Hi guys,

I have a friend with a 97 3L Magna.
It is behaving weirdly. At times when he is at lights, then presses throttle it does absolutely nothing.
It does not go, the muffler does not make any more noise, it is as if there is no throttle.

What could this be?

Throttle position sensor would be my first guess.

Does the engine change note in any way...does this happen if the pedal is pressed completely to the floor or only partially?
My first guess would be a sticky throttle cable.

O2 sensor.
Gerry

Do you have traction control, or cruise control? If there's zero response from the engine on throttle I'f be checking the cable - starting at the pedal and working my way through to the throttle shaft/butterfly.

I would like to think that if the vacuum side of your traction control was on the fritz you would get an engine light.

My money is on something has broken in the throttle shaft/butterfly assembly. I spring broke of something like that.

Clean the TB, sounds like something physical is stopping it from opening sometimes and that it needs to be repeatedly jiggled using the pedal to get it to open?

When you press the throttle does the engine rev properly when you are in Neutral.
When you are driving-especially when the engine is warming up does it bahave as if there is a massive flat spot, then the power comes in with a rush at over 2000rpm.
When you are in drive at idle does the car want to pull away strongly with no accelerator input.

If any or all of these I would investigate the O2 sensor.
If you have a multimeter look for continuity between the white heater leads and also between the black and gray leads.
Gerry

Get someone to check that when your friend pushes the accelerator pedal to the floor, the butterfly on the throttle body actually moves. If it doesn't, you have the problem. The fact that the engine note does not change at all suggests this. If the throttle opened, I would expect the engine to probably stall if there was insufficient fuel to make it rev or even changes revs.

O2 sensor will not do jack at idle

The issue is most likely the throttle plate sticking as there is too much gunk in the throttle body, give this even a basic spray through clean and you will most likely find that this issue will be fixed

No traction control or cruise control on the car.
It doesn't do it all the time, but it kind of stutters at the same time.

So, he'll press throttle and it won't change noise or move, but it will stutter periodically and then move off normally

Guys,
Some more info, it runs much much worse of the AC is switched on. And it happens mostly on WOT at lower rpm. The less the throttle the less the issue by the looks of it.
I assume ISC, TPS, or o2 sensor??

Happened to my GTV while I was O/Seas.. Dont go to Mitsu they'll charge you to replace the TB..

When I got home I simply got TB Cleaner and cleaned it up along with a little lube for the butterfly and BOB's ya uncle!

SuFz :ninja:

So, he'll press throttle and it won't change noise or move, but it will stutter periodically and then move off normally

this part sounds almost like a coil issue, or low spark

I drove the car myself, and as mentioned before if you press the throttle extremely lightly it's fine, but anymore than what feels like about 15% it starts hiccuping, sounding a bit funny (like it misfires) and no power at all, ie, it just rolls pretty much.
Does this help anymore in diagnosing the issue?

this happened in my gfs mirage replaced all the spark plug leads and cleaned the dizzy cap,, no probs been fine now for almost a year,, hope this helps..
DAnny

Update:
Turns out the o-rings for the valve cover were leaking, and oil was going all over the plugs