Hey guys I need some help! I bought a 95 s10 with the 4.3 vortec. The guy I bought it from put a running replacement motor in and did the cap/rotor and now I can’t get it to run properly. It only starts with your foot to the floor and start rough but then evens out. As soon as you touch the throttle it dies. I replaced the MAP, crank sensor, new ignition coil. The throttle position metered out good and same with all the other sensors I tried. I have 62psi for the fuel when I turn the key and 56-ish with it running.

I’m running out of ideas. I don’t think it’s timing cause I reset it right at TDC.

 

95 is a tough year for ODB interface but can you read codes or look at live data?

The fact that it will start with the accelerator fully depressed suggests that you may have a fuel delivery problem. Not sure about '95 but you may be going into clear flood mode and shutting off the injector during cranking. That's a single throttle body injector, correct? Do you know the history for the fuel system?


George

 

it has the fuel spider which is new as well.

 

What was the 10 min leak down fuel pressure after key on?

what sensors have you tested?

did this engine get a compression test?

what do the plugs look like?

what does spark look like at one of the plugs when you touch the throttle and it dies?

is the behavior any different before and after closed loop?

can you read codes or live data?



George

 

I’ll be doing the leak test tonight and same with the compression test. I have metered the TPS, knock, ignition control…going to meter the temp sending unit tonight. I have a code reader but can’t do live feeds. I’m going to be changing the fuel filter tonight as well.

 

There are many versions of the '95 engine controls but it looks like they are all speed density fuel calculation (no MAF sensor). If you have a MAF sensor, unplug it with the engine off then restart and see if the results change.

There are some other sensors that can affect this such as the IAT

I asked about closed loop because of the O2 sensors.

There can also be an exhaust restriction, EGR valve, vacuum leak, ... The lack of live data makes some of this stuff harder to track down.

Start with the fuel pressure leak down test because you can start it in clear flood mode.


George