ecu/engine electrical problems
 

First let me give you some background on my car:
I have a 95 240sx with a fidenza flywheel, a cheapo intake with a nice Apexi intake filter. Those are the only engine mods I have. My 95 is also OBD II, I only use premium gas.

I have recently swapped my auto transmission for a manual I managed to get a lot of parts, but unfortunately since I live in an apartment and have no place to do the work myself, I had it done at heavythrottle in upstate NY.

I first noticed the problem before I had the swap done, once my tach cut out on me while driving. It came on after a driving a while more, so I didn't think much of it. One day I was also fooling around in my engine bay and I had to unhook the temp sensor before the MAF to do something. When I put it all back together the check engine light came on, so I checked the codes, and they were the neutral/park switch, and detonation. I checked the resistance of the temp sensor, it was within specs, so I reset the ECU and it didn't go off for a while ( a couple of months) so I didn't think anything of it. Maybe the car just got angry at me for disconnecting the temp sensor or something.

Fast foreword a couple of months, and I have had the tranny swap for a while now. The check engine light starts to come on again, and when I pull the codes, it's the park/ neutral switch, and detonation sensor. I called up heavythrottle, who were a little dismissive over the phone, the guy told me he really didn't know about it because he was closing his shop, but he did tell me that they did hack the harness up a bit when they switched out the auto/ecu for the manual one, but that was it. He wouldn't even tell me where they cut the harness.

So I reset the Ecu, and tried to think of a shop to take it to. In the meantime my car develops a "shudder" at idle. Sometimes the rpm's will bounce between 750, and 1100 when the car is warm, especially if I have the fan on (haven't tried AC), or the rear defroster (alternator related maybe?). the lights also dimmed, but that is not frequent, only sometimes. I tried replacing the belts, the PCV valve, and doing an Seafoam engine cleaning, to no avail.

Still not being able to find a shop the next time the tach cuts out the check eng light comes on it reads park/neutral switch, detonation, and crank angle sensor. It then does something weird (this makes me think it is really just an electrical short, and there is nothing wrong mechanically) the ecu light will randomly blink on and off if I am driving the car and if I shut off the eng completely and turn it back on again it will stop blinking and stay off. I am not sure what to do or if multiple things are broken. Every two weeks to two months the check eng light will come on, I did take it to two shops that found nothing, so I am not sure. My car runs really nicely otherwise, no burning oil or anything, I even passed an NYC inspection. Please give me any suggestions you can I am really trying to figure this stuff out.


One more time a short list of the problems:
1. Check eng light will come on codes are: park/neutral switch, detonation sensor, and crank angle sensor. It will now sometimes blink randomly. If ecu is reset it will be fine for 2 weeks to two months
2. The rpm's will bounce between 750, and 1100 when the car is warm, especially if I have the fan on (haven't tried AC), or the rear defroster (alternator related maybe?). The lights also dimmed, but that is not frequent, only sometimes
3. Tachometer will cut in and out sometimes.

i'd try a diff ecu

not a bad idea, I will see if I can pick one up cheaply, anyone else have any ideas?

take it back to heavy throttle and demand them to check it since they were the ones who hacked up the wiring harness, they are liable for any damage it has caused.

I spoke to the guys at Heavy Throttle, and they are really not interested in helping. SInce the ECU light was not on when I left their shop, their take on it is that it is not their problem. I don't think short of lawyering up I will get any results from them.


On the plus side I did find a mechanic that seems to know what he is doing. I was driving by my College and I saw a bunch of different types of rare/strange cars (for instance that day he was working on a 1950's Roles Royce) I stopped and asked a couple of questions. The guy that worked there offered to hook my car up to his ECU reader free of charge just to get an idea of what was going on.

After I explained to him the situation, he came up with three ideas of what could be wrong, in this order:
1. Heavy throttle used the wrong year ECU
2. Heavy Throttle did not do a good job hacking the harness, and had some bad connections
3. Two sensors I have may be bad, but he does not think this is the problem (and neither do I)

We will see what happens next, I will go back as soon as I can locate a cheap 95 ECU (my car was made 3/94 so I have to use the earliest S14 manual ECU made) if the ECU swap out does not work I will start going down the list from there. Hopefully I will find something.

gl bro