Stumbling at cruise

[MA71_Static]

The problem I am having with my car is that when I am cruising anywhere between 40mph upto and possibly after 90mph the car feels like its misfiring. Easy way to describe it is power on and power off. Idle is perfect and dead on 750 rpm and the car accelerates great, the miss or surge goes away when I let off the throttle or accelerate at any rate. It was barely noticable when I had my stock airbox on but when I replaced it with a K&N kit the problem became very present. The jolts are more aggressive now and I thought it might be related to the AFM so I replaced it with a known working one from my other Supra and it didn't affect it, any help would be greatly appreciated.

 

[IwantMKIII]

check to make sure everything is secure around your intake filter and back. Also check for any possible leaks. Its possible as you speed up in combination with torqueing the engine, if something is loose, wind could move pieces around allowing extra (possibly unmetered) air into your system causing you strange symptoms.

 

[MA71_Static]

I definately will check that in the morning before I drive to class and when I get there. A possibility I was considering was my EGR cooler gasket, possible leak there cause it opens at cruise and if its getting outside air it will cause a lean miss at cruise but I'm getting alittle ahead of myself lol. I'll go over my car tomorrow and let you know what I find, thanks for the input.

 

[sneakypete]

check your codes first thing. thats a great start at diagnosing a problem. them move on to trial and error?

 

[MA71_Static]

I jumped the diagnostic link and no codes came up, and I plugged in a modus and there weren't any hard codes.

 

[sneakypete]

modus?

 

[MA71_Static]

It's a scanner from Snap-On, the problem is now off and on. Some days it does it and some days it won't. The days it does it I can build up full boost and the car will accelerate extremely slow, like i'm going up a really steep hill in overdrive.

 

[ViR2]

I'd say some plugs and wires...

 

[logan]

I had a vacuum leak that missed/stumbled on cruise . Especially as you replaced the intake, could be that.

 

[rob21a48422]

If it's happening ONLY when you have the CRUISE CONTROL on check your speedometer. Mine was jumpy from the cable being bad and that made my car think I was going faster, slower, faster, slower, and the car would be on the power and off the power trying to compensate. Just a thought...

 

[jetjock]

A possibility I was considering was my EGR cooler gasket, possible leak there cause it opens at cruise and if its getting outside air it will cause a lean miss at cruise

That's a surprising statement coming from a smog tech.

 

[MA71_Static]

I did replace the Plugs but not the wires, will be next tho. The cooler gasket was cracked so I replaced it but that didn't do it. If I could afford the software I would connect a laptop and watch the firing lines, that would be great lol.

 

[MA71_Static]

That's a surprising statement coming from a smog tech.

I haven't been one for very long, about 3 months, would help out if it were a test and repair station and not a Ref (Test Only)