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Running rich

Tiny
PHAREZCATS
  • MEMBER
  • 2005 MITSUBISHI LANCER
  • 1.5L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 1,896,543 MILES
Hello everyone, my car is running rich, -12.5% long term. I have new injectors with seals, spark plugs. I changed my MAP sensor recently to the same part number OEM stamped MAP sensor. The one thing that is troubling me is if I disconnect the MAP sensor all readings goes to 0%, fuel trim, and short term goes from 0% to 1 then -1. My o2 sensor is reading rich then lean, normal wave. I just want to know why is the car running rich everytime I connect the MAP sensor. Any help will be great. Thanks
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Tuesday, April 3rd, 2018 AT 10:19 AM

19 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,505 POSTS
Did this problem exist before you changed the sensor out? If not you have a defective sensor. If so I would check for vacuum at the sensor.

Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Wednesday, April 4th, 2018 AT 11:29 AM
Tiny
PHAREZCATS
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Yes it was before I changed the sensor. One of my coils looks like it is firing weak, it is jumping the gap but not making any sparking.
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Friday, April 6th, 2018 AT 9:08 PM
Tiny
KEN L
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It runs okay when the MAP is disconnected? It sounds like the PCM is having an issue I would try a used one to see what happens. Here is the location.

Any codes?

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Check out the diagrams (below).

Please let us know what happens.

Cheers, Ken
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Saturday, April 7th, 2018 AT 12:18 PM
Tiny
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No codes, there hardly have those PCM down here, that is going to be a pain to find.
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Saturday, April 7th, 2018 AT 2:47 PM
Tiny
KEN L
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Does it run okay without the MAP plugged in because it could be running off of the preset values which means it will be okay if you don't mind the check engine light. Would you like to check the engine wiring to confirm its okay before you get a computer?
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Monday, April 9th, 2018 AT 9:11 AM
Tiny
PHAREZCATS
  • MEMBER
  • 20 POSTS
Yes, the car running Okay, not great, it idles a bit high and all fuel trims are down to 0%, and I am getting the voltage at the map sensor. Only check for five volts.
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Monday, April 9th, 2018 AT 7:46 PM
Tiny
KEN L
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  • 48,505 POSTS
Okay, here is a guide and the engine wiring diagrams so you can go over the wiring to make sure you don't have a bad connection somewhere:

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below).

Please let us know what happens.

Cheers, Ken
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Tuesday, April 10th, 2018 AT 10:29 AM
Tiny
PHAREZCATS
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Okay, so I check the voltage to the map sensor and it is 4.70 volts and it should be five volts, If the map sensor should give a good value at five volts would 4.70 volts make the signal wire send incorrect voltage to the PCM.
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Monday, April 16th, 2018 AT 7:42 AM
Tiny
KEN L
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Yes, it sounds be five volts. I believe you found the problem.
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Monday, April 16th, 2018 AT 9:34 AM
Tiny
PHAREZCATS
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  • 20 POSTS
I have got another next problem. I have a four wire map sensor it got temperature and manifold pressure in one. I am not seeing any wiring diagrams for the four pin map sensor only three pin and MAF.
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Monday, April 16th, 2018 AT 4:33 PM
Tiny
KEN L
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You say MAP in the first post, I see the map in the wiring diagram and you say you have a four wire map I have never seen that only three wire.
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Wednesday, April 18th, 2018 AT 11:26 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,627 POSTS
Which country is this car from? If it has the 1.5L 4G15 in it, that is a different engine control system than the 2.0 sold in the US.
The base engine is the same as sold in the earlier 2002 Mirage, but the US versions have to meet OBDII specs while the other countries do not so they use a slightly different control system depending on the country they are sold in. There still should be the same three wires (five volt, ground, signal) for the MAP but the five volts feeds both the MAP and the IAT.

I would expect the readings to drop when you unplug the MAP as it loses the primary control signal and switches to substitute numbers to make it run. With the MAP in circuit it is pulling fuel out. What did the plugs look like when you pulled them out? If this car is burning a bit of oil the O2 would show it was running richer than it should and cut back on fuel. It would also do that if the fuel pressure was higher than spec. Or if it has a misfire in a cylinder.

What test equipment do you have or can you get a hold of? If you can get a scope you could look at the ignition waveform and see if the burn time in the cylinders match. Even those old Sun monster analyzer scopes could show that.
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Wednesday, April 18th, 2018 AT 1:57 PM
Tiny
PHAREZCATS
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I will have to check my spark plugs and see, it looks like my timing is off by 3/8 of a teeth, the crankshaft sprocket has some play in it, fuel pressure is 40psi an it holds system pressure when I turn the engine off and leave it there.
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Wednesday, April 18th, 2018 AT 10:04 PM
Tiny
KEN L
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I have seen where the lower drive sprocket ends up making a groove where the key way is allowing the timing belt to be retarded. This could be the problem with ours.
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Thursday, April 19th, 2018 AT 9:57 AM
Tiny
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It has no key way sadly.
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Thursday, April 19th, 2018 AT 1:54 PM
Tiny
PHAREZCATS
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This is it, it is like the crankshaft has worn out in the side the sprocket has to hold into. I think my last chance is to buy a adjustable cam gear to get the timing correct.
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Thursday, April 19th, 2018 AT 3:04 PM
Tiny
KEN L
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Was the timing belt good or did it jump a tooth? Here is a guide to help you get the belt back on correctly:

https://www.2carpros.com/diagrams/mitsubishi/lancer/2005

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Friday, April 20th, 2018 AT 9:57 AM
Tiny
PHAREZCATS
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I am really having a hard time, now if I drive the vehicle to long and come to a stop, the ignition timing just goes to -20, and the vehicle just rolls when I have my foot down, I have to wait a four seconds then the car pulls off. This only happens when I drive it long. This vehicle is stress.
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Monday, April 23rd, 2018 AT 7:27 PM
Tiny
KEN L
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This is sounds more like a PCM problem than a timing issue. I would try a used unit to see what happens. Sometimes they need to be programmed.
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Tuesday, April 24th, 2018 AT 11:20 AM

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