MAP problems (code 3 reading)

[deadlikeme]

I keep getting the code 3 reading on my 93 Prelude SI (2.3 dohc), which is the MAP (Manual Absolute Pressure), yet I am unable to figure the problem out. I have already replaced the sensor but the check engine light still comes on and i still get the code 3 reading for the MAP. Does anyone have any suggestions at all? If it is not the sensor then what the hell is it?

[bobinohio84]

When a comp. spits out a code, what u have to realize is that a comp thinks like a comp. If the car is running rich, it adjusts to compensate and eventually can be blowing black smoke as a result of something completely unrelated. If the map sensor isn't getting the correct voltage, that could do it. If u have a vaccuum leak in the intake manifold, etc. That could also cause it. The voltage to the map sensor usually runs at about 5v. Let me know what u read. GL.

[ludeguy]

does the car otherwise run fine? or are there problems starting, with idle, high rpm etc?

i know this is simple, but also did you reset the ecm after you added the new map sensor?

referring to the 92-96 manual, for a code 3, (Electrical failure of map) their resolution breakdown ends up being either the MAP Sensor (which you've replaced), or the ECM (yoikes), or the wiring between the two.



to check the wiring, with the ignition switch on
.
measure the red/wht (+) voltage and ground = 5v
between red/wht (+)and blu/wht (-) = also 5v
between wht/blu and blu/wht = also be 5v.

[deadlikeme]

Ok it is the Knock sensor....not the map..the idiots who took the reading did not have enough common sence to notice the pause between the 2 quick blinks and the 3 quick blinks making it a code 23 reading. So i got a new map sensor because of the assholes who installed my engine when in reality its the knock sensor. But it does run fine....just the annoying check engine light....it does burn a little rich.

[ludeguy]

Originally Posted by deadlikeme

Ok it is the Knock sensor....not the map..the idiots who took the reading did not have enough common sence to notice the pause between the 2 quick blinks and the 3 quick blinks making it a code 23 reading. So i got a new map sensor because of the assholes who installed my engine when in reality its the knock sensor. But it does run fine....just the annoying check engine light....it does burn a little rich.

are you sure it runs fine with a bad knock sensor? usually a bad knock sensor will put your car in limp mode, meaning it pulls timing in the higher revs, limits your rpms to 6,800 and yea - as you said - dumps more fuel - to protect the engine. i'm surprised you are saying it is running well - and that it doesn't have any bogg and hesitation issues - as a faulty knock can cause that also. You might be in for some decent gains - simply by chuckin a new knock in there (if required - read below)

edit: nevermind just read you have the 2.3 so your rpm is limited at 68,(i was referring to the h22's rpms above) but i'm sure if the p14 is in limp it probably lowers your redline even further than that(?) maybe 6400 or something. In any case you get the gyst - it pulls back your redline so you don't do damage trying to detonate your engine!


is it possible your timing is set to advanced? have you checked your timing recently - if it's to advanced it could be pinging - setting off the knock sensor - your car could be trying to tell you something (; timing is advanced by the ecu at the higher rpms (if not in limp mode) but if you idle with an already advanced timing setup it's just gonna get worse from there - .. if you do adjust it - remember to jump the service connector - or the computer will be compensating for the timing while you adjust it. by the sounds of the guys who did your swap - there is a chance they "adjusted" your timing *without* the service connector jumped - but only they would know (the brains at the shop i dealt ommitted the same crucial step when timing my car).

all the best.. let me know how it works out.

[boytiti]

I think this is an old thread but yep, knock sensors send signal to ecu to retard the timing until the engine knocks disappear and then back to normal timing again. retarded timing causes rich A/F ratio (injectors damping more fuel).

[deadlikeme]

I think it's about time for this mechanic to answer up to all my problems with his engine swap. i shall post the results.