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Old 01-28-2013, 05:28 PM   #1
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Default 94 Hesitation when warm backfires through Intake??

Well Here is one for you boys and girls.

This has been an ongoing problem for 2 years. 94z 91,xxxx miles. CIA,SLP exhaust. TB bypass, 180 degree thermo.

This issue came out of no where, and I cant figure it out. Car has a small miss once the car gets warm. When you shut the car off then try to start it right back up it hesitates. It cranks for 5-10 seconds stumbles then comes back to life. I have replaced the Opti Twice. Both with name brand Optis. Nothing. New plugs and wires. Nothing. New MAS, Nothing. Also when the car is warm and you blip the throttle it has a small hesitation and back fires through the intake. It almost sounds and feels like a timing issue. I have taken it to a friend that ran Fuel Pressure test and to test the O2 sensors. Both read great. No Check Engine Lights are one. Car also has a small whine. It sounds like the smog pump is running. Its not the fans because this sounds is not as loud and there is no air moving. I am at a loss. There is a small black wire, Drivers side Near that CIA. I oringially thought it was a ground wire. Hooked up a quick connect to ground it. Come to find out the wire has power. I only have a test light so I cant tell how much. But the light isnt has bright when you hook it up to this wire as opposed to the batter. So 3-5 volts. This wire only shows hot when the car is running and that whine noise starts?? I can not find where this wire goes. I will attach a picture.

Thanks for any help and information. I am trying to keep from taking the car to a shop. Because I know I am going to get killed on Shop time with some guy trying to test everything.
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Old 01-28-2013, 05:32 PM   #2
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The wire with the male quick connect end is the wire I am talking about. Its down near the frame rail, drivers side, near the fan shroud/plastic. It comes out of the main wiring harness that goes into the fuse block and runs under the car support. The black wire with the female quick connect is a factory ground???? These are located on either side of the plastic cover for the radiator and fans.
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Old 01-28-2013, 07:24 PM   #3
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I also forgot to say I put in a new Coil, ICM and looked into the fuel pressure regulator. I also put in a new fuel filter.
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Old 01-28-2013, 07:57 PM   #4
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Have you actually used an obd1 scanner to scan for codes? I ask because there are codes that, when set, don't turn on the check engine light and affect how engine runs.

Seeing your car is 19 years old, I would check out opti wire harness, check all engine and pcm grounds, pcm power wires, then start checking the pcm connectors. Checking the pcm connectors involves the use of a multi meter to check to see if the proper voltages are present at the correct time. Checking wiring to sensors wouldn't be a bad idea either.

Checks of wiring includes looking for broken insulation, ohming wires to check for opens in the wire. Checking connectors for burnt,bent, and poorly fitting pins, etc.

Go to 4th gen section and download the factory 94 service manual. Volume 2 will have driveability section, and complete wiring diagrams. Driveability section also has the pcm connector chart that tells what voltages to expect when testing, as well, as, the pcm symptom chart that tells what symptoms you get when each pcm wire has a fault. Much component testing in section also.

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Old 01-28-2013, 08:06 PM   #5
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Ok, thanks. Can anyone explain what this wire is????
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Old 01-28-2013, 08:10 PM   #6
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Also sorry for the Title confusion, Mind was wondering on another issue on another car?? This has gotten me so frustrated I cant even think strait
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Old 01-28-2013, 09:26 PM   #7
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You wrote something about hesitation. You said you replaced all ignition components. This said the two things that come to mind is the gap on the plugs ( if incorrect could cause you hesitation and the other is your egr valve. A clogged egr can cause hesitation upon an increase in throttle. No need to replace it as most often all they need is cleaned. I have no idea about that wire. It has a newer connector so I assume it will connect to something that your over looking by chance. Good luck!
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Old 01-28-2013, 09:33 PM   #8
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I put those connectors on thinking it was a ground. But its not????
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Old 01-29-2013, 10:29 AM   #9
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Quote:
Originally Posted by 94sleeperz View Post
I put those connectors on thinking it was a ground. But its not????
I would look harder where this wire may have come from or connected to. Or if it seemingly doesn't cause a problem then tape it and forget about it.
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