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I posted a thread a while back regarding a flat spot and/or hesitation namely at lower speed but also at higher rpm's. MMO was use to alleviate the problem. However, on this humid day, the problem returned. It appears that "humidity" is affecting the above problem. When the air is crisp and clean (colder temps) "No Problem". I believe there are three sensors that may be responsible 'Unknown' 1.) EFE 2.) MAP 3.) Barometric Sensor 4.) Would the Barometric Sensor cause the above issue? I've yet to install the EGR valve or change the carb filter which I believe are not the problem. All replies would be appreciated. Barometric Sensor
Olds 307Y or 9 Cutlass does not use a MAP per se. That's found on the V6 cars. They use a manifold differential pressure sensor (MDP), sometimes called a vacuum or VAC sensor. They look similar, but are not. Add a turbo and that is even different as the GN's used MAPs specifically for turbocharged vehicles, along with mass air flow sensors (MAFs).
However, the BARO sensor is the same exact part number as a MAP. The MAP/BARO sensor latest GM part number was 12219931, the only difference is the BARO sensor sits under the dashboard near the computer and doesn't require a hose to the intake manifold. It just monitors the atmospheric pressure the car is driving in.
The MDP sits on the fenderwell under the hood right behind the coolant overflow tank and has a hose going to the engine's vacuum.
On the V8, the EFE sensor (temperature controlled vacuum switch) is actually not part of the CCC system, and only regulates the driver side exhaust manifold on a cold start. It closes the EFE valve forcing the driver side exhaust through the crossover port in the intake manifold. The sensor is located on the driver side back corner of the intake. When the sensed temperature rises enough, I think it is around 85 degrees or so, it cuts vacuum to the EFE valve and opens up allowing the exhaust to pass through the crossover pipe.
The MDP by the coolant tank only has a few numbers- GM part numbers for a G-body Olds V8 MDP sensor is 16006834, 16054920, and 16231141. THAT IS IT for GM part numbers. Standard Motor Parts shows as AS 10, and Borg Warner is EC1618. Another I saw was Niehoff FE1618 and NAPA is CRB219011. At least NAPA website calls it a differential pressure sensor.
Borg Warner is confused as most other people are. Their MDP sensor EC1618 is listed BOTH ways in their e-catalog, in the same picture. Let that sink in. It lists MAP sensor, and right underneath it lists it as an MDP sensor. It IS an MDP sensor. Don't know of the newer ones, but I have an older BWD in the box that has the GM logo on the top of it so that should give you an idea who made them for GM at least for a while. It also has "MAP SENSOR" on the end flap right under the part number. Again, this part is NOT a MAP or BARO sensor. It is an MDP. Yikes! So you need to know your part numbers.
You should be throwing codes if your MDP (Code 34) or BARO (Code 32) sensors give up the ghost.
Olds 307Y or 9 Cutlass does not use a MAP per se. That's found on the V6 cars. They use a manifold differential pressure sensor (MDP), sometimes called a vacuum or VAC sensor. They look similar, but are not. Add a turbo and that is even different as the GN's used MAPs specifically for turbocharged vehicles, along with mass air flow sensors (MAFs).
However, the BARO sensor is the same exact part number as a MAP. The MAP/BARO sensor latest GM part number was 12219931, the only difference is the BARO sensor sits under the dashboard near the computer and doesn't require a hose to the intake manifold. It just monitors the atmospheric pressure the car is driving in.
The MDP sits on the fenderwell under the hood right behind the coolant overflow tank and has a hose going to the engine's vacuum.
On the V8, the EFE sensor (temperature controlled vacuum switch) is actually not part of the CCC system, and only regulates the driver side exhaust manifold on a cold start. It closes the EFE valve forcing the driver side exhaust through the crossover port in the intake manifold. The sensor is located on the driver side back corner of the intake. When the sensed temperature rises enough, I think it is around 85 degrees or so, it cuts vacuum to the EFE valve and opens up allowing the exhaust to pass through the crossover pipe.
The MDP by the coolant tank only has a few numbers- GM part numbers for a G-body Olds V8 MDP sensor is 16006834, 16054920, and 16231141. THAT IS IT for GM part numbers. Standard Motor Parts shows as AS 10, and Borg Warner is EC1618. Another I saw was Niehoff FE1618 and NAPA is CRB219011. At least NAPA website calls it a differential pressure sensor.
Borg Warner is confused as most other people are. Their MDP sensor EC1618 is listed BOTH ways in their e-catalog, in the same picture. Let that sink in. It lists MAP sensor, and right underneath it lists it as an MDP sensor. It IS an MDP sensor. Don't know of the newer ones, but I have an older BWD in the box that has the GM logo on the top of it so that should give you an idea who made them for GM at least for a while. It also has "MAP SENSOR" on the end flap right under the part number. Again, this part is NOT a MAP or BARO sensor. It is an MDP. Yikes! So you need to know your part numbers.
You should be throwing codes if your MDP (Code 34) or BARO (Code 32) sensors give up the ghost.
Thanks very much, a lot of detailed info which I very much appreciate. No codes are showing and the problem is annoying. Again, no problem in colder air or medium to dry humidity.
Seeking Sensor Information/ Functionality
