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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15181
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I got a 2001 chevy blazer it has misfires on cylinder 3,5,6

Customer Question

I got a 2001 chevy blazer it has misfires on cylinder 3,5,6 and the barleys runs. I checked the distributor timing and it s spot on, Replaced cap and rotor, spark plugs and distributor itself was replaced a year ago. I got 60 psi at the fuel line wondering if there something common with these vehicles that I might be over looking.
Submitted: 3 months ago.
Category: Chevy
Expert:  david craig replied 3 months ago.

Hi Im David, the first thing i would do is a compression test. Thats mandatory in my shop as a first step before replacing anything.

Customer: replied 3 months ago.
did the compression test all cylinders are around 156 psi
Expert:  david craig replied 3 months ago.

ok, not bad. have you the wires yet? you may want to. or just swap wires to other non misfiring cylinders, see if it follows

Customer: replied 3 months ago.
I did wires and spark plugs in the misfiring cylinders no change I have to hold the gas just to keep the truck running.
Expert:  david craig replied 3 months ago.

other than the misfires are there any other codes?

Customer: replied 3 months ago.
No codes at the moment is there anything common with these that usually cause this that I can check?
Expert:  david craig replied 3 months ago.

excess fuel entering the combustion chamber can be causing this. i think that the fuel pressure is a bit high, but i would have to check that spec. another thing would be leaky/clogged injectors. do you have a noid light?

Customer: replied 3 months ago.
the spec fuel pressure is 60-66 psi, I don't have a noid light this s10 has that spider fuel system in it
Expert:  david craig replied 3 months ago.

that damn spider....... what a design

Expert:  david craig replied 3 months ago.

ok. Im not sure that you did all of this yet, clean out the throttlebody, iac and egr. and the passages for them. also a backpressure test on the cats wouldnt be a bad idea.

Expert:  david craig replied 3 months ago.

also clean the maf while you are at it.

Expert:  david craig replied 3 months ago.

any update?

Customer: replied 3 months ago.
I checked the spider fuel system no clogged injector or leaking injectors there all spraying fuel. I cleaned out the throttle body out and I did a backpressure test on the cat which it was good. But I finally got a code which is a p1345 code I rechecked the distributor timing and it spot on I even pulled the distributor bolt and adjusted the distributor back and fourth and didn't make a differance
Expert:  david craig replied 3 months ago.

ok. good we have something to go by now...let me do some digging........

Customer: replied 3 months ago.
ok il wait for your response
Expert:  david craig replied 3 months ago.

it has to be a tooth off. or its 180 off. even though you believe the timing is correct, its possible to set it 180 out. pull #1 plug come up to tdc on compression stroke., pull distributor rotate oil pump shaft and reinstall distributor as per normal timing procedures. ill be back in a bit

Customer: replied 3 months ago.
I did that yesterday I pulled the #1 spark plug and hooked up my compression gauge and turn the motor over when the number 1 cylinder was on compression stroke. Installed the distributor as described in the timing procedures
Expert:  david craig replied 3 months ago.

ok my friend. let me figure out our next step then

Expert:  david craig replied 3 months ago.

is that a 4.2?

Expert:  david craig replied 3 months ago.

im meant 4.3, and i know it is, dont know why i asked

Expert:  david craig replied 3 months ago.

ok, I believe now that since the timing is checked and double checked, distributor replaced, plugs replaced, AND you are getting random misfires and the sensor correlation code. the culprit will be the crankshaft position sensor or the wiring to it. have you put a timing light to it?

Customer: replied 3 months ago.
its a 4.3 and I did put a crank sensor in it yesterday I haven't put a timing light on it has there been any timing chain issu or cam shaft issues?
Expert:  david craig replied 3 months ago.

are you able to clear the code? and then start it again see if that particular code comes back?

Expert:  david craig replied 3 months ago.

if that that code comes up, it has got be be off a tooth. pull the distributor up and rotate it one direction or the other. when the distributor was replaced it came with a new cam sensor?

Expert:  david craig replied 3 months ago.

have you checked the wiring from the crankshaft position sensor up? also what about the reluctor whhel that the cranshaft sensor picks up its signal? clean? not bent? not damaged?

Customer: replied 3 months ago.
No I didn't check the wire to the crank shaft, its a new camshaft sensor. I reset the timing again its still runs bad wont idle but it not showing any misfires threw that data on my scan tool anymore. Saying its not misfiring but runs terrible. The code is still showing
Expert:  david craig replied 3 months ago.

wow. have you cleaned out the egr valve?

Customer: replied 3 months ago.
yea I cleaned the egr valve and no difference and the misfire are showing again with the code p1345 on my scan tool I can look at the spark advance and the retard of engine percent what percent should they be at ?
Expert:  david craig replied 3 months ago.

gimme a sec...thanks

Expert:  david craig replied 3 months ago.

See if this procedure is exactly what you did.Timing is not adjustable per-say by turning the distributor, as that function is handled by info supplied to the ECM by the crankshaft sensor and the camshaft sensor. To re-set the distributor, bring #1 cylinder up on compression, align the timing marks on the damper pulley and put the distributor in with the rotor pointing towards the number “6” inside the cap.
There are actually two timing marks on the damper pulley . When you are timing the engine, make sure to use the latter timing mark. If you use the other, engine won't start. First mark is before TDC and the second one is TDC. When you rotate engine, don't use the first mark but the second. At TDC the other mark is pointing at 3 o'clock, not 12 o'clock. You can try both of those it doesn't harm the engine.

When you get it the engine TDC compression stroke point the dist rotor as shown in this picture.
http://files.automotiveforums.com/gallery/showphoto.php?photo=51302
If you try to point it to #1 plug wire where it comes out of the cap it does not work. Crazy caps crossover every which way before the fire goes out of the top.

After you get it running you will need to set the camshaft retard setting with a scanner. You will need a engine data scanner capable of reading the camshaft offset degrees.

It will read them in - or + degrees. You need to get it at least 2 degrees -or + or a close to 0 - or +degrees as you can. If it is over 3-5 degrees off the PCM/VCM may set a code on it. What it does is center the dist rotor dead on with the spark wire terminal. You will have to turn the dist to adjust it while watching the setting on the scanner. It has nothing to do with dist timing which is controlled by crank sensor. i dont know if your scan toll reads offset degrees or percentage.

Expert:  david craig replied 3 months ago.

if there was any discrepancy from the way you did it, let me know. if not we will push on

Customer: replied 3 months ago.
Yea that the way I did it and my scan tool says say it at 0-2 degrees depending on rpms
Expert:  david craig replied 3 months ago.

ok. im going to opt out and let another tech jump in here. im out of ideas. good luck to you.

Expert:  mike switzer replied 3 months ago.

i my name is ***** ***** will see what i can do to help in the endeavor of yours. can you provide me with a picture of you distributor cap with the wires going to the plugs mainly just the drivers side since this is the side you are having issues with?

Expert:  mike switzer replied 3 months ago.

also when you did the compression test did you have all the plugs out on the bank or just the cylinder you were test?

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