Suspected crank position sensor wire problem
06-21-2008, 06:12 PM
#1
Suspected crank position sensor wire problem After my poly motor mounts were installed, I had some hesitation and loss of tach that pointed towards the crank position sensor wires that were damaged or under tension from what I read and was told on here. I could not see any gross defects in the wire on inspection, but the alternator wire did seem to be pressing on them. I rerouted the large wire to the alternator that I thought was pressing on the CKP wires and that resolved the tach issue and there was no hesitation anymore, at least not in typical daily driving throttle positions and rpms.
It would seem that I did not fully resolve the issue though because I have some intermittent hesitation after 3500 RPM over about 63% throttle. I scanned it and the only parameter that seemed way out of line was that while in second gear at almost 3900 RPM while rolling into the throttle the HPT log shows an RPM spike to 5800 RPM that as far as I can tell did not happen based on what I could tell driving the car.
I have seen many references whilst searching of people with problems with the wires, but not to many that spelled out solutions.
Is there a clear answer as to why movement in these wires causes faulty readings? Do they typically hit a primary and get nearly melted, or do the wires pull away from the CKP sensor connector causing loss of signal?
Is there a good way to secure these wires so that this doesn't happen under high throttle?
Is the only real solution to this problem to replace the wires from the CKP to the PCM? If so is there a part for the wires and connector or did most just replace the wires themselves? If so what gauge would they be and how did you run them?
I am going to get under the car again after it cools off to take a look again. If I don't see any burnt spots or breaks in the wire, would wrapping the exposed portrions in electrical tape make an improvement?
Thanks.
It would seem that I did not fully resolve the issue though because I have some intermittent hesitation after 3500 RPM over about 63% throttle. I scanned it and the only parameter that seemed way out of line was that while in second gear at almost 3900 RPM while rolling into the throttle the HPT log shows an RPM spike to 5800 RPM that as far as I can tell did not happen based on what I could tell driving the car.
I have seen many references whilst searching of people with problems with the wires, but not to many that spelled out solutions.
Is there a clear answer as to why movement in these wires causes faulty readings? Do they typically hit a primary and get nearly melted, or do the wires pull away from the CKP sensor connector causing loss of signal?
Is there a good way to secure these wires so that this doesn't happen under high throttle?
Is the only real solution to this problem to replace the wires from the CKP to the PCM? If so is there a part for the wires and connector or did most just replace the wires themselves? If so what gauge would they be and how did you run them?
I am going to get under the car again after it cools off to take a look again. If I don't see any burnt spots or breaks in the wire, would wrapping the exposed portrions in electrical tape make an improvement?
Thanks.
06-21-2008, 09:20 PM
#2
Well I tried to rearrange the wires again, and managed to crush the blue CKP sensor wire in nut for the starter motor wire. I took it out and reassembled it but the car won't start. I think I'm going to have to rewire the damn thing. Any tips on that or removing the starter?
06-22-2008, 02:21 PM
#3
So here is how this morning went.
I got out there and dropped the starter so I could actually inspect the wires decently. Where I thought I had crushed the wire yesterday was just a little scuff on the insulation more or less. But the blue wire and the metal terminal it was connected to was pulled back out of the plastic plug slightly. It was also only connected to the terminal by a few strands of copper wire connected to the very rear of the terminal with a bundle crimped in the front part not connected to anything. Additionally, the rubber plug to hold the terminal into the plastic plug was missing. As far as I can tell someone probably pulled the blue wire out of the terminal at some point and did a hasty repair on it and it the hesitation I felt was a manifestation of that, and me manipulating it yesterday was the last straw for it.
So I thought I would go to the parts stores to see if anyone had a new terminal that I could crimp on. Autozone had some ones that were way too big, as did O'Reilly. The guy at O'Reilly told me he could order the whole plug so I might consider doing that in the future but I needed the car to run before tomorrow. Also NAPA said they could order the terminals but it would take until tomorrow. I stopped by Radioshack because they used to carry a whole bunch of wierd electrical comonents but they didn't have anything useful.
I went back home and tried to see if I could salvage the terminal. I carefully pried the crimp job at the rear of the terminal open, but could not get the really small parts open. I then recrimped as much as I could onto my new wire and then soldered it together. Hopefully it will hold a little better this time. I put it back into the plastic plug but since I had no little rubber piece to hold it I just had to tape it up so the wires wouldn't move (The terminal snapped into place, but did have some motion so I figured better safe than sorry). I soldered my new wire to the original blue wire and taped it up, wrapped all three wires, then covered with a wire loom I had.
After reassembling everything I started the car and it fired right up. It seemed a little off, and when I gave it some revs it would undershoot the idle speed and nearly die. Performed CASE learn via HPTuners and it seems to be running well now. I will try to get some WOT testing in to see if it is completely resolved.
As far as CKP sensor issues with tension on the wires, I imagine a lot has to do with the terminals and the wires coming loose from one another or free from the plastic plug. I had found an old thread where Pro Stock John was having intermittent issues with this and the solution as per GM was to recrimp terminals for the plugs.
I got out there and dropped the starter so I could actually inspect the wires decently. Where I thought I had crushed the wire yesterday was just a little scuff on the insulation more or less. But the blue wire and the metal terminal it was connected to was pulled back out of the plastic plug slightly. It was also only connected to the terminal by a few strands of copper wire connected to the very rear of the terminal with a bundle crimped in the front part not connected to anything. Additionally, the rubber plug to hold the terminal into the plastic plug was missing. As far as I can tell someone probably pulled the blue wire out of the terminal at some point and did a hasty repair on it and it the hesitation I felt was a manifestation of that, and me manipulating it yesterday was the last straw for it.
So I thought I would go to the parts stores to see if anyone had a new terminal that I could crimp on. Autozone had some ones that were way too big, as did O'Reilly. The guy at O'Reilly told me he could order the whole plug so I might consider doing that in the future but I needed the car to run before tomorrow. Also NAPA said they could order the terminals but it would take until tomorrow. I stopped by Radioshack because they used to carry a whole bunch of wierd electrical comonents but they didn't have anything useful.
I went back home and tried to see if I could salvage the terminal. I carefully pried the crimp job at the rear of the terminal open, but could not get the really small parts open. I then recrimped as much as I could onto my new wire and then soldered it together. Hopefully it will hold a little better this time. I put it back into the plastic plug but since I had no little rubber piece to hold it I just had to tape it up so the wires wouldn't move (The terminal snapped into place, but did have some motion so I figured better safe than sorry). I soldered my new wire to the original blue wire and taped it up, wrapped all three wires, then covered with a wire loom I had.
After reassembling everything I started the car and it fired right up. It seemed a little off, and when I gave it some revs it would undershoot the idle speed and nearly die. Performed CASE learn via HPTuners and it seems to be running well now. I will try to get some WOT testing in to see if it is completely resolved.
As far as CKP sensor issues with tension on the wires, I imagine a lot has to do with the terminals and the wires coming loose from one another or free from the plastic plug. I had found an old thread where Pro Stock John was having intermittent issues with this and the solution as per GM was to recrimp terminals for the plugs.
06-24-2008, 01:21 PM
#4
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AWESOME INFO!!! I love LS1Tech! I am having intermittent issues with my car as well, and will be replacing my crank position sensor just to make sure, but I am thinking that the people that "tried" to tune my ride, but told me that my CAM was too big (HAHA - Texas Speed Torquer 2 232/234 .595/.598) probably screwed up the wires...
They originally told me that I needed a CPS, then found out (after charging me and installing it) that they didn't hookup the fuel pump (Walbro 255) properly. They then had to drop the tank again and hook that up, then remove the new CPS. I am sure that they just slammed the thing back together and didn't care about anything...
Gotta love a speed shop that knows nothing! GO *****n**s!!!
They originally told me that I needed a CPS, then found out (after charging me and installing it) that they didn't hookup the fuel pump (Walbro 255) properly. They then had to drop the tank again and hook that up, then remove the new CPS. I am sure that they just slammed the thing back together and didn't care about anything...
Gotta love a speed shop that knows nothing! GO *****n**s!!!
