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Car wont start/way too rich


Spike243

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Hi I'm having a problem with my 82zxt where it wont start at all and I believe its because its too rich. Car was running extremely rich yesterday (~10AFR) and now today it won't start at all. I have checked the chts and replaced it with a new one. The sensor read about 2000 ohms at 60 degrees. I also completely replaced the wires to the computer as to eliminate the sensor reading too much resistance all together. The car has been having recent issues where it will run at stoich up till about -7 vacuum and then immediately plunge to under 10 afr's. The only idea I have at this point is the FPR could be faulty and causing excessive fuel pressure? Oh and I have gone through and cleaned all the grounds and electrical connectors I could find.

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Quick update. I tested the fuel pressure and it is holding about 33 at cranking so that is correct. I pulled the clips off the injectors and manually powered them and they all click open and closed so I don't think the injectors are seized open. I cranked the car over with the injectors disconnected and it will fire and run for about 5 seconds so I know for sure its not a spark issue. I also retested the AFM and it checks out fine. I'm at a total loss to why it is flooding.

 

The car will not fire with the injectors connected.

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To confirm, are you checking resistance directly on the CTS or at the ECU connector?

 

The readings at the sensor and at the ECU connector are identical. The sensor read 4k at about 50 degrees which I believe is within spec. I did get the car to start and run just barely. If I give the car a vacuum leak it will idle easily but it hovers around 10.6 AFR. It is still not drivable due to rich misfire though. Any suggestions?

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Did the engine run right before, and this problem came up out of nowhere, on a perfectly right-running engine?  Or is this a problem that happened after some recent work?

Its been a gradual issue that suddenly got this bad. I just took the car on a 4 hour drive and at cruising speeds the AFR was a perfect 14.7. When the vacuum got to about -5 and into boost the car would go extremely rich. Now the car is reading extremely rich all the time.

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The readings at the sensor and at the ECU connector are identical. The sensor read 4k at about 50 degrees which I believe is within spec. I did get the car to start and run just barely. If I give the car a vacuum leak it will idle easily but it hovers around 10.6 AFR. It is still not drivable due to rich misfire though. Any suggestions?

I have a 280z so I am not sure about the addition of the turbo to the troubleshooting. I had a very similar problem in that my car would run if I also introduced unmetered air to offset the rich condition but mine ended up being a bad wire connection from CTS to ECU. But you have ruled that out. So.....I need to think some more.

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I have a 280z so I am not sure about the addition of the turbo to the troubleshooting. I had a very similar problem in that my car would run if I also introduced unmetered air to offset the rich condition but mine ended up being a bad wire connection from CTS to ECU. But you have ruled that out. So.....I need to think some more.

Yea I'm clueless. Everything points towards a bad CHTS but the ECU connector reads the same resistance as the sensor and the resistance is within spec. 

 

When the AFM is tested the potentiometer is supposed to sweep from high resistance to low resistance?

Edited by Spike243
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Another update: The car is now running properly again. I took the AFM apart and found that the contacts slipped and were rotated far enough counter-clockwise that at full open, they didn't contact the resistor part anymore. When the flap was fully closed the contacts were about 1/4 inch too far rotated and this is what caused the rich situation across the map. It simulated a faulty CHTS almost perfectly. I also tightened the toothed wheel 3 teeth (clockwise)

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