So I have replaced fuel filter, spark plugs, plug wires, checked vaccum lines, fuel pressure regulator, oil change. The thing is its still having a hard time starting in the morning (its like hesiates and chokes out). Once you get it started it runs fine for the rest of the day. Still puzzled on what it could be. Do have the check engine light on saying its the water temp sensor i believe. Any ideas or thoughts would be appericated. Would save me taking it to the shop but its getting to look this way.
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Re: 1991 toyota 4runner hard start
Water temp sensor is used to regulate the amount of fuel that is injected when cold. If its faulty it doen't know its cold and does'nt know it needs more fuel. Replace this sensor and it should fix your problem. If your lucky the clip might have just come off they often break their clips at that age.
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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.
It could be the fuel filter. If it smells a little gassy at the exhaust, and hasn't been tuned up for a long time, you may have to do that also. It may be due for a complete tune up (distributor cap, rotor, plugs,plug wires, fuel filter, air filter, pcv valve) and oil and filter change. Be sure and check all vacuum hoses under the hood to see if one is off, broken, cracked or loose at a connector.
with many new modern fuel injected vehicles its hard to give them a tune up without plugging them into a computer or getting an aftermarket computer chip and programmer.
however, if your toyota is running a little rough and getting bad gas mileage i would reccomend a new set of spark plugs and wires. and maybe a new fuel filter, i would do the spark plugs first, if the results are not satisfactory then change the spark plug wires, and if the results are still not up to your standards comparing the way it used to run to how it runs now then change the fuel filter. doing all these things will make the vehicle run clean and efficient like it should. and if it doesnt than im sure you have a vacum or oxygen sensor problem.
just wanna hop up the performance a little bit and get better fuel mileage?
then i would suggest and personally recommend a complete K&N cold air intake kit.
very likely the fuel injectors are damaged, replace them, the fuel pressure regulator and all rubber fuel lines, also pull the gas tank and replace the short rubber hose at the electric fuel pump, I know this is expensive but even a few miles of running would have wrecked havoc on the rubber components, that rubber debris will flow through the fuel system and will plug the injector's, E85 melts it and skin for that matter.
First thing i would try is a fuel filter. I understand that it seems like it's getting too much, but it might be the opposite. Next, i would change spark plugs, and wires. You should also look for vacuum leaks. Make sure all your bolts are tight, and vac lines are tight, and in good condition. When you have it running, wiggle them around and listen closely for a hissing sound. Use a stethoscope or a length of vacuum hose held to your ear with the engine running.
check all vacuum hoses look for broke crack vacuum lines.replace all spark plugs and wires.if they have been changed in a while.also clean fuel injectors using prestone or gum out .fill gas tank .put a bottle injector cleaner.in tank .drive it around several miles so the injector cleaner will clean out injectors.wait until car cool down .change fuel filter. relieve fuel pressure first before removing fuel filter.