Mechanics

INTERMITTENT ENGINE SURGE

1996 Mitsubishi FTO

Engine Performance problem
1996 Mitsubishi FTO 6 cyl Front Wheel Drive Manual 136000 miles

Hi there.

my car has an intermittent engine surge or misfire and I can't track down where its from or why it's happening. The symptoms are:

1.) The engine will only surge when the revs are between 0-2200rpm

2.) It will only surge occassionally once the engine has warmed to operating temperature - not when it's cold

3.) It will not surge when the air conditioning is on

4.) It will only surge when driving at a constant speed (0-65kmph), not while accelerating.

5.) It surges throughout all 5 gears, just so long as its within the rev threshold of 0-2200 approx.

6.) It does not surge at idle, only in gear and when driving

at higher speeds the engine is completely normal. The surge itself is just a very quick and very momentary loss of power.
I have changed spark plugs, and air filter, as well as spark plug leads. I will be replacing fuel filter asap.

Please, any help will be very much appretiated!


Kyle
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Kyled370
May 13, 2010.




Hi kyled370,

Thank you for the donation.

The item that is likely to cause surging would be the Idle Solenoid Control Valve, also commonly referred to as the Idle Air Control Valve.

Is the Check Engine Light indicating?

KHLow2008
May 16, 2010.
Hi there

Thank you for your reply. The check engine light has never indicated any problems for me. I will get that idle air control valve checked out though, thanks.

So it doesn't matter that the car will not surge at all when it's just idling? Because the only time it ever surges is when its in gear and im driving (forward, not reverse as far as im aware-will check that out tomorrow) with the revs between 0-2200rpm approx.

Tiny
Kyled370
May 16, 2010.
When the IAC does not operate correctly, it sometimes do not surge while ilding but a little throttle opening would cause it to surge.

If it only surges during forward gears, then you need to check for vacumn leakages. Sometimes the engine mounts are weak and when gears are engaged, the engine would tilt. This would cause vacumn leakages as cracks to hoses are exposed when the engine tilts away.
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KHLow2008
May 16, 2010.
I see. Yeah everywhere that I have read on the internet has suggested that is a vacuum leak. I will get a vacuum gauge and check it out.

What was confusing me was that when im driving, it happens when im at a constant speed, it will never do it while the car is accelerating and speeding up

Tiny
Kyled370
May 17, 2010.
When accelerating, the throttle is opened for more air to go in so it would not surge as more air is expected.

KHLow2008
May 17, 2010.

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