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Discussion Starter #1
so, i recently bought a 1990 L98 project car. i wouldn't say there's a major amount of work to do on her but the front end has some damage from a minor wreck, which of course is less than minor when it happens to a plastic car.

anyway, the engine seems to be in fair condition excluding the little random things that break with a car that's 17 years old. while rolling down the interstate to visit my mom, the car drops into limp mode. after trying various things to figure out what was wrong, getting completely rain soaked, seeing my life flash before my eyes every time an 18 wheeler screamed by me, and chasing my dog down the side of the interstate, a friend suggested i disconnect the power from what SHOULD be the MAF sensor.

the clouds dispursed, heavenly voices began to sing, and traffic moved over into the inside lane to make room for me because i was back up and rolling full speed.

long story short, does this thing actually have a MAF sensor on it? i'm a C4 newbie, and at best a novice mechanic. all my knowlege comes from my second brain, google. i've read on several sites that 90-93 C4's don't actually have a MAF sensor on them. if that's the case can anyone tell me what the heck i unplugged?

if this is a MAF sensor and i'm mistaken, could someone offer some guidence on recognizing it, removing it, and any cleaning that i could do with it in case it's just faulty and not completely dead?

i haven't done trouble shooting step #1 and pulled the codes which i plan to do tonight. i know, i know, shame on me.

thanks in advance for any advice.
 

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Discussion Starter #2
to be a bit more specific, i disconnected the power lead that i disconnected was on the passenger side of the throttle body, directly at the intake end of it.

also, is it common that the induction tube coming off my air cleaner and connecting to the throttle body doesn't seem to fit properly on the shroud where it connects to the air cleaner? it fits perfectly to the mouth of the throttle body, but the air cleaner side doesn't fit snuggly any small bump seems to knock it loose. i've looked at some things like this to replace it with. is that the way to go?

sorry for so many questions.
 

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A 1990 model should NOT have a mass airflow (MAF) sensor on it. Instead it has a MAP (manifold absolute pressure) sensor on it that took place of the MAF in 1988. Do you have any pictures of what you disconnected. Did it have a vacuum line running to it? The MAF sensor is located between the airfilter housing and the corrigated tube going to the throttle body. The MAP sensor would be a little square box with an electrical connection and a vacuum line running into the bottom of it and is usually mounted to the rear of the plenum or the firewall.
 

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Discussion Starter #4
i don't have any pictures yet, but i'll take some this evening after work.

the plug that i removed was located directly at the mouth of the throttle body at that end of the corrigated tube coming from the air cleaner.

i'll see if i can dig up a picture online somewhere...
 

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Maf?

Could you be looking at the TPS sensor? TPS= Throttle Position Sensor.It is a sensor with 3 wires.It tells the computer where into the throttle you are and then sends a reference signal to the computer.If you disconnect it then the computer will use a fixed signal to monitor the settings.In a computer driven engine usually if you disconnect the sensor thats bad and it runs better,then the sensor is bad.Might check that
 

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Discussion Starter #6
that sounds a little more like what i'm dealing with.

looking at this picture that's right where the power connector that i unplugged was.
 

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Maf?

Might get a dvom meter and check the operation of the tps.You can use a scan tool also.Need help doing this get back with me
 

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Discussion Starter #8
so i slapped the v/o meter on my tps. it did not show an open on the ohm test. is there anything else i could check on it to see if it's operating correctly?

i went ahead and removed the sensor just because it's small and easy to get it. i'll probably see if i can snag a new one at the parts house just for shits and giggles on the way home.

i'll keep you guys updated. thanks again for the help, and any further suggestions are much appreciated.
 

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If I'm not mistaken the TPS sensor is suppose to show .54 volts when connected to the throttle body and throttle is closed.
Turn on the key but don't start the car and check the voltage and/or adjust the sensor to get that reading.
I know my '88 is suppose to read .54 but since your's is a '90 it may be different.
 

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Loosen the two screws, and carefully turn it and watch your volt meter or scan tool until it reaches .54 volts
 

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tps

When you check the TPS check it full throttle,and at idle.It should go to the high side at full throttle.Check your specs carefully.A little means alot.It shouild move smooth through the distance between idle and full throttle
 

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Discussion Starter #14
Success!

just wanted to update everyone that has been helping me out.

i think i have my TPS properly adjusted, took a bit of fiddling but i went for a 30 minute ride this afternoon and no limp mode. although i didn't run down the interstate i was still able to get well over 60 mph without and problem.

thanks again for the advice guys.
 

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Wait a minute. The 90 does not have a MAF sensor, but does have a MAP sensor. The MAF stopped in 89 and the 90 was changed to speed density. The TPS on the 90 IS NOT adjustable as it is on the 85-89's. You may have just screwed that sensor up. The sensor you disconnected previously was probably the IAT sensor.

Pull the codes and it will be easier to help. If the ECM went in limp home mode, you will have a code.
 
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