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So just purchased a 1993 Z28 with 60,000 miles on it form my buddy. He didn't drive it much. Little quick history before I get to the problem. Its a 2 owner car, I'm the 3rd. Very little miles put on it in last 14 years (17,000). My buddy was driving it and put a fresh tank of gas in it. Drove it about 3-4 miles, no problems. gets up the next morning and it starts fine and goes about a block and then sputterers and dies. He limps it back home and parks it and it sits there for 2 months. he puts a can of seafoam in the gas and it starts right up and will idle but when you put it in gear (automatic) it dies. If you try to drive it it will just die. So we make a deal for me to buy it. I go down to buy it and now it wont even start unless you hold the gas to the floor. It starts and blows nasty black smoke out. Just running really fuel fouled IMO. I trailer it home and have so far changed out the fuel filter and removed the cat(thought it might be plugged). Also tried starting it with the MAF unplugged, still not working. Not sure what to look at next before I start throwing parts at it. Any suggestions would be great as I dont know these motors at all. Im a Ford modular/pushord guy. Thanks.
 

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I would check fuel pressure and see what your pump is putting out
and then check the fuel pressure regulator. Also see if you are getting
a good clean spark out of the coil and then the distributor. If the car is all
stock and little to nothing has been changed or maintained,start looking for corrosion on wires and connectors, If it has orig. spark plug
wires they may be Junk,also plugs could be fouled out. IF YOUR NEW RIDE ONLY HAS 60,000 miles on it,then it could end up being a really nice piece,but on the other hand if it has been sitting for long periods of time
without running there could be many complications regarding how it runs. I
WOULD CHANGE OIL AND FILTER ASAP. GOOD LUCK WITH IT and dont get
discouraged. ed
 

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first thing i'd do with those symptoms are start with the fuel system

take your fuel filter off and dump it out into a glass jar and see what's in there. if there's been a bunch of crap run through it...

you need to check fuel pressure @ the shrader valve at the back of the intake with a fuel pressure tester to make sure that's all working ok..

then lift the rails (its just 4 bolts) and put some rags underneath and hang the rails, and have someone crank the car for you while you watch for spray pattern. make sure they're all squirting a nice FINE MIST of fuel

then after the cranking stops, make sure they are NOT DRIPPING

if that's all good, we can proceed with some different stuff.
 

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Discussion Starter #5
Thank you for the ideas guys, it just seemed quite odd that its running fine, fill it up with gas and within a few miles of driving it doesn't wanna start. The car was driven occasionally, just not a ton. The fuel filter i replaced didn't have anything in it but I'm going to take off the new one I just put on and check it too. What is the fuel pressure supposed to be, I'm sorry i'm not familiar with these engines at all.
Yes Racy it has 60,130 miles on it. I know both previous owners. The interior is mint and the exterior is very nice and straight. No door dings or dents.
 

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As far as fuel pressure, and I know I will probably be corrected, it should be somewhere in the range of 38 psi to 45 psi at idle. There are other
specs for it such as with the key on and the vac line off and so on, but if you have between 38-45 at idle the fuel system is working as its supposed to. ed
PS- And with a nice low mlileage car as you say in good condition,dont
start throwing wrenches and hammers at it when /if you get frustrated with it, got it?
 

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Discussion Starter #7
As far as fuel pressure, and I know I will probably be corrected, it should be somewhere in the range of 38 psi to 45 psi at idle. There are other
specs for it such as with the key on and the vac line off and so on, but if you have between 38-45 at idle the fuel system is working as its supposed to. ed
PS- And with a nice low mlileage car as you say in good condition,dont
start throwing wrenches and hammers at it when /if you get frustrated with it, got it?
Im not a thrower, more of a swearer. :D Ok Ill check the fuel pressure at the rail. I think there is water in the tank from sitting. i just wanna get this thing running right. Well now because I cut the cat off I get to weld that back together too....idiot. :screwy:
 

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Since your coming back to GM and things are new, here's some resources for you.

shbox.com is a great lt1 resource. Be aware, however, that your 93 has some differences from the other lt1 cars from 94-97. Things like no maf, 700r4 trans instead of 4l60e, speed density batch fire fuel injection, etc.

In 4th gen section with title of "GM service manuals" you will find factory 93 manual for download. This is the best resource for your car. Also in sticky threads of 4th gen section, will be the 4th gen parts books for download.
 

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Discussion Starter #9
Oh great so this car is speed density?? Thanks for the links. Ill check em out.
 

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Discussion Starter #10
Jumpered the diagnostic port and it is throwing a #15 code. I searched on here but cant find it. Whats a #15??
 

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Dtc 15 is ect circuit, signal voltage high, low temp indicated. Basicly saying that voltage levels to ect are too high which is giving ecm a false low temp reading. This will mess up the air fuel ratio.

Could be a bad ect or wiring causing the problem.

93 service manual has the full poop on dtc15 and how to trouble shoot it.
 

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Discussion Starter #12
Dtc 15 is ect circuit, signal voltage high, low temp indicated. Basicly saying that voltage levels to ect are too high which is giving ecm a false low temp reading. This will mess up the air fuel ratio.

Could be a bad ect or wiring causing the problem.

93 service manual has the full poop on dtc15 and how to trouble shoot it.
Well that would explain a lot. I looked at the shbox.com site but could only find owners manuals no service manuals. Am I looking in the wrong spot??
 

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Yes, your looking in the wrong place. When I say 4th gen section, I'm referring to this forum. Parts books are in sticky threads, manuals are in regular 4th gen threads.
 

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Discussion Starter #14
Thanks for all the help guys. It was the coolant temp sensor on front of water pump. Went and bought one and plugged it in, didnt even install because I figured ambient air was about the right reading...popped right off!! Now I gotta figure out what to do with the exhaust since some dumbass(me) cut the cat off.
 
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