Author Topic: Car losing power/sputtering on accel.? (Read 2236 times)

4doorwhore · « **on:** February 15, 2012, 08:50:15 AM »

I've been having problems with sputtering and no power after a cold start or after just shutting the car off and starting it again. It will sometimes idle rough or start and shake the crap out of the engine, but for the most part it is on acceleration at 2000-3000rpm. Is this common and what should I look at?

DesktopDave · « **Reply #1 on:** February 15, 2012, 09:24:55 AM »

I'd check the AFM, if it's happening at a similar RPM all the time. The sweep arm will wear out a spot on the resistor track and you'll get incorrect fuelling.

The cold start problem could be a bad return valve in the fuel pump assembly as well. Does this happen in a few hours, overnight, or after a few days?

4doorwhore · « **Reply #2 on:** February 15, 2012, 09:27:42 AM »

Quote from: DesktopDave;110289

I'd check the AFM, if it's happening at a similar RPM all the time. The sweep arm will wear out a spot on the resistor track and you'll get incorrect fuelling.

The cold start problem could be a bad return valve in the fuel pump assembly as well. Does this happen in a few hours, overnight, or after a few days?

Happens every day. In the morning I let my car warm up so I don't notice it, but if I stop at the store and go back out to start it, it starts sputtering unless I let it idle out or high rev which I hate doing.

DesktopDave · « **Reply #3 on:** February 15, 2012, 10:42:04 AM »

Check the stomp codes and maybe the temp sensors. 1223 (engine coolant temp - ECT) and 1224 (intake air temp - IAT) are the codes. If one or both are giving incorrect readings, the car won't run right until it's warmed up. Once the car is warmed up, it goes into closed-loop mode and the O2 sensor can change the fuel mixture much more accurately. Though it shouldn't cool off that much if you're in a store, I'd figure.

Bentley says the DME should be sending 5vdc to both sensors (don't run a resistance test on the harness, BTW - you can damage the DME).

Resistance tests are the same for both sensors...ECT is the one furthest forward on the head. Resistance between the sensor pins should be about 7K ohms at 32degF, and then gets lower as the motor warms up. At operating temp it should be much lower, only 200 ohms (0.2 K ohms) or so.

The IAT has the same ranges, you can test it on pins 4 & 5 of the AFM connector. While you're there I'd test the AFM resistance too...pins 1 & 2 should gradually increase resistance IIRC as the you swing the door open.