ussj4brolli

First things first

94 camaro z28.

Symptoms.
When driving, hot or cold, when driving it feels like the car stops getting fuel, or enough. It boggs, feels like something is pulling on it. It is all the time, fast or slow. When it bogs I will give it more gas, and its like it gets it back power then starts torun fine again. If I leave the gas peddle alone while is in bog mode it will stay like that. Also, when trying to go wot it takes a lot longer to reach higher rpm, almost stops getting any higher.

Psi at idle is 38. Wot is at 41-42. When it has its issues it goes down 1 psi or so.and bounces.

The pump is autozone pump around 1.5 years old. I need to figure out what's causing this as I bought a 383 to be installed.

I bought a racetronics fuel pump and the harness. Hope that will fix it. I bought all kinds of parts for the 383 but need to pinpoint this issue before.

No check engine code.

Injuneer

What mods on the engine? What size injectors? Do you have a cat?

ussj4brolli

Might have misinformed. The engine in it now is a 350 stock. Regular msd upgrades for coil and wires. Yeah I have a cat. Cat back magnaflow exhaust w hooker muffler.

Injuneer

It would make it a lot easier to get answers if you put that kind of info in the form of a "Signature".

ussj4brolli

Sorry about that. Thought that was all in there from a long time ago, guess not.

Are those numbers ok? My fuel pump should be here tomorrow.

MikeGyver

It's fine. A 1psi fluctuation isn't going to cause any issues. The 1psi drop is probably because the engine is stuttering (from whatever is causing it). A stutter for example could very well effect the manifold pressure slightly which could cause small fuel pressure fluctuations.

ussj4brolli

Changed the fuel pump to the racetronix w new wiring harness...still same thing.

So if I am in park at 2.5k it will stay there, maybe go up and down 0.05rpm. But in drive, brakes applied it will bounce up and down about 500-600 rpm. It's bad!

Unplugged maf, same thing. Unplugged map, same. Swapped out icm, same. Fuel pump, same.

What else could it be? My new engine will be here Thursday and I can't install with out killing this bug! Unless its because of a head gasket or something, but would it just do that under load?

Opti? Fuel pressure reg?

MikeGyver

It's likely that it has something to do with your IAC or maybe tuning if you've changed that. Look for pre-02 sensor exhaust leaks and intake/vacuum leaks.

ussj4brolli

I did buy a new iac...but didn't install on this engine. I didn't know the iac "worked" under load.

Same tune for years.

When cold. It won't bounce, but I have no power. From about 3-6k rpm at wot is still takes forever to get to speed. Sounds bad too, can't tell if its under hood or exhaust.

I ran seafoam through the gas and intake thinking dirty, but didn't help.

Possible bad o2s when hot, and a bad cat? When cars off when hot, the cat sounds like ricecrispys.

Injuneer

I asked about the cat 3 weeks ago. Sounds like it may be plugged. Not sure how that would cause a 2,500 RPM idle, but this is the first you mentioned that problem.

ussj4brolli

Wait...!

I am not talking idle at all?
When the car is in park, ill put the throttle to 2.5k at it will stay there as it should, constant number.
If I put it in drive, with the ebrake on (now don't get confused, it does it driving too), same rpm level it will bounce 5-600 rpm down. Huge bog

Injuneer

Not the way I read it, but let's go back to the plugged cat idea. Considered the possibility?

ussj4brolli

yeah.

not sure if the two issues are connected, but most likely. and if so, why if its in drive its got the fluxuating RPM and not in park?

finally got my laptop battery replaced today, i will make some logs of the car tomorrow durring lunch. Maybe you guys can see something on that?

can i just unbolt the cat and "tell" if its clogged? like stick it off to the side or something?

Thanks for all the help...this is killing me

ussj4brolli

ok so i scanned and recorded.
you can see durring warm park 1 (i stayed in one spot, in drive, brake applied) i left the peddle in the same position. i noticed durring my scans that the issues occur the egrdc goes climes to 100 when it bogs. when the rpms clime again the egr dc goes back to 0. normal? the egr is under warranty, and i might aswell replace the vac solenid too... is this the prob?

cold start.uni
warm park 1.uni
drive 2 issues.uni
drive 1 issues.uni

Injuneer

If you were holding it with the brake, why does the "warm park 1" data log show VSS readings as high as 12MPH?

Hard to tell what you were doing in the log. There are three distinct sections 1) to record 180 - shows fairly constant ~26% throttle, fairly constant RPM, constant spark advance, varying MPH, and the EGR DC is at 0. 2) through record 448 - appears you were driving it a bit; 3) records 473 to 795 - exhibits rapid cycling of just about everything, including MPH, RPM. TP% is fairly constant. EGR commanded DC is varying 0 - 100%. Assume this the section you are discussing. If the car was really sitting still, and you were holding the throttle position with the brake on, there is something wrong with the data log or the PCM. Its appears the PCM is commanding the EGR to open, and the RPM rises, possibly indicating an air leak through the EGR system, but if you watch the air flow GPS, that also rises as the EGR is commanded to open up. The MPH also goes up when the EGR is commanded to open. The log also indicates "data error" scattered throughout. Looks like the PCM is possessed.