Got some CEL codes, sound like MAS?

[AlphaAssault]

I got a CEL the other day when my car started bucking and lurching every time i built up any amount of boost. So, I plugged in a buzzer to the diagnostic port, and is spat out 4 different codes. i wrote them down and looked up what was triggering the codes. Heres what I came up with:

12-Volume airflow sensor
13-intake air temp sensor
14-throttle position sensor
25-barometric pressure sensor

This to me sounds like my MAS just **** the bed. Except for that throttle position sensor, what is that all about? does it sound like I need a new MAS? Would a bad MAS cause the shuttering upon entering boost territory? Any other Ideas?

 

[DanThMan1983]

Well I would normally get on alldata and see what ya got going on but my work made it so I couldnt anymore anyways, I would guess intake air temp, baro, and volume air flow are all MAF related and either wiring needs to be fixed or the maf needs to be cleaned or replaced. I have never cleaned a mitsubishi MAF but I clean Ford MAF/Baro sensors all the time. Little bits of dust get on the resistors in the MAF and throw bum readings which throw the codes. Rip the MAF off, if it looks dirty clean it, if not replace it. Thats what I would do

 

[AlphaAssault]

The MAS is all hacked to hell. I dont know if that really matters or not, because before all this it has been running fine. It doesnt look that dirty, but who knows. Ill ###### just replace it because im tires of the crappy idle.

 

[tqmx1]

Has your ECU ever been gone through? If it has not that would be the first thing I would be looking at.

To throw mutiple codes from the same unit would be extremley rare and then to through in the TPS at the same time. Well the ECU is the only thing that comes in contact with all 4.

 

[AlphaAssault]

Ive never been through the ECU before today. I dont know about the previous owner. I dont quite understand though, why does the number of codes produced make a difference? Should it have only produced one code? Also, most of those codes came from the same sensor, the MAS, so why couldnt more than one code be produced?

 

[tqmx1]

The MAS has 3 different circuits 4 counting the TPS. The only thing all 4 circuits have in common is one ground wire(pin 6 on the MAS and pin4 on the TPS) that same ground also goes to the engine coolant temp. sensor. The baro sensor gets it power from pin 23 out of the ECU feeding to pin 4 of the MAS the air flow sensor gets it power from the MPI control relay 12V and feeds into pin3 of the MAS that wire also feeds the injector resistor pack along with the purge control+fuel pressure solenoid valves the O2 sensor heater and the switched hot for the ECU(Pin102). The air temp sensor gets it's power and return signal from pin 8 in the ecu to pin 8 in the MAS. And last but not least the TPS gets it's power from pin 23 also ( goes to pin1 in the TPS) the ground is pin4 and pin 2gives it signal to pin19 in the ECU.

So for all 4 units to take a dump at the same time is highly unlikley.

Bad CAPs in the ECU means bad info every where.

 

[AlphaAssault]

Hmmm, i see... so, what does this mean? Is it time to take out the ECU and replace some parts? Would replacing the MAS do any good?

 

[tqmx1]

Hmmm, i see... so, what does this mean? Is it time to take out the ECU and replace some parts? Would replacing the MAS do any good?

Run a search for ECU or CAPs and you can make up your own mind. Remove it and open it up the odds are it will smell like dead fish or it's burnt all to heck. Check on steves web site he has some good shots of cooked ECUs and would be a good one to fix it if it is. If the ECU has not been touched it was living on borrowed time, they were starting to die 10years ago.

As for the MAS if you want a stock one as a starting point go for it.

 

[AlphaAssault]

I was thinking about this, and I have another question: Why would those sensors, or the CAPs in the ECU, only send a bad signal when entering boost? Because I only get the CEL after a good amount of shuttering (it doesnt give me a CEL if it just shutters a little), it seems like more of a bad sensor reading than a bad ECU.

Also, could this be a timing issue? It sounds like the ECU is already retarding timing when entering boost because of the sensors, could timing be off just a little as well?

 

[p1s70np0w3r]

Sounds like mass switch it out and find out

 

[wolf20043]

Had all the same codes, turned out to be a setting in the AFC got re set, all MAS related. MAS "should" be the culprit.
Mike

 

[tqmx1]

If you feel it's the MAS change it out. If it works good for you. If not you know where to go next.

If you get one make sure it has both honeycombs in it, start out with bone stock and go from there.

All I can tell you that all 3 of my 1Gs 2 90s & a 91 all turbos have had bad CAPS and all 3 have had different symtoms when they took a dump.

Good luck.

 

[p1s70np0w3r]

Had all the same codes, turned out to be a setting in the AFC got re set, all MAS related. MAS "should" be the culprit.
Mike

OH yeah i did have that same problems when i had the safc2 wired up wrong.

 

[AlphaAssault]

If you feel it's the MAS change it out. If it works good for you. If not you know where to go next.

If you get one make sure it has both honeycombs in it, start out with bone stock and go from there.

All I can tell you that all 3 of my 1Gs 2 90s & a 91 all turbos have had bad CAPS and all 3 have had different symtoms when they took a dump.

Good luck.

how can I fix the CAPs myself?

 

[p1s70np0w3r]

If you know how to solder and repair electronics your fine if not... i can or other can...

 

[tqmx1]

how can I fix the CAPs myself?

It will take all of ten min. to pull & check the ECU (shorter than this thread has been running this evening) take the cover off it and then remove it from the base. You will see the 3 caps standing vertical right behind the main plug in. Use your nose and take a big wiff around the CAPS if they smell like dead fish or look like they are leaking fluid you have a problem.


As for repair, unless you are super good with a soddering iron and are good at working on printed circuit boards that is one job I would farm out (and I did). The parts are cheap $10 or less but the labor depending on the shop's experience can quickly add up.

There are some super guys in the the group (Steve is one of them) that can repair the units (unless it's a total FUBAR) and if it is shot they can be picked up in the classifieds for fair $$.