rpms are acting weird

94gt5.o · May 25, 2010

So when im driving or even at an idle I will rev up the car and the rmps drop super slow if im driving and push in the clutch the rpms will actually jump up then the will hang there for a couple seconds. I have no clue what it is please help, thanks guys

TrueBlue95GT · May 25, 2010

When did it start happening? It usually means you need to adjust your idle settings.

Gearbanger 101 · May 25, 2010

Before you go playing with the idle screw, pull off your IAC and give it a good clean up. Visually inspect the rest of the throttle body for gunk and carbon deposits as well. Testing your TPS function wouldn't hurt either. In any case, the stock throttle bodies are factory set so you shouldn't have to touch the idle.

BlackVert · May 25, 2010

sounds to me like the IAC is starting to stick a little. cleaning it might help for a while, but my understanding is that there is a coating that is supposed to help keep it from sticking. after it is cleaned, the coating does not work as well anymore, so it will start sticking again before long.

if you can verify that it is the IAC, then you should replace it.

94gt5.o · May 25, 2010

Ok thanks guys ya ive never cleaned the IAC and i will get a price quote at the local parts store for the IAC and i will get back to you guys after i take a look at it.

94gt5.o · Jun 8, 2010

ok so i bought a new IAC and tried setting my idle settings and now my car has lost some noticeable throttle response. I checked my TBS voltage reading of .95 is this good enough? oh also another problem i can not set my timing at 10 degrees timing other wise it makes a horrid noise when i get on it the noise starts around 3000 4000 RPMs i have to set my car at 7 or 8 degrees to get it to stop. any help would be great thanks guys.

Hef5.0weisen · Jun 8, 2010

balancer may be spun, is it the original? tell tale sign (not so much of it being spun, but wore out) is rubber hanging out of it. may be time for a new one. in effect, you may try to set your timing at 12, but its actually 20 (random numbers) rubber wears out, outer ring spins away from inner ring, timing marks are off, it happens....

good luck

brightredvert · Jun 15, 2010

It's kina off the wall but does your stang seem to be running richer and worse mpg???

I'd check the O2 sensors.

I'm having the same Idle and timing problem with my 94 GT I replaced a harmonic balancer about 8 months ago. When the balancer goes you will get a heavy and I mean heavy vibration from the engine.

You might want check your ignition system (distributor, Cap, rotor, SPOUT etc) if all other things listed above seem to be O.K.

Un plug the SPOUT and see if the problem is still there.

94gt5.o · Jun 15, 2010

you know come to think about it ya its does run rich but im pretty sure the harmonic balancer is going cuz if im cruzing at about 70 i get this weird vibration about every 5 seconds but we willl see thanks for the idea i need to replace them any ways.

asburydan · Jun 16, 2010

RPM shifts

I am having a switch replaced tomorrow on my auto trans since it now "drops out of gear" and the RPM move up 300-500 as if the car is in neutral, with the gas pedal depressed. Maybe something similar is happening to you even with stick shift. Switch is M something (3 more letters, but I forgot).

94gt5.o · Jun 18, 2010

i dont know i dont thinks so because my problem has to do air and fuel mixture (so i think based on how its running)
oh and i took a real close look at my HB (harmonic Balancer) and the rubber is startin to push out so i got my list of parts that need replacing lol

Chythar · Jun 18, 2010

asburydan said:
I am having a switch replaced tomorrow on my auto trans since it now "drops out of gear" and the RPM move up 300-500 as if the car is in neutral, with the gas pedal depressed. Maybe something similar is happening to you even with stick shift. Switch is M something (3 more letters, but I forgot).

You're talking about the MLPS. It's easy to replace on your own, but it's a bit late for that. The original MLPs the auto transmissions got weren't sealed tight ands would eventually corrode. All new ones made hare properly sealed now. Another possible problem could be: if you're in Overdrive, you accelerate and the car drops into neutral, that's your overdrive band wearing out. It's literally a kevlar band that can't really hold the torque of a V8 engine. Too many heavy accelerations in overdrive will wear out the band, and eventually you won't have overdrive anymore.

If the new MLPS doesn't fix the problem, post up in your own thread and we'll go from there.

Chythar · Jun 18, 2010

94gt5.o said:
i dont know i dont thinks so because my problem has to do air and fuel mixture (so i think based on how its running)
oh and i took a real close look at my HB (harmonic Balancer) and the rubber is startin to push out so i got my list of parts that need replacing lol

Take care of that HB real quick, if it's out of balance it can damage the engine. Usually the engine will start shaking while it's running, and get worse the higher the RPM's go. As for losing power, I haven't seen anyone mention the MAF. The sensor wires can get dirty and rob you of power. Clean the wires very gently with a q-tip and rubbing alcohol; keep cleaning them until the q-tip stays clean.

94gt5.o · Jun 18, 2010

ya I know about the MAF i acully just cleaned it 3 days ago with some MAF cleaner not sure if the q tip method is better if it is let me know oh and my o2s have about 160k on them

rpms are acting weird

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