jerky feel when turbo hits

[Fubar231]

Im running 7 lbs. But sometimes (Mostly in second gear), when the boost hits the car jerks around a little.

[willtotheumm]

too much powah to the rear wheels??? lol

hmmm... that rather interesting. Maybe if Jeeves or Bgrieger sees it they'll be able to shed some light on it...

[Fubar231]

it has been raining a lot here and i was wondering if it is LSD kickin in

[Fubar231]

Its only when it hits around 5lbs+ it seems. Under WOT it seems to be fine though. Anyone know of a OBD scanner or something for a 89 supra turbo MA70, not car specific but one that has our car in it...

[Jeeves]

You cannot 'scan' the OBD on our cars, that's an OBDII only thing. You can however check the codes by reading them off the check engine light:

http://www.cygnusx1.net/Supra/TechTi...ror_codes.aspx

Also, the LSD isn't a off/on device, it's ALWAYS there, it's mechanical only.

Jerky. Like the power band isn't consistent? or like you hit a brick wall? or....

[Fubar231]

More like brick wall fuel cut feeling. But it only does it around 5lbs only, not under WOT, and not for long either. It only does it around 5lbs in the 2-3k rpm range. Im gonna bust out the camera and get a video or something. The rpms jerk around when it happens. Also, the car doesnt die out it just feels shitty and then goes back to normal.

[Jeeves]

I'll wait for video then. Might be spark breakup of some kind. What plugs are you running and at what gap? I had a similar issue when I'd just bought the car. Turns out the shop had 'repaired' a spark plug wire with electrical tape, and it was arcing to ground near the coil pack rather than in the combustion chamber.

[Fubar231]

I know its not plugs or wire cause when i got the car like less than 6 months ago i replaced them. I used NGK Coppers and i checked the gap at the time and they matched up to the plugs that were in it already, and i replaced the wires with brand new wires from toyota so i doubt it would be one of those. Im just trying to think of how to get a video, probably going to be digital camera.

[Fubar231]

Could a BHG have anything to do with this? My car smokes a little on startup, but stops once it warms up a bit, white smoke. Pretty positive my HG is gonna go soon.

[Jeeves]

Maybe if you were leaking enough that a cylinder wasn't firing. What plug gap is it set to? Just because it matches the last doesn't mean it's good or correct. If RPM's are dropping/stuttering it's a firing issue of some kind. So, spark, fuel, or something interrupting one of those two.

Smokes on startup? Maybe valve stem seals.

[Fubar231]

Yeah it smokes white smoke on startup untill it warms up a little. I was thinking headgasket cause it idles like its misfiring untill it warms up. Im PRETTY damn sure my headgasket is about to completely go.
Theres also a good loss of power when its still cold and rough.

[Jeeves]

When it's cold and rough it's running on a map that doesn't use the O2 sensor. So, don't boost till it get warm on the temp gauge.

You never said, what's the gap on those plugs? Have you run a compression test?

[Fubar231]

They were all gapped at .030 is what i checked them at. No compression test yet, but i mean when it starts up, its a really rough idle, a substantial loss of power, and white smoke out the exhaust. Once it warms up all these symptoms go away. I think its my headgasket starting to go out and reseating itsself everytime it warms up.

EDIT: The chug on the boost has stopped. Its just feels like a misfire untill it warms up.

[Jeeves]

Originally Posted by Fubar231

I think its my headgasket starting to go out and reseating itsself everytime it warms up.

That's not quite as feasible as it sounds. I'd suggest a compression test.

[Fubar231]

If i drive my car though, whatever causes the rough idle / misfire / lack of power untill it warms up is goning to go away by the time i would drive to a shop and have the test ran. How much do compression tests usually cost?