9T3VETTE

1993 LT1.

So, I installed a set of long tube headers over the weekend and they do not have the AIR pipe fittings.

I pulled the pump located in the drivers fender, the hose from the pump to the bypass valve, the valve itself and the hose from the valve to the metal air tubes on each manifold. There is one vacuum line on the bypass valve going to the intake manifold and an electrical connection. It was my understanding that everything running from the air pump was fair game to pull out.

Well, I got around to starting the car up and it has a "check engine light".

Pulled the code and I get H26. 'H' obviously meaning history, but the 26 refers to this:

Code #26: Quad-Driver Module #1 Circuit.

I was under the assumption on an OBD 1 car I would not throw a code.

Any ideas?

**updated with pictures

9T3VETTE

Well I reset the ECM, i'll see if the code comes back when it's taken to the exhaust shop. Until then, here are some pics

The AIR system taken out



Close up



Vacuum line from bypass valve to manifold caped off

HlhnEast

Did the headers come with the O2 bung? If not you will need to buy a bung and have it welded in and install the sensor. I have read that sometimes a heated O2 is necessary as well. Hopefully someone will provide more info on this or say I am fullofcrap, lol.

Good luck!

aminnich

It just needs to be tuned out of the ECM (egr delete). But like c4cruiser said you will still need the O2 sensors.

c4cruiser

An O2 sensor will still be needed. A heated sensor "tricks" the ECM into going into closed loop a lot quicker. Adding the stock O2 sensor on the collector or reducer works, it just takes longer for the sensor to get hot.

9T3VETTE

Yes, the car has o2 bungs and new sensors in the long tubes. I would have a whole list of other codes and problems if those were not installed

The EGR was not deleted, only the secondary AIR system (see pictures).
It was my impression that the car would only get a check engine light if it was an OBDII car with the emissions delete, but not on an OBDI?

samsonb

You might want to check out your injectors as they look like the bad Multecs that fail.

toptechx6

You only think you have EGR, the AIR tubes are also the supply to the EGR valve, with them cut as you have done no exhaust can get to the intake manifold.

STL94LT1

Once you hit the highway you'll also get an EGR code.

96GS#007

...and you cut some expensive and difficult to get parts when you chopped the tubes like you did

9T3VETTE

Makes sense...

Awesome.

The nuts on the manifold were never coming loose. Tried heat, tried penetrating lube, tried everything. Damn things would not budge, so I had to cut them.

Thanks for the help, guess it will have to be programed out.

toptechx6

Try sending a private message to member mseven. He is an outstanding tuner in your area who has helped many others, good luck.

93 ragtop

I remember when I put my headers on, with the pump disconnected, it set a code. And if you plug the electrical connector into the pump it would not. But that pump running, without piping, sounds like a shop vac under the hood. I ended up plumbing mine in, I needed it for emissions inspection anyways.

9T3VETTE

Great to know! I will defiantly get in contact with him. Thanks for the heads up, i've been looking for a tuner for awhile now.

Also good info, it must be the connection on the pump. I wonder if there is a way to fool it (with a resistor or similar) into thinking its operational??

FLASH92LT1

Try this.... put only the air pump itself back on, and plug it in. See if that keeps the the SES light off. Then you know you'll need a resistor to fool the ECM. I think it only looks for a voltage drop at the pump to be sure it's working. There isn't any 'sensor' that detects actual air flow.

Rick - '92 LT1

FLASH92LT1

WHOOPS!! Looks like 93 ragtop said the same thing!!

Rick - '92 LT1

jaa1992

I took my old manifolds to the exhaust shop and had them remove the AIR tubes when I put on my long tubes with provisions for the tubes.

When I put in the 383 I had AIR & EGR removed and programmed out of the tune.

9T3VETTE

That's what im going to try next. I was reading my FSM and it stated when the ECM sends the signal, it grounds the circuit and turns the pump on. I just have to figure out what pins they are.

9T3VETTE

Update:

Well I ended up putting the pump back in along with the bypass valve, and plugged both in.

In order to reduce the noise I pulled the front cover off the pump and pulled the fan blade out. Put the cover back on with 8 or so screws, and it's very quiet when operating.

Until I get a tune, this will do. Thanks for the help.

MK 82

Your code is not related to the secondary air system. A quad driver module is in the ECM and drives injectors I believe.