Anyone got a guess as to why I have retarded timing in my 1995 Blazer 4.3 CPI OBDI cert? My live data shows all minus timing even above 1000 rpm I see 0 only below 1000 but all is minus from 1000 on up. I've get a new distributor (put in at TDC #1 and dead on the #6 mark), new timing chain, new injector spider, new lower gaskets. I found and fixed all vacuum leaks...but nothing is solving the problem. Since the computer does the timing..that is the only thing I can think of that is a cause. Been fighting this for a year now!

Jan 1995 build date
flat dist cap
16193495 BABB pcm

 

Over 100 people viewed this post but no idea's? OK........I have one that I didn't know could cause that problem because.....I didn't know it had one! How about the KNOCK MODULE? If it was bad wouldn't it cause retarded timing all the time? I ordered another one because it wasn't too awfully expensive so we will see if that is the cause of this dilemma.

 

A lot of people will read threads based on a title. If they don't have helpful information they don't comment. From what I understand 1995 is a very weird year and there are very few people that know much about them. I wish I could offer advice but alas, I cannot.

 

YES.......very weird indeed! Logical it is not but "IF" it was it would stand to reason that if something like the knock module is not working properly it would retard timing "ALL" the time....would it not? I won't get that knock module until July 2nd so I'll have to report back afterwards. Just maybe......this might solve someone else's woe's with this outta place year!


Thank you for stopping by!

 

How does the truck run?

Any codes?

George

 

Sorry for the late response. George it runs like an engine with late timing! Only one code but that is for something unrelated to timing. I was figuring it would have advanced timing if it was above 1000 rpm but it just keeps retarding. Only time I've seen anything close to 0 degrees is below 1000 rpm at a very labored idle. But live data is not accurate below 1000 anyway. It has run really well for about 15 minutes late last year and then went back to crap. I didn't have the scanner at that time. Doing more research while I wait on the knock module to ship.

 

Could the 95 still have the same timing requirement as the 94's?

You would set timing on the distributor with the brown wire disconnected from the module. (Wire is in passenger foot area behind carpet and has a connector there)

This would have to be disconnected to set proper 0 (zero) timing for the distributor. Else the signal would be retarded and the blazer would run as if it had no power, shift late (at high rpm) and not pull through the rpm's.

 

My PCM is out on top of the radiator reservoir. It doesn't have that brown wire to disconnect. My vehicle is part OBDII but only certified to OBD1 standards. Nothing I've found about timing that engine says to disconnect anything to keep it from retarding timing. NOW some 95 models have the old ECM's that will have that brown wire with the ECM being under the dash inside the vehicle........I wasn't that fortunate!

 

Another thing that comes to mind:

You are reading a "minus" (-) timing. That could actually be an advance.
May have to make sure what reading you should have with your scanner vs. ECU

 

Well I kinda thought that myself but........I hooked my scanner up to my other vehicles and they all show no (-) sign which is advanced I think. Also the live data will show some advance below 1000 rpm but will always be retarded above 1000 rpm where the live data will be accurate.


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