Intermittent lean condition...FPR solenoid?

[turboAWDfanatic]

Recently, out of no where, I've been experiencing a problem where all of a sudden my car will run extremely lean under WOT for about a minute, then return back to normal. I have a Zeitronix Zt-2 on my dash with a warning light/buzzer that warns me when I run leaner than 11.5:1 at greater than 10psi of boost. I'll be driving and go to accelerate and the light goes off. I look at my Zt-2 and the AFR stops solid at 13.0:1 AFR and will not go any richer, no matter what the TP or load is. A minute or so later, the problem goes away. This problem appears about once or twice in a 30-40 minute drive.

When its stuck in the lean condition, it reminds me of when the vacuum line pops of the FPR and your fuel pressure doesn't raise with boost...but, since the problem is intermittent, it makes me wonder if I have a malfunctioning FPR solenoid that is cutting off the boost signal to the FPR (or a faulty ECU that is triggering it at random times).

Any ideas? Where should I even start to troubleshoot? I might pull the vacuum lines from the FPR solenoid and loop them to see if the problem persists...


FYI, I'm running a rewired walbro 190 with stock fuel lines/filter/rail/fpr and 660 injectors tuned with the Ostrich/TunerPro setup. I have a fuel pressure gauge, but its under hood so I can't see it while driving. If you think it would help, I'll plug in the data logger and hope the condition reappears while I'm logging and then I'll post the log.

 

[snakeyes711]

Well, check your logger to see what the fuel pressure is while driving?

 

[turboAWDfanatic]

You can log fuel pressure?? I was unaware of this.

 

[jrohner]

Just get rid of that solenoid to eliminate a possible issue. It's useless anyways.

No, a logger won't tell you fuel pressure, there is no fuel pressure sensor.

 

[91-gsx]

You can bypass the FPR solenoid and that should eliminate any potential problem it might cause. It does keep pressure high during start-up and aids the idle slightly, but if your FIAV is in good order, your idle will rise while cold and drop while warm just like it should. I logged my car with MMCD back in the day before I had dsmlink, and it showed some knock during higher rpm. I learned of the FPR solenoid as you did, bypassed it, and the knock disappeared.. I hooked the FPR solenoid back up, and the knock just came back.. Took it off and checked one last time, no more knock. Its worth bypassing just to check. If it is malfunctioning, just take it off.

 

[Calan]

Are sure you are actually going lean, and it's not the connection to the Zt-2? Mine did something similar for a while, but the logs didn't jive with the weird AFR readings. It turned out to be a connection issue between the sensor and the ZT box.

If you are going that lean during WOT (for a minute? ) , you'll most likely have a lot of knock, pulled timing, etc. Do you have any logs yet from when this is happening?

 

[turboAWDfanatic]

OK, didn't think you could log FPR, never knew of any FPR sensor myself. I will bypass the solenoid b/c like stated above I find no use for it. I have a working FIAV, and a rewired walbro 190 so my fuel pressure is a tad higher anyway.

Are sure you are actually going lean, and it's not the connection to the Zt-2? Mine did something similar for a while, but the logs didn't jive with the weird AFR readings. It turned out to be a connection issue between the sensor and the ZT box.

If you are going that lean during WOT (for a minute? ) , you'll most likely have a lot of knock, pulled timing, etc. Do you have any logs yet from when this is happening?

Interesting point. Oddly, no, I haven't noticed knock or timing retard (i have the ability to see knock b/c my boost gauge shows knock). Though, when the buzzer goes off I let off the gas immediately, so who knows. I *was* moving around the ECU the other day which has tugged at the bundle of wires around the Zt-2 box. I'll double check all the connections and log when I get a chance.

Thanks for all the input!!!

 

[Calan]

OK, didn't think you could log FPR, never knew of any FPR sensor myself.

Actually you can log fuel pressure...if you have DSMLink and a FP sender

*****************

I have a hunch that if you were repeatedly hitting 13.0:1 AFR for any length of time, you'd know it...unfortunately.

My money is on a bad ZT connection somewhere.

 

[snakeyes711]

Ok, so why do I have a parameter on MMCD 1.8 that tells me fuel pressure? It also tells oil pressure, and volts going to the pump...? I believe they are on the fourth page.

 

[twdorris]

Ok, so why do I have a parameter on MMCD 1.8 that tells me fuel pressure? It also tells oil pressure, and volts going to the pump...? I believe they are on the fourth page.

OK, did some digging on this because I was kinda curious myself. It appears those parameters were there to support some HSLogger thing that Clinton Battersby was working on back in 2004. I don't think it was ever finished, though, and I can't even find a good explanation of what it was supposed to do.

But I've never actually used MMCD myself, so I'm not sure exactly.

Thomas Dorris
ECMTuning, Inc.

 

[Calan]

Tom's right... MMCD has several unused parameters, which appear to have been included for use with an add-on board of some type he was working on. At least that is what I gather from what I've read and my own experience with MMcD.

Bottom line is that with any logger you can only read what the stock ECU reads... or in the case of DSMLink (err... ECMLink ) and similar systems, certain sensors are supported that you can route to unused inputs of the ECU.

MMCD is obviously no DSMLink...but I have to admit I REALLY like the screen layout on my Palm IIIc. I can't imagine a better way to lay out a logger display on a PDA.

 

[turboAWDfanatic]

Well, today, it happened again and I stayed on the throttle to with a sharp eye on my knock gauge. No knock, no pulled timing, 13:1AFR. I'm actually going to bypass the FPR to rule it out before I start going through all my wiring. If I bypass it and the problem still persists, then obviously I need to check my connections to the Zt-2.

Though, I have to ask, what about a faulty connection to the Zt-2 would make the AFR max at 13:1??? I would think that it would go full rich or full lean, or wig out rather than peg at 13:1 yet still accurately display AFR when I'm cruising. Hmm, might have to email cRock on this one.

Thanks again for the input

 

[Calan]

In my experience, the Zt will "lock" at a certain value depending on how it's reading the sensor data...and it is probably some random unit-specific value.

In my case, the unit had two values that it would lock up on; 9.5 and something around 13. The tipoff for me (besides the fact that the car was running fine and the logs didn't add up), was that it always read one of the same exact two values for several seconds (or minutes), which is highly unlikely even for a perfectly tuned car.

The problem with mine was a bad connection where the cable coming off the sensor plugged into the extension cable coming from the box. Just unplugging it and blowing it out with about 120psi of air and plugging it back together and making sure it was tight fixed it. I assume it could act the same with connection issues at other points though.

The main thing is to watch the logs and other indications for any trouble. If the car is still pulling like a raped ape with no knock, smoke, pulled timing, or a trail of parts behind it... it's kind of hard to imagine it's running at 13.0:1 AFR

EDIT:

I should also mention that mine did lock up a couple times while just cruising around in closed loop...but I didn't notice it until I started looking for it, since normally I only watch the AFR during WOT pulls.

I believe I actually noticed it first as a flat-line in a DSM log while adjusting fuel trims, and I just happened to be logging the AFR.

 

[snakeyes711]

OK, did some digging on this because I was kinda curious myself. It appears those parameters were there to support some HSLogger thing that Clinton Battersby was working on back in 2004. I don't think it was ever finished, though, and I can't even find a good explanation of what it was supposed to do.

But I've never actually used MMCD myself, so I'm not sure exactly.

Thomas Dorris
ECMTuning, Inc.

The computer reads these parameters. I checked it out today, it sits low at idle. But at 5,500 rpm it was reading about 110 psi.

The pressure varies depending on how hard you hit the throttle. I didn't check the other readings for fuel just the pressure.

 

[snakeyes711]

Tom's right... MMCD has several unused parameters, which appear to have been included for use with an add-on board of some type he was working on. At least that is what I gather from what I've read and my own experience with MMcD.

Bottom line is that with any logger you can only read what the stock ECU reads... or in the case of DSMLink (err... ECMLink ) and similar systems, certain sensors are supported that you can route to unused inputs of the ECU.

MMCD is obviously no DSMLink...but I have to admit I REALLY like the screen layout on my Palm IIIc. I can't imagine a better way to lay out a logger display on a PDA.

Well, right on such as the speed sensor, and such there are a few other ones, like two o2 sensors but only one actually works.

I second that about the layout, because I got the Palm IIIc also Great tool. Plus I can keeps notes, and reminders! I just need a better way to mount the damn thing because this sticky velcro gets hot in the sun, and sometimes I find its fallen in the floor board. I need a cradle....

 

[snakeyes711]

BTw I'd check the wiring first also.

 

[Calan]

The computer reads these parameters. I checked it out today, it sits low at idle. But at 5,500 rpm it was reading about 110 psi.

The pressure varies depending on hot hard you hit the throttle. I didn't check the other readings for fuel just the pressure.

Normally...the ECU does NOT read fuel pressure. If your case is different, where is the sensor, and which pin of the ECU is it tied to?

 

[twdorris]

The computer reads these parameters. I checked it out today, it sits low at idle. But at 5,500 rpm it was reading about 110 psi.

Then I have no idea what it's actually showing you. I'm going to guess it's interpreting some other piece of data as a fuel pressure signal and displaying that value inappropriately. For example, maybe that code was written to assume the user had some sort of fuel pressure sender connected to the EGR temp input for logging. Since you do not have that (I assume), the display routine is just interpreting whatever you do have there as a fuel pressure signal and displaying whatever value happens to come out of that conversion.

110psi fuel pressure at the rail would imply about 70psi of boost. You must be hauling!

Thomas Dorris
ECMTuning, Inc.

 

[turboAWDfanatic]

Well after running 2 days with the FPR solenoid bypassed the condition still exists. Like I said, I was moving around the ECU the other day which was tugging at a lot of wires. I'll try and track down the loose connection to the Zt-2 and report back.

 

[snakeyes711]

Normally...the ECU does NOT read fuel pressure. If your case is different, where is the sensor, and which pin of the ECU is it tied to?

If there IS one, and the pin its tied to. Then its been there since I bought the car./ It was mostly stock when I bought it.

 

[snakeyes711]

Then I have no idea what it's actually showing you. I'm going to guess it's interpreting some other piece of data as a fuel pressure signal and displaying that value inappropriately. For example, maybe that code was written to assume the user had some sort of fuel pressure sender connected to the EGR temp input for logging. Since you do not have that (I assume), the display routine is just interpreting whatever you do have there as a fuel pressure signal and displaying whatever value happens to come out of that conversion.

110psi fuel pressure at the rail would imply about 70psi of boost. You must be hauling!

Thomas Dorris
ECMTuning, Inc.

I think your right. Much like the stock boost gauge works. 70 psi of boost is ridiculous!@

 

[Calan]

If there IS one, and the pin its tied to. Then its been there since I bought the car./ It was mostly stock when I bought it.

It's just a bogus reading. See Tom's post above.

 

[phunny]

?