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Speedometer and tach jumping

 
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  #1 (permalink)  
Old 29 Jul 2008, 08:00 pm
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Default Speedometer and tach jumping

I have a 2002 pt cruiser,88,000 miles. It is Intermittantly having a problem, the engine will start idleing high, and the speedometer, and tach will start jumping around, This usually happens at idle, at a stop or in park. Most of the time if you tap the throttle a few times, the gauges start acting normal again and the idle also goes back to normal.

I was wondering if anyone had any ideas, and Thanks in advance...
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Old 29 Jul 2008, 08:12 pm
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Default Re: Speedometer and tach jumping

Welcome to the forum.

How come hardly anybody joins the forum BEFORE they have problems?

Anyway, my guess it that your IAC (Idle Air Controller) is either dirty or bad. You can take it off and try and clean it to see if that help. It's located in the back of the throttle body. See picture.

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Old 30 Jul 2008, 03:53 pm
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Default Re: Speedometer and tach jumping

Thanks for the suggestion, but would that cause the tach and speedo to act crazy?

And I just got the PT a few days ago, have never had one before, so had no reason to be in the forum...........
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Old 30 Jul 2008, 04:08 pm
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Default Re: Speedometer and tach jumping

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Originally Posted by worldtv View Post
Thanks for the suggestion, but would that cause the tach and speedo to act crazy?

And I just got the PT a few days ago, have never had one before, so had no reason to be in the forum...........

Good answer. I was just sort of talking to myself out loud. We get about 3 to 5 people a day with their first posting and it's usually some sort of problem.

Anyway, If the idle is erratic (going up and down) the speedo and tach will follow along with the revs of the engine. Now if the tach is jumping all over the place not in time with the revs of the engine and the speedo is doing the same, forget the IAC because you probably have an electrical problem.
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Old 30 Jul 2008, 06:43 pm
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Default Re: Speedometer and tach jumping

That is exactly what is happening, the speedo will jump around from 50, 60,90, even peg out, back and forth, sitting in park, and at the same time the tach is jumping all over the place, but not with the engine speed, even though the engine speed does go really high.

I really want to thank you for your responses. I just cant figure out what is in common with the speedo, tach, and engine reving.....

Its quite the mystery for me and my little pee brain.
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Old 30 Jul 2008, 06:58 pm
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Default Re: Speedometer and tach jumping

Here's a little something you can try, although I don't what it will prove. It's a way of testing all the guages in the three dials.

There's a little button on the dash that will reset your trip meter. Hold it in, then turn the key to the ON position without starting the engine. The numbers in the center dial will start counting (then let go of the button) and then all the needles on all the dials will go from low to middle to high.
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Old 04 Sep 2011, 06:19 pm
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Default Re: Speedometer and tach jumping

did you find what was causing this problem? i have the same problem with an 02 cruiser. sometimes upon starting the speedometer and tach jump, runs a bit rough and sometimes the automatic transmission will not engage until it settles down. what to do without just guessing?
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Old 03 Dec 2011, 04:34 pm
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Default Re: Speedometer and tach jumping

My 2001 Cruiser does the same thing. The speedometer and tach jump and the car it is clunking and jerking when I move the shifter into reverse or drive. About 8 months ago, the clunking and jerking began, but the battery was weak and replacing the battery immediately solved that problem. However, when the weather got cold about a month ago, the clunking and jerking began again and a week ago the speedometer and tach started jumping. The charging system checked out okay, but as the problem persists. I do not know what the problem is, but I believe it is electrical. I welcome anything anyone has to suggest.
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Old 04 Dec 2011, 02:02 pm
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Default Re: Speedometer and tach jumping

I found a forum which discussed many of the Dodge Grand Caravans doing the same thing. In each case, the problem resulted from one of three things:

1. Battery voltage sometimes spiking. A new battery solved the problem.
2. Bad battery cable. replaced the battery cable the car functioned as it should.
3. Loose connections on the rear of the dash cluster. Re-soldering the connections fixed the problem.
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Old 04 Dec 2011, 10:54 pm
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Default Re: Speedometer and tach jumping

Quote:
Originally Posted by ewlett View Post
I found a forum which discussed many of the Dodge Grand Caravans doing the same thing. In each case, the problem resulted from one of three things:

1. Battery voltage sometimes spiking. A new battery solved the problem.
2. Bad battery cable. replaced the battery cable the car functioned as it should.
3. Loose connections on the rear of the dash cluster. Re-soldering the connections fixed the problem.
Absolutely correct. I also own a 2007 Chrysler Town & Country. We call the problems "Haunted Minivan Syndrome."
--Usually, it is a bad battery. Replacing it solves the problem.
--Some new batteries are just junk and fail fast. Get it checked.
--If the batteries in the car were the normal flooded lead-acid type, that use water, even if you can't actually ADD water, corrosion is going to be a problem.
--Obvious corrosion at the battery terminals needs to be fully cleaned off.
--Not all battery corrosion is obvious. Battery acid has an annoying habit of seeping into the battery cables, underneath the insulation. There, where it can't be seen or cleaned, it slowly eats away at the copper until an intermittent contact or intermittent high resistance will cause weird electrical problems. (This happened to me in a cloud of mosquitoes 120 miles south of the Arctic Ocean back in August. It WAS NOT fun, and it was a factory defect come home to roost in a Ford F-350. A most mucky day.)
--Sometimes, the corrosion will occur in the fuse box under the hood from battery acid mist, or at the starter connection.
--When this has happened, it may be time to replace a bunch of battery cables, from the big, thick ones down to the smaller ones that go to the fuse and relay box.
--All of this can be prevented by using a good quality, U.S. made Absorbed Glass Mat battery (AGM) such as a Deka or an Odyssey. Those won't leak, corrode or cause acid mist, and won't ruin your battery tray. (I recommend against Optima batteries, which I used to use exclusively. See: OPTIMA Batteries - Alternatives, Whatdya think?
--In a situation where a new battery was OK until the weather got cold, I'd (1) check all the connections for corrosion, which ought to be done anyhow, and (2) check to see if the new battery is becoming junk sooner than expected.

Ricardo: I would look at the battery also, for yours if the speedometer is also jumping.
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