crazy rpm needle and acceleration problems

[JohnD1079]

I think that I have found the problem. If everything is good (distributor, coil, wire ground etc.. but the Tach is crazy and the engine misfire, maybe the 15 years old ECU is dying. When I smash on the ECU, the problems goes away for 1 to 2 min, if it happen again, I smash and it works again. Otherwise, I can barely move the car.

I will go the the JY this morning to find a immaculate ECU that still work.

Edit: It does work. So the ECU is not the problems. There is definitly something to do with engine bay temperature because today is a cold day. If I keep driving, the problem disapear. If I stop the engine or I stop at a redlight, the problem will come back.

I am no expert, but im pretty sure the ECU isnt the cause, and smashing it isnt going to help either. Why would you go get salt proofed in July? Anything else that you did that we dont know about?

Usually when you buy a a new dizzy it does not come with the ignitor. Ask the mech if you got another ignitor witht he dizzy or if he used the current one you have. While your at the JY pick upa bunch of ignitors.

When did this problem start happeneing? Anything else you did other then the saltproofing?

[Marcalap]

Thanks for the reply.

The distributor was changed 3 months ago. At the garage, they borrowed me another brand new distributor. It comes with everything (cap,rotor,igniter,sensor etc.. just plug and drive). I also tried another coil and changed all spark plug wires.
I tested another ECU. 5 months ago, I did a big maintenance;air filter, oil filter, fuel filter, spark plug and wires, tranny fluid, brake fluid, EGR PORT CLEANING,IACV cleaning, Fast idle thermo valve check. The distributor (a 17 years old one from a 91 accord) died 1 month after the maintenance.

This afternoon, I will bring the car to another place.

[RiceKillinSi]

Have you checked your main relay? It seems like the dizzy, plugs, and wires are not the problem. and the main relay would explain why you only have problems on hot days.

[Marcalap]

FIXED!!!!!

A ground wire terminal for the ECU was corroded. This wire is 6 inch below the air intake pipe. With an oscilloscope, we can see that signals to the ecu was very noisy.

Thanks for your help.

[xafbx]

hey i have this problem also,
but my ignition swtch stopped working,i have to connect to wires to turn on the car,but ever since that day my rpm goes crazy like making it misfire also/
my car is a automatic,
idk if its cause of the ignition switch is making it go like that or because there is something else wrong with it??
where u say the wire was below the intake?

[wed3k]

FIXED!!!!!

A ground wire terminal for the ECU was corroded. This wire is 6 inch below the air intake pipe. With an oscilloscope, we can see that signals to the ecu was very noisy.

Thanks for your help.

where is this again?

[Marcalap]

hey i have this problem also,
but my ignition swtch stopped working,i have to connect to wires to turn on the car,but ever since that day my rpm goes crazy like making it misfire also/
my car is a automatic,
idk if its cause of the ignition switch is making it go like that or because there is something else wrong with it??
where u say the wire was below the intake?

The tach is driven by a 0 to 0.3V sinusoidal signal. A bad ground could produce signal noise bigger than that. When the tach shows high rpm, the ECU will advance the timing making the engine miss. In your case, if your problem started after the ignition switch broke, it could be related. A wire could be damaged but I don't know how it could corrupt the signal of the tach. ECU ground, Distributor ground etc.. definitly could produce the crazy needle. Check all the ignition switch wire to be sure there is no one missing or something. It could be just a coicidence.
It took only 1 hour for a good professionnal (many did not had a clue) to diagnose and find the bad ground on my car. But it can be much longer because electrical problems are hard to diagnose and have little profiability for commercial garage (only some wires and bolts to change).

In horrible environnement for cars like in my region, corrosion is a big issue. If your environment is dry and your car engine bay is not too corroded, the cause of your problems should not be the same as me. It doesn't seem to be very common anyway.

There is a ground terminal somewhere under the air intake pipe (the pipe must be removed to access this region easely). I am not really sure how to tell where the terminal is located (every things under my hood is black). I will try to find a good underhood picture.