93redz

i have a 93 LT1 speed density with a lt4 hot cam.i had programming by pcm forless.if i reset the computer it runs awsome for a couple miles them starts running terrible like missing and half the power and rough idle and surging when im on it.if i reset the computer again it runs perfect for a couple more miles. please help?

Wilson

Does it only run good for the first couple of minutes when you start up the car? If so, then that means your Open Loop settings are more accurate then your Close Loop settings. When the car is in Open Loop the computer looks at the fixed tables in your ECM without using the O2 sensors to adjust your A/F ratio. Once the car is heated up the ECM jumps into Closed Loop, this is when it starts using different sensors on your car to adjust A/F ratio. Could be that your tune is bad or you have a faulty sensor. Best thing to do is hook it up to a scanner and see what you get.

93redz

i did hook it to a scanner and got no codes and it will run that way in open or closed loop

Wilson

Post your data logs. You can also email them to me and i'll take it a look at it.

93redz

all i have is a snap on scanner but i will list everything it list.
i did see qdm 1 -failed
qdm2 - failed
qdm3-failed what does this mean?

Wilson

The Quad Driver Module circuit is built inside the ECM which controls different components. This might have something to do with a bad ECM or Memcal.

I remember when I had the JET Fan switch module it would throw QDM 3 failed because the JET Fan switch harness would plug into the ECM and the ECM would freak out. Another thing to check is to make sure all your harnesses are plugged in all the way.

Also have you tried putting your stock Memcal chip back into your car and see if your getting the same errors? The LT4 hotcam will run on the stock tune. Try going back the stock chip and see if the errors go away. I have a feeling it could be a bad chip.

Alvin@pcmforless.com

Sounds like a bad sensor to me, Possibly a bad computer.

I've seen a car drive for 3 hours with the passenger side O2 wire cut in two and no SES light or code.

Send us some datalogs.

93redz

i put the stock chip back in and it does the same thing.

Wilson

So, it still shows the QDM #1-3 as error codes? If so, do you know anyone who lives around you that has a 93? Try swapping the entire ECM with them and see if the error goes away. It seems like something is seriously wrong.

BTW- did you clear out the error codes after you swapped back to the stock chip? Also, check the wiring harness on the ECM. Maybe its loose.

93redz

i put a ground strap from the engine to the body and it seems fine now.....i have a question about my o2 sensors though...with the key on and not running one sensor is reading .456 and the other one is reading .506 is this normal?

Alvin@pcmforless.com

not really,

thats almost the first test i do for healthy O2 sensors.

It should be .450 .450.. I would inspect/repace the one sitting on .500

Also, take the O2 wires and giggle them a bit and see if the voltage changes (before cranking car)

93redz

thanks rooster this is scott with the 69 camaro you programmed the chip for.

Alvin@pcmforless.com

Socie?

93redz

yes thats me

Alvin@pcmforless.com

You ought to figure out a way to trailor it to our dyno day we are having up there. That way I can take a look at it. I hate to hear your having problems.

It definately sounds like a bad O2 wire to me.. I know that sounds strange.. but alot of times the wires get baked threw because they are often close to the headers.