I have a hesitation in acceleration at low rpm’s. Last week I checked my ECU and was getting a MAP sensor code but the check engine light wasn’t on. I checked the hose going to it and it looked good. Could this be causing my hesitation and how much is a replacement?
yeah, and where the heck (for lack of a better term) is the MAP sensor? whats it look like?
Augie
MSN: augied@hotmail.com
AIM: AugieD Z88
double check hose again cause i had the same problem and it turned out to be a very, very small hole in the hose that was hard to see, and that was causing my engine to hesitate too
the map sensor is on the fire wall right by if not next to your IM. It’s black and next to the solenoids that conect to your fuel pressure valve and your IM
If you need a new MAP sensor, let me know – I have one I could sell you. Also, many other vehicles have had poor drivability and/or hesitation problems if the ground in the MAP goes bad. Many techs have suggested regrounding the sensor to the chasis to resolve these issues.
The voltage on the MAP can be used to tell you if there’s a vac leak as far as I know. If you’re interested, I’ll grab my old notes and post that silly shyte here. I think there was a good tech2tech article on this.
Best of luck… don’t give up.
Andrew.
aka neex.
i would soooo super appreciate it. i have had to replace MAP sensors in my other vehicles, and now my teg is starting to mimic them, so i think i should change mine. if you could, can you post that info? and you want to sell the other sensor you have? is it good? and how much?
Augie
MSN: augied@hotmail.com
AIM: AugieD Z88
it says map on it also just so you know , replace the hose cause it cost five cents anyways reset ecu drive it and check for another code. most map sensors work from a 0-5volt range except for ford which uses frequency.
I will dig up those notes for you and link them to my web directory or something. About the MAP I have – of course it’s good. I don’t hang on to garbage – lol.
I’ll take $30 for it if you want it. It doesn’t have hoses or the molex connector though – just the MAP itself. Check your’s first before you elect to replace it. It’s really just a 5V reference sensor but it has the most ‘authority’ of any of the sensors. In other words, fluctuations in voltage at the MAP make the greatest impact on the outputs of the ECU to the EFI system.
Let me get back to you after my evening tea… seriously… lol
Andrew.
aka neex.
Ok… here’s a few excepts from old notes…
Honda PGMFI systems use what’s called, ‘speed density’ control that used the MAP and engine rpm as the initial determinaing factor of the pulse width of the injectors. All other sensors simpy ‘fine tune’ the pw – the MAP sensor alone can take the pw from a normal idle rating of 2.5ms to a heavy load condition of 15ms.
Normally (at idle), the MAP’s input to the ECU should hover around 1V (or less – no acc. on). If you measure the voltage at the MAP to be higher than 1V, you will likely be running rich and begin to have drivability problems. To give you an idea of how crucial this voltage level is – if you measured say 1.2V at the MAP and went for a sniff test, you’d fail on the CO readout. It’s THAT important.
When the manifold absolute pressure drops, the MAP sensor will signal the ECU to increase the pw of the injectors. This is why a pulled hose on most PGMFI cars will cause the idle to skyrocket more often than not (unless it goes so high that it begins to flood).
The ECU used the input from the MAP sensor and the engine rpm to source out a value from a preprogrammed ‘table’. This table decides exactly what the right amount of fuel and air trim (namely pulse width) will occur at manifold vac. levels (utilizes VE - volumetric efficiency (I think??). ).
Here’s an excerpt from a table from a '92 Civic (1600 I think??):
================================================
CONDITION-------MAP VOLTAGE-----INJECTOR PW-------EXHAUST CO
NORMAL-------------.94V ----------------2.0 ms----------------.3%
VAC LEAK----------1.13V-----------------2.3ms-----------------6.5%
(on MAP hose)
LARGE LEAK
(on MAP hose)-----1.25V----------------2.7ms-----------------9.9%
===============================================
As you can see, a rip in your MAP hose can put your CO readings near 10%!
:whoa:
TESTING THE MAP SENSOR
simple Simon… 2 wires… a 5V reference system sensor… Black is ground… one of the other wires will be 5V dead on. The wire you need to pay attention to is the other one (feedback to the ECU) that will sit just below 1V if your engine vac and idle are spot on.
…pay attention also to the black wire… you may want to check the resistance of this wire with reference to a good solid chasis ground point… if there’s much drop on that line, you could have some serious problems – try regrounding that wire…
I hope this helps someone. Just so you all know, you can use the MAP output as a better indicator of engine vac. levels that you could read with a pressure gauge… it’s true…
According to many Honda techs, MAP sensors almost never fail
The usual cause of a whacky output at the MAP would be a whacky input from somewhere else. An example could be either messed up cam timing, bad intake/exhaust valve, restriction in the exhaust system or a vac leak. Both these situations will cause the MAP sensor to output a higher-than -acceptable number.
MANY thanks to all the folks at Tech2Tech for the majority of this info…:read: :bowdown: