2005 blazer 4.3L

I'm old school and just wanted to know if its possible If I can check to see if my timing is correct using a timing light or if my only option is to line up the marks and pull the cap and number one plug out ? Is there a wire I need to disconnect ? In the old days it was just a vacuum advance line on the distributor.

 

Timing is set by the crank position sensor and programming in the computer. When the spark occurs and sent out of the coil - this is not adjustable. Only function of the distributor on these systems is to distribute the spark. The system will flash a timing light but there is no purpose for that.

However, distributor rotor position (not the same as ignition timing) is important when that spark comes through, or you can get a misfire by the spark jumping to the wrong place inside the distributor. This position is checked by a setting called cam sensor retard, using a capable scanner. The cam sensor retard should be zero +/- 2 degrees. Causes for this to be out of spec enough to be a problem are worn distributor gear, worn timing chain, or possibly the gear on the shaft 180 degrees out. Small adjustments can be made by elongating the distributor hold-down bolt hole or replacing it with a hold-down that does not lock the distributor in place.

Second generation Blazer distributors are installed by first putting engine on TDC#1 by normal methods you are familiar with. Then you drop the distributor in with the rotor pointing to (as near to as you can get) the "6" that appears on the cap mating surface. The hold down then locks it in place from turning. If you get it on the wrong tooth, a code is set (SES light is illuminated) and you try again.

What problem are you trying to fix?

 

Misfiring is my problem. I purchased a new distributor from china. I use the old gear from the original distributor. My friend took the old gear off the original shaft and installed it on the new one. Maybe he installed it 180 degrees out or I'm just off a tooth when I installed it. I'm gonna check to see if I'm out a tooth. But how would I know if im out 180 degrees on the gear ? Would the truck even run with it the gear out by 180 degrees? I see you said that the ses light would come on if I was on the wrong tooth. I dont have the ses light on so I guess I'm ok there.

Replaced parts...


Plugs
Cap
Rotor
Wires
Distributor
Ignition module
Ignition coil
IAC
MAF
MAP
EGR
ECM
Spider
Fuel Filter
Fuel pump
Crack sensor
All oxygen sensors
throttle position sensor

this thing has been a parts pig I also just replaced the wires cap and rotor yesterday again. I sprayed the acdelco wires I just put on last year with water and seen leakage so I replaced them again. I also noticed that the coil was overheating. I could see white mark's on the side of the coil and checked the wiring and noticed that when the car starter was installed ten years ago the guy did a bad splice job on the sigal wire that goes to the coil so I soldier that and corrected that. I also noticed that when I took off the distributor cap that there was burn marks. I'll post the pictures below

 

The Chinese distributors have been OK for a number of people, including myself. I have 60K miles on mine. Is your vehicle setting a P030x misfire code and flashing the SES light?

#1: If you notice how the material on the terminals are on one side of each distributor terminal (either ahead of or past) it leads me to believe there may be an issue with the rotor position when the spark comes through - either too late or too early. Looks to me that you rotor position is too far retarded when the spark comes through and that causes the buildup on the leading edge of the terminal. When computer advances the timing almost 25 distributor degrees (like during cruise conditions), if the cam sensor retard is significantly off it could potentially start misfiring to the cylinder ahead in the firing order, which are spaced at 60 distributor degree intervals in the cap (+/- 30 degrees for each terminal).

#2: 180 degrees out on the distributor gear will change the rotor position when pointed at #6 from in-between a tooth to on a tooth.


There are 13 teeth on the distributor gear, so that is 27.69 degrees/tooth. 1/2 of this is 13.85 degrees. This means that the rotor position will be 13.85 degrees different, depending on which way the gear is installed. Nice video, but for a distributor with internal spark trigger (points or reluctor on shaft) it makes zero difference. However it does matter for ignition with a locked down distributor, with spark triggered off of a crank sensor (like we have on the Blazer) - so it is very useful.

https://blazerforum.com/forum/diagno...plained-35138/

P1345 is the code that will set if the distributor is off a full tooth. Note that 13.85 degrees (amount for distributor gear installed 180 off) is not enough to set the code.

So first you need to make sure there is virtually zero slop in your distributor gear to camshaft mesh by wiggling the rotor. If rotor raises excessively when turned, then shim the distributor gear properly. If OK, determine your cam sensor retard using a capable scanner and correct if it is not 0 +/- 2 degrees. Note you have to raise the RPMS to above 2000 before reducing and checking cam sensor retard at 1000 rpm. If it is around plus or minus 13 degrees, just flip the distributor gear on the shaft and reinstall the roll pin (or just turn the distributor if you have a non-locking hold down). For smaller amounts the play would be due to timing chain stretch and you will need to modify the distributor hold down or get a non-locking hold down to correct it. Be sure to raise above 2000 each time that you check cam sensor retard.

Not many inexpensive scanners will read cam sensor retard on Blazers. I can point you to an Android software and Bluetooth OBD2 device that can for about $30. Car Diagnostic Pro on Google Play and BAFX Bluetooth adapter on Amazon. If you want additional bi-directional functionality for bleeding brakes, injector balance testing, crank sensor relearn (which you should do after changing crank sensor), etc - best deal I have found is a handheld, the Vident ILink-400 for GM - about $150.

If you find the cam sensor retard to be way off, you should probably replace the cap and rotor again after correcting it.

I think I have all of this correct. I'm sure someone will point it out if I have made a mistake.

Please ask if you have any further questions, but I warn you that you will need the scanner from here on out.

Good luck and best wishes for a successful repair!

 

I have never had an CEL light come on during the misfiring. Changing the distributor and all the other parts never made a difference at all. The truck still runs the same as it always has. So honestly I dont think it has anything to do with the distributor. I dont own a scantool myself to see what's going on but I think I'll have to take it to a shop that I know of. Apparently all the mechanics take there stuff to this guy to trouble shoot there stuff. I think I'll check the timing and see where the rotor sits and if everthing looks good. I'll take it to the shop. If not correct the problem if it's the distributor gear. After watching the video you sent me about the hear being install incorrectly makes me think the truck wouldn't even run if I was 180 degrees backwards ?I'm at my witts end with this truck. Thanks for all your help ...your amazing 😉😊

 

You are welcome, but I really think you are arriving at invalid conclusions (in red). Cam sensor retard is the first thing to verify on a Blazer with misfires. Fuel pressure is the second. Doesn't matter what has been replaced or done in the past. Unfortunately I will not be able to help you further here unless you are willing to do exactly what I say. Taking it to the mechanic that you mention may be a good option. Do me a favor, though. When he gets it fixed, please let me know what the problem was. It's the way I learn if I am giving good advice or not. Thanks

 

Follow Les' advice and he can get you fixed up but like he says your going to need a scan tool. I only want to say (for you and anyone else reading this) that you missed the point of the distr gear video. When you rotate the gear 180 on the distr shaft it does not make the distr 180 out because the teeth are evenly spaced all the way around the distr shaft you still line everything up to drop the distr in. BUT, it matters which way the gear goes on because there is a slight difference in the indexing between all the gear teeth and the rotor and even some new distr have had the gear backwards and then the computer cant set your timing. As Les says, cam retard answers all your questions.

George

 

Like I said I'm old school mechanic....I'm apologize...I have been getting fustraighted with this truck. Give me Chevy 350 or 400 4 bolt main motor with 202 heads in pieces and I'll put it together and make it run like a champ.Your absolutely right I need to take a look at the timing first. I just moved into a condo for the first time in 32 years so things are a little more difficult to do. I'll let you know what I find. If I took it to someone ....it would be a first in 34 years .....I fix all my suff myself !! I'll get her done 😉 your last reply is gonna help me bigtime. Thank you so much !! Thank you everyone for your help.

 

I started in the 60's so it has been quite a journey. I started with a timing light, dwell meter and a points file. I just noticed that I had a typo in my last post and I corrected it to say "When you rotate the gear 180 on the distr shaft it does NOT make the distr 180 out ..." Sorry about that.

Les did a nice write up on cost effective scanning capability here, good luck:

https://blazerforum.com/forum/2nd-ge...24/#post734213


George

 

so I'm assuming that any obd2 that uses torque lite or torque pro is what I'm after to read the cam retard and will work to see if out 180 on the distributor gear ? I might be able to pick one up locally here if that's what I need to verify it ?