19 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHEngine chokes under acceleration
Reported or suspected cause
still there
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause · Original poster
In the early morning I cleaned the MAF sensor without noticing any difference, the problem was still there...
Leading evidence: 'still there' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'still there' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check air filter' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
venturi tubes had hairline cracks in the plastic�good luck
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause
It turned out that the Venturi tubes had hairline cracks in the plastic�good luck
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
Later this afternoon I disconnected the MAF and the engine ran just a bit better with the PSM and ABS mil on...so, I got home and connected my iCarsoft POR V2.0, deleted the DTCs and then the engine started to run worse than before.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
In the last 12 years it only did 10k miles (ims changed 11 years ago), coolant is clean, temperature sticks at 90 Celsius, oil pressure on hot engine at 1.1bar.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
Later this afternoon I disconnected the MAF and the engine ran just a bit better with the PSM and ABS mil on...so, I got home and connected my iCarsoft POR V2.0, deleted the DTCs and then the engine started to run worse than before.
Clean temperature sticks at 90 celsius, oil pressure
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
In the last 12 years it only did 10k miles (ims changed 11 years ago), coolant is clean, temperature sticks at 90 Celsius, oil pressure on hot engine at 1.1bar.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
Later this afternoon I disconnected the MAF and the engine ran just a bit better with the PSM and ABS mil on...so, I got home and connected my iCarsoft POR V2.0, deleted the DTCs and then the engine started to run worse than before.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
In the last 12 years it only did 10k miles (ims changed 11 years ago), coolant is clean, temperature sticks at 90 Celsius, oil pressure on hot engine at 1.1bar.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
19 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T200546Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hi all!
I bought the car yesterday with an issue... Engine chokes under partial and/or hard acceleration. After 4.5-5k rpm there's a drop in torque very noticeable and it's not delivering those 296hp right. Car has 82k miles, 5w50 oil, new spark plugs and air filter also. In the last 12 years it only did 10k miles (ims changed 11 years ago), coolant is clean, temperature sticks at 90 Celsius, oil pressure on hot engine at 1.1bar. It's a 1999 996.1 3.4L C4 manual. Very well maintained car.
I did today about 80 miles. In the early morning I cleaned the MAF sensor without noticing any difference, the problem was still there... applying full throttle from idle chokes and hesitates to raise the rpm smoothly.
Later this afternoon I disconnected the MAF and the engine ran just a bit better with the PSM and ABS mil on...so, I got home and connected my iCarsoft POR V2.0, deleted the DTCs and then the engine started to run worse than before. I did a log with my diagnostic tool and also took some pics and vid (click on the link to be redirected to YouTube).
I don't know if could be a faulty water sensor, Egas miscalibration, clogged injectors/filter, faulty fuel pump, AOS failure, or the cam deviation over 1k degrees (which is strange cause when I bought the car it was on -8.62deg fixed). No smoke wether on cold or hot, oil level just before full, ron95 gasoline, the car has been used and driven very softly within the last 12 years. I'll take out the oil filter next week to analyze it and looking for plastic and/or metal traces.
Link to YT video of the issue
Anyone that had the same issue could tell me how did you repair it? Please don't tell me I need a new engine...I now that is a solution but can't spend over 12k right now on that lol
thanks in advance!!!
It could be many things. I did not look at the vid yet. Here are starter questions:
-what were the codes that you cleared?
-what does �well maintained� mean? (Oil change every 6 months?)(fuel stabilizer used for garage queen?)
-how long has the engine been like this?
Let's see... It has been a garage queen, to give you an example...last oil change was last august and did only 80miles untill last Friday since then right when I bought it. Last owner had it for 12 years and did only 10k miles (most of them at the beginning and oil changes every year or 1.5 years). Well maintained regarding the car itself (interior, tires, brakes, oil changes...)
Untill 2008 maintenance was at the dealer (not sure if only at the dealer or somewhere else besides the dealer) but oil changes were on time by dates but we'll after 8k miles.
The codes i cleared were caused by disconnecting the MAF sensor only. Besides that the engine ran rough but there was no DTC and no MIL.
I must take out the oil filter and look up for other things than oil in it. Bought another filter yesterday.
Camshaft deviation is over 1k degrees which is weird to me. I road tested the car for 1st time last Wednesday and felt a power/torque drop after 5k rpm. Thought about the variocam pads maybe or other faulty sensor (no DTC either and cam deviation at -8.xx deg after a 30min drive)
Check the fuel pump Venturi tubes (in the gas tank). My engine had a similar problem when it was re-built by FSI about 4/5 years ago. It drove them crazy because they could figure out why it would only go lean at higher rpm�s. It turned out that the Venturi tubes had hairline cracks in the plastic�good luck
After looking at your video sounds like you�re over fueling at idle/low RPMs.
Regardless, you need to get rid of that old oil,
drop the oil sump , take a picture of what might be in the sump and check back.
Rent a fuel pressure guage from autizone to verify fuel pressure, check air filter. That eliminated 2/3s of what it could be. Next would be buy a duremetric and learn how to read the telemetry. Or u can just throw money at it and waste time with internet arm chair suggestions.
The AWD cars have the venturi tubes in the gas tank, the RWD cars do not.
The venturi tubes (there are two of them) siphon off some of the pressure/flow from the pump to suck gas out of two lower areas of the gas tank (one each side of the front driveshaft). They are sized so as to not starve the engine for fuel of course. If the corrugated hoses crack more fuel is "lost" to the venturi tubes than was scheduled so the engine can go lean at high power. The fuel doesn't leak out of course because it's leaking inside the fuel tank; it just doesn't make it to the engine.
The other problem that happens on the AWD cars is that a short U shaped line on the fuel pump outlet can split. This also reduces fuel flow and can make the engine run lean at high power settings for a small leak or make the engine not run at all for a large leak.
The venturi tubes are also called "Motive Flow Pumps" and are widely used in automotive and aerospace applications because they have no moving parts.
Damn good explanation. That's the best one I've seen. I imagine problems with either one manifest as decreased fuel pressure or fuel volume.
Does the GT3, which shares it's chassis with the all-wheel drive variants, have the same gas tank configuration and Venturi tubes?
No it does not. It uses the standard c2 tank in a c4 chassis. It does have a unique higher volume pump assembly (but basically the same as a turbo) and (sender is the same as a mk2 c2) that still use the venturi system as a secondary pickup. The locking ring that holds the pump at the bottom of the tank is also unique so u cant just install a gt3 pump and sender into a c2 car.
Pick of what fails on a Gt3 pump assembly. Sorry i dont have a wide shot.
Nice photo. There's an old renntech post about that exact thing. The fuel line splits. Were you able to replace/repair just the line? I am guessing fuel pressures are low if you measure but it's not the pump itself.
I bought a pump assemble because this one had 85k miles and i bought a length of accordian fuel hose from amazon to repair this one to use as a spare.
Low pressure could be either or both the pump and/or internal hose. Fuel pumps fail in different ways and some times the hose can get a pin hole or a large split. Either way if u have a fuel pressure issue plan on going into the tank to investigate.
This is a source reference. Confirm exact model applicability in the original material.
