#ThrottleBody

TTAC Commentator haroldhill writes:

Dear Sajeev,

My wife is driving (and loving) her 2009 MINI Cooper which has been a delight and remarkably trouble-free for 10 years. However, it recently developed a problem which has befuddled us and our highly reputable independent mechanic as well.

Under certain conditions the engine stumbles, feeling somewhat like an erratic misfire on one cylinder or fuel starvation; however, the stumbling vanishes when accelerator load is increased. The required conditions are: fully warmed up (10-15 minutes of driving), engine speed between 2700 and 3300 rpm, and light throttle appropriate to steady cruising. The stumbling will eventually bring on the “check engine” light and a P115C error code (Mass Air Flow).

If the engine is turned off for a few minutes (e.g. for a highway rest stop) the stumbling will disappear and won’t reappear until the car has been driven for another ten minutes, suggesting the fault is something remote enough from the engine that it can cool substantially in five minutes. After a few uneventful driving cycles, of course, the “check engine” light turns itself off. Thanks for nothing. On the other hand, this would be how I got it through emissions inspection…

Thus far the Mass Air Flow Meter has been replaced twice and the Throttle Body once. The latter seemed to help for awhile but I can’t be sure because it’s only recently that I’ve pinned down the exact conditions that will reliably bring this problem on. My wife, who does most of the driving, is a bit of a leadfoot and generally has much less trouble with this stumbling.

Our wonderful mechanic would appreciate any ideas or suggestions.

TTAC Commentator Eiriksmal writes:

I read your plea for questions, so I’ll lob you a softball. Why has my 2005 Maxima’s TPS decided to randomly poop out on me after doing a warm start?

Specs: 2005 Nissan Maxima 6MT. 135,000 miles. Electronic throttle. Stock air intake + (new, put in the first time the TPS acted up 3K miles ago) K&N filter. The car’s now on its third owner, having spent its whole life in Evansville, IN, Lexington, KY, and now Louisville, KY. At the rust belt’s frayed fringe, I guess. No surface rust anywhere on the car, though. Electrically speaking, it’s in good shape. (Save the rear ABS sensors… a rant for another day)

UNCLASSIFIED

I am currently at Bagram Airfield in Afghanistan where I will often find myself motoring around the Forward Operating Base (FOB) in one of the last generation Chevy Trailblazers. It is the straight six variety and it has undoubtedly led a difficult life. My requirements are few however…pretty much I need something that can do 25 miles an hour or so and not strand me on the other side of the airfield. As a bonus, the Trailblazer has a working AC and radio. What it doesn’t have is the ability to do 25 or so miles an hour regularly and get me back from the other side of the airfield.