Hey,
My 2001 Chevy Blazer LS 4.3L 4x4 randomly stalled while driving, lucky i was only an 1/8 of a mile from my house, and now it wont start. All the lights work on the dash and everywhere else, checked all fuses nothing blown. The engine will crank over, but while cranking it intermitently sounds like a small backfire or push of air comes through the throttle body or intake. I have replaced the Fuel Pump, have 60psi of pressure, replaced ignition switch because i thought resistance built inside it, replaced crank position sensor, and now im thinking the timing chain skipped a tooth, theres 171,000 miles on the engine.. What in God's name can be wrong with this Blazer? I've read hundreds of post's and so far no luck. Can a timing chain just skip like that, without warning? No prior poor throttle responce or problems with truck, also no codes. No codes appear and the check engine light stays on while cranking.. Is the next step lining the marks on the harmonic balancer to the tabs on the engine during the compression stroke and than checking the distributor's corlation to #1 plug terminal? Please help i cant stand not having my vechile!!

 

A compression check should indicate whether the crank is properly timed with the cam.

 

This might sound dumb, but how is a compression test going to indicate if timing is off? I don't get it, eh..

 

If the timing chain slips, the cam will no longer be in time with the crank which would mean that the valves would no longer be opening/closing as they should, thereby affecting the compression...

"Timing" isn't just concerning the spark.

 

Ah of course. So, if the intake valve is opening longer than it should that could cause a backfire through the intake valves thus effecting compression, meaning a loss of compression, lower than specs?..

 

yup..

 

Thank you so much. I will remove the spark plugs and do a compression test asap. I will post the results as well. Much appriciated

 

Compression tested fine. Held well within 100psi for at least 4 complete strokes.. eh, this is killing me! Timing must be okay - what would cause a small backfire or push of air if the timing is fine? Going to replace plug wires next... New plugs were put in bout 6 months ago

 

100psi sounds low to me, but it has been awhile since I tested compression on the 4.3L Vortec engine... If memory serves me properly, the compression should be 140-180psi (depending on engine health)...

 

Haynes manual says minimum 100 psi... it was right on 180psi to be excact. tried putting a little gas in the throttle body, only to have the backfire ignite the fumes.. poof! never again