Is there any way to fool a knock sensor. It is retarding my timing when I try to pass somebody. The motor has some piston slap that is causing the problems.

 

piston slap? You could fix that, that would "fool" the knock sensor

 

Yes, I know but I put this motor together a year ago. I bought it with two cracked heads, I was on a budget and just bought different heads, ringed it and put bearings in it. I should have bored it out and put new pistons in it. It was fine for a while, but know it is a real turd. I was hoping to get by for a while.

 

Have you tried unplugging the sensor?

 

I have not, I was told that if it was unplugged the computer would set the timing retarded.

 

Try it and see what happens. Hard to believe it will retard the timing without a signal. Mine didn't, and didn't give a check engine light with it disconnected.

 

I will give it i shot, got nothing to lose. But if it doesn't work, do you know of any way to bypass it.

 

Don't unplug it. That won't do **** for you... make your problems worse, actually. It will kill almost ALL timing advace and it will pour fuel in. Like, eye burning rich. Not good. Its called "limp home mode" and its just that... limping around.

Really, the only solutions are to either fix the piston slap issue, change to aftermarket EFI that doesn't use a knock sensor, or change to a carb.

 

How does the sensor work, does it rely on voltage, resistance?

 

Take the sensor out and coat it in teflon tape. It releys on voltage. It actually creates a voltage based on how much it vibrates.

 

The BEST fix is to retune the Knock Sensor's specifications in the eprom. FYI, on most stock or basically stock TPI cars, the KS pulls out a TON of timing in WOT. I have found disabling or limiting the amount of timing pulled out when in WOT and then re-working the spark curve makes a lot more power.

PS: Don't unplug the KS. You'll only trigger the SES and cause the ECM to go into "Safe Mode" (and the engine will not perform properly as this is considered a major fault and the ECM is trying to get you home so you can fix the problem).

 

Is this a TPI car or a CC Q-jet? I've disconnected it on my carbed setup and didn't recieve any codes and it didn't run different either. I've heard of wiring in a resistor inline to decrease the sensitivity, but couldn't tell you what value to use.

If this is a carbed car, from the 84 manual:

Loss of the ESC knock sensor signal of loss of ground at the ESC module would cause the signal to the ECM to remain high. This condition would cause the ECM to control EST as if no spark knocking were happening.

 

It is a vortec motor with the vortec intake out of a 98 van.

 

What ecm and harness is being used to control the fuel injection?

 

The one from the van.

 

You need software to hack the ecm. It's OBDII, I don't know off hand what software you would need (like LS1edit, LT1edit, etc.) You might want to try what dankhound said. Screw it in just past hand tight to lower the sensivity to knock (just enough so it doesn't leak).

 

where can I get more info about changing the ecm. I am used to working on carbed cars.

 

The software to work on OBDII systems are limited and expensive. Most is for the higher performance cars such as the LS-1s and LT-1s - you may be out-of-luck for the Van.

You might want to consider going with an older OBDI system like those used on our cars. The software is cheaper and widely known on the DIY Prom Board. The ECMs (if you went SD), is readily available from a wrecking yard as well the sensors and very reasonable prices. The wiring harness can be picked up from Painless.

 

PS: By limited, I mean only a couple of companies - not the PCM or software has only limited features.

 

Do you have to go through emissions? If not, a carb intake and distributor swap would fix your problem.

 

What if you just pulled the knock sensor and wrapped it in foam and just tape it to something in the engine compartment...

Really trailer park boys style but it would work wouldnt it?

 

As soon as I get my grade 10 and out of jail, I'll give it a try...

 

Sounds good ricky

 

Thanks everybody. I think I'm going to try the foam and tie it out of the way trick.

 

Im a genious, pure genious

 

 

 

 

but I want to try something simply before I have to tear it apart.

 

That would be funny if you hit a speedbump and it shut your engine down

It wont happen but it would be funny as hell.