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YOUR RESEARCH996 C4 3.4 M96 ? sudden start/stall, runs only on throttle body cleaner
Leading reported evidence
Run normally until one morning it started this behavior
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Performed · outcome unconfirmed · Original poster
Car ran normally until one morning it started this behavior.
996 C4 3.4 M96 ? sudden start/stall, runs only on throttle body cleaner
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Leading evidence: 'Run normally until one morning it started this behavior' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check latter first' (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.
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996 C4 3.4 M96 ? sudden start/stall, runs only on throttle body cleaner
Clean maf or better yet
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Suggestion
I would try to clean the MAF or better yet replace it.
996 C4 3.4 M96 ? sudden start/stall, runs only on throttle body cleaner
Replace )
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996 C4 3.4 M96 ? sudden start/stall, runs only on throttle body cleaner
Replace mass air flow sensor
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Suggestion
I would try to clean the MAF or better yet replace it.
996 C4 3.4 M96 ? sudden start/stall, runs only on throttle body cleaner
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Hi all,
Trying to diagnose a sudden start/stall issue on a 2000 996 Carrera 4 (3.4 M96, electronic throttle body).
Car ran normally until one morning it started this behavior. No gradual decline.
Current symptoms
Engine starts, runs ~0.5�1 sec, then stalls.
If I spray throttle body cleaner into the intake, it starts immediately and runs smoothly for ~5�7 seconds, then dies when the spray is consumed.
If I keep feeding it cleaner, I can hold ~4,500�5,000 RPM and it runs very smoothly.
If I drop below ~2,000 RPM or release throttle, it will not recover and stalls.
Very poor throttle response when trying to recover.
MAF unplug test makes no difference.
Throttle body was replaced (no change).
Problem existed before any intake work was done.
Work already done (after symptoms started)
Oil separator (AOS)
Oil cooler o-rings
Spark plugs and coils
Intake manifold gaskets
Vacuum lines inspected
Throttle body replaced
Exhaust manifold to head gaskets
MAF tested unplugged (no change
)No change at all btw.
Plan to test
Fuel pressure test at rail
Smoke test intake system
Given these symptoms, does this look more like:
fuel delivery issue (pump / filter / regulator / wiring), or
major vacuum leak / crankcase ventilation issue, or something else on M96 that could cause instant start-and-die but clean running on external fuel?
Any known common failure points on 996 C4 that match this exact behavior would be appreciated
It lacks fuel...
Probably you fuel pump has suddenly failed or its fuse has done its job.
Check the latter first.
If fuse OK, then find the fuel pump relay, remove it and connect female terminals corresponding to the terminals on the relay, denoted 30 and 87.
This supplies battery voltage to the pump and it should run immediately, which you will hear.
If it doesn't search for the next diagnostic steps on here.
Just some info for anyone reading this and wanting to use " throttle body cleaner" starting fluid, etc, to start and keep running any engine.
Maybe a short burst to just get it started or help trouble shoot a fueling problem. But a Very Very bad idea to try and keep engine running on this fluid/solvent for seconds on end, very bad..., especially for a m96 score prone cylinders. Cylinder damage can be done very quickly.
The combustible solvent/fluid washes all oil off cylinder walls leaving them bare with no lubrication, many times on a cold dry start.
Dry unlubed lokasil m96 cylinders is the exact opposite of what all M96 need...
IMO, do test fuel pressure test and do not use any type of fluid to run engine any more.
Very good chance you've got a faulty fuel pump or split in tank fuel lines.
jmho
This exact thing happened to me and I though for sure it can't be the MAF, and it ended up being and the MAF. I would try to clean the MAF or better yet replace it.
Likely the U shaped rubber hose in the fuel tank has split.
Make sure you use submersible fuel hose when replacing it. Ordinary fuel hose will deteriorate within days when submerged in fuel. Amazon has short lengths of submersible fuel hose.
It seems to be the fuel line inside the tank that got ripped.
It was really late by the time I finished putting everything back together. My friend had a replacement fuel line at his house, so we had to drive over there around 11 PM. We ended up finishing around 3 AM, and I didn't want to start the car because I don't have mufflers on it. That thing is louder than a Mustang and would have woken up the whole neighborhood.
\
So the final answer will come in the morning when I actually try to start it.
I’m fairly new to these vehicles, but with previous history of other vehicles I’ve worked on I would say your fuel pump has failed or something in line with it. I’m not sure about these engines, but most fuel injection rails have a port that you can hook a fuel pressure gauge to and see if you’re getting fuel pressure. All you have to do is hook up the pressure gauge and turn the key on no need to try to crank, and the needle will jump up showing if you have pressure. if not it’s definitely the pump or pump related
The fuel pressure test is a good idea although with a split U-hose it can make acceptable pressure with the engine off or at idle and not enough pressure under load.
The U-hose can be checked in like 30 minutes. I have changed mine at the track between sessions.
