1999 Trans Am
Ok, got my engine rebuilt and car has been running great. No problems, I just recently passed the 1000 mile break in period. So I’ve been scheduled for a month to get it final tuned and dynoed next Wednesday July 7th. Last night I’m taking the car out for my wife’s bday and about 2 miles from the house it started acting like it was misfiring or had a bad spark in one of the cylinders is the best may to put it. Like I was in first and tapping the gas pedal to make it kinda jump.
When my Silverado starting jumping one day on my way home, doing the same thing. It was a bad spark plug, replaced it and everything was smooth again. It basically started doing that, what the truck did.

but if I got it above 35mph, it would smooth out, I only got up to 35-40.

And during all of this my rpm needle just completely fell off like it does when you shut off the car. Like it had a short. Just cut off. Then would come back on. And then when it would start running rough is when it would just fall down to nothing on the gauge

but I had Rpmson the motor, even when the dial stopped working, it idled fine (atleast it seemed like it, I didn’t have to work it to keep it idling). Just when I would take off in 1st and threw 2nd and into third I would have to rev it up and clutch in and out to keep it moving.
luckily I was close to my house and got it back home. Wish I could post a video I recorded of it when I was driving it back home.

so I don’t know what it could be. But I have a guess maybe.

I installed a electronic cutout last week. Tied into the 12v going to the radio antenna and grounded it right there at a bolt. I have a inline fuse holder for glass fuses. I was using a 14 amp fuse the other day and didn’t have any problems when I drove the car around for 30 minutes. I changed the fuse the night before last to a 1 amp fuse. When this all started yesterday while driving, I had just opened the cut out with the switch, about 20 seconds before that. So I don’t think it would have anything to do with it but always try the easiest stuff first just to see. Swapped it back to the 14 amp fuse lastnight and was going to try it again today and see if maybe there was some short, or bad fuse, or just anything like that. Atleast I’m hoping.
anyone have any thoughts. Ill answer any questions anyone might have.

 

You may have just listed your answer. Are there no codes or anything of the sort?

 

Im really hoping I did. No, no codes or anything. I don’t have much experience with electrical stuff and didn’t know if anyone knew if that was even possibly? For this to happen because of a wrong fuse on something. But I wouldn’t be surprised

 

I would maybe start by completely disconnecting your cutouts. Not physically just electrically speaking. Drive the car around a bit and see what happens, if it is working then great leave the cutouts off for few hundred miles and put them back on just to make sure it wasn't a fluke. If that does not work then I would pull every single spark plug

 

I checked when I got home, and it didn’t work.

But I’m pretty sure I figured it out. I didn’t have any lights come on the dash but I ran my cheap scan tool anyways. A P0336 code came up in the “pending codes” or “stored codes”, something along those lines. And that is the crankshaft position sensor, which basically have all the symptoms of what I was experiencing. Should have a new one today and will try it out and see if that fixes it.

 

Well it wasn’t the crankshaft position sensor. Man it sounded like that was it with my symptoms. Starts and idles fine. When I take off it’s ok with hardly any gas pedal pressure, but when I start giving it more gas it like it’s pulling timing, some cylinders aren’t working. Don’t know if pulling the spark plugs will help? I’m not getting any lights on the dash, but I went ahead and through my obd2 reader and it didn’t have any codes, but still had pending codes and in it was the P0336. Crankshaft position sensor, which I replaced and didn’t work.
Should I erase the code if I can, not sure if that could help reset it. I unplug the battery and plug it back in, but didn’t know if erasing the code would maybe reset it. But I would think it would run fine after I changed the sensor out regardless of resetting the code? I’m lost. Any ideas?

 

I had a similar thing happen to me. I kept getting the p0336 code as well. After many weeks or troubleshooting the issue, i ended up placing a small spacer on the crankshaft sensor to pull it slightly away from the crank. I havent had any issues since. I went through 2 different brand crankshaft sensors and a cam sensor as well. Ended up putting on the old sensors back on.