MoTeC Global Forum

Hey all,

Just wondering how temperamental or perhaps delicate a MAP Sensor actually is?

I've never had an issue with one over the years, however, 3 Bar Delco - brand new - ran fine without issue for engine dyno time and tuning on a fresh engine.

Put engine in car, connect MAP and instantly find a diagnostic error. Wiring is all good.

Car then exhibits all the usual MAP issues:

Hard to start
Sloppy throttle response (very evident on a 900hp motor!)
Stalls
Doesn't want to idle properly
Erratic rich/lean

Sure enough, unplug sensor and plug another one in - fault disappears and issues go away.

Sensor was never dropped or wet, but seems faulty after just dyno hours.

Are these perhaps more temperamental to damage than I have experienced before, or just a bad luck item?

Only thing I could possibly put it down to is the engine is on E85 and has an intake plenum injector. But I doubt any misted fuel (or moisture from sitting) would make it to the sensor - that's quite a stretch!

Anyone ever experienced similar? Curious more than anything.

Exactly what sensor ?

Installed how ?

Wired how ? Has wiring been confirmed as sound, correct 5v feed etc ?

genuine GM 3 bar sensors are rare these days, everyone sells chinese shite.

stevieturbo wrote:Exactly what sensor ?

Installed how ?

Wired how ? Has wiring been confirmed as sound, correct 5v feed etc ?

genuine GM 3 bar sensors are rare these days, everyone sells chinese shite.

Genuine Delco 3 Bar #53003, as supplied by MoTeC with an M800 loom kit.

Installed traditionally - vacuum hose (actually an -AN braided hose and fitting) off the manifold plenum, dedicated line about 300mm long to the sensor, mounted on the firewall.

Standard triple GM Packard Weathershield plug connected to the 3 wire M800 loom. Verified as working and tuned as such.

Then randomly the sensor starts throwing constant errors and fails. Which seems pretty rare to me. I've never seen one not last 15, even 20 + years.

Is the sensor mounted pointing down...and also hose running down so no liquid could ever gather at it ?

Although same as you...I've never seen a genuine GM sensor fail. Have seen a lot of the Chinese ones fail and read all over the place though. And even physically fall apart lol.

stevieturbo wrote:Is the sensor mounted pointing down...and also hose running down so no liquid could ever gather at it ?

Although same as you...I've never seen a genuine GM sensor fail. Have seen a lot of the Chinese ones fail and read all over the place though. And even physically fall apart lol.

It actually isn't (pretty level to hose), but is IS mounted with the hose on the lower side so any moisture shouldn't gather in it. I often see people mount them the other way (hose on top, plug on bottom) - which I would consider upside down.

I suppose we'll see if it was an E85 / moisture problem as it would likely return. Might move to one of those remote / Deutsch wired systems in the long-term even if it doesn't. Seems a much more elegant solution anyway without the hose.

Funnily enough now with the MAP error gone and the engine running better again - it still doesn't want to idle and keeps stalling out. Hopefully it hasn't fouled the plugs as they aren't exactly easy to get to on this setup. Seems like it's running out of spark.

So much fun. Said no-one. Ever.