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    Thread: Where is the IAT Sensor?

    1. 10-14-2005 12:31 AM #1
      My dad picked me up a Performance chip for my 1989 VW Cabriolet, yeah I know probably won't do didly squat but I thought I would put it in anyway. My dad wanted to do a quick weekend car repair bonding day. So here is my problem: It says to locate the IAT sensor (Intake Air Temperature Sensor). Where the hell is that? I have a service manual but it mentions nothing of an IAT sensor. I do see an O2 sensor, Thermo Time switch, Air Flow sensor. My guess is, that it is the thermo time switch. It says that the "IAT sensor is 1" by 1" by 1" two wire circuit that is likely located in the intake tube in the air box or near the throttle body. To verify the location of IAT, test the sensor plug with a voltmeter, it should be a 5-volt circuit." Please help. I do not want to snip the wrong wires and wire this thing up to the wrong thing. Thanks. Also, what is the easiest way to boost engine performance on a 1989 VW Cabriolet?

    2. 10-14-2005 01:08 AM #2
      Are you sure he didn't get you one for a 99? I'm probably wrong but I don't remember being able to chip a CIS car....

    3. 10-14-2005 01:10 AM #3
      My fear is that your car runs CIS injection. You must have the Digifant injection found on 1990 and later cabbies in order to use a performance chip (and to have an IAT).
      Your car's airbox is located right behind the battery. If there are four or five braided metal covered fuel lines leading from this area over to the valve cover area, then you have CIS and are out of luck, chip-wise.
      if there are no such individual fuel lines, then you probably have Digifant, and your IAT is located inside the fuel meter (MAF) located on top of the airbox (w/ the tube that goes over to the intake manifold)

    4. Member backinthegame's Avatar
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      10-14-2005 01:12 AM #4
      Don't do it! messing with the iat (mass airflow as it is on the cabby) will do more harm than good to your engine dumping in fuel you don't need when the engine is warm. I don't recall if digifant was in the 89 cabby (seems to me it started in 90 but I'm sure someone will correct this if I'm wrong) but if your car is digifant check out this thread for a real enhancement chip. I and a few others on here have purchased them and they are the real deal.
      http://forums.vwvortex.com/zerothread?id=1840953
      Sent from my Droid using an escape pod to Tattoine.


      Quote Originally Posted by mad8vskillz View Post
      they're trying to skip out on their contracts via rapture. not very christian of them

    5. 10-14-2005 04:54 AM #5
      i'm with the others:
      1. you have CIS - no chip is available
      2. you do not have an intake air temp sensor
      3. if you did, wiring a resitor in line will not have a positive effect
      4. altering the ratio of fuel to air may result in poor mileage and can damage the engine

    6. 10-14-2005 09:20 AM #6
      The car is actually my wife's that sits in garage and she only drives it a couple of times a month. I do not know anything about cars so I started taking the thing apart and figuring it out and bought a service manual. Doesn't the thermo time switch sense a cold weather start and dump more fuel in? Wouldn't the little chip do the same if I hooked it up to the Thermo time switch - dump more fuel in?

    7. 10-14-2005 09:28 AM #7
      More Fuel when not needed = Rich condition
      Rich Condition leads to:
      Eventual burned out Catalytic Coverter
      Bad Fuel mileage
      Bad running engine
      I've seen these things on the market before, no good comes of them...and i did some research after my last post..you cannot chip a CIS car.
      Considering HOW the CIS system works, that "Mod" will probably cause you more headaches then you ever wanted with it and can eventually damage the engine.....
      Sorry man

    8. 10-14-2005 09:32 AM #8
      Thanks. No problem, I did not loose a cent. What can I do to increase the engine's performance short of putting a new engine in? These stock cabriolet's are pretty guttless. I bought a four new fuel injectors for $100 because one of mine had a funky spray pattern. I am hoping that is what causing the delay from pushing on the accelerator to when it acutally goes. Or is that normal?

    9. 10-14-2005 09:38 AM #9
      CIS is a pretty bulletproof system, there really isn't much you can do to the system...but you can put some more agressive cams in, better exhaust etc... Don't expect 200hp out of it but you can free up some ponies..
      AS for your hesitation...that's not normal and you should fix that before even thinking of any mods...
      As for what to check....I am gonna be forced to quote Ron exactly here
      Quote, originally posted by tolusina »
      Start with a complete tune up, plugs, cap, rotor, wires, (use BOSCH ignition parts, W7DC or W7DTC plugs!!) air and fuel filters, replace your injector seals and idle screw o-ring, tighten the injector holders, replace the injector holders if needed. Replace all the old and frayed cloth covered vacuum hoses, silicone hose suggested. Check your Jetronic grounds. Test your oxygen sensor. Check your throttle switches and idle boost valves, check your CIS system and control pressures, check your distributor's centrifugal and vacuum advance mechanisms, set your timing. Set your mixture while monitoring the duty cycle of the frequency valve, adjust the base idle.
      Once you've made sure all the basic stuff is working as designed, should you still find improper running conditions, report back with your findings and we'll discuss it to a conclusion, more likely several conclusions.


    10. 10-14-2005 10:11 AM #10
      Roger that. I got a lot of work to do. Sounds like fun. After I fix the engine I will start on other cosmetic things. Pain job this summer. I am also wanting to lower the thing. Do you just take the sprins off and buy lowering springs? Someone told me you can take the old ones off and hacksaw it down to lower it? Does that work? - did not sound right to me. Thanks for everything - these forums are awesome!

    11. Member tolusina's Avatar
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      10-14-2005 11:24 AM #11
      Curtis,
      Quote, originally posted by csmurray1 »
      ....... Doesn't the thermo time switch sense a cold weather start and dump more fuel in? .......

      The thermo-time switch grounds the cold start valve when cold, the cold start valve is powered only while cranking, therefore, the cold start valve can only spray while cranking with a cold and grounding thermo-time switch.
      You mentioned you have a service manual, which one? Bentley is the ONE book to have for these cars.
      Before you attempt any engine modifications, make sure ALL the stock stuff is operating correctly or you'll never get it running right.
      Here's a little help, http://dana.ucc.nau.edu/~kaw5/CISidle.htm
      Ron
      Quote Originally Posted by kamzcab86
      I hate reading: "But I bought this car for $500 and don't want to put another dime into it."
      ____(hey, it's VW AND it's electrical, what's not to fail?) neoBentley+



    12. 10-14-2005 12:11 PM #12
      Well, if there is no sensor that is the equvelant to the IAT I will put it on my daughters Toyota Tercel so my dad does not think he wasted his money. I will get started on all the tweaks you all suggested, if I run into trouble I will post again. I will check my service manual, I do not remeber which one I have it is orange, but I do not remeber if it is a bentley. Thanks everyone. What is the best way to lower my wife's cabby? I guess it is not a good idea to shorten the excisting springs, eh? How much should I lower it? 1 1/2 inches?

    13. 10-14-2005 12:41 PM #13
      It's your car, but as I said before, I don't trust those units that play with the IAT sensor....Remapping the fuel curves (Which a performance chip DOES do) is pretty safe...dumping more fuel without adjusting timing and everythign else that a fuel curve will do is just asking for trouble....
      Just my 0.02
      PS, if you want to lower the car, invest in a good set of coilovers or performance struts...makes a world fo difference

    14. 10-14-2005 12:46 PM #14
      Thanks. I will take your advice.

    15. 10-14-2005 01:42 PM #15
      Quote, originally posted by csmurray1 »
      I will put it on my daughters Toyota Tercel

      please don't. we've already explained what poential problems can occur by fooling factory settings with a $0.10 resistor. it doesn't really matter how that resistor is packaged and how good it looks, the effects are still the same.
      don't risk the reliability and economy of a Toyota. especially one your daughter drives.
      as for the 8v engine in the cabby, there's a lot you can do to it. start by searching and you'll find a lot of posts covering the essential upgrades:
      >exhaust manifold, downpipe, cat, cat-back
      >Home Depot cold air intake mod (with K&N air filter)
      >larger throttle body
      >cam and cam gear
      Those are all bolt-on mods that will help a great deal.

    16. 10-14-2005 04:26 PM #16
      Thanks, i will tell him to take it back or make a radio out of it.
      I have searched the forums and can't find the home depot cold air intake mod? Thanks.

    17. 10-14-2005 05:52 PM #17
      This thread details most of the things you can do to your 8v engine, including the Home Depot parts needed to make up an intake.
      http://forums.vwvortex.com/zerothread?id=2163034
      I believe strictlycabriolet.com has a guide on making an intake.
      [IMG]http://*****************.com/smile/emthup.gif[/IMG]


      Modified by -vertigo- at 6:30 PM 10-14-2005

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