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Old 11-18-2014, 07:56 AM
 
Location: DFW
6,717 posts, read 11,162,972 times
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I had the spark plugs, rotor, wires, etc. changed in my Honda Civic (1999, 190K miles) a few months ago and I've noticed higher than usual MPG (it used to average in the low 30s, now it's in the high 30s to low 40s). But the car has been shaking a lot more than usual especially when starting up and stopped at intersections. Does this sound like the car is undergoing fuel starvation? I'd love to keep the higher MPG but as long as the situation doesn't damage the car.
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Old 11-18-2014, 08:44 AM
 
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Engine or trans mounts !!!

Excessive carbon build up !!!

Was the fuel filter changed as well ???
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Old 11-18-2014, 08:46 AM
 
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Quote:
Originally Posted by need4speed2012 View Post
Engine or trans mounts !!!

Excessive carbon build up !!!

Was the fuel filter changed as well ???
CityData has limited exclamation points and question marks available for use, please save some for the rest of us
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Old 11-18-2014, 09:52 AM
 
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Your check engine light would come on if that was the case as the car tries to dump more fuel in and the O2's register a lean condition.

No light on? Then i wouldn't blame it on fuel starvation.

It could be unrelated.


with 200K miles, it's possibly the motor mounts are tired, or something on the crank balancer is failing.
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Old 11-18-2014, 11:08 AM
 
Location: DFW
6,717 posts, read 11,162,972 times
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Quote:
Originally Posted by BostonMike7 View Post
Your check engine light would come on if that was the case as the car tries to dump more fuel in and the O2's register a lean condition.

No light on? Then i wouldn't blame it on fuel starvation.

It could be unrelated.


with 200K miles, it's possibly the motor mounts are tired, or something on the crank balancer is failing.
No light on, no codes, oil change every 4k miles, injector cleaner every 10k miles, O2 sensor changed about 15K miles ago.
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Old 11-18-2014, 11:37 AM
 
8,711 posts, read 8,906,804 times
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Quote:
Originally Posted by ragnarkar View Post
No light on, no codes, oil change every 4k miles, injector cleaner every 10k miles, O2 sensor changed about 15K miles ago.

What about other service according to the owners manual. Coolant flushes, fuel filters, brake fluid, transaxle fluid, air filter, etc.

1999 civic uses a timing belt with a replacement interval of 7 years or 105K miles. With 190K miles, you should be almost due for another timing belt change.

(not saying this is the cause without looking personally at the car)


It could also be something such as improper spark plug gap, wrong choice of spark plugs (Bosch +4's for example....terrible plug) or arcing of the wires due to lack of dielectric grease installed during the wire swap or sometime else related to the service you just had.
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Old 11-18-2014, 11:43 AM
 
8,711 posts, read 8,906,804 times
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Let me ask you this. When the engine shakes, does the RPM on the tachometer jump up and down with the shaking?

Pop the hood and look at the engine while it idles. Does it appear to run smoothly, or does it seem to skip a beat here and there?
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Old 11-19-2014, 11:05 AM
 
Location: Fairfax, VA
3,829 posts, read 2,656,145 times
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Check the plugs and the cables. Shaking may indicate one or more cylinders are "missing".
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Old 11-19-2014, 11:24 AM
 
Location: Tejas
7,504 posts, read 15,962,470 times
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You'd have to define the shaking more for us, when, is it regular etc.
A shake indicates a misfire to me too. That could be a plug or am ignition coil but you say you have increased MPG and it should be the exact opposite with a misfire.

Take it to a mechanic and see if any pending codes show up, autozone etc cant do this.
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