HELP! figure this one out! 4.3 lurching and falling

[wvk1500]

Hi,
New member here but been reading posts for a long while.I have a 94 k1500 with a 4.3 vortec 5speed man. trans. BONE STOCK, The truck starts fine idles fine at cold temp. after about 1-2 min. like when you pull out on the road it will stumble then when you give it alot of gas it runs well at the top end of the gears. on the interstate in 4th at 65 you would think nothing is wrong, but as soon as you go down the ramp it will die. it always starts up quick but no slow cruising power. it will buck and jerk, You have to rev it to start out. here is what i have replaced...............
gas filter,put heat in tank,air filter,plugs,wires,cap,button,ign module,maf,iac,tps,collant temp sensor.switched injectors,cleaned tb,new gasket, paper clipped the ab connection got 32 code, replaced egr valve, replaced egr sensor that connects to egr by hose. it seems to load up at slow speeds, i am stuck! wished i had a intake and carb now, considering a new ecm but $100 at advance auto. im into this now servral bills and ready for the right answer. all comments welcomed!

 

[93 K1500]

You replaced almost everything- Have you checked for vac leaks??? PCV?????

 

[wvk1500]

pcv valve is good and sprayed the whole intake with carb cleaner no result

 

[barebones 1500]

What about the MAP sensor, that will cause similar problems. Thats my best idea that makes sense

 

[SAATR]

What's your fuel pressure, both at idle and cruise? Possible over rich/ over lean condition causing your part throttle driveability issues, which could be caused by a defective FPR or possibly a sketchy fuel pump. I don't remember offhand what the fuel pressure is supposed to be KOEO and KOER, but somebody should have it. If it is low, deadhead the pump (block off the return line from the throttle body) to see if it's the pump or the FPR causing the issue. If it's too high (I haven't seen this on one of these trucks except when the wrong pump is installed) then it's probably an FPR issue (or it could be the pump, if this all started with a new pump). Either way, it's another path to check.

 

[wvk1500]

guys I appreciate all the help I will check the map sensor I think that is 1 I have not replaced, as for the fuel pressure it seems good have not checked the pressure, seems like you can smell gas or rotten eggs when you park it. lol The truck HAS NOT had a pump recently replaced but has alot of miles 190,000. it ran great plenty of power and did not smoke or leak oil. I have checked the cat it flows good and the exhaust is not very hot at the pipe. This truck as soon as you replace any part and reset the comp. it will run fine for about 5 min then progressively gets worse. I talked to a guy today and he suggested the coil maybe breaking down when it warms up. I plan to buy one as it is not too expensive $22 at advance. I may try to replace the 02 sensor also. What do you guys think?

 

[SAATR]

If you haven't replaced the MAP, then by all means do so. It detects manifold vacuum and barometric pressure (hence Manifold Absolute Pressure) and the ECM uses this to calculate load and adjust AFR. If it's faulty it can cause just the symptoms you describe. The coil is a shot in the dark, as they don't fail that often on these trucks. Most of the ones I have had the opportunity to work on had never had their coil replaced, and when I tested with a spare "known good" coil, did not run differently. It's good to have a spare, if nothing else. This would be my procedure (from what you've told me): Fuel pressure test -> MAP sensor -> O2 sensor. There should be a way to test the MAP sensor with a multimeter, by applying a vacuum (with a hand pump) and test resistance across two of the pins or voltage at one pin (with it plugged in). If you can find such a procedure (check a haynes/chilton/FSM if you have one) then do that before replacement.

 

[wvk1500]

I have found a video on u tub that tells you how to check it.I looked at the codes and there is not 1 for the coil. So that might be it. The coil I bought requires you to use your old bracket. So I am changing that will keep everyone informed.

 

[sewlow]

My catalytic converter (catastrophic perverter) gave off a smell of rotten eggs when it was on it's way out. (plugged) Similar performance problems, too.

 

[wvk1500]

well, put the coil on after having to use my old bracket replaced the map sensor, went down the hill to the trash bins (my usual test drive) and coming back up the hill its still there. It seems to be a fuel problem as it is stalling unless you rev it up. Going to check my fuel pressure and maybe take off the cat converter. I have not put this on a obd 1 scanner to see what it says but I can not get any codes to show with a paper clip like I did with the egr sensor. Any other ideas?