Hop, jump, sputter - fixed
 

2005 4.8is with 225,000 miles.

When the thing runs right, it is my favorite car ever. Then there are the times when it is infuriating. I've dealt with a cracked expansion tank, bad master cylinder, the stupid alternator bracket gasket and the dreaded coolant transfer gasket, but the newest problem is driving me crazy trying to narrow down the source. About a week ago, the check engine light popped on with no warning. The codes I pulled were p2177 and p2179, lean fuel mixture on bank 1 and 2. I can't find a consensus on the actual cause, seeing anything from a bad MAF reading, vacuum leak, bad fuel filter, fuel pump or any other laundry list of problems. I cleaned the MAF along with the air filter since I was in there and cleared the codes. Ran good for a day, then suddenly started loosing power when accelerating, the check engine light never came back, but the performance has been horrid. Any idea on where to look first?


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Could be a million and one thing. The description of the problem "Hop Jump Sputter" doesn't really help with a good diagnose, base on the description it could be the whatchacallit or the thingamajig.

I'm just trying to find the right doohickey to start on. 😊

Seriously though, it actually is a pretty accurate description of what happens when I try to accelerate. It is considerably worse going uphill. It just jumps along with minimal power, then suddenly gets a burst strong enough to keep moving. There currently no obd error code or warnings on the dash except check backup lights (which are working fine).


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When was the last time the fuel filter was replaced? If you don't know start there. You can also attach a fuel pressure gauge to the fuel rail and monitor the pressure as you drive. Sounds like it more than the doohickey that needs to be replaced.

Hasn't been done in the 2 years I've had it, so I'm ready to start there.


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Well, new fuel filter seemed to help on the first test drive, but it started acting up again on the way to work this morning. I'm thinking fuel pump might be the next thing to work on.


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Have you tried it in sport mode/manual shift? Does it behave the same then also?

BMW X5 4.8iS 2005

I am gonna steal upallnight's advice to another poster and tell you to check actual values from your sensors. May give a clue on which thingamabob is causing the fuss.

Better to do some testing before throwing parts at it.

How much gas is in the tank?

There's 30 miles on the tank, so it's all but full. I changed the fuel filter, which other than dealing with the skid plate, was an easy job.

I took it out for a test and it was good for about 5 miles, actually felt like it had more power, then the hesitations came back. By the time I got back home, the engine light came back on an I was able to pull P2096 and P2098 codes for post catalyst too lean bank 1 and 2.

I tried testing the fuel pressure, but my gauge is junk. It started spewing fuel from the base of the face when I started the engine, and I only saw a reading around 1.5 bars. Obviously, I can't trust that reading and I need to get a new gauge, but there is at least some pressure in the system.

When I start it up, it seems to idle just fine, but the hesitations start when I press the gas, and it gets really bad over 2000 rpm, to the point where it will not increase no matter how far I press the accelerator. I halfway think it is the fuel pump, but is there somewhere else I should look? Sensors or possibly injectors?

Replacing the valve cover gaskets along with plugs and coils while I'm in there are on my to do list, but I want to take care of this power issue first


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