Change the sensor. If it still runs funny. then you can look into something else, but IMO it is not the distributor being off one notch. If it was, the engine would run very bad, if at all. I have had my 97 Silverado 5.7L sence 2002. I have had my distributor in and out of my truck a lot. I never set my timing with a code reader. I am not saying that you should not use one, I just never have. You can also do an old school check, by pulling the #1 plug on TDC compression stroke. Once you are on TDC CS, the rotor inside the distributor should be pointing at the #1 plug wire on the cap. If it is, then you can't be off one tooth on the distributor timing.

 

Most likely it's the crank sensor. Make sure you use the shim kit to get proper setting to the crank for best reading. I am in need of changing mine too, but can't remember the proper procedure for spacing. As long as you are close to TDC with the distributor, the computer takes care of the fine tuning for the advance setting.

 

Thanks all, I was not aware of proper spacing for the crank sensor. I will have to research that more unless someone on here can advise.

 

If I remember correct the replacement sensor should come with a plastic go no go type gauge to get the right clearance.

 

Hello I am new to this site I have been reading it for sometime now my question or problem that I’m having is I have a 96 GMC 1500 with a 305 the problem that I’ve been having is while I was driving the truck would Chyna cut out the RPM gauge or drop and go back up Also I noticed I had a water leak at the intake So I pulled the manifold did the gasket repair replaced the fuel pressure regulator while I was there put it back together and it drove fine But the engine seem to still do the same thing so then after I was driving it it just up and died after about a month of driving checked the cap and rotor replaced it still would not start so then I just ordered a complete distributor from eBay put it in and it it started drove the truck for about another month and ended up and died again it seemed as I was checking the spark it was kind of week and intermittent I have put a new coil ignition control module and crank position sensor in the truck I’ve had a distributor in and out several times thinking maybe something to do with the timing I’ve checked top dead center And timed it that way reposition the road or so that it points towards number one went through all of that so what I am noticing what it is doing is as cranking over and then as I release the key it kind of fires and backfires a little bit up to the carburetor the truck has 218,000 miles on it is it possible for this thing to have jumped time while I was driving I have not put the scanner on to check for codes that will be my next thing to do any help would be greatly appreciated I am about my wits and and by the way the fuel pump is good I checked it it has 62 pounds of pressure thank you

 

Hello I am new to this site .................. good I checked it it has 62 pounds of pressure thank you

1. John, welcome to GMTC.
2. Ever hear of punctuation, that was difficult to read.
3. We prefer you start your own thread, not hijack someone else's, even if it's the same problem, it's easier to make sure we get you the help you need.
4. BFC is spot on with his recommendation. If you are noticing something different happening with the movement of the ignition switch, and you have changed all that you have changed, I would say next should be the ignition switch.

 

(as cranking over and then as I release the key it kind of fires and backfires ) Could be your first clue of a bad ignition switch. As far as the rest goes start with the basics .....compression check, check all ground connections ect.

 

1. John, welcome to GMTC.
2. Ever hear of punctuation, that was difficult to read.
3. We prefer you start your own thread, not hijack someone else's, even if it's the same problem, it's easier to make sure we get you the help you need.
4. BFC is spot on with his recommendation. If you are noticing something different happening with the movement of the ignition switch, and you have changed all that you have changed, I would say next should be the ignition switch.

Sorry I did not type that out I was talking to text and I should have went back and made changes sorry

 

I remember when all you had to do to correct a "pinging" condition caused from timing being too advanced was back off your timing at the distributor. A experienced mechanic/gearhead could set it no prob no timing light needed, just a wrench.
After surfing around here and reading about the computer and sensor controlled engine problems I'm having trouble understanding why most think its an improvement.

 

Bart, I wondered the same myself until I gained an understanding of the benefits. Years ago they had to add dual point distributors to compensate for the higher rpm engines, and all that other jazz that comes with high performance engines. Going to computer controlled ignition took away the mechanical parts of points opening and closing. You can only open and close that gap so fast before it's no longer making and breaking that circuit. Computers think so much faster than mechanical things can happen. No more vacuum advance, because really, there is only 2 places that advance can sit with vacuum control. The computer can advance the timing based on input from a dozen different sources rather than just one. One that can have problems if there happens to be a vacuum leak anywhere else on the entire engine. Might be more than you were looking for, especially if your question was sarcastic. Either way, there you go, hope I didn't tell you a bunch of stuff you already knew.

 

I do get it Jack, and I wasn't trying to be sarcastic, nor am I offended in any way by your answer. I understand this forum is generally more focused on todays high tech engines/trucks. However I do enjoy the conversations, the people and the information.
You are spot on with your reasoning for the changes in engine management.
I guess I'm just stuck in the old fashion days.
I actually almost went with a points set up with the engine swap I'm doing, but even I have succumbed to technology (just a little) and I'm going with HEI.

Capt Dano,
I hope you get to the bottom of your problem. Didn't mean to mess up your thread.

 

Cool, I use that feature often. Just say period or camma or question mark and it’ll add them in for you.

 

Back to the original post, Dano.

Your question is about timing. The Vortec engine is not timed like the pre-Vortec engines. Yes, you have to get it close with the distributor stabbed correctly with the rotor correctly pointed st #1. However, the the fine tuning has to be completed using a scanning code reader.

That’s where the zero comes in. The cam retard angle must be set to zero, +/- 2 degrees, at operating temp, with the idle set st 1000rpms.

Most of the misfiring issues are due to having the cam retard angle off.

 

You can drill a hole in the cap and watch the spark inside an old cap the goal is to get a straight as possible spark to the plug I believe it's number 5 or 6 closest to fire wall on cap. You can see the angle of the spark thru the hole in cap. Then put new cap on when your happy.