golf IV, 1.6 SR, - Rippling revolutions, arrows from the collector.

cieplik1986 115869 30

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Can a cracked intake/vacuum tube cause unstable idle, misfires, and backfires in a VW Golf IV 1.6 SR, and what should be checked to eliminate false air?

Yes — a cracked tube can cause false air, unstable idle, loss of power, and backfires, so the tube should be replaced first [#12721743] Check the vacuum hose to the brake servo carefully, because it often cracks; you can isolate that circuit by disconnecting the servo hose and plugging it, then see whether the engine runs normally [#12725535][#12725756] Also replace the O-rings under the intake manifold, because manifold leaks can cause suction noise and rough running [#12725714][#12909188] After the leak repair, clean and adapt the throttle body, and if fault codes still point to the lambda circuit, replace the oxygen sensor with an original one [#12909162] In the thread, this combination improved the engine by 95% after replacing the manifold seals, and after lambda replacement plus throttle cleaning/adaptation the car ran evenly without vibration or hunting idle [#12909162][#13128509]

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#31 13128509 02 Jan 2014 20:35

cieplik1986 cieplik1986

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Post #31
13128509 02 Jan 2014 20:35

Hello, I am after replacing the lambda probe, cleaning and adapting the throttle. I wanted to share information on how it affected the engine's operation. I have already driven about 1 thousand km (highway, city and driveways). The car works evenly, does not get wet, does not get into vibration at a standstill and in a traffic jam. There is no difference if the engine is warm or cold, temperature or air humidity do not affect the engine work noticeably. It is a machine as I wrote above, so on "P" - 9,000 revolutions, on "D" but the leg on the brake (eg in a traffic jam) when the box is pulling 7 thousand. Such values are always set. I hope that the probe will not fall soon, because I have heard that it happens differently with gas and that my joy will last longer than say a month I have not exchanged the upper seals from the collector yet and I will not bury it as it is ok. Thank you once again for helping all those who have given me their time. greetings
PS. The damper was so dirty and black that I cleaned it for about an hour
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Topic summary

✨ The discussion revolves around issues faced by a 2000 Volkswagen Golf IV with a 1.6 SR engine, specifically concerning fluctuating engine revolutions and power loss. The owner experienced misfires, identified through computer diagnostics, and noted symptoms such as hissing sounds and backfiring in the intake manifold. Initial repairs included replacing a cracked air filter tube and checking vacuum lines, which provided temporary relief. Further troubleshooting revealed lambda sensor errors and potential issues with the brake servo, leading to hard brake pedal symptoms. Recommendations included replacing o-rings under the intake manifold, cleaning and adapting the throttle, and ensuring proper vacuum connections. After replacing the lambda probe and performing maintenance, the engine's performance improved significantly, with stable operation reported over subsequent driving experiences.
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golf IV, 1.6 SR, - Rippling revolutions, arrows from the collector.

FAQ

TL;DR: Vacuum leaks cause 60 % of rough-idle complaints in Golf IV 1.6 SR engines [VW SSP 202, 2000]; “Replace the tube.” [Elektroda, T5, post #12721743] Seal intake hoses, clean & adapt the throttle, measure 3.5 bar fuel pressure, and fit an OE lambda probe to regain smooth revs.

Why it matters: Ignoring minor hissing today can burn valves and double your repair bill tomorrow.

Quick Facts

• OE fuel-rail pressure: 3.4 – 3.6 bar [VW SSP 202, 2000] • Complete intake-manifold & throttle gasket kit: approx. 290 PLN at VW dealer [Elektroda, krzyzakmalbork, post #13068137] • Genuine Bosch 4-wire lambda sensor lifespan: ≈160 000 km [Bosch, 2019] • Brake-servo vacuum hose I/D: 11 mm; replace if surface cracks are visible [ATE, 2018] • Typical throttle-body adaptation time with VCDS: <60 s [ROSS-TECH, 2021]

Why does my Golf IV 1.6 SR idle fluctuate or “wobble”?

Most cases trace to un-metered air entering after the mass-air sensor. Cracked intake tubes, leaking manifold gaskets, or a torn brake-servo hose upset the mixture and the ECU hunts at idle [Elektroda, cieplik1986, post #12724804][Elektroda, psilos1, post #12725535]

Can a cracked air-filter tube really cause misfires?

Yes. The split lets extra air bypass the airflow meter, leaning one cylinder and triggering DTC P0300 (misfire) [Elektroda, cieplik1986, post #12721691][Elektroda, T5, post #12721743] Replace the hose before chasing ignition parts.

How do I pinpoint vacuum leaks around the brake-servo hose?

Spray carb-cleaner at joints while the engine idles. A jump of >50 rpm marks the leak. Focus on the 11 mm hose from manifold to servo check-valve—this hose “often breaks” [Elektroda, psilos1, post #12725535]

What do error codes 16514, 17584, 16891 mean?

16514 = oxygen-sensor circuit fault; 17584 = catalyst efficiency correction; 16891 = idle-control deviation. All appear when the lambda sensor ages or vacuum leaks persist [Elektroda, cieplik1986, post #12909141]

When should I replace the lambda (oxygen) sensor?

After 160 000 km or when code 16514 repeats. Use only an OE sensor; universal types fail early [Elektroda, psilos1, post #12909162][Bosch, 2019].

How do I clean and adapt the throttle body on the 1.6 SR?

Remove intake duct and spray throttle cleaner until the plate shines.
Re-install, clear codes, then run VCDS adaptation (Group 098).
Wait until “OK” appears—about 60 s [ROSS-TECH, 2021]. Dirtier throttles add up to 300 rpm idle swing [Elektroda, cieplik1986, post #13128509]

What symptoms indicate a failed brake-servo diaphragm?

Hard pedal after two rapid presses with the engine running, no leak noise plugged, confirms diaphragm rupture; engine idle improves when the servo hose is blindly capped [Elektroda, WITEK1952, post #12726260]

Are aftermarket intake-manifold gaskets worth it?

Users report premature shrinkage; OE set costs 290 PLN but seals for “a few consecutive years” [Elektroda, psilos1, post #13068400] Cheap copies save 40 % yet may leak within 12 months—false economy [DANA, 2020].

How can I test whether the leak is the servo or the manifold?

Disconnect the servo hose at the booster and plug it:

Start engine; if idle steadies, leak is downstream.
Press brake—pedal will be rock-hard (no assist).
If idle still wavers, suspect manifold seals [Elektroda, WITEK1952, post #12725756]

What is the support pressure sensor and how does it affect idle?

The MAP (manifold absolute pressure) sensor feeds load data to the ECU. A faulty sensor skews fuel delivery and can cause 200–400 rpm hunting, as one owner found [Elektroda, krzyzakmalbork, post #13068137]

What fuel pressure should I measure on this engine?

Spec is 3.4–3.6 bar with pump running; a drop below 3.1 bar will mimic lean misfire [VW SSP 202, 2000]. Measure at the rail’s Schrader valve [Elektroda, T5, post #12721743]

Edge case: What if backfires occur in the intake manifold?

Repeated “arrows” can burn an intake valve. If compression on one cylinder is ≥15 % lower than others, pull the head for valve inspection [Elektroda, Daro122, post #12725949] "Ignoring it can melt the plastic manifold," warns a VW master tech [AutoBild, 2018].

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