Check engine wierdness, need help

[Uisce]

Ok here's the deal. Every once in a while I get a check engine light, but it doesn't come on and stay on, it flashes. At idle it will go 3 seconds on, 3 seconds off over and over. If I rev it to 2000, it does the same thing, but faster, up to 3000, same thing but even faster, at 4000 it starts to skip a flash every now and then.

It doesn't do it all the time, just a couple of times a week. The problem is that it has now done it every time I have taken it for smog. All three times!

Nissan says there is nothing wrong, but offered to sell me a new ECU for 1200. Gee, thanks :loco:

Any help would be appreciated.

The car is an early 1995 OBDI

[idlafie]

Ok here's the deal. Every once in a while I get a check engine light, but it doesn't come on and stay on, it flashes. At idle it will go 3 seconds on, 3 seconds off over and over. If I rev it to 2000, it does the same thing, but faster, up to 3000, same thing but even faster, at 4000 it starts to skip a flash every now and then.

It doesn't do it all the time, just a couple of times a week. The problem is that it has now done it every time I have taken it for smog. All three times!

Nissan says there is nothing wrong, but offered to sell me a new ECU for 1200. Gee, thanks :loco:

Any help would be appreciated.

The car is an early 1995 OBDI

Stickshift or Auto Transmission????

Remove your passenger side kick panel & unbolt your ECU from the car frame. Look for the little screwdriver slot that allows you to put your ECU into Diagnostic mode.
Put the ECU into Diagnostic Mode by following the procedures listed under this link:
http://www.240sx.org/faq/index.html
Scroll down till you get to "ECM...Reading Troublecodes...DOHC
Follow the listed procedures and see what Diagnostic Trouble Codes your ECU kicks out....if any.
From what you are describing, it sounds like your ECU is already in Diagnostic Mode...which it shouldn't be....???
Anyhow, good luck...
ID

[Uisce]

Its a 5 speed, and thanks for the suggestion! I'm a step ahead of you there, I did that before I went to Nissan. All I get is 55, so there are no codes stored. I also thought it might be stuck in diag mode, but its not, I've checked and re-checked because that would be such an easy fix to such an annoying problem (no such luck).

The flashing very definitely and predicably changes with rpm, so I'm thinking perhaps something wierd with my crank angle or cam angle sensors, or maybe ignition or engine speed signals, but like I said, I get no codes.

[idlafie]

Before you go replacing anything, see if you can hook up with a buddy that also has a 240. Try swapping out his ECU with yours. If the problem disappears then chances are it could be ECU related and not sensor related.
Anyhow...hope this helps..
ID

[toraji]

whisky's problem is that he's an early 95, using an OBDI ecu. its not so common. =/
otherwise I would let him use my ecu. also it came on and went off quite quickly. When I drove his car and spun out, it came on, flickered a few seconds, and went off. it was quite wierdness as the title name states.

[idlafie]

whisky's problem is that he's an early 95, using an OBDI ecu. its not so common. =/
otherwise I would let him use my ecu. also it came on and went off quite quickly. When I drove his car and spun out, it came on, flickered a few seconds, and went off. it was quite wierdness as the title name states.

It's more common than you think....I know of three people, (myself included), that own an early 95 using an OBD I ECU...

Now if the ecu is flickered when you spun his car, then it's possible that he could have a loose or shorted wire somewhere in the ECU diagnostic curcuit. Sounds like this problem is gonna be a royal BEYOTCH to nail down. Easiest way to figure out what the source of the problem is to swap ECU's.

ID