Woman needs help with 97 Tahoe, surging, Is the timing bad?

[Tucci]

I have taken too many times by the local chevy dealer. I took my 97 Tahoe in for a coolant leak. They had to remove the distributor and manifold to get to the coolant leak. When I picked it up, my car had a LOUD ticking noise, which they "adjusted" the timing and it went away. Now, the car is surging, jumping, etc down the road intermentintly. I called the dealer and they again said, "it could be the timing is off". It turns out the dealer does NOT know the correct timing for the Tahoe? Imagine that.

Well, I pulled the plugs today (wires and plugs are fairly new) and all the plugs seemed to be brown on one side? Does this mean the car is firing hot? I lowered the timing a bit,not sure how much, don't have a timing light...yet. It seems a bit better, but know the check engine light is on. I do have AutoTap is will check to see what code it is throwing.

1) Does anyone know what is the correct engine timing for the 1997, 5.7L, 4x4, Tahoe?
2) Could the timing being off cause the truck to surge intermentintly?
3) Could it be the fuel pump? I thought once they went bad, they went bad, there was no interment problem?

Can anyone help me please?
Lisa

[2000CAYukon]

You should like at this thread http://www.automotiveforums.com/vbul...d.php?t=350633

It talks about the correct procedure to time your engine. Unfortunately, you will need a scan tool to do it.

For the surging, timing could be a cause. A dirty fuel filter (or even the pump going out) could also be another cause. You need to find out what your fuel pressure is. On your engine the pressure should be around 60 PSI.

//2000CAYukon

[Tucci]

Thanks Yukon! This was a great thread to read.
However, without sounding too much like a woman. Was is the cam retard?

I am stil looking to find out what the correct timing is for the car also, any guesses? I just ran autotap on the car and it came back with an ignition advance timing of 22.5º. And it gave me a Diagnostic code of P1345 which means...camshaft/crankshaft correalation position. Have no idea what that means....that is out of my league.

Any help would be very much appreciated.
Lisa

[glenncof]

OK, Lisa. Now I see your situation.

You had the intake maniford gaskets replaced and Yes they must remove distributor. Based on you OBD comment it sound like they screwed up the distributor re-install. (Rotor position should be marked prior to removing, rotor will turn as it is removed so also mark that as starting point.)

<The coolant leak on intake manifold is a common problem on these engines, 5.7l. Thin walls, using RTV silicon as seal, streching bolts that require a double pass on torque settings. Kind of a joke.>

I think I have the Chevy OBD codes here, if I can find I'll read up on your code.

I believe I have read a DIY person not mark and casued problem but they took to dealer. So I don't know fix.

Yes, P1345 is "CAM Shaft Sensor Misinstalled". The CAM Shaft Sensor is located on the distributor. Crank shaft has sensor also. Chilton's says "correlation" problem between the two.

Check that it's plugged in as my Chiltons manual say engine will run on last calculated fuel/air if signal is lost. Unlikely the cause of your trouble.

Still don't know how to get Distributor correlated to cam/crank shafts...

[glenncof]

Chilton's manual says basically; set crank shaft to TDC, rotor should align with arrow cast in the distributor base. Arrow will have 8 or 6 near it depending on number of cylinders in engine.

Turn crank shaft with socket wrench (a big one . I would expect a timing mark on the crank shaft pulley, at least it was there in old days for timing light. I'd use ignition key with ignition disabled to spin starter.

If not, read service manual. (BTW, my local library has GM shop manuals.) Remove Plug#1 to top out piston. Air must come out as it reaches TDC otherwise add 360 degrees. I dont know how to listen for air when turning the socket. So I would set it and check rotor/arrow alignment assuming it is off by a fewseveral degrees not 180.

Again, rotor will twist somewhat as it engages cam shaft. The rotor and arrow must align when distributor is fully seated and tighten down.

Also, don't forget to correct the position of the CAM sensor if you moved it. As Yukon said must be readout of ODB system. This will clear your P1345 code once corrected.

G

[2000CAYukon]

Originally Posted by Tucci

Thanks Yukon! This was a great thread to read.
However, without sounding too much like a woman. Was is the cam retard?

I am stil looking to find out what the correct timing is for the car also, any guesses? I just ran autotap on the car and it came back with an ignition advance timing of 22.5º. And it gave me a Diagnostic code of P1345 which means...camshaft/crankshaft correalation position. Have no idea what that means....that is out of my league.

Any help would be very much appreciated.
Lisa

The timing is completely controlled by the PCM. You can not set it. You can only set the cam retard which is relationship between the crank sensor on the cam sensor.

If your autotap can not see the value for the cam retard, then you will need another scan tool to set it.

Here is another article that may help: http://www.motor.com/MAGAZINE/Articles/112004_09.html

//2000CAYukon

[Tucci]

Thank you guys! I will do my best today and let you know what happens. I am printing out this thread and taking out into the garage with me.

I did call the dealer who did this to my car and asked what the timing should be set at and his response was 0º BTDC, and stated to do this using a scan tool. I have to tell you that setting surprises me a bit.


Here I go!

Lisa

[glenncof]

As Yukon is saying you don't set the timing*, the computer does. You only adjust the correlation of the CAM sensor (on distributor) and crank sensor. If they don't match within spec you get the P1345 code.

*As you are probably finding you can screw it up by improper re-install, engaging with wrong teeth of distributor and CAM shaft worm gears. I almost did this when re-installing distributor on my 1985 Porsche which has same set-up. I had marked the location on a plastic cap which was keyed to dist. body but lots of play.

In the OLD days before electonic engine control you would set timing with timing light (strobe connected to #1 plug) by rotating distributor. That is after disconnecting vacuum advance and at low RPM to avoid the centrifical advance. New electronic controls eliminates the need for mechanical timing advance as all is calculated and controlled electronically. To measure timing with stobe light (if main pulley is marked with TDC) you would need to know exact conditions where the computer would not provide advance for vacuum & RPM. But this is generally not useful if you can't adjust the advance.

[glenncof]

"CAM retard" is the timing correlation between the CAM sensor on distributor and crank sensor. I believe the spec on this engine is 0 +/-2 degrees. I suspect the crank sensor is fixed in position and the adjustment only done at the CAM sensor.

The P1345 code indicates that the CAM sensor is misaligned to crank sensor, off by more than +/- 15 degrees.