4age MAP question - Toyota Nation Forum : Toyota Car and Truck Forums

MM401 · 02-05-2009, 02:04 PM

Hey guys

I've been having some trouble with a slightly rough idle, and some slight hesitation once in a while.

So today I tried unplugging my MAP sensor, but it didn't affect the idle or the engine performance, does this mean I have a broken MAP sensor?

The engine is a standard 1989 bigport TVIS 4age.

toyotaspeed90 · 02-05-2009, 02:21 PM

unplugged it how -- electronically or the vacuum line?

MM401 · 02-05-2009, 03:37 PM

Hey, thanks for your quick reply.

I disconnected the MAP sensor electronically.

toyotaspeed90 · 02-05-2009, 07:55 PM

ok... make sure that you have a good vacuum line... and that there aren't any cracks or any sort of buildup in it.....

the vacuum line should be pulling directly from the manifold somewhere.....

if there's a break in the vacuum line then it doesn't matter electronically if it's connected or not -- it will only be sensing ambient air pressure and will not function.

MM401 · 02-06-2009, 03:44 AM

Ok, I will check the vaccum line just to be sure it's not broken.

However, if the vacuum line is fine, shouldn't the engine run differently when the sensor is disconnected?

RED91SR5 · 02-06-2009, 10:13 AM

89 AGE.....I think it should be a MAF not MAP sensor.

Do a code check and see if that comes up with anything. Could be something else causing the ECU to go into open loop mode and ignore the MAF sensor.

MM401 · 02-06-2009, 10:34 AM

If the sensor is connected with two vacuum hoses to the TB and the air filter box, then isn't it a MAP sensor? (I should mention that it is a European engine, so maybe that's why it is possibly fitted with a MAP sensor)

I've checked the codes, and I get 7 flashes, so I think it maybe has something to do with the TPS. Can the TPS cause the engine to ignore the MAP sensor?

BTW Thanks a lot for your help, I really appreciate it.

RED91SR5 · 02-06-2009, 10:44 AM

Quote:

Originally Posted by MM401

If the sensor is connected with two vacuum hoses to the TB and the air filter box, then isn't it a MAP sensor? (I should mention that it is a European engine, so maybe that's why it is possibly fitted with a MAP sensor)

I've checked the codes, and I get 7 flashes, so I think it maybe has something to do with the TPS. Can the TPS cause the engine to ignore the MAP sensor?

BTW Thanks a lot for your help, I really appreciate it.

Ok that would make sense.

If you have a bad TPS then yes the ECU would go into open loop mode and ignore the sensors and run on a fail safe set of values. This doesn't mean that you don't also have a mechanical problem causing issues. I'd test the TPS and replace if need be then go from there: code check, vacuum lines, mechanical etc.

toyotaspeed90 · 02-06-2009, 11:28 AM

no, that's not true....

if the TPS was bad it will send a bad signal.... it won't disregard the map because at that point the map reading would be the main thing that the computer has to go off of..... will cause it to run rough, though.

the map sensor generally has 3 wires and has 1 vacuum port -- directly to the manfold.

I'm guessing your car has A/C.... those generally have 2 lines and an electrical connector on what looks like a sensor -- which is the a/c idle air up control valve -- unplugging this would have very little to no effect (especially if the a/c isn't on).

try unplugging the tps and see how the car runs -- oddly enough if the tps is sending a bad signal the car will run much much much worse than if there's no TPS..... you'll throw a code, but it should run better if the TPS is the root.

the map sensor in ae92's, at least in the 4afe's, are bolted to the firewall.... not sure on the non US 4ag map setups.

RED91SR5 · 02-06-2009, 11:48 AM

Quote:

Originally Posted by MM401

If the sensor is connected with two vacuum hoses to the TB and the air filter box, then isn't it a MAP sensor? (I should mention that it is a European engine, so maybe that's why it is possibly fitted with a MAP sensor)

I've checked the codes, and I get 7 flashes, so I think it maybe has something to do with the TPS. Can the TPS cause the engine to ignore the MAP sensor?

BTW Thanks a lot for your help, I really appreciate it.

A picture would say a thousand words to answer your question.

MM401 · 02-06-2009, 05:23 PM

I will take a picture of the sensor and upload as soon as possible, this will probably make it easier for you to determine if it is a MAP or MAF (or something else).

I have tried unplugging the TPS, which result in a high idle does this mean that the TPS is OK?

I have no problem adjusting the TPS within normal values, but can the TPS still be within specs and broken at the same time?

toyotaspeed90 · 02-06-2009, 09:09 PM

Quote:

Originally Posted by MM401

I will take a picture of the sensor and upload as soon as possible, this will probably make it easier for you to determine if it is a MAP or MAF (or something else).

I have tried unplugging the TPS, which result in a high idle does this mean that the TPS is OK?

I have no problem adjusting the TPS within normal values, but can the TPS still be within specs and broken at the same time?

it's hard to say.....

Toyota TPS sensors have 4 wires, whereas most manufacturers have 3 wires (FYI, those of you with 4afe's or earlier that have a 3 wire.... it's not the same type of TPS). The 4th wire on a toyota TPS is actually a separate switch for when it's at idle.... so unplugging it and the rpm's jumping up a tad only means that the "switch" portion for idle is working properly.

I'm guessing the sensor you are looking at, which has 2 "vacuum" lines (one pre and one post throttle body) that you are looking at the AC idle air up control valve (generally has an electrical connection with 2 wires).

an AFM on a bigport is a large electronic piece (mostly a metal framed box with a plastic top and an electrical connetor near the top of it) in between the air filter and the throttle body -- sometimes attached to the air filter box (in early aw11's, ae92's, and ae86's this is true).

MM401 · 02-10-2009, 10:50 AM

Hey

I've uploaded some pictures of the sensor, so you can see if it's a MAP, MAF, AFM or something else.

A picture that shows the engine, with the sensor circled:

And then one of the sensor close up:

The two vacuum lines connected to the sensor connect to the TB and the air filter box.

I've checked the vacuum lines and they all seem fine. Also today i noticed that after some time the idle started to hunt a bit, but later today there was no hunting idle, just a very rough idle. The car is also having a hard time starting after not driving for a few days.

Can a broken TPS cause all these problems, or do you think the fault is caused by the mysterious sensor in the pictures?

toyotaspeed90 · 02-10-2009, 02:53 PM

that's the AC idle up sensor or has to do with emissions -- not the map sensor.

no afm, so it must be map.