Technical Instructor Master ASE
Category: Dodge
Satisfied Customers: 315
Experience:  14 Years manufacture instructor
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97 dodge stratus: 2.4L..PCM, PVC valve..O2 sensor..check engine light

Customer Question

97 dodge stratus 2.4L problems starting, have to slightly hit gas and hold for a couple of seconds before it will idle. have replaced the following parts, IAC Valve/motor, thottle sensor, PCM, PVC valve, wiring to upper O2 sensor. No check engine light. Mechanic was out of options said it was the brain, replaced it and it still does not want to start the way it should. After each item was replaced car would start fine for about a week then start the problem again. i did just replace the computer yesterday and it has been starting but it goes to 7500 rpm then down to 5000 and finally back to 7500 were it should be. It has already done 1 were the engine was realy pulsing before the IAC kicked in. oh be the way the IAC has been replaced like 4 times. Any ideas?
Submitted: 7 years ago.
Category: Dodge
Expert:  Instructor jp replied 7 years ago.

HelloCustomer

 

Has anyone checked fuel pressure?

 

jp

Customer: replied 7 years ago.
yes, mechanic ran through tests and that checked out fine.
when i start the car i can hear when the IAC opens and i then know that it will idle. The mechanic also checked all the sensors and all were working fine. I also replace sparkplugs, wires, and the ignition coil. also had found that the catalytic converter was bad replaced both manifold and converter.
Expert:  Instructor jp replied 7 years ago.

I know you do not want to hear this but this is one of the times you need to have a scan tool that can give you the values to see what the controller is actually doing . What is the sort and long term memory of the fuel adaptive would be helpful here. That would show what you r injectors are doing or how good they are. I would also like to know if your vapor recovery system is purging at the time of the issue.

I would like to know if the engine is lean or rich during the stumble. What is the TPS throttle position value at idle?

 

Have you tried a good quality fuel injector cleaner?

jp

I am headde home and will be back at 9pm eastern

Customer: replied 7 years ago.
I was checking the vapor purge system and found that if I leave the vacuum line off at the throtle body it starts fine everytime. The valve was not pulsing until sometime after the engine is running.It seems to me that the IAC is not opening at startup. Do you know what the sequence is when trying to start, so many sensors on this car and I do not know which one would cause the PCM to be so delayed in opening the IAC. It seems to take about 3 seconds after start for it to open and control idle at 7500 rpm. The mechanics that have looked at it are mad at themselves for not being able to solve this one. They are and have run scan tests for free because they can not find the problem. If you give me a list of the scans that would help I could have them do that for me.
Expert:  Instructor jp replied 7 years ago.

HelloCustomer

 

You are asking me to give you 25 years or experience and training in a text forum. There is now possible way for anyone to say what is exactly wrong without looking at a data scan tool that has designed software for your car to really offer a silver bullet repair.

" 7500 rpm then down to 5000 and finally back to 7500 were it should be. It has already done 1 were the engine was really pulsing before the IAC "

I hope you mean 750 hundred and not 7500 thousand rpms?

The problem with a IAC is there is no feed back to the ECM for diagnosis. It is a dual DC motor driven in both directions by changing the power -+ several times a second. The controller only knows the wire is intact. It has no way of knowing if it actually moved.

 

The ECM will figure out that the rpm is to high by watching the TPS and crank signal and others small inputs. If the IAC is not able to bring the idle up or down The ecm will attempt to control timing and pulse width of the injectors for idle control. slow at doing this.

 

The problem is that Technicians are telling all is ok when they are not really sure what is what they are seeing on the scan tool. The controller will not lie.

In the above post I asked you to give me the long term and short term fuel memory and tps, iac. I can tell you what the controller is trying to do.

 

I get 400.00 for starters when people bring me their cars for this type of issue. Its not easy and it takes time.

 

jp

Expert:  Instructor jp replied 7 years ago.

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