Stutter after warm(Crank Sensor?)

[cmucky]

As A new member I would first like to say hey to everyone here.

So here is what I have, a 95 Talon ESi. My problem is this, after driving for a bit and the car is nice and warmed up it will begin to stutter and cut power. When WOT it almost sounds like a 2 step system. And it really only happens if I put the car over 3k rpm.

First I thought it was fuel related but after changing the filter the fuel pressure remained the same throughout. After recently joining these forums and doing a large search I have found that the problem appears to a crank position sensor. I have one ordered and it should be here tomorrow hopefully. I am also picking up the pigtail needed to rewire the sensor into the harness since apparently they changed it in the later years of the gen2's.

I guess my real question is this. While searching I have found that the ECM uses both a signal from the Crank Position sensor and the cam position sensor to figure out its ignition controls and firing. Also testing the crank position sensor is hard too because of the limited amount of time to test it since the problem only occurs when the car is hot. Aside from replacing the cam position sensor, is there any way to rule one sensor or the other out to ensure I am replacing the correct one.

Thank you in advance too!
-Cmucky

 

[Focused1]

Based on your symptoms the cam sensor sounds more likely than the crank sensor.
The cam sensor is inaccurate at low RPMs, that is one reason for why there is a crank sensor. On startup the vehicle doesn't know what cycle each piston is in(i.e. exhaust stroke, power stroke, combustion stroke, intake stroke) so it uses the crank to monitor the cranks speed while at the same time randomly firing spark plugs. When the cranks speeds up then that is seen as a combustion event and the ECM quickly learn where each cylinder is in the cycle and fires the plugs on the power stroke and the engine starts. Once the engine is started and up to the proper RPM the cam sensor is relied on because it is more accurate at high speeds.
Since your symptom is at 3000+ RPMs that tells me it is more likely to be the cam sensor. But since you say it happens when it gets hot makes it more complicated. How does it idle when it's hot? Is it high or low, is it steady? I also suspect a ISC valve.

 

[jayson427]

you need to test the ohms and resistance on the cam sensor to find out if its accurate.

 

[cmucky]

Based on your symptoms the cam sensor sounds more likely than the crank sensor.
The cam sensor is inaccurate at low RPMs, that is one reason for why there is a crank sensor. On startup the vehicle doesn't know what cycle each piston is in(i.e. exhaust stroke, power stroke, combustion stroke, intake stroke) so it uses the crank to monitor the cranks speed while at the same time randomly firing spark plugs. When the cranks speeds up then that is seen as a combustion event and the ECM quickly learn where each cylinder is in the cycle and fires the plugs on the power stroke and the engine starts. Once the engine is started and up to the proper RPM the cam sensor is relied on because it is more accurate at high speeds.
Since your symptom is at 3000+ RPMs that tells me it is more likely to be the cam sensor. But since you say it happens when it gets hot makes it more complicated. How does it idle when it's hot? Is it high or low, is it steady? I also suspect a ISC valve.

The seems to idle fine, there are times when it sounds a little lopey like it has a mild cam in it but I think is because of the cam gears that where on the car when I bought it. (Also I have never checked the timing, first interference motor I have owned and I dont own a manual for the car yet so not gonna touch it until I get a manual.) Recently however the car has idled a few times and completely died on me, but this only happens after it has a bad stuttering moment and when I try to restart it, which makes me believe that its the crank sensor, since it is required for the starting of the motor. I have already ordered the crank sensor and the new pigtail(still don't know if I need the pigtail or not). I will go pick up a chilton manual and test the cam sensor like Jayson said. Do you guys know if the resistance range is listed in the chilton manual? And if that checks out I will end up doing the crank sensor. Should be here tomorrow morning according to the parts store.

 

[jayson427]

also your ecu could be having issues. i would read up on that some more. idle issues are really hard to diagnose since it could be a few different things making one problem or just one little thing making it happen. ground wire, bad sensor, ecu, fuel problems ect.

 

[Focused1]

I had a similar issue and it ended up being the ISC valve. It's super easy to check with a mltimeter so I sugeest checking it out. Unplug it and check the resistance of each coil. Connect your leads to pins 1 and 3 then 4 and 6. I believe the exact resistance should be about 30 Ohms but above 80 is definitely a problem. One of mine read 36 and the other was "Over Limits" for the meter which means it was an open circuit. That would be an easy thing to eliminate for free. Let me know what you find.

 

[cmucky]

Well I replaced the crank sensor and it seems to have fixed the problem. The tach doesn't bounce all over the place anymore and it doesn't cut out like it use. I can still feel and hear a slight stutter, like it is still there but it doesn't show itself like it use too. The ICS valve I will check out this weekend and see what that is all doing. For now though I think that crank sensor was the problem and seems to have resolved the issue.