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Discussion Starter · #1 ·
I realize this may have been discussed a thousand times and there's a bunch of sensors, relays and internal failures that can cause rough idle and hard starts but maybe this will help someone out.

I have an 06 LJ but I also picked up 97 TJ as a side project. The 97 had a hard start issue and the notorious surge in idle up to about 1500rpms after about 45 seconds of running on a cold start and then would immediately fall to about 500rpms and bounce and sound rough like a NHRA drag car hitting it's cams. It never stalled so I was not considering a faulty Crankshaft Positioning Sensor.

To cut to it...a new fuel pressure regulator immediately eliminated the hard starts. By hard start I mean would not actually crank until the third try. The rough idle issue was solved by changing out the UPSTREAM O2 SENSOR. And by changing I mean buying a new NTK Brand one....NOT Bosch.

Just another fyi...before arriving at these two parts as the source of those two problems, I had changed the battery, checked the alternator, cleaned the IAC, replaced the TPS, new plugs, new wires, new distributor cap and ran some Lucas High Mileage Fuel Injector Cleaner through it and changed oil and oil filter and added a K&N air filter.

I planned on doing all that anyway but maybe this will save/help someone having similar issues get to the source without replacing a lot of parts. Hope this helps.
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