Give me some ideas.

[RobP]

Well the fuel delivery problem is cured. However I am getting a bad miss anything over say 1/2 throttle under load.
No miss while sitting at idle and revving the engine.
New Cap, Rotor and coil.
Swapped the ignition module out of my 92Z28, same thing.
Does the same thing with the MSD plugged or unplugged. Seems worse with the MSD plugged in.
Autoxray doesn't show much out of the ordinary. I don't see any timing being pulled until the miss gets really bad and you can hear the engine really sputter. The knock sensor is probably picking up on the noise and then pulling timing. Before when the fuel pump was not keeping up you could see the PW on the injectors go sky high as the ecm tried to compensate for not enough fuel.
I guess I need to check each plug wire again, though they are new Taylors and appear to be in good shape. The car drives excellent if you stay below half throttle. TPS appears linear on the scanner. It really feels like a miss due to a grounded plug wires or something.
Thanks
Rob P

[mrr23]

Originally posted by RobP:
Well the fuel delivery problem is cured. However I am getting a bad miss anything over say 1/2 throttle under load.
No miss while sitting at idle and revving the engine.
New Cap, Rotor and coil.
Swapped the ignition module out of my 92Z28, same thing.
Does the same thing with the MSD plugged or unplugged. Seems worse with the MSD plugged in.
Autoxray doesn't show much out of the ordinary. I don't see any timing being pulled until the miss gets really bad and you can hear the engine really sputter. The knock sensor is probably picking up on the noise and then pulling timing. Before when the fuel pump was not keeping up you could see the PW on the injectors go sky high as the ecm tried to compensate for not enough fuel.
I guess I need to check each plug wire again, though they are new Taylors and appear to be in good shape. The car drives excellent if you stay below half throttle. TPS appears linear on the scanner. It really feels like a miss due to a grounded plug wires or something.
Thanks
Rob Psecondary coil windings going bad.

[RobP]

Secondary coil windings? :confused:

[WS6 VERT]

I agree with mrr23, under load misfire is usually some sort of secondary igntion problem. Swap out the coil.

[mrr23]

Originally posted by RobP:
Secondary coil windings? :confused: just to explain. inside the coil there are two windings. primary and secondary. the primary takes the 12 volts from the powersource then feeds it to the secondary windings. the secondary windings is what 'converts' the 12 volts to 26,000 volts or what ever the max the coil can put out. it can be tested. take an ohm meter and place one lead on the positive connector. then the other lead to the coil wire tower. i maybe wrong on this number but, it should measure 18,000 ohms?

the reason we are saying it is the coil is because the higher the rpms the more strain on the coil. it can't keep up. also you said it was worse with the msd.and also it is the reason why you are showing a rich condition. not burning the fuel.

[ May 06, 2002, 22:38: Message edited by: mrr23 ]

[RobP]

Okay, that's gonna suck if MSD sent me a bad, brand new coil. I put the old one back on and test.
Rob

[WS6 VERT]

It doesn't happen often, but it does happen. New or not, you have to rule it out.

[RobP]

Okay, swapped the old, stock coil back in. Same thing. I also swapped in my Street and performance chip in place of the one Bernard and I burned. On the burned chip we bumped the injectors to 24lb, egr off and changed fan on/off temps.
The car ran rougher with the S&P chip. My thinking is maybe the S&P chip is still set up for 22lb injectors. So with a new pump and the SVO injectors, I could be getting too much fuel. Autoxray showed pretty much rich the whole ride home, didn't bounce much between rich and lean.
I'm gonna play with the fuel pressure a bit. I have it set at 40psi, perhaps this is too much. I did notice the injector pw shot up when the car started to stumble with the S&P chip.
Rob P

[Jaysz28]

I know this problem
what is your CST showing on the auto x-ray? Maybe it is reading low and causing to to run rich. This was my problem that I chased for a week.

Just throwing out an idea

[RobP]

Nope CTS is functioning properly. Thats the problem, scanners is really showing nothing out of the ordinary as far as I can tell.

[Jaysz28]

Originally posted by RobP:
Nope CTS is functioning properly. Thats the problem, scanners is really showing nothing out of the ordinary as far as I can tell.Ok, then I will tell you of the chase that I just ended on my Z. Ended up being a bad TPS, but it was intermittent. I think that would show up on the auto xray, but........... you havent mention it either.

Nothing from the knocksensor, so that isn't the problem. Is the disty tight? Internally I mean. I know nothing on your car is that old, but I'm just trying to throw your money away for ya.....

[RobP]

I'll take a look at the TPS on the scanner while the problem presents itself.
About the dist. Along time ago I swapped the one out of the 92 and never switched back. However, that metal cover plate that sits under the rotor seems rather loose. It's just a round metal shell. Other then that, nothing else seems wrong. Could bad pickup coils cause a miss under load?
RobP

[Jaysz28]

yes it could cause that problem. I beleive the helms manual outlines a way to test the pickup coil.

[RobP]

Yeah, I actually did that test on our old work truck once.
You know, I remember I had a similar problem and it seemed it have had something to do with the way the coil was mounted. I added rubber insulators between the coil mount and the coil to fix the problem. I'm sure I added those back in when I swapped the MSD coil on. Is there any requirement for the coil to be grounded or not grounded? I know there was a stock, thin rubber piece originally.