Hesitate, Stutter, Surge - Has anyone nailed this down?

This morning heading to work it is snowing like hell today here in SLC. Because of this we are all doing about 25-30. When I maintain a steady lower speed in either 2nd or 3rd gear, about every 10 minutes the car will suddenly hesitate and then surge (buck) forward. I cuss and flip off the dash board every time. Even when you maintain say 25 miles an hour in second gear I can feel the car hesitating and surging gently - it feels like the gas going into the engine has a dirty sock stuck in it or I picture my MAF sensor being chewed on by grime bugs.

 

I slow down to a light and 50% of the time when I push in the clutch the lights drop down to almost like the car is going to die and then comes back.

 

I shift from first to second, as I smoothly let out the clutch with gas and the clutch is engaged - it hesitates, then surges, bucking the car and again I flip off the dash board. When I was stock, oftentimes the hesitation would cause the engine to die - so I had to over comphensate when shifting by giving it far more gas then normal. It's like the car isn't getting enough gas/air mixture and it chokes? Or it's running too rich?

 

I'm so frustrated because I feel there is nothing I can do. Dealer has flat out told me they won't touch my car with a 10 foot pole because of Stage 2 - even though I know Stage 2 didn't do this to the car - it came that way and was FAR WORSE when I was stock.

 

Why couldn't this LGT be as smooth as my WRX was? Why does it have to hesitate and surge? Why is the electrical system so bad? Why does SOA continue to look the other direction?

 

Frustrated in a Utah snow storm.

be smoother with the damn gas pedal

This happened to me before my throttle body was replaced under warranty. I definitely had the RPMs drop when pushing in the clutch and coasting to a stop, and it got to the point that it would often stall in that situation when cold (and the car had been running 5-10 minutes so high idle was finished). It also caused hesitation/stutter/surge for me in the 2300-3000rpm range, particularly when transitioning from no throttle to light/medium throttle.

 

They finally, after something like 5-10 days in the shop, tracked it down with extensive data logging while they drove it hundreds of miles over that time period. They finally were able to capture logs that showed the ECU adding fuel to raise the idle but that the throttle plate was slow to respond as if it was sticky, particularly in the closed position.

 

Overall, this made my LGT very difficult to drive in 20-30mph traffic. Even getting going smoothly from a stop was difficult because it was difficult to modulate the throttle. Give it a little gas, not much, a little more, not much, a little more, RPMs shoot to 2000+. Yuck.

 

Since having it fixed, it is very, very smooth, the throttle is much easier to modulate in traffic and getting going from a stop at say 1000-1200rpm, etc.

 

It sounds like you might have the same issue. If my car was not actually stalling fairly repeatably on cold 20-30F morning, I don't know if this would have gotten the same level of attention out of the dealer, out of SNE (regional head tech visited car twice), or out of SOA. Maybe this is a more widely known problem inside of SOA now and diagnosis is easier.

 

Good luck.

 

--Lee

Hey thanks Lee, that is a good direction to go in. I'll poke around some of my Subaru mechanic friends and see what they think. Its always good to see someone else who has seen this problem.

 

Thank you.

be smoother with the damn gas pedal

 

The smoother I am with the gas pedal, the higher chance I have of stalling out and having to restart the car. When the car was stock, I stalled out at least once per day. After going Stage II, most of this problem went away and was replaced with hesitate / surge.

 

I feel embarrased in traffic because my car "lurches" forward after starting up or shifting from 1st to 2nd. I can get around this by slipping the clutch with high RPMS. My clutch will probably be dead by 20k miles.

Bad fuel injector(s)

I have the same issue as Lee had.

Solution is new throttle body?

Or have the the system cleaned ie. Injectors, tb....

Any thoughts?

Running some injection cleaner through would be cheap and might help narrow things down. I'm not sure how much better the "professional" cleanings are. TB should also be easy enough for you to inspect and clean.

Could be o2 sensors.. Front and rear...

has anyone figured this out yet? the remedies i've read about include the following:

• get a pro tune
  
• replace driveshaft bushings
  
• torque converter
  
• let the car warm up more
  

My issue JUST started. Its an 05 LGT manual with 54k miles NO mods other than the hogzaust washer thingy. I've put about 4k miles on it without issue. Until the other day, I hadnt driven the car in about 3 days and it was extremely cold out. I let it warm up for about 5 minutes. By the time i got to the hwy, it was fully warmed up (temp guage was almost at half). The hesitation / stutter / shudder was while cruise control was engaged in 5th gear.

 

I never experienced this until it got cold out. It almost acts as if the clutch was slipping, lahtough i'm sure that its not, because there's virtually no load on the clutch while in cruise control. The rpm's would rise for a second and then go back down. It also does this while not in cruise control...but ONLY at low rmp's. One one occassion when it was really noticable, i downshifted (5th gear to 4th gear) it went away, didn't happen again.

 

Any thoughts?

i noticed it mostly when my car was not warmed up all the way...esp with the colder weather.

well, i generally don't drive my car when its "cold" so i'm not entirely sure how it acts in that setting. But i believe that on the occassions i have dirven it without warming up in cold weather, it hasn't done that. Buit i think thats only been like once or twice. IIRC.

 

For example, here in chicago, the weather yesterday was kinda crazy. It was raining and in the high 30's /low 40's. Then the temp dropped into the low 20's high teens. While driving that morning with it being in the high 30's /low 40's, everything was fine. Then, i was by the lake were the temperature is colder (car fully warmed up) it started jearking a bit. Kinda crazy.

 

My problem (i believe) is COMPLETELY temperature dependent (the temperature OUTSIDE and not the temp of the engine).

has anyone figured this out? mine starts bucking so bad while cruise control is on that it throws a code and kicks the cruise off, also has the death while stopping issue, as well as a very touchy, unpredictable throttle (sticky?)

Is this only part of the time? I had a similar problem for 30-60 seconds every morning when it was cold. If I had to stop at any light, it would stall most of the time (5EAT though). Turned out out was a bad coilpack that just didn't like something about that part of the operating cycle.

 

Invest in BTSSM and a VAG-COM cable (what I did) and log. I had predictable misfires on cyl 3 that moved to cyl 1 when I swapped coil packs..

Electrical issues was mentioned above, you need to make sure the battery terminals are clean and tight.

 

My 05 will buck once about two miles from the house in VT if is snowing for the drive home to CT. It hasn't done that in long while, but a few years back, it would do it only when it was snowing.

 

Thinking about it...since the vf52 it hasn't done it.

Also,cleaning your MAF regularly smoothed out my low/jerky idle and completely eliminated my 1000-1800rpm surge/stutter.

 

Zack K.

I had an issue similar to this and it turns out my passenger side ground ribbon to the exhaust manifold heat shield was severed. I replaced it with a 10 gauge wire, which helped significantly. I was also experiencing static in my radio, which was fixed instantly.

 

Cleaning the throttle body seems like an easy thing to try as well, can't hurt and might help. CRC makes throttle body cleaner for a few bucks a can you can pick up at any local auto parts store. Sometimes cleaning the throttle body can pose issues to DBW vehicles (I cleaned my TB on my '07 G35s and the ECU freaked out for awhile, it has a known issue with cleaning the TB though). I'll probably do this the next time I have my intercooler off.