Cmr0z28

Hey guys

Since May my car has had a high RPM miss. It feels like it's falling on its face at around 5600-5700 RPMs, and stays that way until it shifts. It barely wants to make it into overdrive because it struggles to get to the 3-4 shift point at WOT.

I checked fuel pressure, it holds 46psi through the gears.

Plugs and wires are fairly new, no arcing, no burnt wires.

At first I thought the transmission was slipping, because it almost feels like it's hitting the rev limiter..

Checked the coil wire which is also fairly new, and that looks fine.

This started after my electric water pump install (and more specifically, started RIGHT after I put on my Weld wheels with 275/50/15 Nittos) for some reason, so I'm assuming it's the optispark. I have a brand new GM replacement unit right here, so I will install it along with a new coil within the next few days, and I will update this thread for those who suffer from the same problems.

Feel free to post any comments.

Chris 96 WS6

Sure sounds like the opti. Its hard to diagnose just from a message board but the water pump swap screams opti to me. Did you get coolant all over the opti or otherwise disturb it in any way?

Make sure the wiring harness plug is securely snapped into the opti.

Cmr0z28

A few drops here and there...but it didn't start until about 2 weeks after the WP install. I kept rags around it most of the time to keep it dry, but like I said, it did get a little wet.

Cmr0z28

Coil didn't do anything.

MRBoss429x

The recent waterpump install definetly makes me want to say opti but I wouldnt go rushing into it. Check out cheaper little things first. You might want to get a scan tool to help you narrow down your problem.

Cmr0z28

I want to order the www.obd-2.com scan tool, but they're closed until the 12th. Opti is sitting on my desk so I may as well install it.

If the opti was bad, would it show anything on a logged run?

Lt1t56

I had the same problem a while back, new 02's, wires, plugs, opti, coil, and also had good fuel pressure... I was out of ideas.
So I went to auto zone and purchased a $25.00 set of plug wires to see if it would make a difference and it was fixed.
Just a suggestion, but $25.00 cured my problem

MRBoss429x

There might be a trouble code stored. Does the SES light come on at all when you start the car or when the problem occurs? I had an opti problem and I was getting code 36 when it started acting up, but only then. A scan tool can show you this but then again so can a paperclip.

Cmr0z28

Alright, this is strange. I capped up the cutout, and it pulls 99% perfect to redline in every gear. Sometimes it may not pull as hard around ~5700 RPM's, but it's nothing noteworthy.

Gonna go to the track tomorrow. I'll make 2 runs on motor, and however many runs I can get in on a 100 shot.

I know, it's not the smartest thing to do to spray it right now, but I just "tested" it "extensively" and it runs awesome.

If it blows, I'll fix it :P

GMRL

Cutout might be causing some false knock. Have you installed an LT4 knock module yet?

Cmr0z28

Yup....I've had one for almost two years now.

Cmr0z28

test and tune got rained out

Cmr0z28

Welp, the car is still doing it intermittently. I ordered software from www.obd-2.com w/2nd day shipping, so I'll post a few logged runs once I get it.