afm or ecu

[88supraturbowhite]

My car is running good but then sometimes it will just die. pulled some codes and i got 51 so i check the wires and ran it again. this time the 51 was gone but i got code 31 so i pulled the afm and tested it and got 2700 at 66 degrees. so i went to troubleshoot the ecu and i read the tsrm but im lost i dont know what to connect to what. i also wanted to know if there was a way to test the circuit between the ecu and the afm. Im sry if this is a way to stupid question i have a hard time finding information.

 

[boosthead]

My car is running good but then sometimes it will just die. pulled some codes and i got 51 so i check the wires and ran it again. this time the 51 was gone but i got code 31 so i pulled the afm and tested it and got 2700 at 66 degrees. so i went to troubleshoot the ecu and i read the tsrm but im lost i dont know what to connect to what. i also wanted to know if there was a way to test the circuit between the ecu and the afm. Im sry if this is a way to stupid question i have a hard time finding information.

hello to all of you. this is my 1st post but i've been readin for a little while. some of u guys are frikken hillarious! you've been very helpful too. i've had her running for 3 months or so, thanks for that, but stuff keeps poppin up...

like currently, i'm havin the same problem as above. didnt measure the resistance of the afm but i got the same codes and symptoms, oh and i have no boost. i hear the turbo spinnin up but i got nothin. can't find and boost leaks and wires look ok...can you help me and whitey?

 

[a_sesshoumaru]

code 31 is your afm, try another one, code 51 is your tps position, check it. Turbo not boosting might be low fuel pressure, bad timming, boost leaks, turbo tosted, check your codes again

 

[88supraturbowhite]

I tested my afm as jetlock says (but with volts not frequency) i got 4.78 volts from the vc constant and the ks was 4.78 at idle and decreasing with rpm. So now i have the whole engine control harness out of the car to try to find out whats wrong. Break out the soldering iron.

 

[a_sesshoumaru]

try with another afm

 

[jetjock]

Don't try and pin this on me. If you'd really done it the way I said you'd have known the AFM was shot and pulling the harness was not only unnecessary but dumb.

 

[boosthead]

Thanks. I'll check the tps and afm out and try to adjust em.

do you think the non-boost problem could be electrically related. I mean, would the ecu disable boost for some reason since the tps and afm are goofed?

it worked great until i got an oil change and put it 10-w40, seems to have gotten screwed since then...

 

[jetjock]

It'll disable boost in the sense it can't run the engine run properly with one of it's critical sensor inputs (airflow) whacked. You need to fix the codes first, especially the 31. The ecu can easily compensate for most sensor failures but it's ability to compensate for airflow failure is marginal and even then it requires a working TPS to do it. In other words you have you have the worst combination of codes possible for that kind of problem. It also demonstrates why the lowest numbered code should always be repaired first.

If all you have is a voltmeter check both the AFM's resistances and voltages. Unlike the OP use the voltage values specified in the TRSM for determining it's health. I'm assuming you didn't try to clean it. Procedures for setting the TPS are on this site as well as in the manual.

The oil change had nothing to do with it unless the AFM or it's wiring was needlessly messed with.

 

[boosthead]

jet, you are the man! you've helped me a lot and you're funny as hell.

Checked the resistance of afm at three temps (room, freezing, below freezing), checks out ok to the TSRM. It looks pretty clean too. Could there be some other problem with the afm?

After checking out the TPS, I think it needs adjusted. So i gotta lossen those 2 screws and rotate the thing to get continuity at E2 - IDL. Any tips on getting to that pesky lower adjustment screw? Or do I gotta rip apart the throttle hoses and bolts and drain the coolant from it first?

I only measured resistances, i couldn't find any voltage specs in the TSRM....?

 

[jetjock]

Based on your comments I'm assuming you made the same mistake as the OP and measured the air temp sensor in the AFM instead of the far more important part that provides airflow information. They are completely independent of each other. The TRSM has resistance specs for the airflow portion too but better is to measure frequency or voltage. Standard voltage between Ks and ground should be 2-4 vdc. Note number 3 here:

http://tinyurl.com/2hmgzq

Frequency will be 16-22 Hz at idle, increasing with rpm. About 18 Hz is typical for a stock setup.

Yes, the AFM can be faulty and not set a code 31 but since you have the code it's unlikey to have failed in the other manner. Also remember a code does not neccessarily mean a bad sensor, it only means there's a problem somewhere in the circuit.

You have to be creative with the lower screw. Some folks remove the idle speed valve. I set them up with the throttle body off the engine. There is no need to drain the coolant. You won't lose much. Drain a quart if it makes you feel better. See my post in the SME section for tips on dealing with IDL and code 51.

Funny as in ha ha or funny as in strange?