My car has a somewhat erratic idle at start up, almost as if it is searching for the right spot (revving and dipping down, revving again, over and over). After just letting it sit for a few mins, the idle will usually even itself out, but then when I try and drive it, it's a disaster. When I lift my foot off the gas coming to a stop (ie: when the throttle plate closes), the car's idle will dip all the way down, the engine will shudder, and then it will rev back up again. This happens when I just rev the engine a little bit just sitting in my garage too.

A few times while driving it around the block, there will be a slight hesitation before the car will start accelerating. Twice now, the car has also started bucking and simply wouldn't accelerate at all, causing me to have to come to a stop completely (in the middle of the street), and restart the car to limp home.

I'm getting a p1129 code. I've tried the following:
-MAP whack
-MAP cleaning
-MAP complete replacement with another sensor
-Spark plug change
-IAC cleaning (removed, cleaned with carb cleaner, reseated the rubber gasket, etc)
-TPS disconnect (I did this in my garage, just to see if the problem would still persist... it did, plus I got a TPS cel of course)
-Checked vacuum lines for leaks (spent a good 30 minutes on this, checking each one twice)
-ECU reset several times
-Checked ground wires

And I still can't find the problem. I'll reset the CEL, and the p1129 will come back after awhile. The car is almost undriveable, because at every stop, there's a chance the car will shudder and stall out, and on every acceleration, I might bog out, buck or have no acceleration at all. I don't know what to check for. I've searched the UTH section for hours, even made another post a little while back, and I can't figure this one out.

It's a MY05, 38,500mi, only engine mods are a short ram K&N intake and Private label header.

 

P1129 MAP Higher Than Expected

inspect the wires for the map sensor closely. looks to be an electrical issue rather then an issue with the component.

 

Yeah, my "gut" tells me it is probably electrical. I will have to purchase a voltmeter. But I was wondering if other people have encountered these issues before, and if so, what else I should be checking.

 

Any other thoughts?

 

try changing the map sensor.... see if you can find someone who has an s2k and try their map sensor.

 

I'm having the same problem

 

Could it be a fuel related issue? Maybe your pump is on its way out.

 

I've had the same issue with the bogging and shudders. I did the map whack, cleaning map and throttle, new plugs, etc, and still had the problem. Check if your valves need to be adjusted to spec, this fixed my problem. I don't believe it would fix the reason for your cel but should fix your bogging and stalling issues.

 

UPDATE:

As a last ditch effort to fix the car before I took it in to a mechanic, I decided to check all wires going to the ECU, check all grounds (again), take out the O-ring beneath the MAP sensor, clean the whole area with carb cleaner, clean off the O-ring (it wasn't really dirty, but I figured, what the hell), and put everything back together. Fired up the car and no bogging. I let it idle for a good 10 minutes, then I revved the engine up and closed my eyes as I let off the gas... and it dropped down to a normal idle and held steady. My p1129 CEL has not come back yet after about 20 miles of driving the car over 2 days.

I'm not going to trust that it is fixed until I've given it more time, but so far so good. It seems to NOT be my throttle positioning sensor though, which was my primary worry. I'll post up another reply to this thread in a few weeks, just to update.