HELP .1987 v1500 runs rough under load

[Ricko1966]

Fuel pressure and volume are the same hot or cold,and you said it runs good cold. So I'd be looking at the ecm isn't commanding the injectors open long enough on closed loop. Have you tested the wires to the map sensor and the map sensor reading?

 

[nickdean]

Yes Fuel pressure same hot or cold. I think i have voltage to the map sensor i unplugged it and got a reading while running but only on one wire. Unplugging it drastically changed how it was idling.

 

[joewhite]

My 1987 v1500 roughs very rough under load but not at idle. At idle it revs up fine but when I put it in gear to drive it stalls and runs rough.it doesnt die but just falls flat on its face. I replaced all the gaskets in the throttle body. The idle air control, throttle position sensor, map sensor, coolant sensor, threw some Chinese injectors in it. No change so put the factory back in. Plugs,wires,cap,rotor, stator, and ignition control module. Fuel pump, fuel filter. Cleaned all grounds. Alternator is pretty new. And I had the timing checked.

Mine did the same check your egr valve

 

[joewhite]

Check your egr mine was doing the same thing a real pain but good now

 

[gmbellew]

it is easy to disconnect the EGR valve from the solenoid and take it for a spin. it may set a code 32, just be aware of that

 

[YakkoWarner]

Could also be coolant temp sensor reading abnormally high which would fit the "runs right when cold but not when hot" - although that SHOULD also throw a lean code on the computer because the O2 sensor will detect the lean condition.

 

[nickdean]

Well still no luck I ended up replacing the entire distributor. I set timing at 0 degrees with est wire un plugged. No change. I advanced timing slightly no change. But when I retarded the timing it would actually power brake in the garage and drive better. I marked rotor, set at tbc when i put it in, verified piston was all the way up. After driving i pulled cap and rotated to tdc to again verify distributor was put in right.So would that mean its running lean correct?

 

[YakkoWarner]

Since you physically verified the piston was at TDC when your timing mark also indicated TDC, that confirms your timing is set up. At this point I'd consider pulling a plug or 2 and visually examining them, a lean burning plug looks kind of bleached and shows signs of getting really hot, a rich burning plug will be black and sooty.

 

[Ricko1966]

Back probe the oxygen sensor,check voltage that will tell you if you are lean or rich

 

[gmbellew]

Back probe the oxygen sensor,check voltage that will tell you if you are lean or rich

Might be easiest to do that and watch values while driving by back probing at the ECM harness.