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b5a4erik
09-25-2018, 02:33 PM
Hey'all,

So I've done my research and am a bit stumped - The car is a 1998 A4 2.8 30v Quattro:

The car sometimes starts & runs fine, other wise it starts fine then starts acting up and other times it starts up poorly & continues to run poorly... Lately it's mostly been starting well, running okay for a while then intermittently has problem episodes.

An example of a problem episode would be: While driving just fine, the car will start to SPUTTER (dropping of / fluctuation of the revs in blips of about 200-400 rpm), SURGE (giving it throttle with a noticeable lag in power - till it clunkily catches up) and sometimes even STALL when coming to a stop.

Thus far I have:
1. Cleaned the M.A.F sensor
2. Cleaned the sensor in the Throttle Inlet Tube
3. Cleaned the Throttle Body
4. Replaced most of the Vacuum Hosing that connects near the Throttle Body
5. Replaced the Evap Purge Valve
6. Replaced the Suction Jet Pump
7. SeaFoamed the Intake Manifold & Gas Tank

Of course the battery was also connected then reconnected resulting in what I think & hope does a Throttle Body Alignment.

It's running better now comparatively to how it was running prior to doing the work listed above; it's now stalling much less and generally running smoother... yet it still has these problem episodes.

I'm thinking it's an electrical issue... MAF Sensor still bad, O2 Sensor bad, broken wire or what [confused]

As always any insight is appreciated!

Thanks Y'all,

b5a4erik

scaphan
09-25-2018, 02:37 PM
Any codes? Did you take a look at long term/short term fuel trim?


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b5a4erik
09-25-2018, 03:46 PM
Getting codes cleared then read ASAP (not yet do I have them)... I did once in picture form but since working on them the pics have been deleted.

If I remember correctly P0411 was one of them.

And unfortunately no fuel trims; no VAGCOM... however I was told that it has been running Rich.

Thanks, scaphan.

~ ~ ~ ~

P.S - Could the n112/n249 Solenoids be to blame? or maybe the Ignition Coil Pack? How about any Check Valves like the Green one near the Throttle Body? Thanks again for helping me deal with this problem.

LA4
09-25-2018, 07:57 PM
Disconnecting/reconnecting the battery does not magically perform a throttle body alignment, that's a myth which gets reiterated a lot. And a bad o2 sensor will not cause the problems you're describing.

Other than that it's really hard to give any definitive help without codes. If you don't have vag-com it's probably worth paying a mechanic (or finding someone on the forums/local facebook groups) to look at it for you. Will be faster and cheaper than buying parts and throwing them at it.

b5a4erik
09-25-2018, 07:59 PM
Yeah - that's what I've heard (about the throttle body alignment) :/

I'll get these codes read & post em up.

Thanks thus far folks,

b5a4erik

b5quattro_man
09-25-2018, 11:20 PM
If you needed a throttle body alignment, I feel the issue would be more consistent from initial start up. But if you keep unplugging sensors and battery, you're going to need to get it recalibrated. It could be a fuel pump starting to go, a faulty sensor or something completely random. Pulling codes should be the next step in finding out what's wrong. Until then you're just guessing and hoping you get lucky. That can get expensive and time consuming. Look at the fuel pressure, afr and fuel trims. If it's a bad sensor there will be a code pointing straight to it.

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b5a4erik
09-26-2018, 12:47 PM
I Appreciate Y'al!

So I have yet to get the codes cleared, and I also failed to mention that the spark plugs have been replaced recently... and just today while acquiring codes i discovered the battery was going - only 65% there, so I just got a new one as well.

Anyways, The Codes:
P0102 - MAF Sensor Circuit Low Input
P0116 - ECT Sensor / CHT Sensor Signal Range / Performance
P0138 - HO2S (Bank 1 Sensor 2) Circuit High Input
P1127 - Long Term Fuel Trim Add. Air. Bank 1 System Too Rich
P1129 - Long Term Fuel Trim B2 System Too Rich
P1139 - Long Term Fuel Trim Add. Fuel B2 System Too Rich
P0300 - Random / Multiple Misfires Detected
P0301 - Cylinder #1 Misfire Detected
P0302 - Cylinder #2 Misfire Detected
P0303 - Cylinder #3 Misfire Detected

I'll have to get those codes cleared then re-scanned of course...

I'm thinking replacing the Fuel Filter might help (already got one hanging around) and maybe the coil packs? (but as has been mentioned wisely: don't spend $ on guessing).

What'd'ya folks think?

Please & Thanks in Advance,
b5a4erik

scaphan
09-26-2018, 01:57 PM
Next step would be to look at the maf sensor measuring block and see what it is recording. If it isnít within spec then try cleaning. If it is still outside spec then replace.

I think you need vag com. Itís cheap. You donít need a registered version.


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scaphan
09-26-2018, 01:58 PM
Or try unplugging the maf and see if it changes/improves?


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b5a4erik
09-27-2018, 01:45 PM
Or try unplugging the maf and see if it changes/improves?


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Unplugging the MAF led to indistinguishable results... didn't know how it's supposed to change nor what the changes really mean (I found conflicting information online).

Thank you

b5a4erik
09-28-2018, 05:04 PM
Hey guys,

So an update:

1. The car also sends out puffs of black smoke from the exhaust from time to time.
2. The car only does it surging deal when trying to hold the speed steady; at idle its fine, and also while accelerating it's fine (except in gears 1 & 2).

Fresh codes getting uploaded soon.

b5a4erik
09-30-2018, 06:28 PM
*bump*

Same codes popped up, with the exception being: instead of low input @ the MAF, it's high input this time.

warrenzo
10-05-2018, 11:06 AM
Everything you're describing is probably caused by the maf. Getting a graph of the episodes would confirm that, but it's a safe bet at this point, especially since unplugging it doesn't stop the misfires. You should make sure the intake is connected well at the inlet pipe, but I'm sure you would've installed it correctly after checking it the number of times you did. One time, I didn't get the inlet clamped on right, and it was only a small leak but enough to make the car do what yours does (also intermittently). If the MAF is good, that means you've got some wires crossed somewhere. I'd guess your first 2 (and possibly 3rd) codes are all unrelated, but the last 7 are symptoms of the maf.

I'd try replacing the MAF if you can get one that you can return easily, so you don't waste money on it if yours is fine and the issue isn't resolved - or borrow one from a friend? Then it's down to the nitty gritty of chasing crossed wires. I couldn't imagine what else the problem would be.

b5a4erik
10-05-2018, 01:27 PM
Everything you're describing is probably caused by the maf. Getting a graph of the episodes would confirm that, but it's a safe bet at this point, especially since unplugging it doesn't stop the misfires. You should make sure the intake is connected well at the inlet pipe, but I'm sure you would've installed it correctly after checking it the number of times you did. One time, I didn't get the inlet clamped on right, and it was only a small leak but enough to make the car do what yours does (also intermittently). If the MAF is good, that means you've got some wires crossed somewhere. I'd guess your first 2 (and possibly 3rd) codes are all unrelated, but the last 7 are symptoms of the maf.

I'd try replacing the MAF if you can get one that you can return easily, so you don't waste money on it if yours is fine and the issue isn't resolved - or borrow one from a friend? Then it's down to the nitty gritty of chasing crossed wires. I couldn't imagine what else the problem would be.

I figured as much, the MAF being the culprit that is.

However, new Coil Packs and ECT Sensor are on the way, considering they were about a 1/3 of the price of a MAF.

Will of course get a new MAF if those ^ don't do the trick.