QuestionThis problem has stump me.I have a fair bit knowledge but this one won.To start it idles great but starts to break down on acceleration.At quarter throttle the engine starts to back-fire through the intake.The blazer will not run over 30mph.Plus when it does shift to 2 gear it will not accelerate. THIS IS A LIST TEST & CHECK I HAVE DONE....
TROUBLE CODES* NONE stored or while running.
TIMING* set @0 results same as started.I did notice that ECM would retard the engine to up to 30degrees before the loss of power then fall back close to 0degree's. WITH THE TIMING CONNECTOR PLUGED BACK TO GATHER.
FUEL PRESSURE* 57psi@ high idle
VACUM* replaced all hoses vacum running -12 steady
INTAKE LEAK* none found upper or lower
WIRING* form ECM to engine ALL WIRES OMH GOOD
EST and ESC* every thing checked out fine
Just for fun cleaned and service fuel injection system.
CATALYTIC CONVERTER* fairly clean also removed o2 sensor
an run the engine. same as start
PARTS REPACED
TPS SENSOR,MAP SENSOR,PCV VAVLE,COIL,WIRES,CAP,BUTTON,PLUGS,ECM,PROM,KNOCK SENSOR AND HEI MODULE.
THANKS,FOR ANY HELP
LAWRENCE
AnswerHi lawrence.... did you do a fuel drop down test...pressure line with gauge attached...leave for a bit...does fuel pressure stay close to where it was or drop off fast... if it drops off test the fuel pressure regulator by pinching off the vacum line...while running...pressure should increase...if it doesn't then replace pressure regulator. also have you checked firing order... if you have one out of place can also cause that problem....there are 2 differant firing orders for that engine make sure you have the right one...because you have no codes i would lean toward the firing order being incorrect...just had one in my shop for much the same problem and thats what it was...also even though cap and rotor are new check them for arcing inside the cap..i have had bad ones of them new as well...hope this helps
