VTA-E2 Voltages/Resistance

[jetjock]

Ah, I see. You meant timing the sensor sweeps. I thought you meant ignition timing. My bad.

If you followed the TSRM procedure (and it sounds like you did) I'd be very surprised if you got more than around 1 sweep per second. If so that'd be the first sensor I've ever seen do it. Too bad your model Fluke doesn't measure frequency.

Have Cuel check the sensor's average voltage and not just the sweep count. All the better if he has a scope. Average voltage should be 450 mv if measuring OX or 2.5 volts if using Vf with the diag block jumped. The waveform should be clean with no hash. Have him look at injection duration too if he can. Make sure it's opposite O2. It's the only real way to know if the sensor is in command. If you do that let us know what injection duration was in milliseconds at 2500 rpm

Course, it'll probably turn out to be something much simpler. It usually is.

 

[Nick M]

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.


-Austin

Did you consider the source? The one who came up with the 12 volt mod( I think) did it to eliminate a stumble when it switches over in high horsepower situations. Modded cars at elevated levesl. There is no other reason to do 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).

Something else besides pirate air, or false air, is oxygenated fuel. Bigger cities like Houston do it to stop older cars from polluting as much. Most EFI cars with 02 feedback will see a decrease in mileage as a result. The sensor sees that oxygen, and thinks you are lean, just as a leak upstream as JJ pointed out. In Denver with oxygenated fuel, my summer mileage in the 5.0 went down 2.0 mpg each summer, like clockwork.

I don't know how long you owned the car, or when yours dropped. But the fuel switch should have happened recently, in the last month or so.

 

[Dragk913]

I am officially one of the dumber people on SM
Turns out my problem had nothing to do with fuel maps or sensors; the Walbro (w/12v Mod) was pushing too much fuel. When we checked my fuel pressure (with the vaccuum line on, and the engine idling) it was about 55PSI. We hooked up a fuel pump resistor and the pressure dropped to around 35PSI.

Now I need to decide whether I'm going to buy a new Fuel Pump or just buy an AFPR!

 

[3p141592654]

Did you drill out the J-tube restriction?

 

[Nick M]

Did you drill out the J-tube restriction?

I didn't ask, just assumed he did it. Goes to show why you don't assume. :biglaugh:

 

[CRE]

I am officially one of the dumber people on SM
Turns out my problem had nothing to do with fuel maps or sensors; the Walbro (w/12v Mod) was pushing too much fuel. When we checked my fuel pressure (with the vaccuum line on, and the engine idling) it was about 55PSI. We hooked up a fuel pump resistor and the pressure dropped to around 35PSI.

Now I need to decide whether I'm going to buy a new Fuel Pump or just buy an AFPR!

What are you going on about? You just said that putting the resistor back in put pressures back where they should be.... answer seems obvious to me. Why would you replace the pump (again) or spend yet more money on a AFPR?

 

[cuel]

He has the Walbro pump, and, as far as I know, its not meant to be run at 9 volts. I was concerned that it would either burn out the pump or the resistor. His fuel pressure was reading closer to 65 psi. without the resistor, and dropped to around 45psi. with the resistor. TSRM indicates 38-44 psi., so he's still a touch out of spec. I advised him that the best thing he could do is put the correct(oem) pump in it, and get rid of the Walbro.

 

[CRE]

Hmmm, I dunno about it burning up. I do know a couple guys locally who have been running Walbro's for a couple years on the stock wiring though. If it is possible then I suspect it's more a matter of shortening the pump's lifespan a little... perhaps JetJock will pipe in and give us the absolute on the matter.

 

[AJ'S 88NA]

I have the Walbro with the 12 volt mod and no "J" tube and the resistor bypassed. But I also have a AFPR. I think if you're going to run the bigger pump you should have a AFPR.
Helps with the tuning.

 

[jetjock]

I kind of suspected fuel pressure. As I said in post #7 I was puzzled as to why he would install that pump in the first place and curious if it was running on 12 volts. Even more puzzling is why he would do it and not check pressure afterwards, or at least when he started having problems. Ah well, live and learn. Nice job Cuel...proves again the value of starting with basics when troubleshooting.

 

[Dragk913]

Well the car is feels like it's running better, but I'll know more once I get some miles on the tank of gas I just got.

I just wanted to say thanks to everyone who helped...and put up with my over complication of things!:biglaugh: You guys rock.