MAP sensor - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 10 (permalink) Old Mar 15th, 03, 02:22 PM Thread Starter
 
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Angry

If the map sensor in my 89 camaro is bad how might my car act.(idleing and driving). The car idles extremely eratic and it is extremly slow driving. The check engin light comes on sometimes showing codes 23, 33, and 34. I have unplugged the MaP sensor recently and plugged it back. Should I reset my computer. If anyone could help I need it.
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post #2 of 10 (permalink) Old Mar 15th, 03, 05:03 PM
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I know if you disconnect a working MAP, often the engine will stumble and almost die before the computer brings the RPMs up to near 1000RPM. Your description sounds like those may be MAP symtoms.

Do you have a hanes manual or somesuch with a troubleshooting procedure? The reason I ask is that they might have a MAP diagnosis tree which will tell you how to determine if the MAP is working.

Off the top of my head, it seems like there are three wires. The outer wires are hot and ground. The center is a signal wire. If you put a hand vacuum pump on the port and monitor the signal line with a DVM against ground, you'll see a voltage signal that coinsides with the applied vacuum. The signal should be between 0 and 5 volts if you use the sensors ground wire as a reference.

If you have the tools to check give it a try. If the results don't jive with what I've described, try to locate the troubleshooting procedure (provided one exists) to make sure my recollection is correct.

Luck for you, if you want to reset the computer, just disconnect the battery for 30 seconds or so.

-dnult

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========================
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post #3 of 10 (permalink) Old Mar 16th, 03, 06:16 PM
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code 23= Manifold air temp (MAT) sensor-signal voltage is low or high
or
Throttle Position sensor (TPS) error.
or
Mixture control solenoid- open or short circuit problems


code 33=Mass air flow sensor-signal voltage or frequency is high during engine idle
or
Manifold absolute sensor(MAP) sensor-signal voltage is high during engine idle.


code 34=Mass air flow sensor-signal voltage or frequency is low during engine cruise
or
MAP sensor-signal voltage is low during ignition on.
or
Pressure sensor circuit-signal voltage too high or low(carbuerated engines).

These came right out of my OBD book for 1982-1995 GM models. some of these sensors may not be on your car. the MAP sensor is one of those sensors where there is either a problem with the sensor itself or the wiring or vaccum hose is bad. if you have ruled out these two things, then it is something mechanical and will require further diagnosis. the MAP sensor runs off of ported vaccum (vaccum above the throttle blades). check the hose coming from the throttle body for cracks or if it is disconnected. i cant remember what the voltage specs are for it but it goes up as more vaccum is applied. my best guess would be that the sensor is bad because i think if there was a vaccum problem, then it would be giving you an engine code for the EGR or something. but, diagnosing by buying different parts gets expensive quick. anyways, i hope these code definitions help you. i'm sure there are others on this site that can help you with whatever you need. good luck!
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post #4 of 10 (permalink) Old Mar 17th, 03, 07:16 PM
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Greetings eagly'z28,

It would have to be the mass air flow sensor instead of the maniflold air pressure sensor because the MAP was not used until 1990 [img]graemlins/beers.gif[/img]
p.s. If it is the mass air flow sensor thats bad, they run about $350.00 depending on where you look.



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post #5 of 10 (permalink) Old Mar 18th, 03, 06:56 PM Thread Starter
 
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.
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post #6 of 10 (permalink) Old Mar 18th, 03, 06:57 PM Thread Starter
 
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There is definately a MAP sensor and not a MAT sensor. I think I found it to be something else, Thanks for the advice any way. Please check out my new post on the EGR valve question.
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post #7 of 10 (permalink) Old Mar 20th, 03, 02:27 PM
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Trickster: I worked on several cars from the mid 80s with MAP. Not counting some of the early mechanical injection systems, speed density types were the first types used in the early 80's. Even on computer controlled carberators. Are you talking about a specific model? If you said MAF wasn't used until 1990 I'd believe that. What am I missing?

-dnult

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========================
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post #8 of 10 (permalink) Old Mar 21st, 03, 06:10 AM
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My apologies to Dnult and eagly'z28,

In my recent post concerning the maf and map, I left out the fact that the 5.0 liter tbi did have a map instead of the maf. The 2.8l, 5.0l, & 5.7l tpi models all have the maf installed and these were the ones that I was referring to. [img]graemlins/clonk.gif[/img] My mistake in overlooking the 5.0 tbi model. Again, my apologies for creating any confusion or misunderstanding. [img]redface.gif[/img] Next time I will try to be more specific. [img]graemlins/beers.gif[/img]

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post #9 of 10 (permalink) Old Mar 21st, 03, 04:16 PM
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ok guys, here it is. MAP sensors were used on all camaro models except 1988 (from what the Haynes manual says). MAF sensors were not used on TBI units only multiple injector fuel systems. I think that he is talking about MAT (Manifold Air Temperature). I am not for sure but if i had to guess, then i would say that they came out in 1990. Todays cars use more sensors to precisely inject fuel. They did'nt have this in the 80's. and yes dnult, i have worked on those electrical carbuerators (the e2se or whatever it is) that came on the rally sports and z-28's. they were electrical feedback so the only sensors that could really tell you anything about a fuel problem was the o2 and TPS. MAP sensors were called Differental Pressure Sensors on the carbuerated models.
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post #10 of 10 (permalink) Old Mar 23rd, 03, 05:53 AM
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Tuned port cars had the MAT in the bottom of the plenum above the runners. Not sure if the TBI cars had one, but they might. New cars have them in the duct of the throttle body, and they are now called IAT (incoming air temp)

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