Got a tuff one!!!!

[daman]

We have a 1986 T.A 305 TPI that is kicking our butts,

the problem we are having is with the MAF plugged in it will
barely start barly run and stall,the little it does run we get NO ses light
BUT.......if we unplug the MAF plug she'll start right up and run good
idle good everything seems fine but of coarse then the ses light is on
telling us the MAF has a problem,but of coarse because it's un plugged.

Now we have checked the MAF it's good!!!,, we have checked the wiring
for the MAF it's good!!!,,we have checked the MAF burn off relay it's good,
we have checked the MAF power relay it's good.

we have a GM FSM for this car and we have done exstensive checks on
all these cercuts but still nothing.

if we had a ses light to chase it would be easer to diagnose but there
is none.

has any one had this problem????
any thoughts????

Thanks!!!!!!!

[wrightz28]

A bogey TPS sensor will set off what looks like a MAF issue.

[daman]

Originally Posted by wrightz28

A bogey TPS sensor will set off what looks like a MAF issue.

According to my sacn tool there is no problem with the TPS,,at closed
throttle(0%) and full throttle(100%) it's at specs.,,readings shows that
it's riseing and falling correctly.

Thanks!!!!

[wrightz28]

so at idle it's at .54V (+/- .05) and WOT it goes to 4.50V?

ok, just thought I'd toss that one in there. No vacuum leaks? Be sure to check the vent tube for the charcoal canister at the TB. The elbow cracks, un-notiicablly and creates a huge leak.

I'm assuming you tried swpaing the realys and all that other fun stuff right?

[daman]

Originally Posted by wrightz28

so at idle it's at .54V (+/- .05) and WOT it goes to 4.50V?

ok, just thought I'd toss that one in there. No vacuum leaks? Be sure to check the vent tube for the charcoal canister at the TB. The elbow cracks, un-notiicablly and creates a huge leak.

I'm assuming you tried swpaing the realys and all that other fun stuff right?

Yes to the voltage and yes to the vac. leaks(none)... but even if the elbow
was cracked it only runs bad with the MAF pluged in,,unpluged it runs
fine like there's nothing wrong..

the only realy we tryed swapping was the MAF burn off,,the power relay
we don't have one but according to the FSM there's no problem with it..

thanks,

[wrightz28]

With the FSM tho,what are are the GPM's at?

Ultimately, if the engine starts and runs fine in default mode with the MAF disonnected it's wither the realy or the sensor itself, I know it may look ok but otherwise you'll be pulling your hair out, trust me on that one, maf issues suck. So, all I can say is verify the relay is good and if so get a hold of a MAF off a correctly running TPI and see what you got.

good luck.

[daman]

Originally Posted by wrightz28

With the FSM tho,what are are the GPM's at?

Ultimately, if the engine starts and runs fine in default mode with the MAF disonnected it's wither the realy or the sensor itself, I know it may look ok but otherwise you'll be pulling your hair out, trust me on that one, maf issues suck. So, all I can say is verify the relay is good and if so get a hold of a MAF off a correctly running TPI and see what you got.

good luck.

Can't remember what GPM's were,,and thats another thing weird with
the MAF unpluged you still get a GPM reading with throttle movement,,WTF.

LOL....and yea i pulled the MAF off my maro and tryed it on the T.A,,
same prob.,,then i tryed the T.A MAF on the maro and it's good ran fine
so the MAf on the T.A has to be good then.

may try to find another MAF power and burn off relay just to be shure
because we know the MAF is good

thing is pissing us off......

thanks for helping!!!

[daman]

^^^

[Morley]

Originally Posted by daman

Can't remember what GPM's were,,and thats another thing weird with
the MAF unpluged you still get a GPM reading with throttle movement,,WTF.

You will get a gms/sec reading with the MAF sensor disconnected, but is it only a guesstimate from the ECM based on throttle position.
Your burnoff and power relays are the same and interchangeable, swap them around and see if that makes a difference. If you can get 2 new relays and put them in it would be a better test...If yo replace them and the problem persists, you'll need to start chasing wires, you could have a short or a frayed wire that will check good for ohms but can't carry a power load.

[daman]

Originally Posted by Morley

Your burnoff and power relays are the same and interchangeable, swap them around and see if that makes difference.

yup already tryed that don't help.

going to try to find some good used ones.

[Blue Bowtie]

Reconnect the MAF wiring. Back-probe the MAF connector with voltmeter probes between the 'C' and 'A' terminals. Start the engine and try to maintain a normal idle RPM while reading the MAF analog output:

[daman]

so thats what the readings should show?

does it mater witch lead is on witch wire??

[Morley]

Check the harness connector for the MAF sensor. The pins are female and will get stretched out of shape causing poor contact with the sensor. If they are stretched out, use a very sharp pointed awl and bend them back into shape and see if that helps.

[Blue Bowtie]

Originally Posted by daman

so thats what the readings should show?

does it mater witch lead is on witch wire??

The 'A' terminal is signal ground (negative). If you use a DVM, it shouldn't matter since the meter should simply display negative voltage. The millivolt output is what is critical.

And Morely is right - Poor connections will kill the system. The MAF might be working perfectly, but if the signal doesn't get to the ECM, you're screwed. Scanning the ECM for data will only show the erroneous signal, and without FULL diagnosis someone might change the $400 MAF unnecessarily, and be right back in the same situation (ever read that "No refunds on electrical parts" sign at the parts store?).

[daman]

Originally Posted by Blue Bowtie

The 'A' terminal is signal ground (negative). If you use a DVM, it shouldn't matter since the meter should simply display negative voltage. The millivolt output is what is critical.

And Morely is right - Poor connections will kill the system. The MAF might be working perfectly, but if the signal doesn't get to the ECM, you're screwed. Scanning the ECM for data will only show the erroneous signal, and without FULL diagnosis someone might change the $400 MAF unnecessarily, and be right back in the same situation (ever read that "No refunds on electrical parts" sign at the parts store?).

yuuup,know all about it, going to do these checks this weekend
thanks for the tips!!!