964 Check Engine Light Question

[ralendrum]

I know this may sound stupid but it is driving me crazy. I bought a 1990 C4 that is a ROW car (came from Japan but is LH drive). I took it to a "reputable independent shop" in Calgary and they really picked the car apart. One issue was that the person that had it before me had a "chip" installed. As soon as they heard this they went on and on about the check engine light not working and therefore someone had disconnected it. I drove the car home and stored it away for the winter so I did not verify this myself but according to a book (Dennison ?) that came with the car the check engine light was not installed until 1991. Does anyone know anything about this?

[Loren]

Have you run the car's VIN through the VIN Decoder here - to find out what country it was really made for?

I would do that first because there are different OBD requirements in different countries.

[ralendrum]

I ran the VIN ( WP0ZZZ96ZLS401952) and it didn't really give much other than it is a ROW and it is in fact a 1990 C$ Coupe.

[Loren]

Not sure about RoW 964's but a US 1990 C2 did have a CEL and a diagnostic plug.

So you would need the Durametic software or a PST2 tester with the appropriate round connector cable.

[norcal_tom]

According to Adrian Streathers book, only 1991 US cars had CEL's for CA. emmision requierments.

[Loren]

According to the (Porsche) schematics for MY1990 964 - they had the same.

It might have been a mid-model year change.

[ralendrum]

Thanks for the input. I believe that it was supposed to be a mid year change for 1991. Since I don't have this car in my garage I can't even tell you if it even has the light or not. I have a couple of jobs to do on my wife's 2000 996 (used to be ours till I bought the 964) then I will swap them around and look at this one.

Now off to deal with the runaway seat in the 996

[norcal_tom]

Yeah, my '91 has one, and it's an early model build. It would be interesting to know when they actualy started installing them.

[ralendrum]

Just a quick update to the mystery of the Check Engine Light. I removed the gauge and checked. There is a Check Engine light opening on the back of the gauge. The hole was filled by a white plug. The same type of plug filled several other sockets that are not in use in my car. I installed a bulb in the socket and the light comes on when I turn the ignition on and it goes out when the car starts but I don't think it is really connected to anything. I will leave the bulb in it just for curiosity.

[red-roadrunner]

Just a quick update to the mystery of the Check Engine Light. I removed the gauge and checked. There is a Check Engine light opening on the back of the gauge. The hole was filled by a white plug. The same type of plug filled several other sockets that are not in use in my car. I installed a bulb in the socket and the light comes on when I turn the ignition on and it goes out when the car starts but I don't think it is really connected to anything. I will leave the bulb in it just for curiosity.

Leave it in, as long as it is working properly, else, you will fail the SMOG / Emissions test if the light does not come on at the start/off after ignition. I have a different problem, my CEL comes on at pre-ignition, turns off after ignition, and comes back on after 45seconds or so. If the RPMs are 1100+, the light stays off. If the RPMs are at normal idle, the light comes on after 45seconds. If I rev the engine every so often (within the 45 sec window) the light stays off. Doe anybody have any ideas?

[Loren]

Just a quick update to the mystery of the Check Engine Light. I removed the gauge and checked. There is a Check Engine light opening on the back of the gauge. The hole was filled by a white plug. The same type of plug filled several other sockets that are not in use in my car. I installed a bulb in the socket and the light comes on when I turn the ignition on and it goes out when the car starts but I don't think it is really connected to anything. I will leave the bulb in it just for curiosity.

Leave it in, as long as it is working properly, else, you will fail the SMOG / Emissions test if the light does not come on at the start/off after ignition. I have a different problem, my CEL comes on at pre-ignition, turns off after ignition, and comes back on after 45seconds or so. If the RPMs are 1100+, the light stays off. If the RPMs are at normal idle, the light comes on after 45seconds. If I rev the engine every so often (within the 45 sec window) the light stays off. Doe anybody have any ideas?

You need to get your fault codes read - everything is a guess without fault codes.