Phantom Problem With My Q45.

[QFourFive]

I've been having this issue with my Q, here are the symptoms listed in chronological order:

-After high speed maneuvering on the highway (80-90 MPH), my Q began to feel like the engine was studdering.
-When I was trying to accelerate, the car wouldn't. It would just jerk. The jerking felt like it was coming from the engine.
-Once I got off the highway the car ran fine until I got to my destination.
-I left and went home on the highway (about 15 miles) with no problems.
-When I got off the highway the same issue began at residential speeds (40 MPH).
-I pulled over, turned the car off, waited about 15 seconds, and then turned the engine back on.
-When I turned the car back on then engine felt and sounded like it was "surging" like it was on the highway. I was at idle in park. My take on
the "surging" was that it seemed like the pistons were firing off causing the shaking feeling and the noise. My girlfriend says it felt and
sounded like I was revving the engine over and over, this holds true as well.
-Then I pulled off and this problem went away. I went out of the parking lot, across the intersection, and through another parking lot.
-As I was slowing the engine started "surging" again.
-This time the SLIP and the TCS light came on simultaneously and went off. They came on and went off like 5 times in about 10 seconds.
-When I got home the engine still sounded wierd so I decided to check it.
-The "surging" noise sounded like it was coming from the passenger side of the engine.
-I listened to the exhaust and the same sound was coming from the exhaust, and I put my hand in front of the exhaust and you can feel the
air/fumes "chugging" out.
-I let her sit for a few minutes and all issues went away. I turned the car off and went in the house.

I have had my Q for about 15 months now, and this has only happened four or five times minus the SLIP/TCS lights. That only happened once before this instance. I had it diagnosed by Pearson Infiniti of Richmond and they said it was either my ignition coils or my spark plugs. They couldn't tell me if it was one or the other though. They did a power balance on the engine and told me there was a slight misfire but not enough to throw a code.

Previous maintenance since I've had the car (no info on my Q before it was in my hands):
-K&N Air Intake Filter (installed a year ago, cleaned with water twice since)
-Throttle body cleaned (a year ago)
-New Wix fuel filter (almost a year ago)
-Changed spark plugs to NGK Iridium, the Q rejected them, switched to the correct NGK Platinum (about 6-8 months ago)
-Cleaned air intake system minus the MAF
-Routine oil changes with Mobil 1 Synthetic

Thanks In Advance,
Derek

[Q451990]

Coil problems are very very common on the 97-01 Q45. Typically these problems show up with a random misfire code though. Is your K&N filter oiled... if so, you might want to clean your MAF.

Heath

[loystock]

Coil problem is common in Y33 but my 97Q with over 115K miles is still doing great. A failing alternator can give all sorts of problems. So make sure your battery is good, >12.5 VDC with engine OFF, and alternator charging voltage is > 13.8 VDC and steady (spec is 14.1-14.7 VDC).

Since you don't have a trouble code associated with misfire and assuming the alternator is Ok, you can look into the Throttle Valve assembly - Actuator and Throttle Position Sensor and related connectors/harnesses. A failing TPS scan cause hesitation, jerking, etc,

Refer to the BR (Brake) and EC (Engine Control) for additional info from the link below (it's for a 98Q but applies to 07Q as well)

http://www.nicoclub.com/FSM/Q45/1998_Q45/1998_Q45/