Occasional starter fade, won't idle after start

Hey guys, I have two symptoms that started occurring at the same time:

1. Starter won't crank the engine all the way over about half of the time. If I keep cranking the key, eventually it will turn the engine over and the jeep will start.
2. When the engine does start, it won't idle without applying the throttle and then dropping it into gear (auto).

This is on my 1998 XJ. The battery is new and appears to be fully charged.

What do you think? Bad ground? Thanks for your help.

The symptoms described suggest low voltage to me.


For 1996+ Jeeps, the OBD-II engine computer (ECU/PCM) re-boots, and the idle settings are deleted, when you: (1) let the battery run down by leaving the lights or radio on, (2) disconnect the battery for an extended period of time, (3) when the battery goes bad and needs replacing, (4) when the alternator is not properly charging the battery, (5) or when poor battery connections result in a voltage drop at the PCM or poor battery charging. Loose, corroded, or damaged battery cables or ground wires may also cause or contribute to the problem.

A faulty Coolant Temperature Sensor may also cause similar symptoms. Testing of the CTS is recommended as part of the diagnostics. A poor ground at the ignition coil can also cause similar symptoms.

The reboot symptoms are: (1) having difficulties starting the engine without depressing the gas pedal, and (2) the engine will have a low idle and probably stall unless you keep your foot on the gas pedal. (3) The ECU will usually relearn the idle settings after a short period of driving and the engine will sometimes start and idle normally.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Do the same for the grounding wires from the starter to engine block, the ground wires at the coil, and the ground wires from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds.

If the symptoms reoccur, you need to have your battery and/or the alternator Load Tested at a repair shop or auto parts store. This is usually a free service they offer to bring in potential customers. Handheld testers are very inaccurate and will usually pass marginal alternators. Even with low battery voltage, the engine will start, but the ECU can re-boot multiple times and a new battery may be required.

Cleaning the Idle Air Controller (IAC), regular tune-ups, and using fuel injector cleaner should be part of your routine preventative maintenance for smooth starts.

Although you said the battery is new, the symptoms you're describing are what you get with a dying battery. Had the same issues a couple years ago, turned out it was the battery starting to go bad. Try swapping the bat for one of your friends/relitives, or have it tested by a reputable shop. ( I've had places like autozone test batteries for me, say they were bad, and subsequently find out they were just trying to sell me a new battery.)

I'd put a test light on the starter and see if you're getting voltage to it with every turn of the key. The ignition switch could be at fault. Does it engage but not spin?

Starters go intermittent as the brushes reach the end of their service life. $20 worth of new brushes, some cleaning, and repacking the gear reduction is an easy way to get a few more years out of one.

Also, before running injector cleaner I'd replace the fuel filter. I've used it in extreme cases of fuel system neglect, but my 300k mile daily driver hasn't ever seen it, and likely never will if fresh fuel is kept in it.

I pulled the battery terminals apart, cleaned them up and it runs good as new.

This is the third time in the last two years where I've had to clean up or replace terminals after electrical issues, even after a new alternator and battery. Any idea as to what would cause them to corrode so fast?

Recommendations on some quality terminals?

My recommendation is to coat the terminals with a sealer. You can get a spray can of terminal cleaner that will remove the oxidation, then leave a redish sealer.

travisk said:

I pulled the battery terminals apart, cleaned them up and it runs good as new.

This is the third time in the last two years where I've had to clean up or replace terminals after electrical issues, even after a new alternator and battery. Any idea as to what would cause them to corrode so fast?

Recommendations on some quality terminals?

Click to expand...

All my recent issues the last 5 years have been leaking positive battery posts at about 24 months of age on a 5 year battery from Autozone. The Gold line. Been through about 5 of them on my 6 rigs, the sulfuric acid fumes vent right under the post. AZ warrantied every one, but I had to clean up the corrosion mess. I use a wire brush, ammonia, and vinegar step by step to clean the mess up, install a new battery ..... I use reusable brass post clamps.