NEED HELP!! part throttle miss/stumble after little collision/curbing

[FlaBoy]

On the way to work last night, while making a turn, a guy on a bike rode out in front of me. After slamming on the brakes to keep from killing him, i spun a little on the wet road, and ended up curbing the car pretty hard in the rear. I didnt hit the guy, but my rear pass. side wheel swept into the curb at pretty much a right angle. There was no serious damage to the car, but the impact was hard enough that my engine died (?!?!) and on closer inspection i saw that a peice of the outermost rim of my tire had snapped off (the tire seems to still hold air fine). When i restarted the car, I immediately noticed a problem. At idle, it was running rough, sounded like it was mis-firing a little. When i REALLY notice it is on light throttle acceleration. If i am crusiing at a steady speed, it just seems like its running a tiny bit rough. But when i accelerate at anything up to about 1/3 or 1/2 throttle, it stumbles, and bucks and misses like CRAZY. the more throttle i give it, the smoother it runs. Once i get about 1/2 throttle, it smooths right out, and runs fine. When i give it a full throttle blast, it pulls just as strong as before, and seems to have no issues, but the second i get into vacuum instead of boost, it starts stumlbing, missing and bucking again. I have also noticed that as I'm driving, when its in vaccum on the boost gauge is when it runs badly, but as i get closer to zero vaccum and zero boost it starts to smooth out, and once I'm in boost it seems to be running just like normal. I am friggin CLUELESS as to what could be wrong. since i don't want to drive my car anymore than I have to until i figure it out, for fear of doing more damage, and its my daily driver, I obviously need to figure this out quick. Besides the rough running, nothing else seems wrong... the coolant temps, and oil pressure and everything seem fine. I just got a scanmaster, so i dont really know how to interpret its readings yet, but I can post them here if that will help. If anyone has any thoughts or suggestions, i would be very appreciative. Thanks!!!

 

[83ttypecooled]

rough

Hi,
Well,this is a wierd one. About the only thing that comes to mind is the possibility of big vacuum leaks. Do you still have the powermaster, or have you converted to vacuum assist? If so, maybe when you tromped on the brakes, the booster failed. Anyway, look for leaks. You know , Murphy can be pretty sneaky! Just a thought, good luck...

 

[FlaBoy]

I have hydro-boost brakes, not powermaster or vaccuum, and they still work fine. Also, when at idle, and while driving, i have as much vaccuum as before (17-18 in. at idle when warmed up). I would assume that with a leak, it wouldnt be able to pull as much vaccum, especially if the leak was big enough to cause this much trouble. After a visual inspection of my vaccuum lines, they all appear to be intact, and still connected. I may try the old propane trick later to see if i can find any leaks just to be sure. Thansk for the help though... im open to any ideas/suggestions.

 

[83ttypecooled]

leaks

Hi,
Sorry, I didn't pay attention to your car description.I personally like hydroboost, great system, in my estimation.Lots more assist.
That was an off the wall call; I believe that in 90% of problems, a related issue led to the difficulty. Hence, my booster suggestion. Then Murphy surfaces, caos, call it what you will. I get lost there.
You HAVE checked all the basics, right? It can't be fuel, because it runs great at top end, correct? How about your scan data? Does it tell anything? I'm fresh out of ideas, but will let you know when new ones arrive. Good luck!

 

[corsair231]

May be totally out in left field but when you curbed the car do you think you may have pinched your fuel return line. If you did your fuel pressure would spike. Extra pressure might cause it to run rough until the throttle is opened enough to use the extra fuel. Check your fuel pressure and a/f ratio before you drop the tank though.

 

[FlaBoy]

I hadnt thought about the pinched return line... I checked my rpessure gauge right after i started it to make sure i was getting pressure, but I haven't monitored it while driving or anything (my gauge is tucked down under my hood 90% of the time). I'll check that and see what it shows.

I was trying to think of what would make the car act like this, that would have been caused by an impact like that. I mean, the front of the car didnt get messed up at all, only the back got smacked, and even then, I figure the suspension or maybe rear end would have taken the brunt of that. But i guess fuel delivery could def be affected, as all that lies in the back of the car. Also, are there any sensors or modules that are particularly sensitive to vibration/impact? I mean, the bump was a pretty solid one, and it did kill the car, so i was wondering if maybe the big vibration/impact might have jarred something loose in the ECM, or some wiring, or shook something loose in the MAF, ignition module, coilpack, etc. But if that were the case, i wouldnt have any clue on how to check for that anyways, so i guess its a moot point. Man, i wish i knew as much about these cars as I do about the big block buicks i used to play with

As far as scantool readings, as i mentioned, I just installed a scanmaster few weeks back, but I still have pretty much NO clue what any of the values mean, or what they should be at idle, WOT, in between, etc. I cna post any of them youre looking for. And Corsair, you mentioned checking the a/f ratio, thats the 02 mV reading right? If so, what should i be seeing? Thanks for any info

 

[gbsean]

try tapping the MAF check all the plug wires and all the sensor to make sure none of the popped out or are loose.