Rough idle=optispark?
02-19-2011, 02:38 AM
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Rough idle=optispark? Hey guys. I just bought a 95 z28 a few days ago. I drove it for two days and it was perfectly fine. While i was on my way home one night, I took a turn at like 5mph and the car just died on me. I coasted it to a stop, then tried to start it. It started back up but it was idling very rough. I gave it a little gas and it was popping alot. So i shut it off and had it towed home. I looked at the wires and i dont see any arcing. From what i have been reading it could either be the opti, icm, or plug wires. I know the wires and plugs were changed about 5k miles ago. Along with a new cap and rotor, not the whole distributor. The opti has about 135k miles on it so im thinking that it very well could be the opti. I took a video of it for you guys with more knowledge to check out. I tried to scan it for codes and im having a really hard time doing that. You will see in the video that when i start it up, no cel is on until i give it some gas then when the rpms drop down, it goes on. I have scanned it with several different code readers to no avail. They are all able to read obd1. I know all about the 95's being obd 1.5. Im at a loss as to what it could be. It sounds like a heavy cam in it right now. The car is completely stock. It sounds like one or two wires came off or got burnt. Im unable to check to make sure for another few days since i hurt my back a few weeks ago. As soon as i can, i will look forsure. I just wanted to get this out there to see what other people think. Thanks and sorry for the lengthy book..lol..Mike
http://s283.photobucket.com/albums/k...=VIDEO0002.mp4
http://s283.photobucket.com/albums/k...=VIDEO0002.mp4
02-19-2011, 07:45 AM
#2
Id say an opti is in your future. Before you do that, are you POSITIVE that all the plug wires are good, connected to plugs tight, and connected to the opti tight?
You may want to look into chanler(sp) opti. They are cheap and many people have had success with them.
You may want to look into chanler(sp) opti. They are cheap and many people have had success with them.
02-19-2011, 01:40 PM
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Im not a 100 percent that they are connected tight. I will have to check in a few days. As for the coil, what would be the symptoms of it going bad? Thanks for the help.
02-19-2011, 04:32 PM
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its very ez fix just move your intake youll see a wire coming out from under or behind water pump(looks like a spark plug wire) going to the coil it would be that wire being almost disconnected or corroded; plug it back in if it look lose until you buy new one and replace it a new coil wire around 20$. mine had sim problem, it was kind of shaking hard when stopped , sounding like it gonna die out , rough idle.
02-21-2011, 06:58 AM
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Ok I just looked at the coil wire. It was on there nice and tight. All the wires are connected tight. The wires are fairly new too. Im starting to think its the opti. Should I have the icm tested before I start preparing for a opti install? Any other ideas? I apreciate all the help. Mike
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02-21-2011, 10:59 AM
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Trust me im not the type of person to just throw parts at it. I have just got the icm tested and its fine. The only reason I think it could be the opti is cause its popping out the exhaust when I give it just a little bit of gas. Plus I think its the origonal opti on it. The cap and rotor were replaced two years ago but the opti wasnt. How do I go about checking the fuel pressure?
02-21-2011, 12:07 PM
#10
yeah but it could be fuel problem also. You need a fuel pressure gauge. You can get one from the parts store.
There is a shraeder valve on the back of the intake. It looks similar to the valve on a tire. There is a black cap on it. Remove it, screw the pressure gauge on it. Then prime the pump and see what the pressure is(turn key all the way without starting it) be around 45-50ish. It should hold steady in the 35-40's for a while once the pump turns off. watch the gauge for a few miutes. then start the car and watch the pressure. should be in the 40's. If its not in the 38+psi range then you have fuel issues.
There is a shraeder valve on the back of the intake. It looks similar to the valve on a tire. There is a black cap on it. Remove it, screw the pressure gauge on it. Then prime the pump and see what the pressure is(turn key all the way without starting it) be around 45-50ish. It should hold steady in the 35-40's for a while once the pump turns off. watch the gauge for a few miutes. then start the car and watch the pressure. should be in the 40's. If its not in the 38+psi range then you have fuel issues.
02-21-2011, 12:56 PM
#12
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Have you pulled the plug while it was running to see if there is a spark?
What about the timing chain? It sounds just like my K5 that skipped a tooth. When was it last replaced?
What about the timing chain? It sounds just like my K5 that skipped a tooth. When was it last replaced?
02-21-2011, 02:16 PM
#13
The rotor and cap are good to change, but when an opti goes bad...its usually the high/low res encoders inside the opti that control the ignition.
If it was a fuel issue, I'd be looking into an intermittent/failing pump and the FPR. Check the vacuum line to the fpr to make sure it's getting the proper reference from the intake manifold as well.
If it was a fuel issue, I'd be looking into an intermittent/failing pump and the FPR. Check the vacuum line to the fpr to make sure it's getting the proper reference from the intake manifold as well.
02-21-2011, 07:09 PM
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Max - I havent pulled any plugs while running. The car is having a hard time starting now due to the battery being drained. The timing chain im not 100% on. Im assuming that it was replaced when the motor was.
Qc - i understand that the optical part of the opti is what goes bad. So it could very well still be the opti? I will check the fuel pressure with a guage tomorrow. As far as checking the reference from the vac line to the fpr, could you enlighten me a little more as to how and what that does? I appreciate the help. Mike
Qc - i understand that the optical part of the opti is what goes bad. So it could very well still be the opti? I will check the fuel pressure with a guage tomorrow. As far as checking the reference from the vac line to the fpr, could you enlighten me a little more as to how and what that does? I appreciate the help. Mike
02-21-2011, 11:32 PM
#15
The fuel pressure regulator...regulates your fuel pressure! it does this based off the engine's vacuum. The more you open the throttle, the less vacuum will be in the engine, and the fuel pressure will increase.
If the vacuum line is damaged, this can cause your FPR to not function properly.
If the vacuum line is damaged, this can cause your FPR to not function properly.
02-23-2011, 12:39 AM
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Ok because of the weather we had today, i had no time to check anything. I will be checking in the morning so i can update with the numbers from the fp test. As far as the cooliant temp sensor, i cant see how that would have anything to do with it. If i am wrong then please correct me. I already looked over the intake tubing as i took it off and there is no rips or anything on it so that isnt it. Thanks for the help guys, mike
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