Lately I purchased a car which had serious acceleration issues ..A lot of things were checked and maintenance / replacement done .. Sharing my knowledge on it ..ur comments and suggestions will be highly appreciated
Basic Tuning
. Throttle body service : A common step these days, technically its not to be done unless there is a serious issue but since every one is doing it so i do it as well .. just spray some carburetor cleaner in throttle body
. Plugs : check gap .. new plugs come with 1.0 or 1.1 gap .. older can be set upto 1.3 gap .. for cng vehicles set gap to 0.8 .. clean plugs .. plugs used more than 40k (iridium) may be replaced and normal plugs after 25k km. always use OEM recommended genuine plugs .. those cheap rs 160/- plugs have irregular currents and can cause damage to coils etc
. Air filter : Genuine filter only .. exception for cng vehicles as there filter is changed more frequently
. Oil : OEM recommended .. Thinner oil like 0w20 or 5w20 may be replaced with 5w30 for hotter climate areas .. do not shift from fully synthetic to semi and back .. use a type for once .. its better to use fully synth for first 75k km or 100k km then shift to semi synth like 10w40 .. but if compression is good keep using fully synthetic .. thicker oil chokes internals and causes all kinds of problems .. so stick to OEM
PCV : choked PCV builds up excessive pressure in crank case, causing smoke in exhaust and may also cause reduced performance of car
Max Speed Not being Attained
. CAT ; if clogged will restrict exhaust gases and maximum speed .. Clean CAT but never remove or damage its mesh .. U will end in disturbed air fuel ratios, high fuel consumption, poor idle and loud engine sound .. replace CAT if required
. Fuel pressure ; Use of substandard fuel causes strainer to choke or pump to decrease efficiency causing poor pick up and /or high speed .. the best way to check is to attach a pressure guage near the fuel injector rail .. if the presure is 40psi or more then things r ok
. Injectors : same problems as above .. individual injectors can be checked by removing wire clip while car is in idle .. clogged injectors r cleaned on ultrasonic machine and treatment with injector cleaniners also helps but frequent use can damage rubber parts .. though injector cleaners r not very efficient
Poor Acceleration
. EGR : this was one culprit which caused my car acceleration problem .. clean it and make sure to clean its passages as well
. VVT timing : cam shaft in vvti engines has cam phaser (timing advance / retard mechanism) which gets stuck when thicker oil is used and sludge is formed .. solution may be in flushing engine and giving a slight movement to cam phaser .. in severe cases cam phaser has to opened and cleaned
. OCV : oil control valve operated cam phaser so this has to be clean alongwith its filter
. Coils : weak coils can also cause acceleration issue .. always use quality plugs or ur coils will die early
. CVT : cvt oil and cvt performance can also cause accleration issue .. oil can be physically checked but cvt can only be checked on a obd scan tool
Poor Economy
. General tuning : do a general tuning, as explained above
. Fuel Trims : buy a mini diagnostic tool (ELM -327, approx price rs 1000/-) works on most cars, runs on android application "torque" .. check fuel trims .. meaning fuel adjustment before and after engine .. a lean or rich mixture indicates the problem area .. like O2 sensor issue, MAF sensor problem .. temperature readings tell how CAT is working
. Sensors : ur air fuel ratio is disturbed so clean MAF(or MAP) and O2 sensors first. In further investigation, u may check functionality of sensors and wiring / signals from ECU
. CAT
. Plugs / Coils
. Fuel Injectors
This is all for now .. these r general items a more complex fault may also lead to speed issue
do point out mistakes, missed items
do share experience
Thanks