97 Vortec 350 with a p1345 code

[61_FL_Apache]

This is in my 97 Tahoe and has been coming up lately.

For the most part the truck runs ok, but when hot it can be hard to start and if it starts it idles rough until it clears up.

This truck has 175k miles on it and has been running great since I bought it 5 years ago.

From what I found online, this may be a crank position sensor. I wanted to confirm this before buying one that I cant return if its not.

Thanks for your help.

[bighaas79]

Need to have the cam retard reading checked. Needs to be 0 degrees +/- 2 degrees. If its out of that range it will set that code.

[61_FL_Apache]

How is that adjusted?

[bighaas79]

with a scan tool and turning the distributer. After u turn the distributer u need to crack the throttle above 1000 rpms to update the reading on the scanner.

[tasian]

i'd check the distributor liked bighass said my brother in law built a vortec in his burb and he had to take it to a shop to have the distributor timed

now if the distributor timing doesn't help he also got that same code i believe when his timing chain wore out which eat the distributor gear and caused slack between the cam and crank speed but the distributor timing is pretty common so i'd start there

[61_FL_Apache]

Thanks for all the info. I'm used to ole school timing adjustments, this seems different.
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[rickpilgrim]

Before we had the Snap On Modus scanner every time our 98 L31 350 ate a distrib gear(about 50K mi each) it was back to the dealer and $65 bucks. You need a bi-directional scannner to do this, our Acutron's could not.

[SWEET7T]

Originally Posted by 61_FL_Apache

Thanks for all the info. I'm used to ole school timing adjustments, this seems different.
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Similar but different is a good way to put it. To adjust the cam retard timing (aka crank/cam correlation), you turn the housing of the distributor just like you were setting the timing on an older vehicle. The Vortecs adjust the timing inside the dizzy so the dizzy needs to be set at 0* TDC (+-2*). Only way to do it is with a scanner that can read the parameter. Cost me $65 at Tunex when I replaced my heads.

[61_FL_Apache]

But if its a timing issue, why does it run great most of the time?I would figure if the timing is off, it would run bad all the time and wouldnt rather hot or cold.

[spudz]

the timming is off.....

[bighaas79]

Originally Posted by 61_FL_Apache

But if its a timing issue, why does it run great most of the time?I would figure if the timing is off, it would run bad all the time and wouldnt rather hot or cold.

Adaptive stragety ability of the pcm can make a out of whack engine run pretty good.

[61_FL_Apache]

Ok!! I get it!! Its timing....

Joking aside, I appriciate all the help with this. Now I need to find some one with a good scanner to help.

[SWEET7T]

Originally Posted by 61_FL_Apache

But if its a timing issue, why does it run great most of the time?I would figure if the timing is off, it would run bad all the time and wouldnt rather hot or cold.

It is a timing issue, but the computer can advance & retard the timing pretty far, and it compensates for the out of spec distributor location but throws the CEL to let you know something is out of whack.

Ever heard of Torque Management? On our era 4.3/5.0/5.7 the engine power is controlled by timing, it retards the timing way out just before a shift to reduce engine output to reduce stress on the drivetrain. On the new electronic-throttled 4.8/5.3/ect throttle position is reduced even though you have your foot to the floor.

[61_FL_Apache]

Sweet7T, I have not heard of that but it does make sense. The closest vehicle I had to this was a 94 Caprice with the LT1/Optispark ignition in it. I never had to mess with that one thankfully.

Again I appriciate the education and help with this. Im going to have to farm this one out cuz I dont have the scanner to do it.

[speedygonzales]

It appears to be heat related. Not timing position related. Since the code means there is a correlation problem between the CKP and the CMP, there is a good chance one of them is breaking down when it is heat soaked.

This would also make more sense if you have NOT messed with the distributor timing.

Both sensors appear to be about the same type. So it's a toss up as to which one it is. If it were me looking at your vehicle I would heat up the CMP first since is easy to get to. Use a blow dryer on a cool morning and heat it up to the point you can just barely touch it. If that doesn't show anything, move to the module in the distributor.

[61_FL_Apache]

New cap and rotor did the trick for this issue. All the contacts were oxidized under the cap.

[bighaas79]

Good to hear. Still wouldn't be bad to check to make sure your timing is in spec tho. They can be out of spec quite a ways and still not set the code off, and having it out of spec can affect your fuel trims, which relates to your mileage.

[61_FL_Apache]

Well..... Just when you thought it was safe to go outside..... It happened again..

The mechanics at my work suggested changing the fuel filter. I did last friday. You would not belive the black gunk and fluid coming out of it. I didnt have a chance to drive it much, but so far it run much better.

[61_FL_Apache]

......and the same code popped again.

[spudz]

Have you had the timing set yet with a scanner? This is your problem.,...

[68C15]

from my experience I find the V8's like -8* on cam offset while the 4.3s like -10 to -12*.

I am leaning more towards the CKP having issues warm. most likely the signal filter portion is failing and sending out at corrupt signal at incorrect time. I would verify it at work with a lab scope but since you don't have one try swapping in one from a buddies/relative's truck.