Hey guys,
Just bought a 97 Z28 30th from my cousin.. Let me say first in order to get the car to my house I had to replace the starter as half of the 'nose cone' was blown off (cracked) of the old one.
So it seemed to run OK (not the greatest) at first but then as I warmed it up and topped off the coolant and started home with it it started dying at every stop sign and being difficult to restart. Then starting out it was dying. (also bad misfire at 1200-2500~ RPM) I ended up pulling over and letting it cool down for an hour and a half thinking it was perhaps something Opti/Heat related. Didn't help.. I ended up just twitching throttle and slamming it into drive and blew every stop sign on way home just to get it there.
Pulled out my cheapie code reader and there were 2 P300 DTC's (I've never seen 1 code thrown twice before but thats a moot point).

I went through it last night and noticed the number 7 Cyl plug wire lying on the Collector/Header so I moved it to the heat shield and pulled it tight to hopefully keep it there (Best info I could find showed thats how it was supposed to be).
I noticed the vacuum line that runs under the throttle body intake (the hard plastic one) was cracked so I got out some vacuum line and fixed that .. Also noticed the Orfice/Filter vent tube that runs from the Opti was just hanging in the engine bay . Someone had put a Moroso CAI kit on the thing and theres no hole that I can see for that vacuum line (I was just going to punch one of the rubber boots after the MAF and stick it in there.

The plug wires on it are obviously the really cheapy flimsy ones (Gray wire black boots.. Duralast?) the plugs from looking at that #7 one don't appear that old but I know that doesn't mean anything either.

The car is very hard to start (have to press on gas for some reason. it seems like and misfires while starting) then still continues misfire at lower rpms.. My gut is telling me its the optispark or ICM(coil) since from talking to my cousin they were having problems with overflow boiling (Air in Coolant system).

My question is where to start.. Replace plugs and wires or should I just go for the opti aswell ? I don't have a ton of money to throw useless fixes at it.

I can see 2 of the exhaust manifold bolts nearly out on the drivers side which makes me wonder if someone was going to drop the manifold to do those wires/plugs but who knows.. Opti has oil all over it from leaking front seal.

is a 97 even supposed to have a vented opti ?

Thanks

 

Vented Opti was used 1995 - 1997. The line with the flow restrictor and check valve runs from the driver's side of the intake manifold to the nipple on the Opti. The air supply line starts at the intake elbow (drill a hole, don't "punch" it), and goes to the second nipple on the Opti. Does not connect to the CAI in any case. Shoebox has the correct info:

http://shbox.com/1/opti_vacuum_harness.jpg

http://shbox.com/1/opti_vacuum_conn.jpg

Heat soak can attack the ICM, the optical cam position sensor module in the Opti, and the fuel pump. Have the ICM tested at an auto parts store. If it's got an intermittent problem, it should still set a code. When they test it, ask them to test it multiple times, to heat it up, are blast it with a heat gun while testing.

If the exhaust manifold bolts are loose, it's screwing up the O2 sensor readings on that bank. The moving exhaust gasses can pull in (educt) fresh air into the exhaust, the O2 sensor sees the oxygen, and the PCM pours extra fuel into the engine to cure a false lean condition. Inspect the spark plugs and see if they are badly fouled.

If the #7 plug wire was laying on the manifold, it's probably toast. The insulation will be burned through, and now its probably arcing on the heat shield.

A code can be stored in memory more than once, or it can be a combination of a stored and active code. Do you have access the an OBD-2 scanner with GM "enhanced parameters"? That would allow you to pull up the misfire count by individual cylinder, to see if it is truly a "random" misfire, or actually associated with specific cylinders.

With regard to the hard start, will it start faster if you cycle the key several times from off to run, before turning it to start? If not, will it start easier if you put the accel pedal on the floor before you turn the key to start, and keep it there until the engine starts (clear flood mode).

You have to fix the obvious stuff that you have already identified first. Then it may be easier to home in on the exact cause of the problem.

 

The scanner is a 'actron' OBDII autoscanner.. Cheap and I don't believe it has that feature.. I borrowed it..
It indeed did seem to start easier if I turned key on off a few times AND held pedal down. I was thinking this was the fuel filter perhaps (No idea when it was last done and car didn't seem properly maintained other than engine oil level). What do those 2 things indicate ?

Strangely enough the #7 wire that was lying on the header is not burned through .(Don't know how!) but my Dad said it did look thinner right there.. Needs to be replaced in any case.. engine seemed to miss alot less with it not lying there but still hard start.

So I guess a good plan of attack would be Plugs/Wires (As this should probably be done anyway) and pull the ICM for testing..


Thanks for your response/input!

 

So just had the ICM tested.. failed .. putting new plugs and piecing back together .. Hopefully that was the only problem !

 

So after Icm replacement and plugs wires (plugs didn't look fouled though) it started right up the first time and then all the sudden died and now won't start at all. Auto zone didn't have ability to test coil so that is still an unknown as well as cap rotor status. Just threw a p300 again nothing else where too now ??

Sent from my SM-N900T using Tapatalk

 

not sure if this is relevant but I noticed the pink wire on the coil plug has been cut .. looks like someone replaced this plug .. is the coil plug supposed to have 3 wires.. does anyone have a picture ??

Coil

(Cut) blk 12v
| | |

 

Slow start can be the result of fuel pressure dropping off too rapidly after the pump primes for a couple seconds, then shuts down. You would need to put a fuel pressure gauge on the Schrader valve, turn the key to "run" (not "start"), check the pressure when the pump shuts off, and watch to see how rapidly the pressure drops. If it drops more than 10psi in 10 minutes, you have a problem. It wouldn't be the fuel filter. Pressure loss would be due to 1) a leaking fuel pressure regulator; 2) leaking check valve in the fuel pump; 3) leaking injector(s); 4) leaks anywhere in the system plumbing, including the flex hose in the tank that connects the fuel pump to the sending unit.

Scan again.

Shoebox has the wiring diagram for 96/97:

http://shbox.com/1/1996_ec_03_ign_system.jpg

Note that the 96/97 coil has a single connector with 2 wires (not counting the coil-to-distributor wire) - pink on terminal A and dark green on terminal B.