O2 Sensors with Comptech headers help

[PeachyMomo]

Hi all,

Does anyone have paperwork/diagrams for a comptech header?

I purchased a 95 last November and one of the previous owners had installed a comptech header and exhaust system. The car has been stumbling at low rpm's (feels like a large loss of power, I don't really push it into the higher end >4k, its just a mental thing. Recent purchase so I'm afraid of punching it when it's not working so great) so I've been going through the usual check list, I've:

-Cleaned throttle body (this fixed RPM's dying to 300 when I came to a stop)

-Replaced Spark plugs, I'm in Jersey and I am using it as a daily when the weathers above 60. Water has gotten into the rear bank and I've purchased some rubber strips that I plan on diverting the water to the sides with. I took out the coils the other weekend but didn't see anything wrong with them. I hit them with some compressed air and then some of that quick dry electronics cleaner. I popped them back in and went for a 30 minute drive and the car drove like it never did before. Threw my head back into the chair during acceleration.

- Now I'm chasing that high and from what I've read the o2 sensors are next. I did the recommended unplug the connectors on top and take it for a spin, it was smoother but the acceleration still wasn't anywhere near as that perfect day was.

- After I do o2 ill probably just splurge and get the new coil packs if needed.

Anyways back to my original point. I can access the pigtail connectors from the engine bay on top quite easily. I have no idea where the other ends, the actual o2 sensors, are going. I'm guessing it's something I'll have to do from underneath but any information would be helpful rather than going in blind.

 

[Old Guy]

I don't have any details on the Comptech headers; but, some relevant observations. If your car is 1995 production and North American market (you are in NJ) it should be OBDII which means that it should have four O2 sensors. One in front of the cat and one behind the cat on both front and rear cylinder banks. The O2 sensor in front of the cat does all the mixture control and the O2 sensor behind the cat just monitors the operation of the cat. All four O2 sensor connectors are accessible (sort of) from the top. Which ones did you disconnect because disconnecting the sensor behind the cat will not affect engine operation and should only generate an error code (which the front sensor would also do).

You can find copies of the service manual for your car on Prime, just use the search function. That service manual show you where the O2 sensors are on the OEM system and they should be in approximately the same location on the Comptech system. The O2 sensors are only accessible from the bottom of the car. Jack stands might work; but, a hoist would be the treat. If you know what the sensor looks like they will be fairly easy to spot on the exhaust system; but, not so easy to access.

If your car is OBDII, you should be able to use a scanner to check for stored error codes. A good scanner would also allow you to check the fuel trims while the engine is running. If you have no O2 sensor or fuel mixture codes and your fuel trims are small numbers (low single digits) I would be inclined to look elsewhere for problems.

If your car is 1994 production; but, called a 1995 because it was first registered in 1995, then it will not be OBDII and will only have the pre cat O2 sensors. The VIN number should decode the actual production date. You can still use the service check connector to retrieve any stored error codes in the ECU which would flag obvious problems with the O2 sensors. Unfortunately you cannot monitor fuel trims with the pre OBDII ECU. The service manual for the earlier cars will also show you approximately where the O2 sensors should be located.

Having just gone through this recently, the ignition coil covers have a rubber gasket along the side of the cover that faces the intake. There is no gasket along the side facing the exhaust. When I recently replaced my spark plugs, I discovered that when the plugs were last changed, the coil covers were switched front for back which resulted in the rubber gasket being on the exhaust side (easy enough to do if you are not careful). This means that water falling on the top of the engine can potentially run into the area where the coils are. That said, even though I wash my engine once or twice per year (with low pressure water) I did not have any sign of moisture in that area. When you fit your coil covers make sure that the gasket is on the intake side of the cover and that the gasket is in good condition and properly fitted on the cover. If the gasket is distorted at all you need new gaskets. I applied lots of silicon dielectric grease to the gaskets to help them slip into place on the valve cover without getting distorted. Each ignition coil also has a round rubber gasket on its base where it fits into the spark plug well. Grease this up well with silicon dielectric grease and it will help prevent any moisture from getting into the spark plug well if water does happen to leak past the coil cover. In addition to sealing stuff, the silicon grease reduces deterioration of the rubber gasket. Not sure on how you plan to install the additional rubber strips; but, I would not apply additional rubber strips under the sides of the coil covers. Anything that fits under the cover is likely going to lift it up reducing the sealing of the gasket along the top side of the cover making the water problem worse. If the top coil cover gaskets are in good condition and properly installed the coil covers seem to seal pretty well as long as you don't use a pressure washer on them. If you grease the coil base gaskets, even if the covers leak a bit the base gasket should prevent water from getting into the spark plug wells which is when you can get tracking and ignition misfires.

 

[PeachyMomo]

Thanks for the quick reply

It does indeed have the obd, after I unplugged the two connectors I found I pulled up the codes and got P0151 and P0131 which was exactly what I was looking for. I haven't taken a look at the fuel trims but that's something I'll take a look into.

As for the locations I was using this service manual I attached as a guide. The rear primary I have a relative understanding by just feeling around with my arm as to where it is, the exhaust manifold is just further towards the trunk than i thought it would be and I don't have a real angle from the top to get to it. The Front primary I have absolutely no clue. I was able to find an extension wire that ran from the front gasket cover all the way to the rear. I went diving with my hand around that center screw as seen in the diagram but there is nothing running back there. I'll try to upload some pics of that extension later this week (waiting for some rain to pass).


As for that last piece on the additional rubber, I'm not putting anything attached to the engine block itself. I'm planning on attaching something to the body trim that sits right under those vents or whatever they are called. Got the idea from this https://www.youtube.com/watch?v=bUx5blckXZs and https://www.facebook.com/DavisDesignFab/

Note I'm not buying it from that fabricator but it will be a similar implementation.