simple question

[mitsubishimanic]

how would a car act with a bad mass air flow sensor

 

[MacDizzle]

Not positive if this applies to dsm's but on my SRT it would fluctuate the idol real bad and surge and/or feel under powered while maintaining highway speeds because it can't properly register the air flow into the engine. I would assume the symptoms would be about the same for most any car but I have only had the problem on my SRT.

 

[98GSXtacy]

When you start the car it will struglle very bad to idle and when you give it gas it will want to die even more. I have only had it unplugged once when I forgot to plug it back in one day, but with how rough the car was running i shut it off and noticed it was unplugged right away. Plugged it back in and it ran like a champ.

 

[Misterbeechy]

you will notice a tremble as if it were misfiring.. the motor would have a shake and you could hear it a little rough in the exhaust..

 

[iwillnotbleed]

With my car, it will start a bit odd and rest at an idle. It will idle a little high. If you give it quick throttle, it will want to die. If you ease on the throttle ever so slowly the RPM's will go up smoothly but when you let off it will either try to die or die. And it will run really rich.

 

[mitsubishimanic]

Ok sounds close my car. It will start and idles a little rough but if i give it gas it dies. if i slowly ease on the peddle it will go up about 2 grand and then try and die.

 

[amacrugby]

i have the same problem, so just buy a new maf?

 

[iwillnotbleed]

Before you replace it do a boost leak test and make very sure you have no leaks. A bad MAF and a boost leak have similar symptoms most of the time.
I've never had a MAF go bad on me before but i've heard from many different mechanics it will give off a "rotten egg" smell. Don't quote me on that though. I have no idea if that's true.

 

[mitsubishimanic]

ok well its throwing a CEL now. its is putting out code twelve air flow sensor. so i have another MAF on the way it will be here in a week or two ill let every one know how it goes. but any more thoughts would be awesome.

 

[JStrateger]

I'm not sure if this is true with mitsubishi but with a nissan, if the MAF is bad the car won't start unless it's unplugged.

 

[iwillnotbleed]

Manic, that sounds like that's what the problem is. The new MAF should fix the problem. I saw that you have a new coil pack and transister in your mods. Do you have a 91-94 ECU in that car?

 

[mitsubishimanic]

yes i do.

 

[iwillnotbleed]

Ok. I'm guessing that everything was done right? My friend has a '90 and was running somewhat like what you are describing. We figured out that before he got the car someone swaped the ECU pin's and the ECU without changing the transister, coil or the rest of what that swap need's. We put a '90 ECU back in it and found out that they swaped pin's on the ECU harness that shouldn't have been swaped in the first place. Just another possibility if the new MAF doesn't work.

 

[My2gGSX]

you will hear noises from your engine bay

 

[CODE4]

Not positive if this applies to dsm's but on my SRT it would fluctuate the idol real bad and surge and/or feel under powered while maintaining highway speeds because it can't properly register the air flow into the engine. I would assume the symptoms would be about the same for most any car but I have only had the problem on my SRT.

Are you referring to an SRT4? Because they do not have MAF sensors.

 

[mitsubishimanic]

i followed this when doing the swap. http://www.dsmtuners.com/forums/art...4-ecu-swap-into-1990-dsm-ignition-wiring.html i have a bad tps as well the are both on the way.

 

[iwillnotbleed]

My first question should've been, was the car running fine after the swap? No CEL's or anything? Did you follow Steve's wiring or Spoonman's?

Edit: Are pin's 6 and 14 on the ECU harness still swiched.

 

[guseclipse]

Unplug the maf and see if it runs better than it is now.

 

[mitsubishimanic]

I followed spoonmans. After the swap this started happening. I got car for 500 with fryed ecu and other miner problems. Swapped ecu and power transistor and it started up and it threw a cel with code 12 mas and 14 tps. The car ran ok before the ecu fryed no cels.

*edit* yes the wires 6 and 14 are still switched.
p.s. thanks for all the help im still new to dsms this is my first

 

[iwillnotbleed]

Not a problem for the help. I read through that swap again and pin's 6 and 14 should stay in the stock location if you swap everything correctly. And if I remember right the ECU wire's that you swap, pin 6 and 14, correspond to the code's that you're pulling. I would switch those pin's back and see what happens.

 

[mitsubishimanic]

ok switched them back and now im getting no cels sweet BUT it starts and idles rough and when i rev it it will go up to about 2 grand and wont rev any higher so problem is not fixed yet. now i have to start figureing out the actual problem now that my cels are gone. thanks for all the help new ideas would be awesome.

With my car, it will start a bit odd and rest at an idle. It will idle a little high. If you give it quick throttle, it will want to die. If you ease on the throttle ever so slowly the RPM's will go up smoothly but when you let off it will either try to die or die. And it will run really rich.

sounds just like my car now exept my car wont rev higher then 2 grand.

 

[iwillnotbleed]

Ok, I'm pretty sure this is being caused by something between your ECU and the harness side of the transister. I know the harness for a '90 is a 6 pin and a '91 is an 8 pin, so those two extra pins need to be found and put in the right place's. I meant to tell you earlier, in that swap link that you gave in one of your post's, no offense to anyone else but follow Steve's diagram's.

Edit: This info thank's to Steve. The two wires the '90 is missing are 5 and 6 (on the '91 transister). Those two wire's need to be found and connected to the right thing's. Between the two transistor's they also have a couple of the pin's in different place's. Make sure when you put them in the harness they're in the right place's.

90 Power Transistor Module

1=Yellow/Green Collector 1 (OC1) Coil A
2=Yellow Base 1 (IB1) ECU pin 54
3=Black Ground
4=NC
5=Yellow/Red Base 2 (IB2) ECU pin 55
6=Yellow/Black Collector 2 (OC2) Coil B

91+ Power Transistor Module

1=Yellow/Black Collector 1 (OC1) Coil B
2=Yellow/Red Base 1 (IB1) ECU pin 55
3=Black Ground
4=NC
5=White Tach Gate output ECU pin 109 and Gauge Cluster
6=Black/White +12 IG1
7=Yellow Base 2 (IB2) ECU pin 54
8=Yellow/Green Collector 2 (OC2) Coil A

 

[SpawnedX]

Actually when you unplug the MAS on my car it idles pretty smooth because the ECU runs off base maps, but it wants to stall out when you give it gas and then it rides rough and bucks.

 

[iwillnotbleed]

That's the same thing my friends car would do. Then he found the '90 ECU so that's about as far as I got. I know that harness side of the transister has a lot to do with it. I would think it has to. with those pin's not being switched it screw's the signal being sent to your coils way up.

 

[mitsubishimanic]

Ok, I'm pretty sure this is being caused by something between your ECU and the harness side of the transister. I know the harness for a '90 is a 6 pin and a '91 is an 8 pin, so those two extra pins need to be found and put in the right place's. I meant to tell you earlier, in that swap link that you gave in one of your post's, no offense to anyone else but follow Steve's diagram's.

Edit: This info thank's to Steve. The two wires the '90 is missing are 5 and 6 (on the '91 transister). Those two wire's need to be found and connected to the right thing's. Between the two transistor's they also have a couple of the pin's in different place's. Make sure when you put them in the harness they're in the right place's.

90 Power Transistor Module

1=Yellow/Green Collector 1 (OC1) Coil A
2=Yellow Base 1 (IB1) ECU pin 54
3=Black Ground
4=NC
5=Yellow/Red Base 2 (IB2) ECU pin 55
6=Yellow/Black Collector 2 (OC2) Coil B

91+ Power Transistor Module

1=Yellow/Black Collector 1 (OC1) Coil B
2=Yellow/Red Base 1 (IB1) ECU pin 55
3=Black Ground
4=NC
5=White Tach Gate output ECU pin 109 and Gauge Cluster
6=Black/White +12 IG1
7=Yellow Base 2 (IB2) ECU pin 54
8=Yellow/Green Collector 2 (OC2) Coil A

ok well i know that the white number 5 wire on the 91 PTM needs to be led to pin 109 on the ecu.

the black/white number 6 wire on the 91 PTM has to be spliced into the matching wire on the coil but ill check it all over with steves diagram tomorrow.

ok rewired my power transistor unit to steves diagram and shes alive. yay. finally now i just need to tune her so shell run good. thanks for all the help every one espesialy IWILLNOTBLEED ive been trying to figure this out for almost a month and a half.