StaggerLee

Howdy Gentlemen:

Had an issue crop up recently that has me pretty well stumped; thought I'd bounce it off the collective to see if anybody's had any experience with this.

In a nutshell, car is un-driveable with MAF plugged in. Starts & idles fine, but immediately upon transitioning from vacuum to neutral or positive pressure, all hell breaks loose; backfires, sputters, jerks, the whole deal. Almost feels like it's out of gas (it's not). Unplug the MAF, and aside from stalling once in awhile at idle, it runs great.

The really odd thing is that the car is throwing zero codes, other than random, multiple misfires from the bucking & kicking. At idle, the MAF g/s is within spec; dunno how it performs at WOT as I can't get there. I checked the fuel delivery per the Bentley and it's well above the min specifications.

The easy answer, of course would be to throw a new MAF in and see if that solves it, which is probably what I'll do. I just find it odd that for all intents & purposes, the current MAF checks out OK. I really prefer to have conclusive evidence that something is bad before I go about replacing parts; aside from logging block 002, are there any other diagnostics that can be run on the MAF?

Gjaime

How many g/s are you seeing at idle? on the MAF. Also check for leaks. After MAF

You have no dtc codes throw? Post your dtc's

Is the car stock? or turbo kit?

I have a saved document. Read it and see if it helps you. Mainly on the fuel trim reading in vag-com

http://www.wak-tt.com/vagcom/vagcomamm.htm


-Jaime

StaggerLee

I can't remember off the top of my head what the g/s was at idle; I do know that it was within spec. I'll log again this evening and post the results. I haven't pressure tested the system yet, but I have checked for split hoses and found nothing.

It doesn't throw any codes until it gets into boost, then it starts throwing misfire codes for all 4 cylinders as well as random multiple misfires.

Car is running APR Stage III with the Wild 93 programming (hence the Profec). Plugs are newish copper core NGK's, same thing I have been running for years.

Good info in those links; thanks for those. I'd love to know what my g/s looks like at full snort, but the damn thing won't let me spin it up that high.

Gjaime

Ahh ok, I see you have the APR stage 3 wild 93. I am also running this Program on my Apr s3 ATW. Hard to say if it's the same program as you.

But I would definetly recheck maf at idle. block 002. Then with vag-com on block, 20 if timing is being pulled, which I bet it is. How much?

Also since you are running a program not off the shelf. I would check fuel quality. Make sure it's 93.

I had to move to texas for close to 2 years, I had to switch to a 91 octane program. Because I couldn't get 93. The wild 93 wouldn't run, I would get misfire and it would retard timing.


-Jaime

StaggerLee

Yeah, I'm unsure what version of the W93 program I'm running. I got it from Ray a little more than a year ago, and have been running it ever since.

The best fuel we can get at the pump in Oregon is 92 octane, so that's what I've been using with no ill effects. I also have a Snow Perf W/M injection system installed; unless I somehow got a tank full of diesel or water, I don't think this is fuel quality related.

I ran a quick log of blocks 002 & 032 last night; I didn't get any data from block 032 but I think that's from clearing the codes after plugging the MAF back in. At idle, I was seeing a g/s of between 2.6 & 3.



From TS 1.37 to 12.97, I had my foot fully into the throttle in first gear, but it was misfiring so bad I couldn't get past 3400 RPM. I scanned for DTC's immediately after this run and got nothing. The misfire codes don't pop up until the flashing CEL.

I think I can also safely rule out the MAF; I borrowed a known good unit from a buddy's shop last night and put it in; no change at all.

I'll run block 20 logs today and see what's going on with the timing; hopefully that'll point me in the right direction.

StaggerLee

Awright, I logged blocks 115, 002 & 020 a few minutes ago.



At TS 30.07, I buried the throttle; you can see the ERCU requesting a wad of boost but nothing being delivered. Was misfiring like crazy, but it wasn't pulling much timing. This was with the good MAF installed.

Once the flashing CEL came on, I pulled codes; Random/Multiple Misfires, Misfires in all 4 cylinders, MAF no signal. Also had a new one: B1 S2 O2 Sensor, No Activity.

Gjaime

To eliminate variables, Do you have the water injection on or off?

If on, I would turn it off. During the logs.

Also run a log on misfires. Interested to see where and which cylinder you are misfiring on. And how many the count is. I would double check gap also.

Being that you are seeing a MAF low signal dtc would tell me, you might have a break in the wiring. I would try wiggling those wires at idle and see if you can duplicate a no signal.

Since you are showing maf g/s in range on your previous log at idle. I don't have access to your full log, But I would look at what rpm or point in your log your g/s signal went to zero.

Also during your logging, you can hit the space bar and put a marker in your log. To mark an event, like flashing cel.


I would be careful with the flashing cel, don't want to break anything.

-Jaime

StaggerLee

All logging has been with the injection on. I considered disabling it, but figured if it was causing the misfires, it would do it regardless of the MAF being connected or not. It's an easy variable to eliminate though, so I'll yank the fuse and see if anything changes.

Misfires? I got plenty:

<img src="http://i264.photobucket.com/albums/ii181/Staggerlee101/8-3a.jpg">

I'm pretty sure the MAF no signal DTC is from cruising around with the thing unplugged. Once I plug the MAF back in and clear the codes, it doesn't come back. I've jiggled the harness and everything looks tight; I haven't gone so far as to check for continuity at the ECU, but that may be next.

So with the MAF unplugged, does the ECU ignore input from all the related senders; MAP, O2, TPS, etc?

Gjaime

I'm re-read your posts from the begining. I would start at the top again.
I would pull plugs and re-check gap. I personally use feeler gauges, I find it more acurate that those .99 cent gappers.

Or throw in some new NGK BKR7E 4644, which I believe you are using. Just to eliminate variables. Cheap enough 1.99 each.

With water injection off, maf plugged in, clear all dtc. Then take a short drive. Showing block 015, 016 and 003.

Just to see where you are having misfires at, if any.

Then check your block 032 to see where values are.
Block 031 will show your voltage. I would try to do a run with block 031 and block 003 to see how the o2 is working. B1 S1.

Let's see what happens there. Of course, I would make sure I pressure tested your system to look for leaks. You can build one out of a pvc end cap with a tire system, I made mine like that. Then I made a plug for the throttle body side. Here's a video showing how it's done if you don't know.

http://www.youtube.com/watch?v=s29Q77hK-i4

With maf disconnected, from my understanding you can drive with O2, not the best but drivable. I had to drive for 3 days waiting on a failed MAF for my car. Also I had a dtc for b1 S1, replaced that. Then threw in some fresh spark plugs. Everything back to normal on my car, no more misfires on WOT. Or any dtc errors. Of course I'll always see B1 S2 no activity because of the test pipe.

-Jaime

Gjaime

I don't see an edit button. disregard the last comment about throttle body. I meant to say intake, but the video shows pretty clear how to do it.