It's definitely not timing. I've got it dead on TDC at the compression stroke. I went ahead and pulled the 703 injectors off and have them sitting in a fuel injector cleaner bath.

I didn't get to around to pulling the O2 sensor today, but I did clean my intake prior to all of this and I wonder if the cleaner screwed up the sensor.

 

So I got a JY TPS and connected it without mounting it to the TB. Backfires stopped. Still a little sputter but you wouldn't notice if you werent looking for it.

If I pushed down the throttle while pushing down the lever on the TPS it would kinda die. I'm going to mount it when the engine cools and see if anything changes.

Maybe the TPS and ECM are having a hard time getting the fuel//air ratio with the 703 Neon injectors?

Also, the CTS took a beating it looks like and is not connected. I'm going to try to hard wire it. Thinking that if it's connected correctly it won't run rich/lean, whatevers causing the backfiring as well.

Might solve my low idle too?

 

Hard wired the CTS (wires are the same color, 50/50 chance) no change. Replaced the TPS and tuned it, no change. If I take it off it doesnt back fire but does sputter a little.

I've got the old injectors in the their bath. Guess I'll try putting those back on unless someone else has another idea.

I can tell all the cylinders are firing because I took the injector plugs off one by one and the engine lost power each time.

All the bolts are tight on the intake.

Anyone ideas everybody?

 

well, putting the old injectors on didn't help. Kinda made it worse actually. Idles lower and less power.

So weird that when the TPS is on it back fires. I replaced it and tuned it and it still back fires. When it's off it doesn't as much.

 

weak valve spring? Not closing fast enough and letting unburnt fuel into the intake and backfires? flat cam lobe? These are just some more things to check just throwing it out there.

 

Well, I've done every outside component of the engine. Another guy at the JY mentioned the timing chain may have skipped, but I thought that would cause it to run like crap always if at all.

How hard is to check and/or replace the valve springs? Can I just take the valve cover off and see if they're opening and closing? Can I see the cam lobes with the valve cover off?

 

You said ,"ideas, ANYBODY.."...so here goes: My '99 is doing almost exactly what yours is doing, but mine waits until it reaches Operating Temp. before hesitating/stuttering.
Catalytic Converter R&R time!