VTA-E2 Voltages/Resistance

[Dragk913]

My EFI system has been out of whack (ECU thinks it's running lean, so I'm now running rich) for a while so I finally broke down and started testing.

I was testing voltages (per FI-32 in the TSRM) and everything was within spec. except for VTA-E2 (Throttle Valve fully open, it read "3.63")

After completing the testing of page FI-32, I started working on my VTA-E2 problem (page FI-37).

My Results:
-Correct voltage between VC-E2
-TPS is fine
-Wiring Between ECU and TPS:
E2 Wiring Resistance - 0.8 Ohms
VTA Wiring Resistance - 1.0 Ohms
-I don't have another ECU to play with


I was wondering if someone could tell me if those resistances are correct?



Thanks in advance!

 

[CRE]

For copper wire those resistances sound fairly high.. I'm not sure where they should be though. The TPS typically supplies ~.5v to the ECU when closed and ~3.5v fully open.

The TPS isn't going to cause you to run lean the whole time either.

 

[Dragk913]

For copper wire those resistances sound fairly high.. I'm not sure where they should be though. The TPS typically supplies ~.5v to the ECU when closed and ~3.5v fully open.

The TPS isn't going to cause you to run lean the whole time either.

Hmm...well to be honest I'm not sure when it runs lean/rich. I do know that I don't get the gas mileage or performance I used to and when I start the car it smells worse than before (smells richer...kinda like the ECU thinks it's running lean, so it's overcompensating when it doesn't need to).

I did a VF Check and it read around 4.0v (on a Fluke Multimeter, and 6.48v on some cheap MM). I tested my Oxygen Sensor and it was good, so I went on to testing with a MM like the TSRM says. That's what got me to the ETA-E2 (and it's only 0.38v off of the minimum it's supposed to be).

I'm not too great with electrical stuff && am having a hard time figuring all this out. So any help is greatly appreciated.

 

[CRE]

Aside from the TPS, how's the Walbro wired up? Do you have any error codes?

It's been a while since I've had to know, so I looked up the resistance values for copper wire... 18AWG should have a resistance of approx. 6.385Ω per 1000' (that's about .0064 per foot). Of course keep in mind that branches in the harness can cause varied readings from what's expected... the harness could be just fine.

You could try jumping some clean wire from the ECU to the TPS and see if it helps... but I don't think that's the whole issue. Watch Vf while someone else drives the car, not just while at idle.

I've never tested an O2 sensor... not a narrowband sensor anyway. That is one of the first things I'd suggest though. If possible you might want to try swapping it just to make sure.

 

[jetjock]

If I may butt in for a moment: The wiring and TPS are OK. It's not possible to accurately measure low resistance without special gear. He could have that much in the meter leads alone.

 

[Dragk913]

Aside from the TPS, how's the Walbro wired up? Do you have any error codes?

It's been a while since I've had to know, so I looked up the resistance values for copper wire... 18AWG should have a resistance of approx. 6.385Ω per 1000' (that's about .0064 per foot). Of course keep in mind that branches in the harness can cause varied readings from what's expected... the harness could be just fine.

You could try jumping some clean wire from the ECU to the TPS and see if it helps... but I don't think that's the whole issue. Watch Vf while someone else drives the car, not just while at idle.

I've never tested an O2 sensor... not a narrowband sensor anyway. That is one of the first things I'd suggest though. If possible you might want to try swapping it just to make sure.

The only thing I did with the Walbro is get rid of the Resistor (I ran the wires back into eachother. Sorry, I'm not great with the "lingo").

No codes.

Would watching the VF, while manually moving the TB Valve work the same as watching it and driving?


If the O2 sensor was bad would I still get a VF reading?


(Thanks for butting in JJ, I would like to run new wires as little as possible)

 

[jetjock]

As CRE pointed out the TPS can't be your problem. Frankly, I'm not sure you even have a problem. Since you're initial post is confusing I have a few questions:

1) You're saying the engine is rich. How do you know that for sure? Just because Vf is calling for more fuel doesn't mean the mixture is wrong. In fact, since Vf is within limits, I suspect you'll find it's right. Or is the aim of your efforts to simply get Vf back to mid range?

2) Why would you put a Walbro on an N/A and run it at 12 volts all the time?

3) How did you test the O2 sensor?

3) What model is your Fluke?

If it turns out you actually have a problem, and since the TCCS is not usually at fault in these situations, I'd be looking at basics first. Timing, fuel pressure, pirate air, things like that. Only then would I go into the EFI system and I'd start with the AFM and coolant temp sensor. After that I'd do what CRE suggested and verify closed loop. You can do that by watching Vf with the engine off idle and T and E jumpered.

 

[CRE]

I had no intention of having you permanently replace the wiring... it was just a suggestion so you'd get it out of your head.

2) Absolutely no idea... and in that case I'd bypass the relay not just the resistor.

 

[Dragk913]

1) I started getting about 14MPG when I used to get 20+, and it smells more rich than it used to. Also, my new catback/muffler has a rather thick layer of black "soot" after only being on for 3 weeks.
I would like to get the VF back to midrange as well.

2) My fuel pump was going out and I plan on going Turbo one of these days. I did the 12v mod because everything I read said it was a good idea (Probably my first mistake:nono.
Just for some clarification: I've had the Walbro on for around 5-6months and I just started getting bad gas mileage about 4-5 weeks ago.

3) Exactly how the TSRM (Page FI-119) says to, while it is on the car. The voltage fluctuated about 20 times during the 10 second period.

4) Fluke 77III


What is Pirate Air?



The AFM is within spec's according to the TSRM, and I think I'm going to replace the Coolant Temp. sensor. It's kinda "wiggly".


If I need to rephrase anything let me know. Sometimes my hands don't translate what my mind thinks.

-Austin

 

[Dragk913]

I had no intention of having you permanently replace the wiring... it was just a suggestion so you'd get it out of your head.

2) Absolutely no idea... and in that case I'd bypass the relay not just the resistor.

Oh, lol. Well I'll take you guys' word for it, ya'll have more experience than me.

 

[CRE]

What is Pirate Air?

Caribbean Airlines (Well, that would depend on if you're going lean or rich... simply put check to make sure you don't have leaks in the intake and vacuum system.)

I think I'm going to replace the Coolant Temp. sensor. It's kinda "wiggly".

wiggly???

 

[Dragk913]

Caribbean Airlines (Well, that would depend on if you're going lean or rich... simply put check to make sure you don't have leaks in the intake and vacuum system.)



wiggly???

Lol. I've gone over the vacuum lines/intake about 4 times now and can't find anything. Hopefully, on Sunday I can get a smoke test.


Ya, the Sensor doesn't sit tight in its fitting. The threaded section is tight, just not the plastic part. I always get a correct reading, but it doesn't feel right.

 

[3p141592654]

If you disconnect the sensor it will default to normal operating temp and set a code. It should run well once warmed up. If th sensor is bad and indicating cold temps all the time, then you will never get out of warm up mode. Symptom will be a permanent fast idle and of course bad gas mileage.

But as JJ says, do you really have a problem? Not so clear to me and I doubt the temp sensor is it.

 

[Dragk913]

If you disconnect the sensor it will default to normal operating temp and set a code. It should run well once warmed up. If th sensor is bad and indicating cold temps all the time, then you will never get out of warm up mode. Symptom will be a permanent fast idle and of course bad gas mileage.

But as JJ says, do you really have a problem? Not so clear to me and I doubt the temp sensor is it.

When I'm getting over 45 less miles to a tank than before (and I'm driving the exact same) I think there's a problem. I don't think the temp. sensor is it either, I'm just following CRE/JJ's advice.



When testing with "Closed Loop", the voltage kept jumping from about 1.86v to 2.48v. It never sat in one spot, even when I kept the TB Valve in one spot (off idle).

 

[CRE]

I've yet to see a tune which is so reliable that the Vf doesn't move at all... if you get that going something's more likely wrong than anything. A moving Vf signal doesn't mean much by itself.

Only a 45 mile difference? Could it have been a mixup at the pump? Wrong octane in the tank.

Depending on how I drive alone it can mean the difference between 260 miles per tank and 380 miles to a tank (that's all city).

I'm not saying that a change in your driving is the issue though.

Have you changed ANYTHING around the time this started?

The TCCS' only means of determining whether of not the engine is running lean is the O2 sensor.

 

[Dragk913]

I've yet to see a tune which is so reliable that the Vf doesn't move at all... if you get that going something's more likely wrong than anything. A moving Vf signal doesn't mean much by itself.

Only a 45 mile difference? Could it have been a mixup at the pump? Wrong octane in the tank.

Depending on how I drive alone it can mean the difference between 260 miles per tank and 380 miles to a tank (that's all city).

I'm not saying that a change in your driving is the issue though.

Have you changed ANYTHING around the time this started?

The TCCS' only means of determining whether of not the engine is running lean is the O2 sensor.

Oh alright, I wasn't sure if it was supposed to move or not:biglaugh:


Well I used to average between 300mi. and 320mi to a tank; and now I can't get more than 270mi. So it ranges from 45-60mi. less per tank. It might not seem like too much, but with gas prices the way they are - I want to get as many miles as possible.

I'm trying to remember when I first noticed it was running more rich than Supras normally do...
The only things I've done are:
2.5" Catback w/Magnaflow - 4 weeks ago
Apexi Intake - Christmas
MSD Wires - A couple months ago?

Other than that, I haven't messed with the timing (it's set at 10* BTDC) or A/F Ratios, or anything.

I started using 87 Octane gas a couple months ago, but I don't remember it affecting my mileage back then.


I tested the Oxygen sensor with it in the car, and the voltage jumped about 20 - 24 times during the 10 second period (FI-119). So unless I misread, my 02 sensor should still be good.

 

[jetjock]

Vf should hold steady during cruise, preferably at mid range. Also, I seriously doubt your sensor cross counted that many times in 10 seconds. You really ought to check it in diag mode using Vf with the engine off idle. And just because the sensor is cross counting doesn't mean the mixture is stoich. Bottom line: until you accurately verify closed loop operation you're pissing into the wind.

Btw, did you get a smoke test? If so did they smoke the exhaust?

 

[Dragk913]

Vf should hold steady during cruise, preferably at mid range. Also, I seriously doubt your sensor cross counted that many times in 10 seconds. You really ought to check it using Vf with the engine off idle. Until you accurately verify closed loop operation you're pissing into the wind.

Btw, did you get a smoke test? If so did they smoke the exhaust?

I saw the voltage change atleast 20 times while I had someone else timing it. I might just be retarded, so tomorrow when I get off work I'll retest the O2 Sensor and closed loop VF.

I haven't gotten the smoke test yet, I'm going to see Cuel tomorrow, so hopefully he can squeeze in a Smoke test and maybe check my fuel pressure.

 

[jetjock]

If someone else was timing it you must have been at idle. You had to be or timing isn't possible. There is absolutely no way the sensor could cross count that fast at idle. It won't do it even at 3000 rpm.

I asked about the smoke test because a leak in the exhaust system upstream of the O2 sensor will shift it lean and decrease fuel economy yet everything will look OK. For example I once had a guy bring me a car with your complaint. Scoping his O2 sensor showed it to be cross counting but spending more time on the lean side of stoich. Sure enough, my gas anaylzer showed O2 out the tailpipe to be high, around 2%. Smoke revealed a blown out EGR cooler gasket. After that was repaired not only did the O2 level (and the sensor signal) return to normal but his fuel economy came back.

 

[Dragk913]

If someone else was timing it you must have been at idle. You had to be or timing isn't possible. There is absolutely no way the sensor could cross count that fast at idle. It won't do it even at 3000 rpm.

I asked about the smoke test because a leak in the exhaust system upstream of the O2 sensor will shift it lean and decrease fuel economy yet everything will look OK. For example I once had a guy bring me a car with your complaint. Scoping his O2 sensor showed it to be cross counting but spending more time on the lean side of stoich. Sure enough, my gas anaylzer showed O2 out the tailpipe to be high, around 2%. Smoke revealed a blown out EGR cooler gasket. After that was repaired not only did the O2 level (and the sensor signal) return to normal but his fuel economy came back.

The person was sitting in the driver's seat, holding the RPM's at 2500, while I was at the diagnostic block. I could have sworn I did everything right, but if the results I got aren't possible I'll just recheck it today.

Ooh. I'll have to see if Cuel can smoke the exhaust too. I hope it's just something easier like an exhaust leak.


I'll report back in a couple hours.