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3.5 Engine miss

1K views 11 replies 7 participants last post by  ITrep96 
#1 ·
I have a '96 Intrepid with a 3.5 with 188,000 on it. The engine has always run well. I have a problem that has me stumped.

About a month ago, I started to have a problem where the car sometimes did not want to idle. I thought that it was the Idle Air Motor sticking, so I pulled it out and cleaned it up. That seemed to help, but the problem returned, mostly at cold. The computer finally threw a 1391 code - Crank or Cam position sensor intermittent. So I replaced those.

Now is where it gets a little weird. The idle problem has gone away, but now the car occasionally has an intermittent miss and rough running at about 2500 to 3000 rpm under load. Again, the computer has thrown a 1391 code. It seems like the original problem has moved to a higher RPM.

Anybody have any ideas?
 
#2 ·
It idles that high on it's own? If so, I'd be returning to the IAC. There may be a leak in it somewhere, or the plunger may not be working. With the IAC unplugged the car will not idle. With the IAC removed, as soon as you start the car, it will take off with the RPMs. I shut the key off at about 3500 or 4000, but I would guess it would keep going. So, my guess would be that you are somewhere inbetween. Check for leaks in that area or a bad plunger. Just my 2 cents
-Taaf-
 
#5 ·
Have you checked plugs and plug wires lately? If your plug gaps are worn too wide it could be causing a miss. Also it could be a bad intake manifold gasket...this is very similar to what my dad's car did when he had a leak.
 
#7 ·
I changed plugs when I first got my car and they were WAY over 0.050, possibly in the 0.060-0.070 range and it was running fine. Switched to Bosch 4+ Platinums and I think I lost a little power because of the small 0.035 gap :(
 
#10 ·
Here is an update...

I still have the problem and here is what I have tried:

As I mentioned above, I had replaced both the cam and crank sensor.

I have since replaced the following:

New plugs, Champion 2412 gold plugs
New wires and coil pack
Replaced powertrain control module.
New fuel filter and I checked fuel rail pressure (while driving with the car having the problem) and it is on the money

I have probed various signal wires (cam, crank, coil drivers, fuel injection, etc.) with an oscilloscope (again on the road) to see if any of them go haywire when the car has the problem. All seemed to be ok.

The car always throws a 1391 code and the check engine light is always on. Here is another clue: when the car is bucking, the check engine light blinks off and the tach needle jumps, sometimes faster, sometimes slower.


Anybody got any ideas? I am runing out of things to try.

Bob
 
#12 ·
Check your the wiring to your ignition coil. I had a problem with the ignition wiring after I lost a timing belt last fall. The shop found it and fixed it and so I have no idea where to look or what to look for. My symptoms were a rough idle, low acceleration and power, and occasional while braking to a stop. The check engine light would also blink from time to time.
 
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