1995 k3500 7.4 timing issues

[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

Thank you...

 

[k1500 97]

If you set the timing at -4 btc when it's unplugged it stays. But if you plug it in it goes eratic

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.

 

[Schurkey]

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

15 BTC, and 15 degrees advanced is the SAME THING.

it has a new distributor

1. Possible distributor pickup-coil/magnet issue. Less likely since you say the distributor is "new".

2. Possible distributor ignition module. Very likely since you say the distributor is "new". "New" distributors often have the worst, bottom-feeder junk modules when shipped.

3. Possible distributor-to-ECM-to-Distributor wiring harness problem.

idk if you can constantly run it that way tho

Sure, it'll run. Power will be poor, fuel economy will be poor, spark plug and catalytic converter life will be poor. Oil life will be poor. Harmful emissions will increase.

You'd basically ruin the engine over time.

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

4. Possible ECM problem. Somewhat likely since you say it's been "flashed" and perhaps incorrectly. WHY was it "flashed"? Maybe it was already defective?

I don't have the average mechanic tools or scanners to do this **** with. Nor can I afford them.

Tools, including a decent scan tool (NOT a crappy "code reader") better get put on the "priority" list.

Trying to fix computer-controlled vehicles with no way to communicate with the computer is two steps away from hopeless.

 

[k1500 97]

15 BTC, and 15 degrees advanced is the SAME THING.


1. Possible distributor pickup-coil/magnet issue. Less likely since you say the distributor is "new".

2. Possible distributor ignition module. Very likely since you say the distributor is "new". "New" distributors often have the worst, bottom-feeder junk modules when shipped.

3. Possible distributor-to-ECM-to-Distributor wiring harness problem.


Sure, it'll run. Power will be poor, fuel economy will be poor, spark plug and catalytic converter life will be poor. Oil life will be poor. Harmful emissions will increase.

You'd basically ruin the engine over time.


4. Possible ECM problem. Somewhat likely since you say it's been "flashed" and perhaps incorrectly. WHY was it "flashed"? Maybe it was already defective?


Tools, including a decent scan tool (NOT a crappy "code reader") better get put on the "priority" list.

Trying to fix computer-controlled vehicles with no way to communicate with the computer is two steps away from hopeless.

the ECM had to be flashed cuz it was new and needed flashed for the new transmission. Idfk I'm at a loss I'm trying to help him out he ain't trying to fix itso fck it.


Thanks guys much appreciated!!!

 

[99xcss4]

being a 95 it is obd1 if you look on the aldl connector you may need a light and a magnifier glass to find them you want to find leters a and b with the key off jumper them with a wire or metal paper clip turn the on do not start it the check engine light will flash the #12 3 times after that if there are any codes it will flash them here is an example for 12 flash---flash flash if you have no codes it will just flash 12 over and over