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General Forums => The Mess Hall => Topic started by: jonzjeepyj on January 20, 2009, 03:18:43 PM
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After doing the 4.0L TB upgrade , I have been throwing a code on the Jeep that is a #13
*Manifold Absolute Pressure (MAP) Sensor Vacuum* code. Could this be due to the TB upgrade?
I'm not running a wide band O2 sensor which ties in to all this. I did use the TB of a 96 and newer
Jeep and capped off the extra port for the map sensor. Or is it the MAP sensor going bad.
When I start up the Jeep in the morning to warm up, after running for about 20 seconds, the idol
drops off and it runs really rough for 3-5 seconds and then returns to a normal idol. This will throw the
check engine light. If I stop and start it up again , the check engine light goes off and I notice nothing
wrong.
Your opinion on what it might be?
O2 Sensor ?
MAP Sensor ?
The Jeep adjusting to the larger TB ?
Thanks, John
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Did you change the IAC motor and housing?
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Yes, I reused the 2.5L IAS on the 4.0L TB
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This started 2 weeks after I installed the 4.0L TB. It ran fine for 2 weeks and only started
doing this a few days ago. It runs and drives fine after it returns to normal with no other
symptoms except for the thrown code.
The check engine light goes off and no more problems or symptoms. If I get in it and drive
imeadetly, it does not happen?
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Just thinking out loud,
Could it be that I'm NOT running the wide band o2 sensor and it cant adjust fast enough in the cold weather?
Could it be an intermittent problem and the MAP sensor is going bad?
Due to me upgrading the TB and boring out the intake, is it just adjusting to the larger air flow?
Or is a a vacuum problem and it's not sensing the air flow at the TB / Bad venture?
Again, I'm just throwing out some ideas
John
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Dang... you've got me stumped...
I'll throw this one out there too; did you restart the system by touching the positive battery cable to the negative terminal? Should drain any capacitance in the ECU...
I know it was a dumb question, but may have missed it?
And I doubt you should need a wide band O2... it's not THAT much more air flow (nothing like forced induction at least)!
And you didn't say whether you re used the 2.5L IAC HOUSING too... I'm pretty sure they are different... I'm not trying to insult you or anything, just being thorough!
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Your problem is not common to the 4.0 tb or 62mm tb upgrades, nor is it related to the o2 sensor. Your stock sensor is fine, wideband is primarily used for an AFR guage.
Make sure you used the 2.5 IAC & IAC housing, and the IAC gasket is intact and housing is tight.
I recommend a good bench cleaning of the TB & IAC. Then try a different MAP sensor.
As a last resort, buy one of my 62mm TB's ;-)
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Just to restate,
I did use the 2.5 IAS motor and housing and all sensors
off the 2.5 TB on the 4.0L TB I bought a new gasket
from NAPA and replaced the old one. I did not ground
out the ECU for 30 secs. yet but that would only clear
the codes, Not solve the problem.
I think a good bench cleaning is in order also. I also wanted
to try Sea Foam through the motor. It doesn't happen every time
I start it up either. I'll do the cleaning and Sea Foam and see
what happens.
Thanks,
John
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I remember someone had a problem where the bushing for the shaft that the throttle plate(probably wrong word but...) is connected to went bad and let air leak in... but that would happen all the time so :puzzled:
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Just to restate,
I did use the 2.5 IAS motor and housing and all sensors
off the 2.5 TB on the 4.0L TB I bought a new gasket
from NAPA and replaced the old one. I did not ground
out the ECU for 30 secs. yet but that would only clear
the codes, Not solve the problem.
I think a good bench cleaning is in order also. I also wanted
to try Sea Foam through the motor. It doesn't happen every time
I start it up either. I'll do the cleaning and Sea Foam and see
what happens.
Thanks,
John
Grounding the ECU would not only clear the codes, but reset the a/f maps that the ECU has learned from your old system. I think it takes 40 warm-up cycles for the computer to "learn" your engine's correct maps.
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Correct, but it's 50 warm-up cycles. Probably a good idea to speed up the HP and mileage gains.
Yes occasionally the throttle shaft bearings/seals will wear out and cause a vacuum leak, generally leading to a high idle. But I think it would happen more regular that what he's describing.
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i would reset the ecu. after i did my swap i had a messed up idle at times. then i got a new ecu shartley after due to the old one dyeing and all problems fixed.!
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OK, I'll ground and discharge the ECU to wipe everything off and go from there.
It was a idling problem but a very low idol and sputter for about 3-5 seconds and
then back to normal. It hasn't done it again so I will leave it for now. I will discharge
and ground the ECU right now though.
John
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I just read a site that recommended this for resetting the ECU.
Disconnect battery and touch pos. and neg. cables together for 30 sec.
Reconnect.
Turn ignition to run (not start).
Turn headlights on, then off.
Turn ignition off.
I'm not real sure what the headlight sequence has to do with it, but it's not the first time I've seen it recommended. Anybody else know?
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Does just disconnecting the pos. on the battery reset anything?
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The ecu probably has a solid state memory that will retain its current state (1 or 0) when simply disconnected, but touching the terminals together will drain the on-board capacitors and erase the "1"s, setting everything back to "0". All that is speculation though...
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The ecu probably has a solid state memory that will retain its current state (1 or 0) when simply disconnected, but touching the terminals together will drain the on-board capacitors and erase the "1"s, setting everything back to "0". All that is speculation though...
When I did my 4.0 TB swap and the 62mm TB swap I just undid the pos. on the battery. I thought that it cleared the ecu. Maybe it didn't :confused: But I have not had any problems with either swap.
If it didn't do anything will it still take 50 warm up cycles to become readjusted?
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Got this off of Quadratec's website:
Jeep Electronic Control Unit Reset:
When installing new power or performance accessories how does the computer for the Jeep know that it has a new accessory? Most of the time the computer does not. The computer would need to be reset to take full potential of the performance accessories you have added.
The Electronic Control Module, or ECU as its commonly called, stores the information for your vehicle and your driving habits in its memory. The memory is maintaned by a series of capacitors that hold a charge and maintain power for the ECU when the vehicle is turned off. The following procedure will allow you to reset the memory and allow the computer to 're-learn' how to drive by adjusting to the drivers habits and the vehicles modifications.
1. Disconnect the battery by removing the positive battery cable. Remember, the positive battery cable.
2. Ground the positive cable to the negative cable for 30 seconds to erase the electric charge in the capacitors.
3. Reconnect the positive cable to the battery.
4. Turn the key to on but do not start.
5. Turn the headlights on.
6. Turn the headlights off.
7. Turn the key off.
The ECU has now been reset to its factory settings. For the next 50 warm-up periods the ECU will re-learn the engine and driving habits for your driving conditions and the newly installed parts.
http://www.quadratec.com/jeep_knowledgebase/article-89.htm (http://www.quadratec.com/jeep_knowledgebase/article-89.htm)
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Got this off of Quadratec's website:
Jeep Electronic Control Unit Reset:
When installing new power or performance accessories how does the computer for the Jeep know that it has a new accessory? Most of the time the computer does not. The computer would need to be reset to take full potential of the performance accessories you have added.
The Electronic Control Module, or ECU as its commonly called, stores the information for your vehicle and your driving habits in its memory. The memory is maintaned by a series of capacitors that hold a charge and maintain power for the ECU when the vehicle is turned off. The following procedure will allow you to reset the memory and allow the computer to 're-learn' how to drive by adjusting to the drivers habits and the vehicles modifications.
1. Disconnect the battery by removing the positive battery cable. Remember, the positive battery cable.
2. Ground the positive cable to the negative cable for 30 seconds to erase the electric charge in the capacitors.
3. Reconnect the positive cable to the battery.
4. Turn the key to on but do not start.
5. Turn the headlights on.
6. Turn the headlights off.
7. Turn the key off.
The ECU has now been reset to its factory settings. For the next 50 warm-up periods the ECU will re-learn the engine and driving habits for your driving conditions and the newly installed parts.
http://www.quadratec.com/jeep_knowledgebase/article-89.htm (http://www.quadratec.com/jeep_knowledgebase/article-89.htm)
Thanks!
What happens if you don't do this? I just takes longer to re-adjust or it won't re-adjust because it does not know that the TB was swapped?
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I don't know, there are differing thoughts on this. Some people say the computer will adjust to and others say it wont because it doesnt know its there. Now the other weekend I completely killed my battery on accident, and after I got it recharged and started it up my Jeep ran 100% better. It didnt do any more of the high idle when it firsts starts up or anything like, and I had not reset the computer since I put the new PD kit, Injectors and 4.0 Throttle body. So after that my thoughts are if it doesnt know than its not going to adjust or its going to take much longer to adjust
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OK,
I unplugged the + terminal and grounded it to the - terminal for over 1 minute.
I then turned on key (not start) and then flipped headlights on . shut off the headlights and
turned key off. From a cold I started it and within 20 seconds it did it again. Idol dropped
off and ran rough for about 5 sec and check engine light came on and stayed on. It then
went back to a normal idol after 5 seconds with the check engine light still on. I shut off
the jeep and imideatly started it right back up and the check engine light went off.
Hmmmmmm ! ? ?
I read the codes and all codes normal except #13
The rest were ...
12
16 ?
33
62
55
I don't know? ? ?
John
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Sure you got the #16 correct?
Try replacing the MAP sensor, find a buddy to temporarily swap with if you don't want to buy a new one.
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I'll verify the 16 but I did it twice. I'll let you know.
#12 isn't on the list. I thought that #16 was another # not on the list?
How much is a MAP sensor?
John
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Ah Haaaaaaaa ! ! !
I was doing some research on the MAP sensor problems and codes.
No where does it say ANYTHING about the mysterious code *16* I was pulling.
I came across a trouble and repair article on a auto zone web page and it told
me how to test the MAP sensor.
When testing the supply voltage at the MAP sensor terminal C, the voltage should
be 4.5-5.5 volts. At terminal 16 of the ECU wire harness connector the corresponding
wire harness terminal is #16 There is the code 16.
I'm guessing the wiring harness is going bad or a lead is loose.
Test the MAP sensor output voltage at the MAP sensor connector terminal B for 4-5 volts.
If you notice it's also telling you to test the output voltage at terminal #33 for the supply
voltage to the MAP sensor.
***(code 33)***
M.A.P. SENSOR
The MAP sensor is attached to the plenum chamber near the hood latch.
It reacts to absolute pressure in the intake manifold and provides an input
voltage to the ECU. Manifold pressure is used to supply mixture density
information and ambient barometric pressure information that is necessary
for computing the air/fuel mixture. A vacuum line from the throttle body
attaches to the MAP sensor to provide its input pressure. A Manifold Air
Temperature (MAT) sensor is located in the intake manifold and measures
the air/fuel mixture temperature to allow the ECU to compensate for air
density changes during high temperature operation.
TESTING
MAP sensor connector terminals
(http://i270.photobucket.com/albums/jj95/johnebquick/0900823d801fe7a9.gif)
Inspect the MAP sensor vacuum hose connections at the throttle body and
sensor and repair as necessary.
Test the MAP sensor output voltage at the MAP sensor connector terminal B
as marked on the sensor body, with the ignition switch ON (engine OFF). The
output voltage should be 4-5 volts.
Test ECU terminal 33 for the same voltage described above to verify the wire
harness condition. Repair as necessary.
Test the MAP sensor supply voltage at the sensor connector terminal C with
the ignition ON. It should be 4.5-5.5 volts. This voltage should also be at terminal
16 of the ECU wire harness connector. Repair or replace the wire harness as necessary.
Test the ECU with Diagnostic Tester MS 1700, if necessary.
Test the MAP sensor ground circuit at sensor connector terminal A and ECU connector
terminal 17. Repair the wire harness, if necessary.
Test the MAP sensor ground circuit at the ECU connector between terminal 17 and
terminal 2 with an ohmmeter. If the ohmmeter indicates an open circuit, inspect for
a defective sensor ground connection on the flywheel/drive plate housing near the
starter motor. If the ground connection is good, replace the ECU. If terminal 17 has
a short circuit to 12 volts, correct this condition before replacing the ECU.
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I just wanted to update you and tell everyone that it has stopped and has
smoothed out a little more since I grounded out the battery and reset the ECU.
It did do it a little while after I reset it but it has stopped now. I think it was
seeing the inrush of air and trying to adjust.
Thanks all for all your help.
John