I have an 87 Iroc TPI that originaly had a 305 and I put in a remaned stock 350. my question is since I never changed the knock sensor what kind of problems would I see from that? this car has been a headache since I put the new motor in. it doesn't seem to have the power I had expected, and its always fouling out the plugs(every 100 miles). I have checked and or replaced all of the common things that would cause this with no luck. I haven't driven the car since before thanksgiving and I miss driving it. It's had me puzzeld for 3 years now. thank you for any help you can give me.

 

You could try to change out the sensor but I don't think that is your problem. Did you change out your eprom or ecm for the 350 engine calibration?
To my understanding the knock sensor is a micraphone that relays engine knock noise to the ECM wich will cut back feul and spark when niose over certain levels are detected, this keeps the engine from rattling it's self to peices and helps with longevity.
I think if you want to test the sensor using premium feul if you already don't. If the engine response with more seeming power then the sensor is fine as premuim feul reduces knock and allows the car to run at full feul/spark ratios.

 

I have one of the GM Performance Parts proms (which can be used in both applacations) in the car and I always use 93 octane gas.

 

Not sure... could be a bad sensor created a to rich feul mixture or to weak of a spark. Maybe someone else has some ideas? Are all plugs carbon fouled or just some?

 

all 4 in the left bank go bad within a hundred miles or so. the lft bank take about four to six hundred miles then they are shot. this summer I'll be pulling the motor and riping it apart since I can't seem to get it fixed. there is 10,000 MI on the motor.

 

Welcome to the boards, you've picked the right place to come ! A knock sensor adjusts the engine timing to reduce engine knock. If you have one for a 305, get one for a 350. What condition are your fouled plugs? Are you using plugs that fit a 305? You may have the wrong heat range. Is the gap correct? Did you get 350 fuel injectors when you installed this engine? Where is your engine timing set? What is your fuel pressure? Check all these factors before you tear in to that new motor. Keep us posted.

 

Thanks for the welcome, the plugs will have a crusty matte black gobs of I guess carbon built up so bad that they won't fire. I use 350 plugs gapped to the specs in the Chilton manual (.035 I think), I tried both 24lb. SVO injectors and stock 19lb with higher fuel pressure ( as per TPI Specialties), timing has been anywhere from 4* to 12*, and fuel pressure has been run from 36 to 48lbs. I've tried it all over the last 3 years with no luck. The only thing I never knew about till I came here was the knock sensor. For the first 40 to 50 miles after I put in the new plugs the car runs great then goes to crap. Oh yeah, I bought this car for a beater so ever time I drive it I beat the s**t ot of it, bt the plugs should last longer than that.

 

Yes they should, even if it is beat on. Do you use a platinum plug? I know it sounds strange, but that's what GM recommends, and again, make sure they are in the correct heat range. Where's the timing set right now? What grade of fuel do you use? If all these things are checking out, I would definitely change that knock sensor. I'm willing to bet money it could be causing your problems.

 

I always use 93 octane, I did always use Bosch platinum plugs untill the last time I changed them ( too expensive ).It's been about 7months since the last time I even opened the hood on the car or driven it but I think the timing is somewhere around 8*. I'll try the knock sensor but if that don't work I'm just going to pull the motor and tear it down. If I still can't find whats wrong there may be an IROC for sale. Any more comments and info will be greatly appreciated. Thanks all.