Engine misfire, jerking & power loss problems are among the most common issues with automobiles, now a days. These issues are also coupled with low engine performance that cause hesitation during acceleration. Such issues are generally faced by relatively older models or cars with higher mileage. In this article I’ll try to draw attention of readers and automobile owners towards certain most critical aspects of maintenance that would help resolve such issues.
Ok let’s start the discussion:-
Refreshing the Basics
We all know that as the machines get old, effects of wear and tear become pronounced and the performance of machine deteriorates over the passage of time, however, these adverse effects can only be delayed if the machines are maintained as per the defined maintenance schedules. Critical monitoring of following three aspects helps in prolonged trouble free drive of automobiles:-
- Timely preventive maintenance.
- Quality of maintenance by qualified / expert mechanics
- Usage of good quality spares
Possible Causes Of Engine Misfire, Jerking & Power Loss (Pick) Problem
There could be multiple possibilities that can lead to engine misfire, jerking & power loss problems. Broadly we can categories them as:-
I’ll briefly cover each category one by one.
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Isolating Problematic Fuel Supply System
In most countries, automobiles also use alternate fuels, such as:-
- LPG (Liquefied Petroleum Gas) or
- CNG (Compressed Natural Gas) etc.
Before proceeding with corrective maintenance, isolate the problematic fuel source. If problem is observed with both fuel supply systems, then the troubleshooting equation gets entirely different. It has been observed that, in most of the cases the problem remains unnoticed in gasoline (petrol) mode due to better combustion and engine power, however the problem pronounces when the car operates on alternate fuel (LPG or CNG). In such a case the operator thinks that the problem is with the alternate fuel only, whereas, in reality, the problem is common for both fuel sources.
I’ll first discuss the scenario where engine misfire, jerking & power loss (pick) problems are observed in both fuel modes.
Electrical System Checks
Before replacing any part, thoroughly inspect the electrical system for any abnormality such as worn out wire insulation, loose bonding connections, wire chaffing or short circuiting etc. Also ensure that all the sensors are working perfectly. For understanding of working and failure symptoms of sensor, i’d recommend going through this article. Moreover, ensure serviceability of following areas of electrical system:-
- Battery terminals must not be loose.
- Bonding wires, attached to the car body, must have good connections.
- Loose fuses, connectors or relay grips. Also check salt deposits on terminals, connectors especially in high humidity / coastal locations.
- Serviceability check of High-Tension (HT) leads, usually known as Spark-Plug wires must be ensured.
- Serviceability check of Ignition Coils must be confirmed through resistance check. Weak engine coils or old HT leads often result in poor initial pick especially when moving from stop position in first gear.
Engine Component Malfunction Checks
Efficient engine performance is a combined outcome of all engine components. Components perform actions as per their designed roles, however in the event of malfunction, the engine performance becomes unsatisfactory. To identify the faulty component, step by step trouble shooting is essential. Minor maintenance remains the priority, but if the problem persists, deeper maintenance will be the only option. Deeper maintenance requires expertise and special tools/testers for fault isolation. In order to address engine misfire, jerking & power loss problems, following steps may be taken in the priority sequence, so that exact cause could be determined with least expenditure. The fault isolation actions are as follows:-
(a) Use of Good Quality Fuel
Good quality of fuel is a life line for any engine. For gasoline engines, un-leaded fuel must be used. Leaded fuel results in fouled spark plugs, inefficient Exhaust Gas Regulator (EGR) and also contaminate Lambda (O2) sensor with carbon deposits etc
(b) Incorrect Oil Grade
Loss of engine power may be a consequence of incorrect oil grade. Operators’ manual mentions the correct engine oil grade for every automobile, regardless of the atmospheric temperatures.
(c) Engine Cooling System
Bad engine cooling system also effects car engine power (acceleration). Use of anti-corrosive coolant and periodic serviceability check of thermostat valve and radiator ensures optimal operating temperatures of engine.
(d) Throttle Body
Check Throttle body for carbon deposits. Contaminated throttle body may results in bad engine performance including Engine misfire, jerking & power loss problems etc.
(e) Idle Air Control Valve
If idle RPM are also observed to be unstable then Idle Air Control (IAC) valve could be malfunctioning. IAC valve also get contaminated which results in restricted movement of valve. Periodic cleaning of IAC valve is considered a good practice.
(f) Exhaust Gas Regulator (EGR)
With the passage of time, carbon deposits cause blockage of EGR (Exhaust Gas Regulator). Blocked EGR may also result in engine misfire, jerking & power loss (pick) problem.
(g) Lambda / Oxygen Sensor
Poor performance of Lambda sensor (O2 Sensor) due to carbon deposits, may also contribute towards engine misfire, jerking & power loss problem. Hesitation during acceleration could also be a symptom of faulty Lambda sensor. Lambda sensor can also be reused after cleaning with the Carburetor cleaner spray.
(h) Catalytic Converter (CAT)
Catalytic Converter (CAT), converts the burnt toxic gases into environment-friendly products, before sending them to atmosphere. CAT is installed in the exhaust pipe. Carbon deposits often contaminates the Catalytic Converter, which can also cause engine misfire, jerking & power loss problem. For extended service life of Catalytic Converter, safeties mentioned in Catalytic Converter (CAT) Failure Symptoms and Precautions must be followed.
(i) Engine Tappet Adjustments
Improper adjustment of engine tappets can cause loss of engine power or hard engine rotation.
(j) Core Engine Performance
Worn out piston rings will not generating enough compression resulting in loss of engine power along with other multiple issues. Engine (piston rings) condition can be verified through compression test.
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Alternate Fuel Checks (CNG/LPG)
If issues of engine misfire, jerking & power loss are confirmed to be with alternate fuel (CNG/LPG) only, then following checks must be carried out:-
- Make sure that there are no gas leaks, starting from cylinder till injector outlet pipes going to the intake manifold. Soapy water helps in identification of pressure leakages from connectors/lines. Location of Landi Renzo Omegas CNG/LPG Kit components, installed on Suzuki Liana, can be seen in this video.
- CNG filter should be replaced after 30000 kms, replace the filter if life expired.
- Remove the solenoid (black round thing with wire) from the ‘CNG regulator’ and clean the rust /contaminants present on the solenoid with the help of carby cleaner or sand paper. Refer to video for location and removal procedure of Solenoid.
- Check earth-wire coming from the CNG kit is intact and is not loose, if there are any joints preferably re-solder them.
- Carefully check the wire going from positive terminal of the battery to the solenoid valve. Re-solder joints if any, remove the FUSE installed on Positive (+ve) wire and clean its terminals. Also spray-clean the fuse receptacle, and make sure that the contact of the wire is not loose at any place that also includes all the connectors till the solenoid valve. Location of FUSE on Suzuki Liana CNG Kit can be seen in this video.
- Also clean the connectors of LPG/CNG ECU (electronic control unit) located behind the glove box under the dash board with contact-cleaner spray.
- If the problem persists, reset the LPG/CNG Kit ECU by disconnecting the connector for five minutes and then reconnecting.
- Periodic calibration of LPG/CNG Kit ensures trouble free engine operation on alternate fuel. Landi Renzo Omegas Kit requires patent software for calibration.
- A word of caution, Never ever wash the car engine during servicing, only use compressed air under the hood. Water may short-circuit any of the sensors which will be an expensive deal thereafter.
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