Check Engine Light, goes off @ 4000 ish rpms

Unknone86
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Check Engine Light, goes off @ 4000 ish rpms

Postby Unknone86 » Tue Oct 22, 2013 5:59 pm

Hello,

Its been a while since I've been on the forum, like the new look.

I'm having issues with my check engine light. Basically stock early 4age, with MSD 6al.

It is on until about 4100rpm then goes off and stays off until the motor drops below 4000.

The code is saying to change the coil or distributor. I've changed the coil with different MSD coils and no luck. I rebuilt the distributor a few years ago and don't have a different one to try.

Any ideas? Is there a way to check the distributor?

Can the check engine light be turned off by resetting it some how?

Thanks

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jondee86
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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby jondee86 » Fri Oct 25, 2013 5:33 am

Inside the distributor is all solid state... just reluctors to read the timing
wheels, and generate very low voltage signals for the ECU. You could check
the wiring for signs of chafing or damage just where the wires enter the
distributor and flex a lot... and make sure the connector plug is pushed
all the way in.

ECU reset happens any time you disconnect the battery for a few minutes.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby Unknone86 » Mon Oct 28, 2013 9:44 pm

Thanks jondee86. Yeah I figured that the only ecu reset was disconnecting the battery but I had to check.

I'll look over the distributor wires one more time but I might have to go old fashion and disconnect the bulb.

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BakaBaka
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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby BakaBaka » Sun Nov 03, 2013 8:11 am

Just because the light isn't there anymore if you take the bulb out doesn't mean the problem is gone. I would look into it more thoroughly. The AE86 is simple mechanics.. shouldn't be too hard to solve. If the CEL is pointing to ignition coil/timing, I'd start there. Does the car behave abnormally when you go past 4k rpm? Any bogging/misfiring.. etc?

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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby OG UTOTMO » Sun Nov 03, 2013 8:55 pm

Tps sensor needs to be replace i know this since it happened back in 2000 on my car. the car runs fine is just the check engine light is on but once you pass 4k it goes away

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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby boogaov » Mon Nov 04, 2013 4:12 am

My car has been doing the same for many months now. It's code 6 if I'm not mistaken which in theory has nothing to do with the TPS. My light goes off at 4K and the car behaves normal during all rpm ranges.

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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby jdmbrazilian » Tue Jun 23, 2020 12:45 pm

was this ever resolved having the same issue code 6 and light goes off after 4200 RPM on the highway

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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby totta crolla » Wed Jun 24, 2020 1:36 am

Ok I'm going to throw this out there and it is what I'm thinking, not what I know for certain but it may be worth discussing...
Could an O2 sensor be at fault, one that is configured in the ECU to go open loop at above 4200rpm so it would stop reporting a fault over this rpm? Is there another sensor that would act consistently in this way? Is anything else triggered around that rpm? TVIS is approx. 4650rpm and has no fault reporting as far as I'm aware.

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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby TwincamBoricua » Tue Feb 23, 2021 9:02 am

Was this ever resolved? I’m having the same issue on my FX16. Check engine light turns off right at like 4100rpm and as soon is it drops below that it turns right back on. It originally turned on after I did a burnout/hard pull. I was wondering what was done to fix it. I get codes 6 and 11. I checked the plugs on the distributor and the tpms but they looked normal. Gonna test the resistance on the distributor when I have a chance. Any thoughts?

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jondee86
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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby jondee86 » Tue Feb 23, 2021 3:57 pm

1. Does the CEL light come on in every gear at around the same rpm ? Like if you go from
a standing start and rev to 5000rpm before changing... does it on come on in every gear
or only when you get to 3rd or 4th ?

2. If you raise the rpm to 5000 in neutral while stationary, does the CEL come on ?

The factory Service Manual indicates that the primary reason for a Code 6 being set is a
problem with the Ne (rpm) signal from the distributor to the ECU. The Ne signal is generated
bu the VR sensor on the trigger wheel with the greatest number of teeth (typically 24 teeth).
The output of a VR sensor can be influenced by a number of factors... airgap too wide, wiring
or connector plug resistance too high, damaged or faulty VR sensor.

Testing the Ne sensor resistance at the distributor with the wiring connector plug disconnected
is a good place to start. Check the airgap between the VR sensor and the teeth on the trigger
wheel. Look very carefully at the wiring where the sensor wires exit the distributor to see if
there are any "soft spots" in the wire that can indicate the wire is broken inside the insulation.
Tug, shake, push, pull the wires every which way with your multimeter attached to see if there
is any change in resistance as you manipulate the wires.

The Code 11 is likely a separate issue. Maybe your TPS has a problem if it is the original
factory item with 300,000 miles on it :)

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby TwincamBoricua » Thu Feb 25, 2021 8:56 am

The cel comes on and stays ON when I start the car. The cel turns OFF about 4-5 seconds after the rpm goes over and stays above 4100rpm. As soon as it goes below 4100, it turns back ON. And the cycle repeats the 4-5 seconds when I go over 4100.

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jondee86
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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby jondee86 » Thu Feb 25, 2021 12:43 pm

My bad... was thinking the light went off at high rpm but wrote that it came on... DOH !!!
You can make the checks and tests that I suggested. And if the light is ON when the engine
is idling you can get someone to watch the CEL while you manipulate the wiring near the
distributor.

When the car is running and you accelerate past the point where the CEL turns off, do you
notice that the engine suddenly pulls a bit harder ?

Does the engine seem a bit gutless while the light is on ?

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby TwincamBoricua » Fri Feb 26, 2021 5:20 am

I don’t really notice a power difference, just a bit more torque in the higher rpms which is normal and no gutless feeling in the lower rpms. It pulls pretty good all the way up the rpm with no noticeable change when the light goes off. And to answer your earlier question of does it matter what gear I’m in, the light goes off anytime the I rev over 4100 whether I’m at a complete stop in neutral just revving it up or no matter what gear I’m in, as long as it’s over 4100, it will turn off.
And thank you so much for your input on this!
I appreciate it!

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jondee86
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Re: Check Engine Light, goes off @ 4000 ish rpms

Postby jondee86 » Fri Feb 26, 2021 3:41 pm

No worries... I love a good mystery :) Was thinking that maybe the Ne signal from the
distributor was weak until the engine reached that 4100rpm tripping point. If it was and
if you have the VAST ignition system, then the ignition would stay at base advance (10 DBTDC)
until the signal got strong enough for the ECU to start controlling timing.

Doesn't seem likely given that you don't notice the engine pick up when the light goes out.
But it might be worth putting your timing light on the engine while it is idling (without
jumping the diagnostic plug) and see what you have. Should be around 15-16deg. Then if
you jump the plug the timing should drop to around 10deg and the rpms drop a little.

If your engine does not behave like that more investigation will be required :)

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.