On my 1990 gmc truck with a 5.7 liter V8 i have a dead miss. I replaced the plugs, wires, rotor button, distributor cap & egr valve. It still misses I have set the timing per mfg's specs and s
On my 1990 gmc truck with a 5.7 liter V8 i have a dead miss. I replaced the plugs, wires, rotor button, distributor cap & egr valve. It still misses I have set the timing per mfg's specs and still misses and I dont hear any vacuum leaks, so if anyone could help me out i'd appreciate it.
Re: On my 1990 gmc truck with a 5.7 liter V8 i have a...
Check the compression on each cylinder. Also check for proper valve operation. You may have a flat cam lobe or bad rocker arm on either the intake or exhaust side which will give the rough idle you are experiencing.
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Could be a long list of things including dirty injectors or a leaking EGR valve. The coil could be weak or the distributor cap and rotor may be shorting to ground. Has the fuel filter been replaced ? You'll have to go down the list and try to eliminate components to narrow down your options. Does it happen all the time, only when you are accelerating, etc.
engine missing could be caused by faulty spark plugs and wires,bad ignition coils,dirty fuel injectors,leaking egr valve,low cylinder compression,intake vacuum leaks.many things will cause engine to miss, first do minor fix,replace distributor cap and rotor,replace spark plugs and wires,clean fuel injectors,replace fuel filter and air filter,if this minor tune up dont help engine and engine still missing, do a vacuum test and compression test to check condition of engine.engine could be worn out have low compression by worn valves and pistons rings.
You've already eliminated the spark plug & wireset, distributor cap & rotor. Sounds like your car needs a tune-up, specifically, the PCV (positive crankcase ventilation) valve, and/of the EGR (Exhaust Gas Recirculation) valve.
Components checked/replaced during a tune-up are: air filter motor oil motor oil filter breather filter fuel filter(s) fuel strainer PCV valve EGR valve spark plugs spark plug wires ECM or distributor cap & rotor cabin air filter transmission oil filter transmission oil engine coolant check all vacuum hoses and lines
Troubleshooting the no-start condition - from the 1990 Mitsu Mighty Max Repair Manual:
Priority Action Part Type -- Cause 1 Inspect Battery -- Battery Discharged or Faulty. 2 Inspect Battery Cable -- Corroded, Broken, Shorted or Poorly Connected Battery Cable. 3 Inspect Distributor Cap -- Distributor Cap Cracked or Burned. 3 Inspect Fuel Filter -- Clogged or Dirty Fuel Filter. 5 Inspect Ignition Coil -- Faulty Ignition Coil. 6 Inspect Wireset -- Worn, Damaged or Faulty Spark Plug Wire(s). 7 Inspect Spark Plug -- Incorrectly Gapped or Fouled Spark Plug(s). 8 Inspect Starter -- Starter Motor Faulty. 9 Inspect Fuel Pump -- Low Fuel Pressure. 10 Inspect Solenoid Switch -- Faulty Starter Solenoid Switch. 11 Inspect Fuel Pump Relay -- Faulty Fuel Pump Relay. 12 Inspect Fuel Injector Pressure Regulator -- Faulty Fuel Injector Pressure Regulator. 13 Inspect Ignition Switch -- Improperly Connected or Faulty Ignition Switch. 14 Inspect Starter Drive -- Faulty Starter Drive. 15 Inspect Fuel Injector -- Dirty or Worn Fuel Injectors. 16 Inspect Fuel Pump Strainer -- Clogged or Dirty Fuel Pump Strainerat. 17 Inspect Engine Control Computer -- Incorrect Operating Information Being Delivered and Sent From The EEC. 18 Inspect Fuel Tank -- Fuel Tank Empty. 19 Inspect Carburetor -- Carburetor Flooded or Faulty Choke. 20 Inspect Distributor -- Worn, Loose, or Incorrectly Installed Distributor.
The combination of heat and missing tells me that you have an ignition problem. Warm the engine as much as possible and take a water mister and mist the exhaust manifold with the water mist at each cylinder where the exhaust comes out of the cylinder. The cylinder(s) that doesn't evaporate as quickly as all the others is the one that's missing (no combustion = no heat out the exhaust for that cylinder). The next thing to do is to pull the spark plug. examine it for dirt built up around the electrode. If it's dirty then just replace all your plugs. If the plugs look good ( not worn - no contaminates around the electrode) then suspect plug wires. If all the cylinders evaporated the water pretty much the same, then your coil wire to the distributor cap or the cap and/or rotor itself is faulty. Examine the rotor cap and rotor for thin black lines running along the inside. If you find evidence of arcing (the lines inside) then replace the cap and rotor at the same time. The data you gave though sounds more like plugs or plug wires if I were to guess... For best results you should plan on replacing plugs/wires/rotor/distributor cap at the maintenance intervals suggested in the owners manual. But now that you're having these issues you should have some kind of concrete evidence before replacing these items - that is unless you've never replaced them ever before. In which case it's high time to have replaced them.