Ignition timing on Silverado

chevrolet
1500

#1

Hello All,
My son and I recently rebuilt the 5.7 vortec in his 1997 chevy silverado. It had rod bearing issues and we replaced the bottom end. It is now back in the truck and we reconnected everything and started it yesterday. It sounds good and runs well except it seems to have a timing or fuel issue, perhaps a vacuum leak. I sprayed carb cleaner around the intake when running and it did not change anything.

There is a fault code available and we will be trying to get an OBD2 reader today.

I have a question about the spark timing. I am old and I’m used to timing lights and such. For this project, we followed a manual for the 5.7 and set the #1 cylinder at TDC on the firing stroke and then set the rotor to the “8” printed on the distributor housing, just like the manual shows (not sure if this is deg of advance or what). I rechecked it once the whole thing was together in the vehicle and found that the balancer and timing tab are nearly impossible to see if the vehicle is running.

With the thing running like it is, I do not know how to check timing while it is running. Is there anything I can do here other than check fault codes?


#2

Did you align the paint mark with the pre-drilled hole?

Tester


#3

I believe we are in good shape that way. We had to play with it a bit to get the housing in the right place WRT the plastic part of the intake, oil pump shaft, and cam gear. In the end it looks correct and complies with this:


#4

Looking on utube, there is apparently a fault code P1345 that is coupled to error in between the crank sensor and distributor location. We are in the process of buying an OBD2 reader right now (kid on way to store). Will the error code and check engine light go away automatically if we adjust the distributor and fix any discrepancy between the two components?


#5

I just replaced the distributor gear after inspection it was worn over half the gear tooth thickness. Stiff does not run well and gives P1345 and P0300 faults. Reading with new fault code reader we purchased.


#6

You need a scan tool which is capable of displaying cam sync . . . sometimes it’s shown as cam retard

If you have the entire service manual, it will show you how to do it. I believe it’s only possible to adjust cam sync at around 1000rpm. Then you loosen the hold down bolt and rotate the distributor to bring it within the correct range. 0 degrees, plus or minus a few degrees

Do you in fact have P1345, or is that just speculation at this point

BTW . . . if your cam sync is massively off, you may be off by one tooth, and may have to remove and reinsert the distributor. There is only so much adjustment, before having to remove and reindex, so to speak

what shape are the plugs and wires in . . . ?!

If I were you, I’d look at misfire data on that scanner. Even though you have a random misfire code, there’s often a particular cylinder which is a real problem. In other words, you could get a P0300, but the data will reveal your main problem is #3 cylinder, for example

This particular engine has a somewhat finnicky fuel injection system. I wouldn’t worry about it just yet, unless/until you get cam sync in the normal range, you’ve eliminated the secondary ignition components as the cause of the misfire, and you’ve still got a persistent miss

At that point, we’ll further advise you, as needed


#7

I indeed have a P1345 fault now. I went to the store and got a crankshaft position sensor, cap, rotor, and camshaft position sensor. I figured I would just replace the crank sensor first. Now I am curious about relearning, etc.

I found that the distributor might have been off by a tooth and when we put the new gear on, I realigned everything to match the “capture2.jpeg” above. It still runs bad.

How can I replace parts or do adjustments one at a time without the expensive scanner? I only have the Bosch OBD2 reader.


#8

Bring that crank sensor back.

If it were bad, the engine wouldn’t run at all.

Tester


#9

You might try looking at the cleaning the throttle body and cleaning with the appropriate cleaner if needed. Air filter good?


#10

Air cleaner is brandy new and intake and injectors have been cleaned as part of the total engine rebuild.


#11

P1345 has absolutely no connection to a dirty throttle body, imo

And if it somehow does, somebody please explain the science to me


#12

I pulled out the crank sensor and it is not showing any sign of contact with the pulse wheel on the crank. I reused the existing crank sensor. Moving on to the distributor. Will check and replace the cam sensor possibly. Will check for witness marks on the inside of the distributor for alignment. I suppose if it seems okay, I will leave it alone. Maybe replace cap and rotor if it seems like good candidates for replacement.


#13

Taking the cap off I find that the distributor housing is cracked where the distributor cap screws go in. Now replacing the distributor housing…


#14

How is this engine configured, timing wise? It’s electronic ignition, right, no points and condenser. It has a conventional distributor, and a single coil and igniter module that is shared-use between all the spark plugs, right? Does a gear on the camshaft drive the distributor shaft and oil pump? Are the timing sensors inside the distributor, measuring the dizzy rotor position, and the crankshaft and camshaft timing inferred from that,;or are the crank and cam sensors directly measuring the crankshaft and camshaft? I’m presuming the later … if so …

  • Cam and crank position sensors have to be properly gapped for the distance between the sensor & the thing they sense. Double-check that.

  • The sensor can be ok, but the thing they sense can be worn or damaged. Usually it is an array of ridges cast into the flywheel or crankshaft pulley etc that rotate by the sensor as the engine turns. If those ridges are damaged, worn, it can make the sensor output intermittent. The engine may still run, but will run poorly. If you changed that part with the bottom-end change-out, definitely a suspect.

  • W/poor running symptoms and no clue what the problem is, it is usually a good idea to go ahead & replace the normal tune-up stuff with new, like the dizzy cap, ignition rotor, spark plug wires, spark plugs (properly gapped), coil, ignition module, and even the entire distributor.

  • Compression test

Edit: Confirming timing w/timing light. What is the issue with this? Is the problem that the harmonic balancer can’t be seen when everything is installed enough to make the engine run? Is there anything you can temporarily remove and the engine will still run so you can see it long enough just enough to check the timing? Like the alternator? Power steering pump, etc. Radiator? Can you see the harmonic balancer marks from below the car; i.e. jack the car up and check the timing from below ?

Even if you can’t see the harmonic balancer marks, you can still hook up a timing light to the number one spark plug wire, and check to see if you get a steady flash rate, or if the flashes appear to skip once in a while.

If you have a way to get a shop to do an o-scope analysis on the ignition system, that would probably be very informative. Isn’t overly expensive and that would probably be money well spent.


#15

P1345 is not occurring because of a faulty camshaft- or crankshaft position sensor or contact with the pulse whel

You are wasting your time and money replacing those parts

I strongly suspect your problem is because your cam syn/retard is far enough off to throw the code

You want to replace the entire distributor, in that case, and reindex it correctly. Get an ac delco part, complete with cap, rotor and camshaft position sensor. Then also replace the plugs and wires. If you’re lucky, that will take care of P0300

They are non-adjustable on this ignition system


#16

I have decided to not replace the sensors and found a Dorman part to fix the cracked mounting screw boss. I replaced the cap and rotor only since I had new parts and the old ones were 2 years old. I admit, it cranks over now and does not run at all. Took cap off, everything looks fine, the crank sensor looked fine and I double checked my re-installation, looks properly seated in the timing chain cover. Packing it up for tonite.

db4690, I suspect you are on the correct path. Things seem like they should be a simple replace and go, with something to do with the cam sync’ing. If I remove and replace the entire distributor with a new one, is there a relearning sequence that is required? Can I perform that without the Tech2 scanner?

With the OBD2 reader that I have, I found a parameter called IGN ADV, is this the correct one to check cam sensor/crank sensor sync? If not, it seems like there is no hope to tune by feel and that getting it “close” is nearly impossible (why? I dunno. This is not my first rodeo but this one has got me.) Is there a way to do this w/o the Tech2?

Thanks for all the help from everyone so far, this has been a struggle for this old dog in a brave new world.


#17

Following leads from trailvoy


#18

I have encountered my fair share of dirty throttle bodies . . . including plenty that generated all sorts of fault codes, rough idles, misfires and check engine lights

But I’ve never encountered a dirty throttle body which resulted in P1345

I’m taking that link with a grain of salt

BTW . . . on some GM engines, if you clean the throttle body without relearning it with the scan tool, you’re opening up a can of worms. Rough and/or sky high idle, accompanied with a check engine light and a code which basically says you messed up


#19

In the old days we used to look for the 5, 7 cross. Those used to have the wires on the wrong plug so check for that.


#20

I have not set the distributor on a GM engine of the period. My experience is with Dodge magnum engines, rotating the distributor housing will not change the ignition timing.

The ignition timing is comes from the crankshaft position sensor and the PCM. The distributor contains the cam sensor, this is used to time the injectors and to fine tune the ignition timing. If the distributor housing is replaced it (the cam sensor) must be set/synchronized with the crankshaft position sensor.

With the proper scan tool you will be able to enter “utilities” or something similar with a selection to allow to set the cam/crank signal.