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Tuning or fix jetta 'goes flat' ~4500+RPM

547 Views 2 Replies 3 Participants Last post by  tolusina
This is an 87 Jetta - 8valve 5 speed.
I got this car cheap and its in ok shape. It runs pretty well, but when you mash the throttle and rev it out, it gets to 4500 or so and doesnt want to rev anymore, it acts like it is way rich. I have been over the basics timing is good ignition stuff is new, fuel good, etc. Also the WOT switch is moved all the way back so it doesnt get activated. When i corrected this it wont rev out at all - it smokes and seems even richer.
I put it back and tried it and the same as before i messed with it. From the book i have on the car it seems that the switch is to increase the current to the Differental regulator, which would increase the pressure and richen the mixture. The car seems rich all the time IMO.
Also- The red light is on for the O2 sensor on the dash, but i am reluctant to buy one, should I? I just know how old EFI cars are with these different lights.
Any suggestions? Someone has probably seen this? Thanxxx!
Modified by phart2005 at 6:15 AM 3-17-2008

Modified by phart2005 at 6:16 AM 3-17-2008
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Re: Tuning or fix jetta 'goes flat' ~4500+RPM (phart2005)

All I know is I had virtually the same car as you a few years ago and it did almost the same thing.... couldn't figure it out until one day my timing belt snapped. I guess at low revs it held together but once the revs got closer to 5000 the belt was stretching and the engine was losing power due to the valve timing being all goofy. Might be worth checking.
Re: Tuning or fix jetta 'goes flat' ~4500+RPM (phart2005)

Set the DPR current to 10mA, see how it runs. Many DVOMs have an ammeter scale in that range. You'll need to fabricate some leads.

The OXS warning light is simply a 30k interval service reminder, it is in no way connected or associated with the engine management.
Look for a counter box, follow the speedo cable up to the firewall, push the button with a pencil or some such (fingers won't fit the recess).
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