2 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHEngine Racing to 6K RPM at Startup
Leading reported evidence
Disconnect during the fault code
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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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
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Performed · outcome unconfirmed · Original poster
P0102 - Hot film MAF sensor (not necessarily indicative of a faulty MAF; present because the MAF connector was disconnected during the fault code check)
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
If the engine idle speed is stable and within limits at that point, would it be safe to say the MAF is erroneously signaling the ICV to upwardly adjust the idle speed??
Leading evidence: 'Disconnect during the fault code' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Adjust idle speed' (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.
Disconnect hose supplying the throttle body intermediate piece was
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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 performed work without a confirmed outcome
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Performed · outcome unconfirmed · Original poster
The disconnected hose supplying the throttle body intermediate piece was reconnected.
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
Continued inspection revealed the presence of a rat's(?) nest in the air filter housing, missing throttle housing retention hardware, untightened clamps for the air intake boot supplying the throttle housing and a disconnected large diameter breather hose running from the air/oil separator to the intermediate piece to which the throttle body bolts.
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
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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
With the MAF's wiring harness again disconnected, the engine was allowed to idle long enough to check for stored fault codes.
Reconnect disconnected hose supplying the throttle body intermediate piece
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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 performed work without a confirmed outcome
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Performed · outcome unconfirmed · Original poster
The disconnected hose supplying the throttle body intermediate piece was reconnected.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Adjust idle speed
No successful repair reported for this finding.
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Reported fixes
0
Unsuccessful attempts
1
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Discussions that contain suggestions
1
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Suggestion · Original poster
If the engine idle speed is stable and within limits at that point, would it be safe to say the MAF is erroneously signaling the ICV to upwardly adjust the idle speed??
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
So leave to MAF disconnected untill you have found all the air leaks ( don't forget to check the bellows under the AOS for air leak) and have it running well without the MAF, then if connecting the MAf causes it to run poorly replace it, then retest.
Disconnect ), spray some starting fluid into the throttle body(
No successful repair reported for this finding.
0
Reported fixes
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Read evidence and context
Discussions that contain suggestions
1
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Suggestion
To get the engine to its MAX RPM with closed throttle (and MAF disconnected), spray some starting fluid into the throttle body(use the spray as a fuel enrichment device), if the engine revs above 650, you still have air leaks.
Discussions that performed work without a confirmed outcome
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0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
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Performed · outcome unconfirmed · Original poster
P0102 - Hot film MAF sensor (not necessarily indicative of a faulty MAF; present because the MAF connector was disconnected during the fault code check)
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
Continued inspection revealed the presence of a rat's(?) nest in the air filter housing, missing throttle housing retention hardware, untightened clamps for the air intake boot supplying the throttle housing and a disconnected large diameter breather hose running from the air/oil separator to the intermediate piece to which the throttle body bolts.
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
Continued inspection revealed the presence of a rat's(?) nest in the air filter housing, missing throttle housing retention hardware, untightened clamps for the air intake boot supplying the throttle housing and a disconnected large diameter breather hose running from the air/oil separator to the intermediate piece to which the throttle body bolts.
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.
2 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 · 1 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T165820Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Have stepped in here to help revive a 1999 911 Carrera, with 70K miles and a shady service history. Vehicle was purchased used at 50K and ran without fault until about a year ago. At that point the service history gets very muddy and the car sat unused because of an inability to idle. Now, a year later, I been asked to step in and troubleshoot the engine problems.
On initial inspection, no fault codes were present other than P1602, due to the battery having died. Following battery renewal, engine cranked readily but could not achieve a stable idle. During the course of attempting to nurse an idle, the engine suddenly raced to maximum RPM at which point the engine was immediately shutoff.
Continued inspection revealed the presence of a rat's(?) nest in the air filter housing, missing throttle housing retention hardware, untightened clamps for the air intake boot supplying the throttle housing and a disconnected large diameter breather hose running from the air/oil separator to the intermediate piece to which the throttle body bolts. Upon further disassembly the mount gasket for the throttle body was noted to be fatigued and leaking air. The engine's air filter had been chewed through by rodents and numerous small pieces of air filter element with rubber base attached were found in the MAF sensor's housing.
The air filter housing was thoroughly cleaned, the air filter element renewed, and the air filter debris present in the MAF sensor housing was extracted. The MAF sensor was removed from its housing and inspected: no gross faults were noted and the unit was reassembled. The rubber sleeves and the resonance tube supplying the intake distributors were inspected for the presence of oil; the throttle body mount gasket was renewed, the throttle body thoroughly cleaned and then reinstalled with all of its proper mount hardware. Engine oil level dipstick and oil filler cap were renewed, due to fatigued seals. The disconnected hose supplying the throttle body intermediate piece was reconnected.
Following completion of this service the engine was started and observed for performance. The engine started readily and idled, within reason, as long as the MAF's electrical connector was left disconnected. The idle was not perfect however and a vacuum leak was apparent. Everytime the engine was started with the MAF connected, it immediately raced to redline and its speed could not be attenuated by blipping of the accelerator pedal.
With the MAF's wiring harness again disconnected, the engine was allowed to idle long enough to check for stored fault codes. With the engine thoroughly warmed up, both the oil filler cap and the engine oil dipstick could both be easily removed from the engine.The following codes were listed:
P0102 - Hot film MAF sensor (not necessarily indicative of a faulty MAF; present because the MAF connector was disconnected during the fault code check)
P0300 - Misfire detection
P0304 - Misfire cyl 4
P0305 - Misfire cyl 5
P0306 - Misfire cyl 6
P0150 - O2 sensor ahead of cat conv. bank 2
P1316, 1317, 1318, 1319 - misfire, emission relevant for cyls 4-6
Following code retrieval, the idle control valve was removed for inspection; approx. 40% of the valve's mount gasket was missing, permitting a vacuum leak. The valve was seen to be functional in both directions by use of a 9V battery check.
Based on this information, is it possible the MAF is responsible for this grossly elevated idle speed? Or does the fault more likely lie with the idle control valve? The next logical diagnostic step would be to fix the ICV gasket and then attempt to run the
engine with the MAF sensor connected and the ICV disconnected. If the engine idle speed is stable and within limits at that point, would it be safe to say the MAF is erroneously signaling the ICV to upwardly adjust the idle speed?? If replacement of
the MAF is warranted, is the consensus that the Bosch units are suitable replacements for the factory branded component? I understand the manufacturer is Bosch, just curious as to how they have been holding up over the Porsche boxed units.
Thanks.
Bosch MAF's are exactly the same as Porsche/Bosch MAF's.
MAF does not control ICV, it is controlled by the DME.
Sounds like you have a leak(s) in the intake system, causing extra air to enter the engine, and also a failing MAF, causing extra fuel to enter the engine. Extra air + extra fuel = high RPM's, same as pressing the throttle (extra air +extra fuel = high PRM's )
You can't really diagnose a runaway engine, so you have to stop the extra air or the extra fuel in order to even diagnose it. So leave to MAF disconnected untill you have found all the air leaks ( don't forget to check the bellows under the AOS for air leak) and have it running well without the MAF, then if connecting the MAf causes it to run poorly replace it, then retest.
With the throttle plate closed (properly, with a preset leak/gap ) and the ICV blocked off ( bolt a business card under it) the engine should NEVER be able to go above 650 RPM unless it is getting air from somewhere that it is NOT supposed to. To get the engine to its MAX RPM with closed throttle (and MAF disconnected), spray some starting fluid into the throttle body(use the spray as a fuel enrichment device), if the engine revs above 650, you still have air leaks.
This is a source reference. Confirm exact model applicability in the original material.
