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Tachometer Doesn't Move, Engine Rumbles
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Falstad007
New User
Jan 29, 2016, 6:30 AM
Post #1 of 8
(1792 views)
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Tachometer Doesn't Move, Engine Rumbles
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1997 Pontiac Grand Prix GT 3.8L - 78,000 miles.
When driving my tachometer usually hovers above 2.2-2.4, but after a few seconds it will dip down to about 1.4 and not move at all, despite giving it more gas. Giving it more gas will cause the car to shake.
I can completely remove my foot from the gas and re-apply pressure to get the RPM around 2.2-2.4 again, but it will dip down to 1.4 and the issue will repeat itself.
What's causing this issue?
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kev2
Veteran
Jan 29, 2016, 7:13 AM
Post #2 of 8
(1783 views)
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Re: Tachometer Doesn't Move, Engine Rumbles
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1st -scan for codes post ALL the codes -
2nd Tell us is vehicle STOCK - no add on or modifications... this is the factory tach?
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Falstad007
New User
Jan 29, 2016, 8:24 AM
Post #3 of 8
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Re: Tachometer Doesn't Move, Engine Rumbles
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Stock everything.
No codes. I recently had to replace the forward wheel hubs and the VSS as they were throwing back codes, but since then I haven't had any others.
It's also worth noting that this had been an issue before the hubs and VSS failed.
(This post was edited by Falstad007 on Jan 29, 2016, 8:25 AM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Jan 29, 2016, 6:18 PM
Post #4 of 8
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Re: Tachometer Doesn't Move, Engine Rumbles
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If you step on the gas, it doesn't accelerate, and the engine is surging and running bad, you should check fuel pressure first. You will probably need to hang the fuel pressure test gauge on the windshield, so you can see it while your driving. If the pressure isn't within specifications(48-55psi) or drops while your accelerating, you have a low fuel pressure issue.
Note: Be sure your gauge isn't leaking and it is routed away from rotating or exhaust components. It would also be wise to have a fire extinguisher in your vehicle if you test drive with the gauge attached.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jan 29, 2016, 6:25 PM)
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Falstad007
New User
Jan 30, 2016, 7:55 AM
Post #5 of 8
(1729 views)
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Re: Tachometer Doesn't Move, Engine Rumbles
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Thinking back, around six months ago the rubber hose on the bottom pic had become fractured:
As it should be:
My engine:
We ended up tightening it up with some duct tape, not really thinking it would be an issue.
I'll look around for a new L-shaped housing, but hopefully that's the source of my issue.
(This post was edited by Falstad007 on Jan 30, 2016, 8:06 AM)
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Falstad007
New User
Jan 30, 2016, 10:02 AM
Post #6 of 8
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Re: Tachometer Doesn't Move, Engine Rumbles
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I'm not sure what the name of the L-shaped bit is, can't seem to find anything on Google.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 30, 2016, 10:44 AM
Post #7 of 8
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Re: Tachometer Doesn't Move, Engine Rumbles
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? "L" shaped bit? I don't see what you mean in those pics. Can it be fixed or made from angle iron from hardware?
Hose elbow just might be EXACTLY a spark plug boot size! Gettin' old, have a box full of those too when you made your own and puts on ends needed.
Other back when you said tach could just stop at one spot at stay there. This vacuum stuff, fuel regulator I just don't know how that's involved. It's more likely electrical to dash has a problem if this vacuum stuff it tight and not a cause of engine rumbles (whatever that means) it may get the wrong signal for real for RPMS and throws off the show,
T
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Discretesignals
Ultimate Carjunky
/ Moderator
Jan 30, 2016, 12:08 PM
Post #8 of 8
(1705 views)
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Re: Tachometer Doesn't Move, Engine Rumbles
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It won't fix your problem, but it should be replaced.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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