Bad MAP sensor symptoms?

[wolf_06]

Any of you had a bad MAP sensor before?

I have an intermittent lean fuel code, got 2 new O2 sensors, new plugs, coil packs are good, fuel pressure is fine, no vacuum leaks.

The car have a rough idle, vibrating when cold, smell of gas sometimes on cold start, when idling, the rpm can go up and down just a bit, and also have intermittent hesitation on maintained highway speed. Also harder on gas.

I suspect the MAP sensor being lazy of not working properly, or the TPS sensor.

What do you guys think? I had the code p2096 several time, which is Lean fuel Trim Bank 1.

 

[Doog]

Exhaust leak?

 

[wolf_06]

Originally Posted By: Doog
Exhaust leak?


Hum maybe, I had the flex pipe replaced a while a ago...

 

[ARCOgraphite]

Is this the Hyundai?
Doesnt the accent have a MAF? Could be pre cat ex leak - that would make the ecu go rich . Also Make sure all the intake plumbing (post filter box) is OK. I had a split on my '91 626 I4 intake hose and didnt see it until I pulled the the hose off to remake the connexions. when I flexed it a bit there was a big split in one of the accordion pleats that opend when the engine torqued over. The car was only 2 years old!

 

[wolf_06]

Originally Posted By: ARCOgraphite
Is this the Hyundai?
Doesnt the accent have a MAF? Also Make sure all the intake plumbing (post filter box) is OK. I had a split on my '91 626 I4 intake hose and didnt see it until I pulled the the hose off to remake the connexions. when I flexed it a bit there was a big split in one of the accordion pleats that opend when the engine torqued over. The car was only 2 years old!


In 2006 they a MAF, mine is a 08 with a MAP.

 

[ARCOgraphite]

I have not seen a modern engine that doesnt have a MAF on the intake box(denso) or on the TB(fuji). Are you sure?

 

[salv]

Hyundai uses MAP sensors in a lot of vehicles. Here is the diagnostic specified by Hyundai.

1. PCV(Positive Crankcase Ventilation) valve check
(1) Key "OFF".
(2) Disconnect PCV valve.
(3) Check the movement of plunger by putting in and out a thin stick.


(4) Is the movement of plunger normal?
YES
1) Go to "Injector check" procedure.

NO
1) Substitute with a known - good PCV valve and check for proper operation.
If the problem is corrected, replace PCV valve and go to "Verification of Vehicle Repair" procedure.

2. Injector check
(1) Key "OFF".
(2) Disconnect injectors.
(3) Check clog on injectors..
(4) Measure the resistance between terminal 1 and 2 of injectors(Component side)
A. Specification :
Temperature[°C]
Resistance[Ω]

20
14.5±0.7

(5) Is the measured resistance within specifications ?
YES
1) Go to "Sensors related to air/fuel ratio check" procedure.

NO
1) Substitute with a known - good Injector and check for proper operation.
If the problem is corrected, replace Injector and go to "Verification of Vehicle Repair" procedure.

3. Sensors related to air/fuel ratio check
(1) Check the output data of sensors related to air/fuel ratio (HO2S, MAPS, TPS, ECTS, PCSV, Injectors, etc) on scantool. (Refer to each DTC guide procedure.)
(2) Are those sensors normal?
YES
1) Substitute with a known - good ECM and check for proper operation.
If the problem is corrected, replace ECM and go to "Verification of Vehicle Repair" procedure.

NO
1) Repair or replace as necessary. And then, go to "Verification of Vehicle Repair" procedure.

 

[440Magnum]

I've had one MAP sensor go bad on a Chrysler vehicle. It would stall on initial acceleration (unpredictably) and finally threw a code. But this was back in the OBD-1 days (1993 vehicle).

Everything you're suggesting sounds a whole lot more like a leaky injector or O-ring than a MAP sensor. The lean bank one might indicate that the leaky injector is on the OTHER bank, and the system is trying to trim to compensate. I don't think the MAP sensor is even used during cold idle, so if you have a roughness and gasoline smell under that condition its probably not to blame.

 

[grumpy]

A bad MAP sensor will give you a very unstable idle. It would be sending bogus information to the computer about how much load the engine is under. At high vacuum, it would lean out the mix, and at low vacuum, tend to enrich the mixture for more power. If it is scrambled, it will be sending variable load information, thus messing up the idle.
You can use a Hz meter, which is on some DVOMs, to measure the MAP output. It will send, in most cases, a different frequency depending on Manifold Absolute Pressure. Thus you can watch the frequency change as the vacuum in the intake changes.
tom

 

[ARCOgraphite]

This engine only has one bank. I4. But doesnt the car have a MAF too?

 

[wolf_06]

Originally Posted By: 440Magnum
I've had one MAP sensor go bad on a Chrysler vehicle. It would stall on initial acceleration (unpredictably) and finally threw a code. But this was back in the OBD-1 days (1993 vehicle).

Everything you're suggesting sounds a whole lot more like a leaky injector or O-ring than a MAP sensor. The lean bank one might indicate that the leaky injector is on the OTHER bank, and the system is trying to trim to compensate. I don't think the MAP sensor is even used during cold idle, so if you have a roughness and gasoline smell under that condition its probably not to blame.

Could be very possbile, is it complicate to check injector O rings?

 

[Doog]

Originally Posted By: wolf_06
Originally Posted By: Doog
Exhaust leak?


Hum maybe, I had the flex pipe replaced a while a ago...


I would check that first. Doesn't take a huge leak to throw a really annoying code that will keep re-appearing.

 

[Doog]

Originally Posted By: wolf_06
Originally Posted By: 440Magnum
I've had one MAP sensor go bad on a Chrysler vehicle. It would stall on initial acceleration (unpredictably) and finally threw a code. But this was back in the OBD-1 days (1993 vehicle).

Everything you're suggesting sounds a whole lot more like a leaky injector or O-ring than a MAP sensor. The lean bank one might indicate that the leaky injector is on the OTHER bank, and the system is trying to trim to compensate. I don't think the MAP sensor is even used during cold idle, so if you have a roughness and gasoline smell under that condition its probably not to blame.

Could be very possbile, is it complicate to check injector O rings?


You may just want to give it a double dose of Techron and reset the code and drive it a while. Might just be a dirty injector.

 

[wolf_06]

Originally Posted By: Doog
Originally Posted By: wolf_06
Originally Posted By: 440Magnum
I've had one MAP sensor go bad on a Chrysler vehicle. It would stall on initial acceleration (unpredictably) and finally threw a code. But this was back in the OBD-1 days (1993 vehicle).

Everything you're suggesting sounds a whole lot more like a leaky injector or O-ring than a MAP sensor. The lean bank one might indicate that the leaky injector is on the OTHER bank, and the system is trying to trim to compensate. I don't think the MAP sensor is even used during cold idle, so if you have a roughness and gasoline smell under that condition its probably not to blame.

Could be very possbile, is it complicate to check injector O rings?


You may just want to give it a double dose of Techron and reset the code and drive it a while. Might just be a dirty injector.


Maybe, we dont have techron here in canada, in my area. Im not sur a ''Fix in a bottle'' will fix this, but maybe, any other injector cleaner could do the job too?

 

[440Magnum]

Originally Posted By: wolf_06


Could be very possbile, is it complicate to check injector O rings?[/quote]

Well, first I should clarify that I'm not even sure your engine is designed such that the injector O-rings could leak fuel into the manifold- many vehicles are such that an injector-to-rail O-ring will leak externally. Some (like my former Chrysler 3.5) are made so that one O-ring will leak externaly, and another internally. But you could have a leak THROUGH an injector that would do the same thing as far as the symptoms you're seeing.

An easy test to rule a leaky injector out is to observe the fuel rail pressure leak-down overnight. Put a pressure gauge on, and watch the pressure over a few hours (or overnight) after shutdown. If it drops very little, you do NOT have an injector or O-ring leak. If it drops very fast, you probably do have a bad injector, but it could also be something more innocuous like a leaky fuel pump check-valve. The only way I know to positively test is to lift the injector/rail assembly from the manifold and pressurize it (if possible) and look for leaks, or else pressurize the injectors in a test rig.