novajeep17

Hey guys, new to the forum...this problem has already beat two good local mechanics so hopefully someone here has an idea or two that I can look into or better yet, has had the same issue and found a way of resolving it.

So, as described in the title, the jeep has a rough idle and often times wants to stall when showing down to stop, or pull into a driveway. Sometimes, I'll throw it into neutral and keep the revs up while I coast to a stop sign or light. Under load or rolling down the highway it seems to be ok. Also, I noted that the problem tends to get worse as the engine warms up but this isn't always the case. The engine light is on. This issue started last October and since I had other transportation options I just left it with a mechanic who tried various things with no success and then tried another mechanic who also couldn't solve it. Both isolated the fuel system and determined that it wasn't the cause. Also, a new computer was brought in on spec but the old one was ok.

Between the two mechanics the:
- spark plugs were replaced
- injector rails were cleaned
- TPS was replaced
- O2 sensor and MAP sensor was replaced

Now up until a few days ago it seemed to be working better - less stalling and better idle. I wouldn't give to my wife to drive but it was manageable enough to get back and forth to work. This lasted for about a month but now it's back to working the way it was.

Hopefully, this all make sense and that someone can help me out with this. The jeep is in great shape otherwise and I would like to keep it but I need reliable transportation and don't want to throw too much more money at an old vehicle. Anyway, thanks in advance for any help anyone can pass along.

dave1123

Welcome to CF!

You say the Check Engine Light is on. What are the trouble codes? You can get them with the "key trick." Turn the key on until the warning lights come on but not engage the starter, then off, on, then off, on again and wait. The codes will show as "P" codes in the odometer, as in (my favorite) P0740 which is torque converter clutch malfunction. It's my favorite because I've had it for 50K miles! When it's shown all the codes, it will say "done". A decent mechanic should have a DRB scan tool that plugs in and will display faults on a handheld flatscreen monitor. They cost about $1000 or I would have my own. You can buy a simple scanner for around $100 which I have. The DRB will show faults that don't set codes as well.

There is one thing that comes to mind. You could have a weak spark from a worn out coil rail. The coil rail has 3 coils in it that fire 2 plugs at once, one on compression and one on exhaust. They tend to short circuit internally sometimes. I'm surprised your mechanics didn't replace that first before condemning the computer. The only other thing was the TPS which I see they changed.

I can't say this enough. When you buy sensors, buy Mopar instead of aftermarket ones. They are much better quality and last longer. Of course, they cost more. rockauto.com has started to sell Mopar parts and they are cheaper than the dealer for the most part. Problem is you have to wait for delivery. I bought a Standard Motor Products coil rail for $68.79 and have 30K miles on it already. The engine has 216K miles on it.