FAQ
TL;DR: Opel Meriva Z16XEP with a 1‑cylinder misfire: compression OK is reported, and “The B1S2 probe error has no effect on engine operation.” Focus on ignition, fueling, vacuum, and EGR checks before swapping ECUs. [Elektroda, Doktorr, post #16628966]
Why it matters: This FAQ helps DIYers quickly isolate a stubborn single‑cylinder misfire on factory‑LPG Meriva 1.6 16V without wasting money on parts.
Quick Facts
- Engine/code: Opel Meriva 1.6 16V, Z16XEP with factory Landi Renzo LPG. [Elektroda, pawliszon1981, post #16635014]
- Reported idle manifold vacuum: ~0.35 bar; judged “close to correct.” [Elektroda, Doktorr, post #16632997]
- Typical ignition coil price noted: ~PLN 300 for OE unit. [Elektroda, pawliszon1981, post #16627172]
- Recorded DTCs in thread: P0141 (O2 heater, B1S2) and P1405 (EGR). [Elektroda, pawliszon1981, post #16635014]
- Downstream O2 (B1S2) fault does not affect engine running behavior. [Elektroda, Doktorr, post #16628966]
How do I quickly narrow down a single‑cylinder misfire on a Z16XEP with LPG?
Confirm spark, fuel, and air on the suspect cylinder. Swap LPG injectors/hoses and spark plugs between cylinders. If misfire stays on the same cylinder, look at ignition coil pack, wiring, vacuum leaks, or EGR effects. Users swapped injectors, hoses, and plugs with no change on cyl. 2, pointing away from LPG hardware. [Elektroda, pawliszon1981, post #16627172]
Does the car run evenly on petrol, or only on LPG?
The case described runs evenly on petrol but shows hesitation up to 2500–2700 rpm, while LPG idles roughly and misfires on cylinder 2. That behavior suggests an issue visible on both fuels at low load. Check ignition and air management first. [Elektroda, pawliszon1981, post #16627172]
What does DTC P0141 mean here, and does B1S2 affect drivability?
P0141 indicates a heater circuit fault for the downstream oxygen sensor (Bank 1 Sensor 2). In this case, the expert notes B1S2 does not affect engine operation, so fix it separately from misfire diagnostics. “The B1S2 probe error has no effect on engine operation.” [Elektroda, Doktorr, post #16628966]
What idle manifold vacuum should I expect, and what does 0.35 bar imply?
Reported vacuum was ~0.35 bar at idle and judged close to correct. That level helped rule out false air, a stuck‑open EGR, and burned valves in this context. Next steps should shift toward ignition control and mixture on the affected cylinder. [Elektroda, Doktorr, post #16632997]
How do I perform the EGR unplug test on the Z16XEP?
- With engine off, unplug the EGR electrical connector.
- Start and drive until the ECU logs an EGR fault.
- Compare idle and low‑rpm smoothness with EGR disconnected.
If it improves, investigate EGR sticking or control. [Elektroda, Doktorr, post #16632997]
Could the ignition coil be the culprit?
Yes, coils can cause single‑cylinder misfires. However, in this thread the coil pack was replaced and the fault remained, so the coil was excluded in that vehicle. Always verify with cylinder‑specific spark checks before buying parts. [Elektroda, pawliszon1981, post #16630110]
How can I rule out an LPG injector or rail issue?
Swap LPG injectors or even cross the hoses between cylinders. If the misfire does not move to the other cylinder, the injector/rail is unlikely. Here, swapping injectors and hoses left the misfire on cylinder 2, so attention moved elsewhere. [Elektroda, pawliszon1981, post #16627172]
What does squeezing or disconnecting the LPG hose to the bad cylinder tell me?
If clamping or unplugging the LPG hose to the suspect cylinder barely changes idle, that cylinder contributes little at idle on gas. It suggests an ignition or mixture issue local to that cylinder. Use it as a quick isolation check. [Elektroda, pawliszon1981, post #16627107]
Is my compression healthy? I measured 17 across all cylinders.
A reported 17 (bar) on all cylinders indicates strong and even compression, so mechanical sealing is likely fine. Focus diagnostics on spark, fueling, EGR behavior, and intake tract issues rather than internal engine wear. [Elektroda, pawliszon1981, post #16627107]
What does P1405 after unplugging EGR mean for drivability?
P1405 flags an EGR‑related issue after unplugging its connector for the test. In the case described, the only change was occasional idle fluctuations. That result aligned with vacuum being near normal, reducing suspicion of a stuck‑open EGR. [Elektroda, pawliszon1981, post #16635014]
I replaced the Landi Renzo LPG ECU and the car won’t start on gas—what’s missing?
You must connect and configure the new controller for the car. After replacement, it should still run on petrol if the LPG ECU is operational. “You have to connect and set it.” This is a common edge case after ECU swaps. [Elektroda, psooya, post #16670992]
Will a downstream O2 heater fault (P0141) cause my misfire or rough idle?
No. The downstream sensor monitors the catalyst and does not control mixture. Fix the heater circuit for emissions compliance, but continue misfire diagnosis separately. This separation saves time and avoids chasing unrelated faults. [Elektroda, Doktorr, post #16628966]
Does swapping petrol injectors help isolate the fault?
Yes. The thread notes petrol injectors were checked and tight, and swapping LPG components did not move the misfire. If petrol injector swaps make no difference, keep focus on ignition, wiring, or intake/EGR effects. [Elektroda, pawliszon1981, post #16627107]
What should I check if low‑rpm hesitation appears on both fuels?
Shared symptoms on petrol and LPG point to non‑fuel‑specific causes. Inspect ignition coil control, plugs, wiring, manifold vacuum integrity, and EGR influence. Vacuum judged near normal helped deprioritize air leaks and valve issues in this case. [Elektroda, Doktorr, post #16632997]
Any cost tips before I buy parts blindly?
An OE coil was cited at ~PLN 300. Before spending, swap components side‑to‑side, verify spark on the suspect cylinder, and run the EGR unplug test. This reduces unnecessary purchases. [Elektroda, pawliszon1981, post #16627172]
