Hello,

I am having issues with my 98 Blazer 4.3L engine, it starts and idles fine with 89k Miles. in park/Neutral when i Rev it the engine bogs down and starts to choke up. it will eventually stall out after 20 seconds or so of RPMs above idle.
testing fuel pressure at the schrader valve, it is sitting at 56 PSI - and 60 when RPMs go up. just changed the spark plugs on it yesterday, and it wasn't the issue. no Engine codes to go off of, what should i be looking at next?


Even with the stable fuel pressure should i be looking at the spider injector as the culprit? i dont want to take it out of park and attempt to drive it, as im assuming it will just bog down and die immediately. thanks for any help i haven't been able to find anyone with problems like this anywhere.

 

What kind of diagnostics have you done?

 

not too much all together,
*i changed the spark plugs, and the spark wires to the distributor cap,
*i did a fuel pressure check at the schrader valve and it stayed at 55 PSI for 10 minutes,
*i pulled the C02 sensor before the catalytic converter to see if it would improve RPMs above idle
*i looked for any loose wiring or obvious hose damage.
*i took off the MAF sensor and TB sensor to see if that changed RPM above Idle

and so far none of that has done anything. i let the truck sit for a few days, and went out today and it started up just fine. there wasn't any major bucking or RPM stutter above idle at first but the longer i sat there and revved it every now and then the worse it started to get. so i shut it back off.

 

Ok, good at least you’re trying

Static pressure seems ok, but did you check with engine running? My point is it could be starving of fuel as soon as you open the throttle. When was the last time you changed the fuel filter?

 

only bought the car a few months ago, so im not sure on the fuel filter. with the engine running Pressure stayed at 55, and under revving ill have to check again because the engine was bucking and wanting to choke out, but through the shaking it looked like it was roughly at 60 PSI

 

Fuel, spark and air is all you need. What could go wrong? LOL.

At some point you should do the fuel pressure test in the sticky but since you have adequate pressure at the schrader during a snap throttle test this may not be your issue. Your going to need to asses the quality of the spark at the plug end of the wires. Your looking for 1” of strong blue spark with good timing across an air gap. The best way of evaluating the ignition quality is with an O scope but you can learn a lot once you get some experience watching spark gap. Compare the spark between idle and during your snap throttle experiment. You might see the spark get wonky indicating an ignition is struggling under a load. What brand of ignition components did you use?

George

 

George,

thank you for the advice, ill test spark at the plug, and see if i get the gap i need. plugs and wires are what i have replaced and they have been AC Delco parts