i just replaced my fuel pump with the oem delphi, starts up perfectly,
right before the pump quit (2 weeks before) when i started it up, the rpm would sit there at 1000, then drop to 500 then rev up to 1500, then idle rough, then return to 800, then when i drove it for a minute it wouldnt idle rough, and was normal at lights and stop signs. i assumed it had to do with the fuel pump being bad.

now this is the first full day ive had the pump in, i havent been able to really drive it because im waiting for that link to come in for the fuel strap on the front strap and dont wanna take the chance. now i just went to start it, and it did the exact same thing as in the above paragraph,

what can it be?
also no codes or cel on

TIA!

 

it would help if you had access to a fuel pressure gauge to monitor if the fuel pressure is changing during those idle changes. its possible it could just be a coincidence, maybe a egr valve or other issues causing it

 

I had a similar problem once, it would start up and then surge and then go right back to where it was supposed to be, and then surge every once in awhile while driving. I had no codes and no Check Engine Light ever come on. Eventually it started pinging as if I'd put cheap gas in. I eventually found out what the problem was, just by chance I purchased a new AC Delco MAP sensor and all of the symptoms went away. Very easy to swap out.

 

my egr was recently cleaned out, using the thread on here, i was also told IAC could be clogged and causing randomly jumps in the idle, will have to check MAP sensor, where exactly is it or what does it look like?

 

It just pushes on, it has no screws, it's held on by the pressure of the tight fitting rubber seal.

 

awesome visuals thank you ! how much did it cost you? if its cheap, it couldnt hurt

 

2000 GMC JIMMY 4.3L V6 : Fuel/Air : Manifold Pressure (MAP) Sensor
More Information for ACDELCO 213796
As per RockAuto: Alternate/OEM Part Number(s): 09359409, 12614973, 16249939, 213351, 9359409


Ebay listing:
GM Map Sensor 12614973 Buick Cadillac Chevrolet GMC Hummer Isuzu Oldsmobile | eBay

GM MAP SENSOR 12614973 BUICK CADILLAC CHEVROLET GMC HUMMER ISUZU OLDSMOBILE


Price: US $19.99

Shipping: $5.12 Standard Shipping

 

thats about 20 bucks cheaper than i found, which the cheapest was amazon at 45. i just cleaned my iac, the rpm looked like it wanted to rev, but didnt, it was really dirty, i had only enough to spray that, not the hole

 

update: cleaning the IAC did not work, as much as i hate throwing parts at a car to hope it fixes im going to try getting the MAP sensor, im sure its the original one, yet come to think of it i dont remember seeing ac delco on the one in there, i checked yesterday

would i also be able to get the delphi ps10000?

 

since it only does this rev crap at start up, can i rule out vacuum lines being the culprit?

i just bought the delphi IAC valve, will be here tuesday, hopefully this will be the fix, will post results either thursday or friday