Skip to main content ↑ ↓
Topic: Bad speed sensor = backfiring? (Not cat/bird related) (Read 852 times) previous topic - next topic

Bad speed sensor = backfiring? (Not cat/bird related)

I'm curious if someone could explain this to me as it's confusing. A co-worker had some backfiring under load in a Dodge Caravan and the solution ended up being a replacement output speed sensor that I assume heads back up into the ECU. In what ways would a speed sensor be used for managing spark timing? I've just NO clue how a bad speed sensor would cause ANY vehicle to have ignition timing issues.

Crank sensors I can understand but vehicle speed sensors (or whatever Dodge calls them)?!
1988 Thunderbird Sport

Bad speed sensor = backfiring? (Not cat/bird related)

Reply #1 –
I get an error code related to my vehicle speed sensor, I don't have backfiring though.

Bad speed sensor = backfiring? (Not cat/bird related)

Reply #2 –
Oh, not that it matters, but the vehicle didn't throw a code for a bad vss, or any codes actually. Replacing it fixed the backfiring under load. It makes no sense to me.
1988 Thunderbird Sport

Bad speed sensor = backfiring? (Not cat/bird related)

Reply #3 –
makes no sense at all. the vss does not control timing or have any matter in it. But it does control abs, cruse, and obviously the speedo. But not timing. unless it was back feeding in some way?
2001 Buick Regal LS (DD):hick:

Got that fox rash again!

-Resident smartass! :ies:

- Don't listen to the naysayers. For every person who actually helps with your project there will be 10 who will discourage you all the while thinking that they are helping. 99% of all people have good intentions. That doesn't make them right.- XR7 Dave - SCCOA.Com
 

Bad speed sensor = backfiring? (Not cat/bird related)

Reply #4 –
Yeah - I just don't believe a second of it. I've never known of any ecu that would base ANYTHING off of the speed sensor. Vehicle's a 1996 Dodge Caravan - I don't think those even have a crank position sensor so I doubt it could be mixed up with that although supposedly the sensor IS on the transaxle or something.

I was just curious if I was crazy. Either I'm not or I'm not alone - either way, I feel better.
1988 Thunderbird Sport