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Topic: just wont rev

in Forum: C4 Engines


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Re: just wont rev (15/25)
 7/13/12 2:18pm
Adams' Apple
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Duncanville, TX - USA

Vette(s):
1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.


Joined: 3/18/2009
Posts: 2230

I think you're looking at a failing ignition module, Howard. Classic symptoms. The "SYS" on the dash readout usually has to do with the traction control/abs, but I'd need to check on the '90. Perhaps Dave( eddie20890 ) would know, since he has a '90 model. It would help if there were any codes...

|UPDATED|7/13/2012 11:18:45 AM (AZT)|/UPDATED|


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Re: just wont rev (16/25)
 7/13/12 5:09pm
SAYWHEN
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Posts: 82

I agree with Joel....it sounds like symptoms of failing ign. module....eng. hot no and/or poor spark...engine cooled down ign. system works great until hot again. The SYS light can also come on with a weak/failing battery even though the charging system is good ( not meaning to imply that's your problem..just sayin' )
 
Have you actually checked for codes using the paper clip method from Joels' previuos post since the SYS light was on? It's possible a "history" code may show up.
Re: just wont rev (17/25)
 7/13/12 7:42pm
ANNICORVETTE
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BILOXI, MS - USA

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1990


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it has a new battery (been checked twice ).
 if it rains tonight i will try the clip method tomarrow if it doesn't ran i will spend the day mowing the front lawn (approx 6 acres ). any pics of the ignition module being posted?
Re: just wont rev (18/25)
 7/13/12 9:38pm
SAYWHEN
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This is a pic of the module...remove the dist cap and rotor and you'll see it. They can be tested at some parts stores .but IMO a waste of time when the module in your case may be intermitant...they would be testing it cold..not hot when you have your issue. As i said in my post i didn't mean to say your battery was bad..I was simply saying that is one thing which can turn on the SYS light (usually with out your running issues) as will ABS..ASR and believe it or not sometimes a aftermarket radioThumbs Up 
Re: just wont rev (19/25)
 7/13/12 11:14pm
ANNICORVETTE
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BILOXI, MS - USA

Vette(s):
1990


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started researching distributor modules for the 90 (only corvette would do this)guess i will run the codes and check which module is on the 90 tomarrow.





(resized large image-aapple)


|UPDATED|7/13/2012 8:14:34 PM (AZT)|/UPDATED|
Re: just wont rev (20/25)
 7/13/12 11:06pm
Adams' Apple
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Duncanville, TX - USA

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1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.


Joined: 3/18/2009
Posts: 2230

The module is inside the distributor. You'll need to remove the cap and rotor, as has been noted. Then there are two small screws that hold the module to the dist., and two wire connectors. These connectors get brittle over time, so if you change the module, be careful unplugging it. New modules usually come with a small package of grease....USE IT. It needs to be smeared all over the bottom of the module, where it fits on the distributor. Not using this grease will cause the module to overheat quickly, and you'll be right back where you started...replacing the module. Sometimes, a bad coil will cause the module to fry, too. It's best to replace the coil if you replace the module...



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Re: just wont rev (21/25)
 7/14/12 8:40am
eddie20890
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lanoka harbor, NJ - USA

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1990 L-98 white/ red/black leather interior targa top auto 1975 L48 blue/black leather interior t tops auto


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ANNICORVETTE said: started researching distributor modules for the 90 (only corvette would do this)guess i will run the codes and check which module is on the 90 tomarrow.





(resized large image-aapple)



the top module is what is in my 90. also if it stock distributor, coil is in the cap. as joel said you have to use the pack of grease that comes with it. if not there use diselectric grease. make sure both surfaces are clean and spread a thin even coat. just another tip--make sure if you replace the coil (or even if you don't) that the secondary ground strap is installed. when i bought mine i was tuning it up and there wasn't one there. figured with the computers they figured out another method. WRONG. was having a lot of trouble and finally decided to replace the coil and in the box in bold letters was DONT FORGET TO INSTALL SECONDARY GROUND STRAP. a $2.00 part caused me a lot of headaches. without it it will burn out a module.

years back if the module went the car wouldn't run. newer modules seem to do as you are describing---act up and then don't, until they get to the point of no return. if you bring it to autozone they will check it for you but if you go thru the trouble of removing it, for roughly $25.00 you can put a new one.

hope you can figure this out and if you need anything let me know.

dave




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Re: just wont rev (22/25)
 9/26/12 2:41am
ANNICORVETTE
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BILOXI, MS - USA

Vette(s):
1990


Joined: 3/19/2009
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well i am back to working on the 90 still wont run when it heats up. have checked everything that has been mentioned in this thread. still no codes even had the code checked at a shop last week replaced the whole distributor with the same results. i feel it has to be electrical in some way. just i am so stuborn i want to find the problem, anyway the dealships here wont touch it and everyone i talk to gives me the same things i have allready done.
 
still needing HELP
Re: just wont rev (23/25)
 9/26/12 11:08am
davep85c4
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Joined: 4/4/2009
Posts: 254

Oh, come on. This is the classic multec injector issue. The second post in the thread describes the multecs, and describes how to check them.

So, Have You Checked Them? Go buy a $5 meter at harbor freight, and do it.
Re: just wont rev (24/25)
 9/26/12 11:26am
ANNICORVETTE
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BILOXI, MS - USA

Vette(s):
1990


Joined: 3/19/2009
Posts: 27

have a meter and all injectors read approx 16 ohms, did notice that several of the wires to the injectors looked like they had been repaired and electrical tape covering the repairs, aybe i should untape and check these repairs.
Re: just wont rev (25/25)
 9/26/12 1:47pm
396c4
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Old school checks the fuel system first. New school - check the electrical first. Seems odd to me that you would loose 8 injectors at once and you appear to have been through the distributor and the battery. That leaves me with one more, obvious and mostly over looked link ... grounding. If the battery ground is good and I assume it is with the battery change, I'd be checking the other end. Your manual will tell you where the major ground points are but the one that bolts to the (driver's side) bell housing has a bunch on a common stud, even though stud connections are "no-no" by most electrical standards. I don't know why GM doesn't add proper ground blocks. You might stringing some jumpers to see if that makes any difference. I've added ground runs from the bellhousing stud, MSD and data logging equipment directly back to a ground block at the battery to eliminate chassis/engine block issues and electrical noise. Only the starter relies on chassis ground. Good luck.

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