tdehne

I swapped out the turbo on my 87 turbo II, with one that had less shaft play. Now when I try to accelerate the car dies. It will start and idle fine. If I slowly accelerate it is fine, but as soon as I get any kind of boost the car dies. So I put the original turbo back in it. Same thing happens. I do believe I got all the hoses back in the right place, frankly I can't see where any of the hoses could reach into another place. There are no unusual noises in the engine compartmemt. It should be noted that I tried to disconnect the AFM by the Phillips head screws next to the connector on the unit. Once I saw that more stuff came out I put it back and reconnected the Phillips screws. Did this screw up my AFM? IF so why does it run just fine with no boost, and then die when i give it some? Has anybody run into this before?

tdehne

by the way, I tried to bypass the AFM by jumpering the fuel pump connector and that did not help. Still the car died when boosted.

classicauto

iTrader: (3)

very interesting....
when it idles, does it hunt at all?
any vac leaks?
does it flood out after it stalls or just die?

from a first guess standpoint im gonna say AFM since you tried to take it apart, and that would make the most sense but im just not 100% on it....

HAILERS

****It should be noted that I tried to disconnect the AFM by the Phillips head screws next to the connector on the unit. Once I saw that more stuff came out I put it back and reconnected the Phillips screws. Did this screw up my AFM?********

Not good. If it were me, I'd get a digital meter out and go to pin 2E on the ECU. With the key to ON, I'd watch the voltage as someone pushed the vane in the afm all the way aft then let it return to close. The voltage should fall and rise as the vane is opened and shut.

On the other hand, maybe your leaving the purge checkvalve out of the rear of the turbo inlet duct or maybe the bov (air bypass valve)?.

tdehne

Thanks for your quick replies. I have pm'ed a few people about a used AFM and will try to pin it out thursday, when I can get back to the car. But please tell me more about the purge check valve. Where exactly is it? Does this come off of the tube that goes from the turbo up to the intercooler? I might mention that this is a stock system with a RB downpipe and presilencer.

tdehne

the car idles as well as it did before I started to work on it. It lopes a little, but holds at around 750-800 rpm. Doesn't seem to be any vacuum leaks. All hoses went back like they were before. Could a vacuum leak cause the engine to die only when boost is applied? If i rev slowly, the car runs just fine, only when it gets a slight amount of boost does it die.

ALSO, if I jump the fuel pump lead on the passenger side shock tower, shouldn't the car still run regardless of what the AFM is doing?

HAILERS

No, it's that silver checkvalve that shoves into the back of the turbo inlet duct. Just a bit below the bov if I remember right.

Even a non turbo afm would start that car if it was a afm issue. Just FYI

tdehne

The Turbo Inlet Duct (TID) goes from the AFM to the Turbo then? I don't remember putting any silver thing on that. I just reinstalled the TID (this is the black hose) on the turbo and the other end on the AFM... is there something I missed? Do you have any pics?

IF I left that purge valve off, then would the car idle fine, and run ok if not under boost?

Would the fuel pump connector by pass the AFM ?

tdehne

Oh and you said that the NA AFM would start the car, would it run the car too with boost? Because my car starts and runs, just can't handle any boost.

HAILERS

The afm has a switch inside that gets *made* when the vane opens. That puts a ground on a circuit opening relay which in turn lets the fuel pump run. I doubt very much if that particular function of the afm is bad. Just forget about jumpering the fuel pump check connector (which bypasses the switch in the afm).

It's the other functions of the afm that might be giving you problems. In particular the wire that goes to 2E on the ECU. But then again since it idles, I start wondering if there is a problem with the afm at all. And you said or implied that you could drive gently with the car so that makes me wonder if it's something other than the afm.

If it's a stock turbo inlet duct for a series four, then there should be two items plugged or shoved into the back of the duct. An approx 3/8 hole for the purge checkvalve and a larger approx one inch hole for the BOV or air bypass valve in Mazda terms.

Maybe either the intercooler hoses are blowing off during acceleration or maybe the turbo inlet duct is blowing off during acceleration. Or one of the hose b/t the turbo and the intercooler inlet.

I'm starting to shy away from thinking its the afm.

Yes. You can put a non turbo afm on and boost the car/engine. Been there/done that. But I run with a turbo afm as a general rule.

tdehne

Thanks for the help, I have seen your posts a lot and I know I can trust your advice. I do remeber plugging one thing in to the TID, but not two. Where is the least obvious one. I remember the one I did plug in was real obvious.

Also on a second note, is ok to run the turbo withOUT heat shields? Those things suck.

tdehne

Oh, I forgot, I CAN drive the car, just as long as I can stay out of the boost. OF course right now the car is at the bottom of a big hill I can't make it up, so you see my urgency and trying to figure out what i did. Has to be something simple, but not obvious.

tdehne

I don't have the car here(it's at the bottom of big hill) but the FSM only has one thing plugged into it. Of course there is not a good pic or even the best angle to see what is going on. Do you know what the FSM would call the purge valve?

HAILERS

The online 88fsm, Fuel Section, page 4B-5 shows the two items plugged into the back of the turbo inlet duct. Also make sure the air bypass valve has a vacuum line coming off it goint to the inlet manifold.

tdehne

The air bypass valve for sure was connected. Now that is the small tube off the top of the valve that goes to the intake manifold. RIGHT? I know I connected that one up.

I have the 1988 Mazda Workshop manual, and the fuel emissions and turbo are in section 7. Where do I go for the online one you are talking about?

tdehne

Nevermind, I found the FSM and looked at it. I did plug that one in too. It is tough because I don't have the car here, but I do remember plugging that one in. Please if you would have any suggestions, Please let me know. I will test the AFM, like you said, but it does run and will run well up to redline, as long as you stay out of any amount of boost.

crilleswe

i have the same problem but on a s5.
if u rev in neutral does it still do it?? mine didnt at first but it does now, also have no problems reving it by pulling the throttle wire under the hood(the one going over by the charcoal-canister), only when pushing the pedal like 20% it stalls. pushing at low load i can rev it all the way.



only mods are open filter and cat-back( has worked fine with both before)

HAILERS

My error. 4B-5 of the 87manual.

SpAm@FC

iTrader: (4)

i've had exactly the same problem on my TII when i have installed a AFM from a non turbo...

i say check your AFM or get one from a friend to try it

tdehne

A good AFM fixed my problem. Now the car runs great.

crilleswe

gonna have to try and get hold of a afm to test then, too bad the nearest rx7 owner is 200km away

can a mecanic shop check the afm if i just unplugg it and give them or do they need to test it in the car ?