Sometimes, after idling, I will push the gas kinda hard and instantly get a weird stumble. Its as if the motor shuts off for a split second and makes you jolt forward in the seat. It will do it once and be fine like nothing happened. This does not happen every time however. Maybe once a week or so.

Sometimes I do hear an odd sound when this happens that is pretty hard to describe. The only way I now how is that its like a sucking sound as if my CAI was extremely loud for the brief moment.

I haven't noticed any other misfires or stumbles at all other than today after driving in the rain a little bit, but that seemed to smooth out. I guess the opti had a little moisture in it and dried out?

Im wondering if it may be fuel related. like my fuel pump may be going out and not sending fuel when it needs it sometimes. guess i'll have to buy a fuel pressure gauge tomorrow. What are symptoms of a dying pump?

Any other thoughts?

 

Check the intake bellows/elbow for tears, or not being fully on the throttle body.

 

Be sure the gauge is long enough so you can run it up to the windshield and watch as you drive. Sometimes the pump will just die. When my pump went it would just die out of nowhere and have hard starts.

 

I just went and checked. There was a gap where the CAI had pulled away from the MAF, but nothing else I can see.

Thats almost what it feels like. It feels like it just dies for a second and then begins pumping fuel again.

 

if the gap is before the MAF you won't experience any stumble caused by the MAF getting a bad reading, it needs to be after the MAF to cause problems, my green Camaro will be hard to start after sitting for a few days unless I cycle the key 3 times to get the fuel pressure up, if I do that it starts perfectly every time, if I just turn the key and try to start it right away it will take several tries, that car definitely needs a new pump

 

is it possible that the MAF could be going bad?

 

have you checked the wires and/or connector to the MAF? if they are compromised that will definitely cause a stumble

 

You might also want to check the TPS sensor to make sure its working correctly. Rapid opening of the throttle tells the PCM to start adding fuel ASAP, because the engine is going to see a huge gulp of air. If the MAF sensor doesn't read that amount of air correctly, or if the the TPS sensor did not warn the PCM that it was coming, its going to stumble from lack of fuel.

Then check the fuel pressure regulator, to make sure the vacuum line is still attached, and the FPR is controlling the pressure correctly. Again, as the throttle rapidly opens, intake manifold vacuum drops, and the fuel rail pressure should increase to maintain the correct differential pressure across the injectors. If the FRP isn't working, or the vacuum line is not connected, fuel pressure isn't going to respond correctly.

 

I was get a VERY hard shaking when the car was under a heavy load earlier today, and didn't sound quite right under easy acceleration. The worst was when I would try to accelerate at, or close to WOT in a higher gear(4-6). The shaking felt like I was driving over a bunch of tiny speed bumps. It did however smooth out after about 5 minutes of driving. The car was then shut off for about 3 hours and when I drove it back home all seemed fine. I couldn't find any loose or disconnected wires with a quick inspection.
Opti collecting moisture in it and drying out when driving? possibly bad 02's or MAF?

 

just connected a gauge to the valve and see where the pressure was. when the pump was running the gauge goes up to approx. 42psi, then drops to approx 39 once the pump stops. When the car started the gauge went up to about 45psi and then settled back down to 39-40psi. When revving it immediately jumps to 42 and back to 39-40. I have not been able to drive it with the gauge on yet( I didn't listen to the earlier post and the hose doesn't seem long enough, it just come right up to the wipers and can't really read it when in the seat)

the vacuum line on the FPR is still on and connected to the intake manifold too.

How can I check that the TPS is working correctly, or even if the MAF is working properly? I guess I can search on these topics later.

Can this issue have something to do with what I posted here?
https://www.camaroz28.com/forums/sho...d.php?t=673630

If so, then these two threads can be merged. I wasn't sure if they were related/

 

First, check the voltage that the PCM is supplyhng to the TPS by measuring between the gray and black (ground) wires. Should be 5.0V.

Check the TPS voltage across the dark blue and black wires. Should be in the range of 0.20-0.90V with the blades closed, with something around 0.65V for a stock TB. Open the blades slowly, and watch the voltage rise. Make sure there are no flat spots, dropouts or spikes in the voltage as you rotate the blades. Should rise smoothly. When you reach WOT the voltage should be roughly the value you started with closed (e.g. 0.65V) plus 4V.

The MAF can be checked with a scanner. Typical idle values are in the range of 6-10 GPS. Maybe a bit higher if you have a 1,000rpm idle and a lopey cam. At WOT, max RPM with the mods you describe, you are probably looking at 360-380GPS. If you don't have a scanner, look for a multi-meter with a frequency counter. At idle you will be looking at about 2300-2900 Hz. At WOT about 10,300 Hz.

I'll merge the threads.

 

I guess these are things that anyone with VERY limited electrical knowledge can do? It will probably make sense once I get down there and look at it.

From searching around, I guess the fuel pressure readings I got are pretty typical?

And from you merging the threads, I take you think the two are related? That thing about the bad shaking when at WOT really had me confused and only did it that one time.

 

If I am doing this correctly(again, VERY limited knowledge/experience with the electrical side of this) with the TB closed I get a reading of .5 and 4.47 with it fully open. The voltage did rise steadily as the blades were opened up.

Which wires do I go through to check the frequency for the MAF?

 

just drove it again a short distance. it feels like its missing in every gear now...the shaking just gets worse in higher gears.

 

before I drop the money for a new opti. what else can I look at? plugs looked ok...I have seen much worse and plug wires are on tight.
i do not have a scanner, but the SES light has not come on if there are any codes.