DavidFeygin

Hello all,

I have complete loss of power above 4500rpm. So much so, that I can hardly get it revved up to 5500 in neutral. I have had a small hesitation for years that I have never figured out, but have attempted numerous fixes. If I keep the engine reved around 5000rpm while in gear for more than a few seconds, the engine idles very, very rough as though it is firing on 2 cylinders. It also bucks like crazy if I try to keep accelerating in a higher gear (around 2-3k rpm). After 30 seconds of rough idling or bucking, the engine returns completely to normal and is smooth. My theory is that the mixture goes completely rich or lean at very high rpm, under load, and when the engine compensates, it screws up the mixture at idle. Once at idle for half a minute, the mixture returns to normal. Again, this is just a theory which I will attempt to check over the week by monitoring the two o2 sensors. Does the theory sound plausable? Does anyone have any other ideas or has anyone experienced anything similar? Could it be something else?

I could not find any air leaks or vacuum leaks. The 02 sensors have about 15k miles on them. New plugs and wires. Just did a professional decarbonization.

Thank you.

MikTip

Sounds like a possible fuel pump going bad? ;O)

DavidFeygin

I just had the shop check fuel pressure and flow and they are within spec...Thanks though.

MikTip

The pump need to be checked for how many amps it draws! ;O)

How about the fuel pump relay?

zeems

Maybe one (or both) of your catalytic converters have broken chunks in them-blocking the air from exiting. Might want to check your cats to eliminate that possibility.
Goodluck,
-Azeem

RoadTrippin

I have the same exact problem but with the 5 cyl. I changed the oxygen sensor, fuel filter, plugs, wires, cap, rotor, air filter is brand new.

Same solution? Fuel pump?

sconney

My problem was a year in replacing parts, computers, etc only to find out the Hall sensor was bad inside the Distrib Cap. The car ignition would kick out while going up hills or at fast speeds. Your gig might be diff? The tach would drop to Zero . car in essence would shut off.

DavidFeygin

Although this may still be the problem, I have unplugged the little blue caps on the catalytic converter test tubes and this did not help at all. From what I understand, there would be a small but noticeable difference when these are unplugged.

DavidFeygin

My tach seems to show the correct rpm even during bucking. Thanks.

DavidFeygin

If you ever figure it out, make sure you post.