1991 Ford Bronco Erratic Idle.
Posted in Ignition Systems | Asked on Aug 14, 2010
My 1991 bronco with a 5.8 351 has a very erratic idle. It has lost much power and runs like crap overall. IT ran fine but all of a sudden it got worse and worse. The rpm’s very from 600 to 1500, it dies constantly and then wont start for like 10 minutes. While driving it backfires, misses, stalls, etc. It smells like gas or exhaust really bad after its been running to.The passenger side of the engine heats up at least 100 degrees hotter than the drivers side. ( After driving 20 minutes it melted some of the heater box and wheel well), i just cut off the cats and it got much better but it is still hotter. Im running out of ideas. In the last month ive already replaced the tps sensor, intake manifold, valve cover gaskets, plenum gasket, spark plugs and wires, rebuilt the distributor, a new set of fuel injectors, new egr valve, new idle air conrol valve, and fan belt. Its getting really expensive so i need to narrow it down a bit. I’m mechanically inclined so i know how to work on it, Ive even taken it to a shop but still cant make it run right. Any advice is greatly appreciated. I was thinking , bad cam sensor or even the whole camshaft, maybe a week fuel pump? Maybe the computer is messed up? I don’t think it has a vacuum leak because i tested it and so did the shop and all was clear.
There are One Answer
Often, idle problems on your Ford Explorer will be easy to diagnose and fix with the right information and tools on hand. If you have the time and the will to tackle the problem yourself, dedicate a weekend afternoon to doing so. You will learn more about your Explorer engine and save some money on the way.
Types
1. You may encounter three common idle problems on your Ford Explorer: you may notice the engine idling erratically, at high speed, or one of the cylinders failing to fire during idle. Very often, these problems come from lack of engine maintenance. However, if your Explorer engine has high mileage, critical engine parts or components like the head gasket, timing chain or camshaft may be worn out.
Approach
2. Narrow down the likely cause of the problem as much as possible. Consider the most logical component to start troubleshooting on the system you suspect is causing the problem. If you are testing a component on the ignition system, for example, you might want to check for a good spark at the end of the spark plug wire first. Then work your way down to the ignition coil to make sure they are working according to manufacturer specifications.
Troubleshooting
3. Check these components and systems if you have noticed an erratic idle: inspect vacuum hoses and intake manifold for leaks; check the air and fuel filter for obstructions; troubleshoot the fuel pump for low pressure; also check the ignition, fuel injection or engine control systems. With excessive idle speed, check for vacuum leaks as well, a sticking throttle linkage. Then check the fuel injection and engine control systems. If the engine is missing during idle, check for a clogged fuel filter, vacuum leaks, and problems in the ignition and emission systems.
Information
4. Your Ford Explorer vehicle service manual will give you detailed steps to troubleshoot specific systems and components to identify failed components. The manual list manufacturer specifications for the different components on your Ford explorer when required, which you can compare against the numbers you obtain during your own diagnostic procedure. You can find this manual at most auto parts stores.
Tools
5. Most of the diagnostic tools to check for the most common causes of idle problems on your Explorer are relatively inexpensive: A vacuum gauge and hand vacuum pump will help you test for vacuum pressure and vacuum operated components; a multimeter will be essential to test the various components in the ignition system; and a fuel pressure gauge can help you confirm if the electric fuel pump on your computer is failing.
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