94 z28 lt1 shuts off
#1
94 z28 lt1 shuts off
good day all new to the forum
well my z28 shuts off while driving, I've changed out the mass air flow sensor, icm, manifold sensor, just shuts off like i turned the key off, i was getting a engine light but not anymore, sometimes it starts right back up other times i have to wait 5-10 min, i know other lt1 have had this problem, is there a way to rule the opti spark out, any help please
cheers
well my z28 shuts off while driving, I've changed out the mass air flow sensor, icm, manifold sensor, just shuts off like i turned the key off, i was getting a engine light but not anymore, sometimes it starts right back up other times i have to wait 5-10 min, i know other lt1 have had this problem, is there a way to rule the opti spark out, any help please
cheers
#2
Re: 94 z28 lt1 shuts off
Scan it for codes. If the SES light was on, the codes will be stored in the PCM, unless you pulled the battery cable. And, one code that shuts the engine down or prevents it from starting is DTC 16 for the cam position sensor in the Optispark. That code does not turn on the SES light.
Have you checked for spark at the plugs when it won't start?
In the meantime, here is a way to check that the Opti signals are reaching the PCM/ICM/coil:
Courtesy of Shoebox
4th Gen LT1 F-body Tech Articles
Have you checked for spark at the plugs when it won't start?
In the meantime, here is a way to check that the Opti signals are reaching the PCM/ICM/coil:
Courtesy of Shoebox
4th Gen LT1 F-body Tech Articles
#4
Prominent Member
Join Date: Jul 2010
Location: Born on the Florida West Coast, now where can I retire?
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Re: 94 z28 lt1 shuts off
A dead giveaway of the Opti failure is missing tach indication while cranking. Normally it should show 100-200 rpm while cranking.
Last edited by GaryDoug; 06-23-2016 at 08:45 PM.
#5
Re: 94 z28 lt1 shuts off
so i was playing around and when the engine warms up it shuts off, i pull a plug wire and put a spark plug on the end to see if i got power and crank the engine and there is no spark so does that mean my optispark is going.or my coil
#7
Re: 94 z28 lt1 shuts off
so it was not starting after it warmed up and then shut off on me, so i put a spark plug on the end of the wire to see if there was spark while cranking it over, no spark, went to check the tach to see if it moves and it starts up normal, so now i have spark, i'll bet when it dies on me ill have no spark at the plugs again, let it cool down starts up fine,
#9
Re: 94 z28 lt1 shuts off
ok did injuneer's test and my numbers came back good, only thing is when i was testing while cranking over the engine i was suppose to see a 1-4 volts while cranking, my volts were all over the place, i stuck my multi meter on the icm harness b to ground. How can i test my coil while cranking the engine over
#10
Prominent Member
Join Date: Jul 2010
Location: Born on the Florida West Coast, now where can I retire?
Posts: 1,505
#12
Re: 94 z28 lt1 shuts off
so went and put a new coil in it, ran for 10 min then shut off, would not fire up again
so it now has a new coil,icm,tbs,mass air flow sensor, map sensor, wires are newer,
So when the car warms up and shuts off i have no spark,and doesn't want to start right away, i know my coil and icm are good, so could it be the pcm or opitispark
so it now has a new coil,icm,tbs,mass air flow sensor, map sensor, wires are newer,
So when the car warms up and shuts off i have no spark,and doesn't want to start right away, i know my coil and icm are good, so could it be the pcm or opitispark
#13
Re: 94 z28 lt1 shuts off
ok did injuneer's test and my numbers came back good, only thing is when i was testing while cranking over the engine i was suppose to see a 1-4 volts while cranking, my volts were all over the place, i stuck my multi meter on the icm harness b to ground. How can i test my coil while cranking the engine over
#14
Re: 94 z28 lt1 shuts off
In the meantime, here is a way to check that the Opti signals are reaching the PCM/ICM/coil:
Courtesy of Shoebox
4th Gen LT1 F-body Tech Articles