Pillsbry10

iTrader: (1)

quick question... what exactly would happen if the knock sensor was unpluged or making a bad connection.

i put in the new knock sensor today and connected the new plug and it seems to be running a lot diffrent(i dunno if its better or worse though) the exhaust not being hooked up makes it hard to tell what its actually doing, loud *** v6.

bassically it led me to wonder what the ecm actually does when the sensor goes bad or is not connected well?



before i did all that i did get a code 43, which by the service manual is pretty much just a bad knock sensor or bad connection as far as i can tell and it only came on once, didnt come on when i ran the car after the new installation

something else that i just thought of as well... when we were timing the motor after the first start and before i changed out the knock sensor and connector we couldnt advance the timing to the 10* anything over 0* and it seemed to run like crap

86ttopbird

I think the ECM will just run a flat timing curve. Something similar to whats built into the ignition module when those lovely little things fail. Probably certain things wont work like highway enlean and such. I am not positive about it but I'm pretty sure. A bad KS will make the car run like poop.

Pillsbry10

iTrader: (1)

so could the "bad" knock sensor be the reason i couldnt adjust the timing? and if thats the case thats why it sounds funny today now that it is all hooked up right becuase i need to adjust it to 10*

86ttopbird

This might be a dumb question but did you unplug the EST connector by the AC stuff on the firewall while setting the timing?

Pillsbry10

iTrader: (1)

yeah i did...the timing changed but it ran like poop the more it was advanced.. sounded best at 0*

86ttopbird

How is your timing chain? Is it stretched? Also was the dizzy removed at any point? If so its possible that it is a tooth off.

Pillsbry10

iTrader: (1)

the entire motor is brand new... if the knock sensor not being connected right would cause the ecm to go into a set mode then that would explain why adjusting the timing wasnt working or was making it run worse. now that i have the stuff hooked up right it sounds totally diffrent, wish i had the timing gun here id try to adjust it to 10* again and see what happened

86ttopbird

Give it a shot. It might surprise you

Pillsbry10

iTrader: (1)

it was running pretty steady and strong at 0* timing(havent driven it down the road yet) but it did die and run super rich

today when i started it it almost sounded like it was stumbling a bit at idle, not real bad but enough that i could hear it. sounded strong when i brought the rpms up to around 2000ish

86ttopbird

Where is your TPS volts adjusted at?

Pillsbry10

iTrader: (1)

its within spec..i forgot what it was exactly

86ttopbird

Usually .53 to .55 will do it. My car likes it at .49. Its on the low end of the spec but thats where it runs the best.

Pillsbry10

iTrader: (1)

i think mine was around .54 but i really cant remember... i need to hook it up to a computer and see exactly what its doing

86ttopbird

you can use a digital DVOM. Just probe the blue and black wires. That will tell you where its set at.

Pillsbry10

iTrader: (1)

yeah i know how to test it i just dont remember what the number was.... i just remember it being in spec lol

if anyone needs a knock sensor plug they stock them on the shelf at orileys...little beter made than the stock crap ones

Maverick H1L

iTrader: (8)

90-92 cars don't necessarily need to worry about the TPS voltage as the ECM will (read as: SHOULD) adjust itself based on the reading when the engine is first started. Which is why the spec in the 92 FSM is around .92V or less.

I would check the connections to the MAP, especially the vacuum line and hose, and the signal there. And the knock sensor itself as well. How well does your intake allow setting the timing?

Pillsbry10

iTrader: (1)

All the connections to the map are good, all vacuum lines are new.

My intake allows for just as much timing as the stock intake. When we bumped it up to 10* it sounded like poo, so right now it's just at 0* it does sound way diffrent with knock hooked up correctly..

RBob

iTrader: (1)

I was wondering if this is with the 3.4l engine. IIRC they don't have a timing mark on the damper. But if are like the 3.1l dampers do have 3 other marks. One of which that you may be using.

Note that with the EST/BYPASS unplugged the knock system (ESC) won't have any affect on the timing. All timing will be controlled by the module. There is built in advance in this mode so be sure to set the timing at an idle idle.

With the EST/BYPASS closed and the ECM in control of the timing, an active code 43 (SES on) will pull a set amount of timing at all times.

RBob.

racethesunlive

This is correct as I had a similar knock sensor issue... with a code 43 your timing will be pulled back and you'll lose a lot of power

Pillsbry10

iTrader: (1)

So I guess I should prob try to time it to 10* again and see what happens

Maverick H1L

iTrader: (8)

What I was getting at was that you should check 2 things.
1. That there is actually vacuum going TO the MAP sensor from the modified position of the port you are using (assuming you're using the tee into which the brake booster is connected) or any other port (MUST be manifold vacuum and not ported).
2. The voltage signal between the green and black wires at the MAP. Should be between 1 and 2VDC at idle. If a reading closer to 4-5VDC is indicated, there is a problem in the system, especially if the reading is even higher (12VDC).