1995 k3500 7.4 timing issues

[k1500 97]

So me n my dad are trying to get the base timing set on his 7.4, when you disconnect the plug on the distributor and set the timing it holds but when you plug it back in it goes erratic from 15btc to 15degrees advanced some veriation. I believe it should hold its timing when you connect that plug back in. Any help is appreciated ask as many questions I'll try to give my best answer thank y'all.

 

[termite]

So me n my dad are trying to get the base timing set on his 7.4, when you disconnect the plug on the distributor and set the timing it holds but when you plug it back in it goes erratic from 15btc to 15degrees advanced some veriation. I believe it should hold its timing when you connect that plug back in. Any help is appreciated ask as many questions I'll try to give my best answer thank y'all.

The timing is going to vary once the single wire is plugged back in as it is controlled by the ecm. Base timing is set with the wire unplugged (below the glovebox in my 95 w/ 7.4L) and engine at operating temp. I believe the spec is 4 degrees advanced at idle.

Wire plugged in at warm idle, I think mine is around 20 btdc.

 

[packer0440]

On a 95 the plug you need to disconnect is under the glove box, not in the engine compartment.

I did have this happen before, where unplugging the wire would make the timing steady but plugging it in would make it erratic and backfire. Tried a known good ICM on it and no change, a new distributor fixed the issue

 

[k1500 97]

On a 95 the plug you need to disconnect is under the glove box, not in the engine compartment.

I did have this happen before, where unplugging the wire would make the timing steady but plugging it in would make it erratic and backfire. Tried a known good ICM on it and no change, a new distributor fixed the issue

Ok, it has a new distributor I told him it's probably defective, and yk dads can't argue. But yeah we unplugged the one under the dash to it wouldn't work it would hold time unplugged n stay that way, idk if you can constantly run it that way tho

 

[k1500 97]

It does have a newly flashed ECM maybe it wasn't flashed right. Idk

 

[termite]

But yeah we unplugged the one under the dash to it wouldn't work it would hold time unplugged n stay that way, idk if you can constantly run it that way tho

Elaborate a bit on the "it wouldn't work" while the est wire was unplugged. Wouldn't run? Timing was jumping around at a steady RPM?

Normal operation is for timing to advance and retard with the est wire plugged in based on multiple parameters in the ECM and sensor inputs.

 

[k1500 97]

Elaborate a bit on the "it wouldn't work" while the est wire was unplugged. Wouldn't run? Timing was jumping around at a steady RPM?

Normal operation is for timing to advance and retard with the est wire plugged in based on multiple parameters in the ECM and sensor inputs.

Meaning as it wouldnt do what it should.... Like to set base timing then when you plug it back in it doesn't hold its timing.

correct the timing was jumping around at a steady idle

 

[termite]

Meaning as it wouldnt do what it should.... Like to set base timing then when you plug it back in it doesn't hold its timing.

correct the timing was jumping around at a steady idle

It is difficult to grasp what you are seeing via text over a forum. Can you put some more detail into describing exactly what your observations are (i.e. set base timing to X degrees with est unplugged and engine at operating temp. Plug est wire in, timing goes to X degrees at warm idle and stays steady or fluctuates between X and X with no throttle input). The more detail you provide us, the better we may be able to troubleshoot remotely.

 

[99xcss4]

I think what @k1500 97 is saying that with it unpluged the base timing will set but when pluged back in it dose not have a stable idle also I think he was asking what would happen if the est stays unpluged and you drive it like that

 

[k1500 97]

I think what @k1500 97 is saying that with it unpluged the base timing will set but when pluged back in it dose not have a stable idle also I think he was asking what would happen if the est stays unpluged and you drive it like that

Correct, sorry if I didn't elaborate it in a way to understand..... I don't have the average mechanic tools or scanners to do this **** with. Nor can I afford them. All I'm trying to say is when the base timing is unhooked it holds its timing. But as soon as you plug it back in it goes eratic, it varies from -35btdc to like 15advanced from what I see on the crank pulley that's the only way I can see the timing is off the crank with a timing light