95 Blazer Ignition Module Failures
#11
04-18-2013, 09:19 PM
This is very good info thank you captain. I am have a problem with hard starts and stalling yet the fuel system checks out good. Just put a used ecm on it for another reason and these problems started.
#12
04-20-2013, 10:02 AM
Originally Posted by Captain Hook
If/when the crankshaft position sensor and/or timing cover are moved, removed, replaced, or disturbed in any way, the crankshaft position sensor relearn must be performed. Without performing it, the PCM uses the data from the last relearn, which is now incorrect. Calculations and adjustments that the PCM commands for ignition timing, injector timing, injector pulse width, EVAP, EGR, etc etc are all based on correct crankshaft sensor data. It requires a "high end" scan tool to initiate the relearn, and takes maybe 15 minutes to do it. The crank sensor has nothing to do with the ignition module failing.
If the distributor has been removed, camshaft retard must be checked and adjusted using a "high end" scan tool, (another 15 or 20 minute job). If cam retard is off significantly, it can cause the ignition coil and/or ignition module to fail prematurely, without ever setting a DTC or turning the check engine light on. There needs to be a thin coating of heat sink paste applied to the back side of the ignition module when it is replaced, (available at Radio Shack).
The PCM's in these things are darn near bulletproof and rarely fail. There are more PCM's replaced due to a misdiagnosis, than actually fail and need replacement.
I've removed my CKP more than once and never had to do CASE relearn on it
I've only ever seen adjustable distributors on V8 trucks. All of the V6 trucks I've come across use the distributor hold down that fits snugly on two flats on the distributor shaft so it can't turn.
To "adjust" the timing on the Vortec V6, all you can do is remove and restab the distributor on the next tooth. You're not actually adjusting timing, but if it's wayyyy off, you'll be able to tell on a scan tool and know that it's a tooth off or something.
#13
04-20-2013, 10:26 AM
Originally Posted by midnightbluS10
I've removed my CKP more than once and never had to do CASE relearn on it
Originally Posted by midnightbluS10
I've only ever seen adjustable distributors on V8 trucks. All of the V6 trucks I've come across use the distributor hold down that fits snugly on two flats on the distributor shaft so it can't turn.
Originally Posted by midnightbluS10
To "adjust" the timing on the Vortec V6, all you can do is remove and restab the distributor on the next tooth. You're not actually adjusting timing, but if it's wayyyy off, you'll be able to tell on a scan tool and know that it's a tooth off or something.
#14
04-20-2013, 10:51 AM
Sorry. I used the wrong word. Had a brain fart. You're correcting cam/crank correlation, in degrees. Still, there is no adjustment that I've ever seen on a Vortec V6. I've even heard of and read about others having to enlarge the hold-down bolt hole to only gain one or two degrees of adjustment. I've never seen anything that even says that the V6 hold down has 11* of adjustment built into it just by moving the bolt hole around the bolt and tightening it down.
That'd have to be a really hogged out bolt hole if what people are doing theirselves is only gaining them 1-2*, and it supposedly gives you 11* of adjustability from the get-go, ya know?
Everyone I've ever talked to says this engine has a distributor that in non-adustable. No one has EVER mentioned 11* of adjustment. Not even our factory service information(GM) at work says there is 11* of adjustment. This is actually the first I have ever heard of this.
That'd have to be a really hogged out bolt hole if what people are doing theirselves is only gaining them 1-2*, and it supposedly gives you 11* of adjustability from the get-go, ya know?
Everyone I've ever talked to says this engine has a distributor that in non-adustable. No one has EVER mentioned 11* of adjustment. Not even our factory service information(GM) at work says there is 11* of adjustment. This is actually the first I have ever heard of this.
Last edited by midnightbluS10; 04-20-2013 at 10:55 AM.
#15
04-20-2013, 11:28 AM
Elongating the hold down bolt hole will gain a couple of degrees, but if you're going to the trouble of that, for $4 you might as well just replace the hold down bracket and make it fully adjustable. On 90% of the ones I've done, ~11 degrees is plenty. Can't remember for sure, but I think the difference in diameters is about .250" which is enough to get the ~11 degrees total adjustment. Remember, it rotates on an arc, not a circle.
EDIT: Your GM manual explains how to adjust camshaft retard, it needs to be done when you install the distributor. Even the aftermarket scan tools, (Snap on etc) explain how to do it. Rotating the distributor is the adjustment for the camshaft position sensor.
EDIT: Your GM manual explains how to adjust camshaft retard, it needs to be done when you install the distributor. Even the aftermarket scan tools, (Snap on etc) explain how to do it. Rotating the distributor is the adjustment for the camshaft position sensor.
Last edited by Captain Hook; 04-20-2013 at 11:33 AM.
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