Cant fix this damn studder!!!

ggeiss240sx

New Member
Nov 8, 2005
82
0
0
Laramie, WY
www.cardomain.com
Ive replaced, the plugs, wires, distributor cap, rotor, fuel filter, adjusted and re-adjusted the TPS 10 times, messed with the timing God knows how many times to get it right and experiment with it. The thing ran great 2 weekends ago, smooth as ever, then I replaced the exhaust gaskets and adjusted the TPS cuz the throttle responded funny below 2k rpm. Then I get it out on the highway and it doesnt pull for shit. cruising at speed, everything is smooth. Then put a tiny bit more pressure on the pedal to pass or speed up it studders like mad, not violently, more like the car doesnt have any power and vibrates. After I reach 75+mph I can step on the gas and no problems at all. So I put the TPS back to the way it was before and it didnt fix it a bit. Oh and of course its not throwing any codes. When its in park or neutral it idles fine and smooth. Then when I put it in drive it gets loaded down about 500RPM from 1100. It revs smooth in neutral or park but I guess that wouldnt help since its not under load.

Im going to replace everything on this whole car before it runs decent. My father thinks its a sticky injector, ive read its a mis-adjusted TPS, im thinking possibly a bad AFM. Either way its getting tedious... Could a fuel pump do this too? My 5m never caused me this much trouble....not even close.
 

ggeiss240sx

New Member
Nov 8, 2005
82
0
0
Laramie, WY
www.cardomain.com
The plugs were a graphite color, I cant remember what they were exactly but decently expensive think NGK's, and im almost positive they said "do not gap" on the boxes. Also I should mention that it will only studder until the tranny will downshift and bring the revs over 3500RPM, then its smooth again and pulls great. But any pedal at all until it does this is as mentioned above...

PS - If the plugs were wrong or not gapped wouldnt it run shitty all around? atleast idle rough?
 

tubbie

Yes, powerful Jedi....
Apr 4, 2005
821
0
16
Hoschton, GA
My mini van (GM) is doing the same exact thing... I haven't been able to figure it out either... But when cold, it works great, even at full throttle. Once warm, it goes okay, but push the gas down more and it studders, let off a little and it continues to go just fine......... Clogged cat? Bad air meter?
 

theDon

The Don
Mar 31, 2005
552
0
16
Med-City, USA (Rochester, MN)
ggeiss240sx said:
The plugs were a graphite color, I cant remember what they were exactly but decently expensive think NGK's, and im almost positive they said "do not gap" on the boxes. Also I should mention that it will only studder until the tranny will downshift and bring the revs over 3500RPM, then its smooth again and pulls great. But any pedal at all until it does this is as mentioned above...

PS - If the plugs were wrong or not gapped wouldnt it run shitty all around? atleast idle rough?

To add to my thought, after I switched from the expensive NGK's and went to the Autolite 3923 coppers, it went away - go figure. Oh and after looking at pulled NGK's the gap was not right. Never trust "pre-gapped", do it yourself it only take a few minutes. And yes I would think that this could be part of your issue that shows up at higher RPMs. At least it's a easy thing to check/fix too :)
 

blake

New Member
Apr 25, 2005
66
0
0
Minnesota
I was reading your description of the symptom and it really evoked a strong memory but I couldn't for the life of me remember what. Turns out it wasn't even the Supra.

I had the exact same symptom in an '87 BMW 325i. Turned out to be a failing AFM.

... man is that ever a bad feeling. Basically the reverse of hitting the brakes and not knowing what to expect.