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Old 11-03-2008, 07:10 PM   #1
Eatoniashoprat
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Join Date: Mar 2007
Chapter/Region: W. Canada
Location: Saskatoon
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1971 Super Beetle
EJ20g Platinum Grey

Default EJ20G TPS signal - More problems Need help!

Hi, I'm just getting my ej20g fired up after installing it in my 72 super beetle, and am having some issues. trying to diagnose the problems, I checked the sensor outputs with PFC using datalogit, and it shows the TPS voltage being ~4.8V throttle closed, and then as you open the throttle it goes to 0.5V at WOT. I've checked all four wires for continuity to the ecu plug and to make sure they are going to the right terminals and they are. Is this normal or should the TPS Voltage be 0-5 V (closed to open) like everything else? Thanks

I have other engine issues that I'm sure I will be asking about later, but I'm narrowing it down. I've attached a pic for interests sake.



Mike
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Last edited by Eatoniashoprat; 11-04-2008 at 03:26 PM.
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Old 11-03-2008, 07:18 PM   #2
fishheadback
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& MK6 GTI

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Im 95% sure thats how the voltage runs. Its been a while since I dinked around with it. If the pinouts are all correct you should be fine voltage wise.


Props on the conversion. Always wanted to do that.
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Old 11-03-2008, 07:26 PM   #3
Eatoniashoprat
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1971 Super Beetle
EJ20g Platinum Grey

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Also, if the voltages are backwards (no idea how that could be since the wires are going to the right terminals of the ecu) then which 2 of the 4 wires would you switch?
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Old 11-03-2008, 07:52 PM   #4
Eatoniashoprat
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1971 Super Beetle
EJ20g Platinum Grey

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Quote:
Originally Posted by fishheadback View Post
Im 95% sure thats how the voltage runs. Its been a while since I dinked around with it. If the pinouts are all correct you should be fine voltage wise.


Props on the conversion. Always wanted to do that.
Thanks, but maybe save the props until it actually works! lol

The only reason I question the voltage is because I've never heard of it being this way and other ej20g datalogs I've seen have been 0-5V (closed to WOT)
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Old 11-04-2008, 01:47 PM   #5
fishheadback
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hmmm, I just remember on my old car when I set up my safc I had to set the tps scale to read from high(closed) to low(WOT) voltage. Im not really too sure.

Are you having issues related to the tps??
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Old 11-04-2008, 02:41 PM   #6
Eatoniashoprat
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EJ20g Platinum Grey

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Quote:
Originally Posted by fishheadback View Post
hmmm, I just remember on my old car when I set up my safc I had to set the tps scale to read from high(closed) to low(WOT) voltage. Im not really too sure.

Are you having issues related to the tps??
Well, when I saw the voltage reading I thought maybe that was my problem, but if I trick it, ie give it 0V instead of 5V nothing changes.

The problem is when I try to start it, it will rev up to about 4000 rpm, come back down quit. If I feather the throttle as its coming down I can get it to idle but its extremely rough and misfiring. Sounds like a cammed up V8. The plugs (brand new) are all very black and sooty, indicating rich. I've isolated each cylinder (unplugged injector) to verify that each cylinder is firing/running (all cylinders have spark and fuel).

I've plugged in the PFC, a Z4 and the original H4 ecu and they all yield the same result. I once suspected that it sounding like a major vacuum leak but or IAC problem, so I taped everything off including breathers and IAC and no change.

The only thing I can think it is that there is something restricting my fuel line/rail and the pressure is way too high, causing it to run rich. I've been banging my head against the wall for about 2 days trying to figure this out. I'm heading out to buy a fuel pressure gauge to verify that the pressure is correct. I've got a 100gpm 5 psi Carter pump feeding a 0.8L surge tank, then a 255 walbro inline feeding 3/8" line to the engine. Return is 5/16" and there is a 3/16" that bleeds the air out of the top of the surge tank and tees into the return just before it goes back into the fuel tank.

Mike
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Old 11-04-2008, 05:29 PM   #7
theonlygreat
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What is the input from the MAF when you get it idling? How does it start if you unplug the MAF?
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Old 11-04-2008, 05:47 PM   #8
fishheadback
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What is the input from the MAF when you get it idling? How does it start if you unplug the MAF?
Sounds like MAF issues to me also.
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Old 11-04-2008, 06:43 PM   #9
Eatoniashoprat
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1971 Super Beetle
EJ20g Platinum Grey

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Maf signal is 0.28 not running, then if you start it and not touch the throttle, it revs up to 4000rpm, back down, and quits. When it does this the MAF goes from 0.28 up the 2.1 max and back down. Is this ok?

The car this motor came out of I drove 3 hours to the spot where I pulled the engine. It ran great. since it has been out of the car I have changed the fuel system (although I just checked and the pressure is ~40psi, so its not the problem) and coil packs, and modified the wiring harness. I've also switched the fuel rails from side to side.

Mike
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Old 11-04-2008, 09:15 PM   #10
Eatoniashoprat
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1971 Super Beetle
EJ20g Platinum Grey

Default

Quote:
Originally Posted by theonlygreat View Post
What is the input from the MAF when you get it idling? How does it start if you unplug the MAF?
If I unplug the MAF it fires then quits.
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Old 11-04-2008, 11:46 PM   #11
Eatoniashoprat
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1971 Super Beetle
EJ20g Platinum Grey

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Update, I tried the MAF sensor off my van ('98 ej22, same numbers on MAF) and it didn't change anything.
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Old 11-05-2008, 10:36 AM   #12
Eatoniashoprat
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1971 Super Beetle
EJ20g Platinum Grey

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Problem solved. The way it was acting was exactly like there was a large vacuum leak, so I had tested the intake and couldn't find anywhere that air was leaking out, well, I had part of the intake off and was looking around and saw that the intake manifold gasket was half off hanging out the side. Fixed that, fired it up, runs like a champ.
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