I'm having some issues with my my car. It is an '97 ls/vtec that has been converted to OBD1. It's on Hondata S300 and uses a GM 3Bar map sensor (p/n 16040749). Everything has been great until recently...

The car started bucking wildly in boost and was semi-driveable in part throttle. It would still buck but not all the time. If I put the car in neutral while coasting to a stop sign and let off the gas to decelerate, the car would die. I would start it back up and it would then hold an idle. Upon decelerating, I would also get a CEL which was for the map sensor. When the CEL came on, I had zero throttle when I pushed on the pedal. Eventually the car was completely undriveable. It would buck and stall immediately once I gave it any gas and tried accelerating.

So I bought a new sensor thinking maybe it just went bad after a few years of use. The car ran smooth in part throttle for about 20 miles on the highway. Boost still bucked, but it was driveable at least. Once I got off the highway it stalled again when decelerating. Then on city streets it started repeating the above paragraph until it was again completely undriveable. It's as though my car is eating map sensors or something. I have not a clue what would be causing this....any input?

 

goddamn!!.. i posted a thread like this a week ago and ro replies, so i went and bought another map sensor and awaiting delivery.

what you said is what happens to me exactly

which map sensor did you go for?

 

Did you mount the MAP in a spot where it gets hot?
Mine acted the same way when I had it on the intake itself. Moved it to the firewall and it never acted up again.

Also, just a fyi- the way the older GM MAPs are designed, if you over-tighten them you can crack the crystal inside fairly easily. I have at least one customer a year learn that the hard way.

 

I bought this one

1.) It's mounted to an angle plate that is on my firewall right next to the fuel filter. The plug is facing downward.

2.) fuuuu.jpeg + an extra side of rage. I'm interested in hearing more about this crystal and what it does. I did tight it down pretty good, didn't think I murdered it but it is pretty tight. How much pressure does it take to crack the crystal inside of it? Perhaps this is the link between my two sensors and my problems. Maybe my old sensor was bad and I over-tightened the new one causing it to be bad immediately as well....while making me think something else is going on?

 

I'm not an expert on MAP sensors by any means, by my layman explanation is: the crystal in the sensor varies resistance at various vacuum/pressure levels and that varied resistance is the map signal to the ecu.

From Wiki: Two main groups of materials are used for piezoelectric sensors: piezoelectric ceramics and single crystal materials. The ceramic materials (such as PZT ceramic) have a piezoelectric constant / sensitivity that is roughly two orders of magnitude higher than those of single crystal materials and can be produced by inexpensive sintering processes. The piezoeffect in piezoceramics is "trained", so unfortunately their high sensitivity degrades over time. The degradation is highly correlated with temperature. The less sensitive crystal materials (gallium phosphate, quartz, tourmaline) have a much higher – when carefully handled, almost infinite – long term stability.

Don't have a torque spec, we just tell customer's to snug them down. Don't crank them down hard enough to dent or distort the plastic by the mounting screws/bolts.

it's possible...

 

And now that I'm thinking about it, the 1st sensor was subjected to a pretty severe shock in the past as well. Maybe that shock broke the crystal. I have only driven the car 55 miles since March and I seem to recall it acting funny ever since that initial shock. Thanks for the info! At least I have a little hope so far...