Thanks for any input on my problem.

I have a 96Z28 that is having problems starting cold. Takes 2 to 3 10 second cranks to get her started, and I'm not driving it until I get this figured out.

Only code is PO 300, and has been having a slight miss at idle for a few days.

Can hear fuel pump prime, and car has slight fuel smell on startup out of exhaust. Probably from having to crank it a lot though. Will check fuel pressure and leakdown though.

The first 2 or so times I try to start it is tries to catch, but doesn't.

I don't know if I am hearing things, but I can hear a slight intermittent electrical snapping (like a plug wire arcing) when it is running. Like 1 time every 10-15 seconds. Does the opti do this when it is arcing? I haven't had a distributor car in years.

The electrical snapping could be coming from the coil wire or opti area.

Only mods are CAI and elbow.

LMK if you have any ideas, on Monday I will check out the opti, coil, and fuel pump with the procedures from this site.

No recent mechanical work. 94,000 miles. Newer O2 sensor.

Thanks

 

PO300 is a misfire code. Start with the basics: plugs, wires, especially the coil wire (from experience). After that, you will need to start going deeper. But check these things first.

 

Definitely get plugs and wires installed first. My plugs were once so fouled they would not spark correctly causing the same problem.

 

Don't forget that coil wire!!

 

Thanks guys, I'll give everything a good check up on Monday. Plugs are 1 yr old AC Delco brand and wires are Summit brand the previous owner put on less than 10,000 miles ago.

 

Since they were changed lately it doesn't appear that the plugs and wires are the cause. You'll see soon enough when you check things out on Monday.

In the meantime, consider that it could be a fuel delivery issue. If the check valve in the return line is shot, the fuel line will take a while to get up to pressure. Try turning the ignition to on (not start) waiting for the pump to go off then turn the ignition off. Repeat three times except trying to start it on the third go. If it starts right up you may have found the gremlin. You'll need a FP gauge to diagnose further.

This check valve shouldn't affect anything once the engine is running so you can have good FP when running and still have this issue.

The electrical arcing sound you hear could certainly be the wires as decribed above. You should also be able to see any arcing if you take a look under the hood in the dark...

Good luck!

 

Update, but not finished with diagnosis.

Key on Engine Off fuel pressure, 44PSI, 1-2 PSI dropoff after 10-15 minutes

Engine on fuel pressure, just under 40, goes up about 10 PSI when vacuum line is removed, no fuel in vacuum line.

Still takes 2-3 10 second cranks to start from cold, tried to catch and runs for about 5-15 seconds on 1 or 2 cylinders. On third or fourth try starts somewhat normal. I will try to scan a bad startup to see what it looks like.

Looked at coil wire and see no obvious breaks/tears etc, but haven't had time to look too closely.

No obvious misses upon acceleration, verified by scanner.

When warmed up for a couple minutes it starts normally.

I will try to get out tonight and see if there is any arcing under the hood, and get under the car tomorrow if I get a chance to ohm out things and test the opti and coil. But there are no codes for the opti showing or pending.

 

Ok, did more testing.

Coil tests at 5630 ohms
Coil Wire tests at 245 ohms, with no obvious breaks, etc. Jegs brand, not Summit like said before.
ICM wires have 11.8v on A and D
The other wire goes to ground with about 30 ohms of resistance.
Don't have anyone yet to help me check the white wire while cranking.
If I remove the intake after the MAF when it is having problems while it is sputtering trying to start, I can see raw Air-fuel mixture being pushed out of the MAF while misfiring. And I can hear an air pushing sound pushing the air out of the intake intermittently. After it starts though it runs well.

 

Well, car is now dead pretty much and a new Delphi opti from thepartsladi has been ordered even if it isn't the problem it is the only thing left.

Car now makes an electrical snapping noise every second and the miss comes along with it. Car dies and is very hard to start.

Looking at the engine bay at night, I can see no arcing.

 

Almost certainly the opti unit if your fuel pressure is ok. I replaced mine last week and had the exact same list of symptoms that you're exhibiting (including the electrical noise). I also couldn't upshift at WOT. Replacing the wires, coil and opti cleared it all up. Good luck!

 

Well,

I got the car fixed.

It was the opti.

I ended up changing the opti and opti harness and it started right up and runs well.