Around here, the O'Reilly stores have the Bosch OBD 1300 scan tools as their "loaner" scan tools. It's a higher end scan tool.

I've used it to pull airbag codes and ABS codes from my 1996, and for early OBD diagnostics on a 1994 Chrysler and a 1995 Toyota. It has the ALDL cable for the early GM ALDL connector and will read from the 16 pin ALDL connector with the OBD-II cable. I've also read transmission/drive line codes from some Jeep vehicles that are a challenge for the simpler OBD-II scan tools at other chains.

A guy at one of the stores in a nearby town (father in-law of one of my neighbors) said he used it to check/adjust CMP offset on his Chevy truck. I will know more from first hand experience in a day or two.

I got pulled away from the Oldsmo-Blazer today because the wife drove over the transmission of her Jeep (not quite, but it won't even pull up the driveway in 3rd gear limp home mode). The Olds should be on the road a few hours after I take care of the Jeep (I hope it's just the crappy solenoid pack). Once I'm on the road, I'll run by and verify first hand at O'Reilly. I'm signing off for now because Fedex just arrived with the Jeep parts.

 

Thanks everyone for the help!!
Later

 

If it is running again with no P1345, then the only thing you can do is to check cam sensor retard or CMP retard or CMP offset (all the same).


Like I said before, timing is determined by the PCM based on the crank sensor. But still the rotor in the distributor has to be pointing to the correct terminal or a misfire will occur. Rotor position becomes particularly critical in a system with computerized timing and a no-advance distributor as the spark has to jump different distances from the rotor to the terminal, depending upon the timing at the moment.


Inside the distributor is the camshaft position sensor, which is used to tell the PCM which cylinder is firing. It is used for misfire detection and to time fuel injector pulses. It also turns out that the cam position sensor can be used to precisely align the rotor position with the distributor cap terminals, so changes the PCM makes in timing does not cause the spark to go where is isn't supposed to and cause a misfire. This is done by monitoring cam sensor retard with a scanner, and making sure the reading is 0° ± 2°. Only then can you be assured that things are optimal. You can turn the distributor to change the cam sensor retard value, but this is NOT adjusting the timing - just changing the distance the spark has to jump to go from the rotor to the distributor terminal. Go too far turning the distributor and spark can jump to places it shouldn't (like to the wrong terminal).


Note that the factory distributor hold-down clamp prevents the distributor from turning. If you get the distributor in on the right tooth, no P1345 will be present and the factory clamp should get you close to a cam sensor retard of 0°. If not, you can make the bolt hole in the clamp oblong so you have a little bit of adjustment.


Not many cheap scanners will do Cam Sensor retard. I have been recommending Car Gauge Pro as the only one that I know (see my other posts). If the Bosch OBD1300 scanner from O'Reileys also does it, then there is another cheap option. Still waiting for RacerX to confirm his own experience - but sounds promising.

 

Okay, I need just a little more info...
So my truck seems to be running ok, other than a little rumble or something at idle. So I took your info about the Bosch reader and my settings showed 19 to 20 degrees off. but the truck seems to run....not bad. I didn't notice if it was negative or positive but according to my original marks,..I need to rotate the distributor body about 1/8" of an inch to reach my original marks...counter-clockwise. The truck seems not too bad as is....but this is way off.
Help me..thanks
Greg

 

Were you reading "CMP Offset" or "CMP Retard"? Or were you reading the timing with the Bosch tool? 19 to 20 degrees sounds about right for timing advance, but that's completely irrelevant to the adjustment.

YOU CAN'T ADJUST TIMING!!! Don't look at timing or ignition advance or anything like that. The computer picks what it wants, and you can't change that. Turning the distributor doesn't change timing on this engine.

What you can adjust is the position of the dizzy (camshaft) position sensor relative to the crank, which also adjusts the position of the rotor relative to the posts in the cap at TDC. That's what "CMP Retard" or "CMP Offset" is all about. Did the Bosch tool show "CMP Retard" or "CMP Offset" as one of the PIDs you can monitor in the live stream? I've been told it offers that, but I haven't verified that yet with my own eyes.

If you just want to align your marks, while you're at the parts store, look for the Mr. Gasket 1009 distributor clamp. It will be with the engine "dress up" parts. Take the stock clamp off, put the chrome Mr. Gasket 1009 clamp on and align your marks.

 

On the Bosch scanner, under advance ignition, I showed the Guy that we neede to see either cmp offset or retard. I will have to look back but I thought someone said it was the same thing. I very well could be mistaken and sorry if I stated something wrong.
I'm not driving it for a couple days till I can try to align my original marks a little better.

 

CMP Offset is the same as CMP Retard. Did this read 20° with the unaltered factory hold down? If so, use a different tooth on the distributor. 360°/13 teeth = 27.7°. The right tooth should get you at 27.7°-20°=7.7°. I would imagine that a P1345 would have been triggered if it was really 20°.


In the meantime, roll your engine over to exactly TDC#1 by lining the marks on the balancer with the mark on the timing cover and look where the rotor points. It should be pretty close to the "6" stamped in the top of the distributor housing.

 

Yes it was with the unaltered clamp. It also did not have a p1345 or any other code.
It did however have a slight rumble like it was off somewhat...

Will I be able to roll the engine over with a wrench?

 

P1345 will not set unless CMP retard is ~26 degrees off, (one distributor tooth). Rule of thumb here is if P1345 is not set, the distributor is timed correctly with the camshaft, and CMP retard must be "fine tuned" to spec by rotating the distributor. If you can't get it in spec using the original distributor hold down bracket, it must be modified, or install an old style SBC hold down bracket.
EDIT: yes you can use a socket & ratchet to rotate the crankshaft clockwise only.

 

Alrighty then. Once again, thanks for the info!