Drivablity issue...

[zeeman]

Have you checked fuel pressure? you mentioned it wont hold pressure after prime. That's not right. bad pump or regulator to me. Pull plugs and see how its running.

[NullHead]

Correct me if I'm wrong, but the fuel pressure could bleed off through the return side of the fuel system and show the pressure dropping and you'd still have a good fuel pump check valve, right? The gauge is connected to the pressure side. Isn't there a check valve in the fuel rail somewhere to hold those injectors at 40psi for startup?

Also I'd look into the EGR valve or plugged cat.

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[NullHead]

Just looked in my service manual, the flowchart and instructions both say the fuel system should hold pressure key on engine off. The spec is 40.5-47psi. So that issue would either be the fuel pressure regulator is leaking fuel back into the return side, or the check valve in the pump is bad.

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[MeenZ28]

The regulator is fine. I took it apart just to see the diapham and its good (as i expected). Once i get the new injectors in if the fuel pressure issue persists im taking the new fuel pump out and sending it back. Thats the only other posibility.

Since the top end is apart, do you know any way to check if the egr valve is operating properly? Is there a way to clean it?

[NullHead]

Unplug the vacuum line and cap it, then slip a "block off valve" under the EGR gasket - pop cans work good if crafted carefully. If when it's blocked off everything gets better, then your EGR valve is causing the trouble.

[MeenZ28]

So clearly my iac valve is broken....

Any chance this could play into my issue? Could act like a vacuum leak?

[NullHead]

Um, well anything's possible I guess. There's a good start! Ordinarily that valve would close under throttle, but if air seeps through I guess it could act like a vacuum leak.

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[zeeman]

Nott to rain on your parade, but the break looks fresh,like it just happened. But since you have to replace it anyways......

[hoogiesngrinderz]

Not likely the issue, but you need to replace that.

[MeenZ28]

Aic valve replaced, new bosch 3 injectors in.... Still no improvement. Im suspecting that the new fuel pump is to blame. Im going to drop the old one back in and see if it looks better at the gauge. But even if theres an improvment there i dont think that fix the stumbling problem. Im starting to think it actually is ignition... But what part?

[MeenZ28]

The old pump is definatly better than the new. Shes holding pressure better after prime. Still drops but slowly like it should. No improvement to the stumbling issue as i expected. Anyone got a set of plug wires laying around? Im just about out of money now...

[MeenZ28]

So after reading several several several posts on various boards slamming Bosch platinum spark plugs i decided since plugs were cheap and reasonably easy to change out i picked up a set of NGKs at autozone today (cashed in my rewards for them) and put them in after work tonight.

All better. Strange, these Bosch plugs had less than 6000 miles on them. Ill stick with NGKs or Delcos from now on. If i remember correctly i think the only reason i bought these were they were on closeout from Rockauto. Maybe now i know why.

So...
fuel pump
injectors
fuel filter
lines
iac valve
spark plugs

*sighs*

[MP81]

Sounds like a worse version of what I went through only to find a new tank of gas fixed it.

Well glad to hear you fixed it! I generally run either Delco or NGKs as well. Delco if I'm running the factory plug (so, the Cav), and NGK if I have to run a colder temp (Cobalt).

[1BADAIR]

What I win?

[DanDalessandro]

a fake check for ten quadrillion billion pesos

Glad to see you worked it out.