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Discussion Starter · #1 ·
I have a 89 coupe 306 stage 1 trick flow cam, ported and polished head E7s, 1.72 rockers and usual bolt on GT40 upper 73 C&L calibrated for the 19lb injectors, aftermarket trottle body dont know the size,
The problem is I can not fiqure out the codes codes 81 thermactor air bypass TAB and code 82 thermactor Air diverter TAD I dont know really what these two sensors are, what I changed was TPS, Mass air meter and Idle air control valve, and check for vacume leaks and check all the grounds. The idle air control valve I changed off my 88 Gt that I asume was good, with no change.
how the car acts is at start up it goes up to 2200 and slowly falls with the CEL light on, when the car comes down to 1000 the CEL goes off, as soon as you touch the throttle is comes back on, when driving the car it seems to go off if the engine is under a load. The ohms at the connector for the Idle air control valve with key in run position engine off is 5 ohms? TPS is in range.
The car does not seem to idle great even when it comes down to 1000 rpm
I have been messing with this thing all day, and would like and appreciate some help to try some things tommorrow. When you have these code what is usually the cause?
Thanks any help would be appreciated
Lane
 

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Discussion Starter · #3 ·
I have been reading and I think the two seilinoids are the ones on the back side of the passager side shock tower, the electical connections are made but no vacume roution, the car has no smop epuip. is there a way to trick so to speak these? That is if I am on the right track, the map sensor does have a vacume line to it, but I think that is correct on a Mass air car?
Thanks keep them coming.
Lane
 

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81 or 82 will not trigger a check engine light. If the car is mass air as an 89 should be it will not have a vacuum line running to the map sensor as it is now called the baro sensor (same thing except no vacuum line) the baro sensor is used to figure elevation for fuel mixture adjustment. if you have a vacuum line running to the map you will have al kinds of problems. unhook it from the map but leave the port open. plug the vacuum line but DO NOT PLUG THE PORT ON THE SENSOR
 

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Like 472 said the TAB and TAD codes will not trip a CE. The TAB is the Thermactor Air Bypass and the TAD is the Thermactor Air Diverter. The solenoid just control where the smog pump pumps air to, either the cats or the back of the heads. If all that stuff has been deleted or isn't hooked up then I wouldn't worry about it too much.

On the MAP sensor. Only the 87-88 SD cars have a MAP (manifold air pressure) sensor since the MAP is what they use to determine how much air is being taken into the engine and how much fuel needs to be added. On these there is a hose from the MAP to a manifold vacuum source. 89-93s have a BAP (barometric air pressure) sensor. Basically it measures the ambient air pressure. So it should not have a hose from the BAP to the manifold. Just pull the hose, cap it at the manifold and leave the BAP port open.
 

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I have been reading and I think the two seilinoids are the ones on the back side of the passager side shock tower, the electical connections are made but no vacume roution, the car has no smop epuip. is there a way to trick so to speak these? That is if I am on the right track, the map sensor does have a vacume line to it, but I think that is correct on a Mass air car?
Thanks keep them coming.
Lane
Those codes will not cause any driveability problems or turn on the CEL indicator..... if you want to fool the system into thinking they are still connected, you could install a 75 Ohm 3 Watt resistor in the solenoid connector to "simulate" the solenoid coil resistance. The system will not throw the "8x" codes.

 

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Discussion Starter · #7 ·
evething is fine now no CEL. by taking vacume away from the Baro, the only thing now is when you fire it up it goes to about 2 grand then works it way down, But I do have very exstensive blowby, noted in another thread, title help with blowby, if you want to read and give you 2 cents,
Thanks for all the help Joel I owe you alot of beers
Thanks again
Lane
 

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Just to add to this old post:

If you get code 81 or 82 on a MAF fox, especially if you are hearing a whistle while you are driving and then not hearing it when you are under the hood, check the vacuum line coming off the diverter valve. The diverter valve assembly is on the hose that comes off your charcoal canister. The vacuum line that comes off of the diverter valve is prone to having its rubber fitting tip stretch out over time, making the seal around the valve nipple not tight. You may think it's tight but just change the tip, or the entire line since chances are it's damaged from anytime you've taken off your air intake. They crack easily, especially in cold weather states. This will cause a big enough vacuum leak to run like crap. I've come across this issue 3 times now in the 18 years I've owned foxes. The first time was a nightmare I'll never forget. Spend a lot of time and money chasing it. Do not underestimate this as the cause, especially if you have replaced almost every ignition system part, TPS, IAC, MAF, EGR, etc. You are hearing a whistle. Don't ignore what you are hearing. It is a vacuum leak.
 
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