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The surge comes and goes. It's more prominent while in neutral, but it does it in Drive too.

I replaced the engine in my '93 RS. Old one had a LOT more problems, but this wasnt one of them.

The newer motor was a complete engine, I bolted up the trans and dropped it in.

I know that an air leak in the intake system can cause this, aside from that, anyone have any other suggestions as to the cause?

yeah the sohc's come stock with a weak alternator and only 2 decent ground cable. if the power fluctuating isnt that bad then just build a ground kit for it (search for the how too in the forum) if that doesnt solve it swap the alternator out for a gs model alternator(also search for the how to)

temp sensor - replace both (there are two)

do a search and you will find (try 'temp sensor' in the 4cycl forum)

how could that be the problem?

mazdamx3sohc wrote:how could that be the problem?

temp sensor is kicking in and out, sending a signal that the engine is cold, the n warm, then cold, then warm, causing the high idle to kick in and out.

- Bochek

hey you know what, mine does that. i hear the fan kick in for 2 second then off 2 seconds on 4 second off for 1 second on for 3 you get the idea. whats the exact part i need?

My car does the same, but only when i have the music on or the lights..but if everythin is shut off it idles perfect

yeah thats the weak alternator thing

I know this isnt related to the actual problem but it's a symptom that could help us diagnose..

I've noticed that while the engine's doing it's surge thing, if I turn on the A/C( compressor kicks on and the idle-up solenoid bumps up)

the surge goes away!..

other than those two things, I don't think the A/C does anything else related to the engine.

Anyone think it could be a funky idle jet in the throttlebody?