possible Motronic sensor problem

[Jim Burnette]

I have a 1991 164 Base model with about 110,000 miles. It has just recently started to have problems with possibly the electronic ignition. This started happening only very rarely but has rapidly started occurring more & more often until now it happens about every 10 to 15 seconds apart. The engine will idle fine but if you rev it up to say about 2000 RPM or higher you can sit and watch the tach needle and it will just suddenly drop to zero and immediately go right back to the RPM you are holding it at. It is like the ignition spark was cut off and immediately turned right back on. When this happens the "check engine" light flashes on and then immediately back off. The engine does not have to be under a load as I said you can sit in neutral and rev it up and it will do it.
I would really appreciate any advice.
Thanks,
Jim

[Alfisto Steve]

First thing to be suspect of is spring loaded carbon button inside center of distributor cap or rotor.

Pull 3 8mm hex head bolts and inspect inside cap to be sure buttom not worn out. If OK check rotor tip and then use meter to test resistance from center where carbon button rubs to tip for 1k ohms.

[Jim Burnette]

Thanks, I just got back in but I will check the distibutor cap out tonight.
Again, thank you for your advice.
Jim

[rj7630]

I had the exact same probelm with an older Nissan Maxima and it turned out to be the crank angle sensor going bad. You might check that out too.

[Alfissimo Int.]

Quote:

Originally Posted by Jim Burnette I have a 1991 164 Base model with about 110,000 miles. It has just recently started to have problems with possibly the electronic ignition. This started happening only very rarely but has rapidly started occurring more & more often until now it happens about every 10 to 15 seconds apart. The engine will idle fine but if you rev it up to say about 2000 RPM or higher you can sit and watch the tach needle and it will just suddenly drop to zero and immediately go right back to the RPM you are holding it at. It is like the ignition spark was cut off and immediately turned right back on. When this happens the "check engine" light flashes on and then immediately back off. The engine does not have to be under a load as I said you can sit in neutral and rev it up and it will do it. I would really appreciate any advice. Thanks, Jim

[Jim Burnette]

Hey Guys thanks for your help. I just got the chance to check the distributor cap and you were right. The whole end of the rotor was broken off, I am actually amazed it would run at all. I was so certain it was one of the sensors that I did't take the time to check the basic things first.
Again thanks Steve, Randy & Jason for replying,

Jim

[Alfisto Steve]

Good deal as sensors do go bad but usually they sense something else is wrong.