I recently took my 93 Civic to get a smog check for some tags. However, the car has previously had its motor swapped with an Si motor. The mechanic said that the car was running rich but there seemed no issue with the actual engine. One of his suggestions was to buy new cats but they are really expensive and there was no guarantee that it would help. He then said to look for the original PCM/computer because the map had been changed because of the motor swap. The problem is that I purchased the car on OfferUp meaning I don't have contact with the original owner. Does anyone know where to get an original pcm or if changing it would actually work. I am asking for help because if I have to get the new cats I will but I don't want to buy it if I can just get a new PCM.

 

First, lets assume that your "Si" engine is a D16Z6. If this is the engine that you have, and it is internally and externally stock, you will need an ECU for an Si. The factory part number is 37820-P28-A00. The last three digits may vary slightly... but you will want the first digit to be the letter "A", a ZERO next, and then something between ZERO and five last. So, "A00" through "A05". If you find an ECU with an "A3X" or "A5X", and "X" being another number digit between ZERO and NINE, these will be an automatic ECU.
What is the part number of the ECU in the car currently ? Have you opened it up and checked to see if it is "Chipped" ?

 

The mechanic said that there was something wrong with the chip. So he asked me to look for a bone stock pcm or chip because the one installed is one used for every intergra/civic swap from a non vtech to the vtech version. Does the car being an automatic have anything to do with it. Also how would I check to see if it's chipped.

 

Take the lid off the ECU, take a pic of the internals, and post it up here for us to see.

 

Also, if the ECU is a P28, you could always remove the J1 jumper and essentially convert the programming back to stock. The mechanic should know this. Just seeing a chip inside the ECU doesn't tell you what programming is on it... nor the quality of the tune. If it wasn't programmed specifically for your engine, it is crap.

 

I went out to take a picture of the engine to see what it was exactly and then also the inside of the pcm to see if it was chipped or not. Also the there were two cables that were not connected to the pcm that can be seen in the second picture.

 

Pic 1: That ECU is TOTALLY STOCK. So if the mechanic states that the "Chip" is bad, he is referring to the large chip near the bottom left corner of the pic... with the "304" labeled on top.
Pic 2: The two open plugs are actually for testing: The 2-pin plug is to check MIL stored codes, and the 3-pin plug is used to monitor real time data with high end scan tools.

Look closely around the eight power capacitors to see if any liquid has leaked out. This can damage the board and cause major issues with specific circuits within the ECU.

 

So then would there be any other reasons that the car is running lean. Because if not the mechanic suggested to purchase new cats, but he said a specific part number and everything oem. However, I found aftermarket cats on a different website for half the price of the one he is making me buy. He said that it won't work the same and I'm just not trying to spend half the price of the car and still risking it not working. Any other suggestions on what to do?

 

Your Cat is NOT the problem. A clogged/bad cat will make the car lose power, overheat and choke out/stall.
You mentioned that the chassis is an automatic... the ECU you have pictured above is for a MANUAL car. What you need is a P28 for an automatic and not a manual... the last two digits of the part number will be between 31 and 53 as I stated above. For example: 37820-P28-A51. This will help the A/F values improve slightly because the auto transmission loads the engine differently at nearly all times. Now, depending on how "Rich" the readings are now, a computer change may not fix your issue completely and you pass smog.

Get the proper ECU, and then monitor your short term and long term fuel trims to see if they stay within +/- 12%. If they don't, you may have a bad O2 sensor or an exhaust leak ahead of the O2 sensor causing it to read falsely.

 

First off, I'm super confused because you said the car is an automatic but your picture clearly shows a manual trans. Also, if the car was running an auto trans with that manual ecu it just plain wouldn't work.

I imagine you are in California or a similar state that likely requires an OEM or CA exempt aftermarket cat. If you get a "federal" cat installed on the car, it will cost about half as much but won't pass visual inspection because states that require the better cats also cross check the numbers on the converter to confirm its correctness. Without knowing your location or the part number that the mechanic gave you, it's hard to help here.

- Check and clean your grounds and inspect the wiring for issues.
- Wiring will last a long time, but as soon as you start disturbing decades old things (taking your ecu in and out, swapping engines) it will go wrong quickly.
- Find a mechanic who has a scan tool for these old cars and look at your fuel trims.
- Make sure your MAP sensor is reading the same as your Baro sensor at key on/engine off.
- Make sure your oxygen sensor is reading correctly.