Intermittent idle surge

1998 HONDA CIVIC
249,110 MILES • 0.5L • 4 CYL • 2WD • AUTOMATIC
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MATTBMENIFEE
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My car intermittently has an idle surge only in second gear that begins to surge at 2,000 up to 2,600 RPM. If I hold it steady the surge is persistent but once throttle is applied/depressed the surge becomes non existent. If I get on the throttle slowly it accelerates fine/normal with no sign of surge or problem. If this surge was being caused by a small vacuum leak would the surge not be present at idle? I am stumped on when (RPM wise ) this is occurring? To me it should be at idle not when under load. I am scratching my head at this one. Any advice would be much appreciated.
Thanks, Matt
Nov 18, 2018 at 11:59 AM
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STRAILER
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Hello,

it sounds like the TPS sensor is starting to go out but to be sure lets run the codes to see what comes up.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Here is the TPS sensor location. Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Nov 20, 2018 at 2:12 AM
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MATTBMENIFEE
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My transmission is flaring 2nd-3rd as well so here's a list of parts replaced:
TPS

ECT

MAP

IACV

New intake manifold gasket

New o-rings and seals on Fuel injectors

Cap, rotor, PLUGS

o2 sensor downstream

STFT live data from scanner fluctuating 10 to -10 (high numbers but better than they were) -50 sometimes.

Tested spark plug wires=good

Installed a transmission cooler

Drain/fill transmission three times with genuine Honda ATF fluid.

New coolant, bled air out of system.
Oil change 1,100 miles ago.

I have a small crack in intake manifold/catalytic converter that is growing above upstream o2 sensor that is definitely a must need replacement just cannot afford the $500.00 California legal catalytic converter At the moment.
Pretty sure that is going to be main culprit of all issues?

Transmission after some research is hopefully the CPC valve spring and not a slow destruction of the transmissions life.
Nov 20, 2018 at 4:17 AM
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STRAILER
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We should stick to the same problem per post have you got anywhere with the idle issue?

Please post your new question here, you must be logged in.

https://www.2carpros.com/questions/new

Cheers, Ken
Nov 23, 2018 at 2:55 AM
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MATTBMENIFEE
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I haven't done any troubleshooting/replacement of parts on the car because of the holiday. The idle surge has NOT shown back up at all the past week. The idle has pretty much been doing whatever it wants for the last 4 to 5 months, meaning starting high(open loop) and never dropping down to normal rpm numbers even at operating temp. If I turn the car off and back on the idle will usually find a good number (860_940)
Thanks, Matt,
Nov 24, 2018 at 7:26 PM
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MATTBMENIFEE
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I am pretty sure the IAC valve is the culprit.
Nov 24, 2018 at 7:29 PM
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STRAILER
  • ✓Experienced Mechanic
  • 55,554 POSTS
Yep, sure sounds like it. Here is a diagram and guide to help you change it out:

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

Check out the diagrams (below). Please let us know what you find.

Cheers, Ken
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Nov 26, 2018 at 2:03 AM
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