another 3800 rpm wall... I've tried everything
03-31-10, 02:58 PM
#1
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another 3800 rpm wall... I've tried everything
Here is the deal. I have been following related threads for the past few days trying to solve this problem for myself with no luck. The car revs smoothly until 3800 rpm and falls an its face. If I accelerate at part throttle it will pull harder above 3800 than at full throttle.
The car:
88 n/a convertible
Just replaced motor
Things I have tried:
callibrated tps
set timing
swapped out secondary injectors
tried new injector clips
checked voltage at secondary injectors (good)
checked for 12v at the four light green wires on small ecu plug (all good)
checked for 3.5 volts at ecu connector 2b (good)
checked all pressure switch wires (all good)
intercepted pressure switch ground wire and re-grounded (no change)
opened up ECU to look for burned circut (all good)
intercepted ECU grounds and re-grounded (no change)
added various engine-to-chassis grounds (no change)
ran car with pressure sensor capped (no change)
ran car with auxilary ports wired open (no change)
Sorry to post on this subject again, but I am out of ideas here. Any advice would be great!
Thanks,
-John
The car:
88 n/a convertible
Just replaced motor
Things I have tried:
callibrated tps
set timing
swapped out secondary injectors
tried new injector clips
checked voltage at secondary injectors (good)
checked for 12v at the four light green wires on small ecu plug (all good)
checked for 3.5 volts at ecu connector 2b (good)
checked all pressure switch wires (all good)
intercepted pressure switch ground wire and re-grounded (no change)
opened up ECU to look for burned circut (all good)
intercepted ECU grounds and re-grounded (no change)
added various engine-to-chassis grounds (no change)
ran car with pressure sensor capped (no change)
ran car with auxilary ports wired open (no change)
Sorry to post on this subject again, but I am out of ideas here. Any advice would be great!
Thanks,
-John
03-31-10, 03:20 PM
#2
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taken from the FAQ
https://www.rx7club.com/showthread.p...55#post5131155
Originally Posted by Icemark
I have this hesitation whenever I accelerate right around 3500-4000 RPM
The dreaded 3800 RPM hesitation is cause 90% of the time by poor ground connections between the engine, the battery, and the car. Clean or replace all the under hood ground connections. On 86 model year cars , replacing/regrounding the pressure sensor's ground wire has helped (do not re-ground a 87 or later model year). If there is still a problem after that, look at cleaning the fuel injectors and (on a N/A) that your 5th/6th ports are operating correctly.
The dreaded 3800 RPM hesitation is cause 90% of the time by poor ground connections between the engine, the battery, and the car. Clean or replace all the under hood ground connections. On 86 model year cars , replacing/regrounding the pressure sensor's ground wire has helped (do not re-ground a 87 or later model year). If there is still a problem after that, look at cleaning the fuel injectors and (on a N/A) that your 5th/6th ports are operating correctly.
03-31-10, 03:33 PM
#3
You could check for the pulsing of the secondary injectors by using a led light. Use the positive wire of the led light and backprobe pin 3I (Black/White wire). Then take the negative wire of the led and backprobe pin 3H (LG/W) which is the fron secondary injector and run the car up to the point where the problem occurs and see if the light pulses rapidly. Do the same thing with rear secondary, pin 3F (LG/R). Also, are you sure your newer injectors are high impedance?
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