formula315

I've been rebuilding my car for some time now! I have it before it was wrecked in 2013. Ever since I had it running and on the road it's had a weird hesitation issue and I can't seem to wrap my head around it! now I've replaced the plugs,wires,opti,tps,water temp sensor, injectors it's had,egr valve, egr solenoid, I'm running out of hope!!

Now sometimes it runs strong from a dig wot and Rollin as well while cruisen! But other times it will lung back an forth but it's not like a misfire! My rpms fluctuate between 500 rpm jumping up and down while maintaining a constant speed, if I apply a little more throttle it snaps out of it and runs smooth! Full throttle on the other hand it's hit an mis I raced a lightning had him till 110 and car stumbled he caught me, from a dig my car goes full potato and hesitates poorly but it dosent misfire I'm lost please help!!

formula315

Not sure if an 02 sensor or leak in the manifold could cause something like that or the maf/iat sensors could be the problem I'm at a loss

Boxxx

Sounds like the mass air flow sensor could be giving fits, should be able to find a testing procedure for it online before you just replace it. Though it should throw the check engine light. The rpm's fluctuating while driving is odd though, almost like it's going in and out of overdrive. If it surges at idle I'd look into the idle control valve.

Next time it happens take it out of overdrive and keep it in third and see if that stops it.

formula315

Alright I didn't think to do that I'll check it out here a little later.but I have unplugged the maf sensor troubleshooting and it does it either way I have also had my transmission replaced 2 times already after losing the 3-4 gears so i hope it's not cofused on whether to stay in OD OR not. ive had a problem with it ever since i bought the car! It's weird because it's hit an miss some days flawless!! But it acts like it starves of fuel or like it's surging maintaining a constant speed and Wot only! in park/neutral it revs perfect, I got an intake temp sensor and a map sensor gonna test those out today but would an exhuast manifold leak trip the o2's possibly? It just gets me because it's not constant for example full throttle it will sometimes hesitate poorly then snap out of it hit higher rpms and start surging bad it gets ugly but if I go 3/4 throttle it pulls hard and smooth while continuing to climb no problem!!

formula315

Also it idles fine!! It can sit parked running for hours no problem!! Starts fine as long as I turn the key and wait 2 seconds to pressure the rails

Boxxx

If all the electrical checks out I'd check for vacuum leaks in general, with the EGR and smog pump being prime suspects. It's common for people to mess with both and if they didn't do things right they're a source for leaks, even not being tampered with they can leak some times,

Though being you have to let it sit before starting it sounds like you have an injector leaking down or perhaps an issue with the fuel pressure regulator.