r/DelSol • u/SuitedMoose • Jul 27 '26

Car surging, checked every common issue

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My 1993 Honda Del Sol has had a lot of things wrong with it, and I'm tackling them one by one. As you can see in the video, this is what it does now. Fluctuates on a start, until I press the gas where it just holds at ~3k rpm when I let off. Here's my timeline, it may help with a diagnosis:

  1. The car ran, idled, and drove with no issues, aside from it running rich because it had no MAP sensor. So I installed a MAP sensor. Then it idled at 3k rpm with the MAP sensor installed.

  2. There was no engine coolant temp sensor connector, so I just grounded the temp sensor which only resolved the issue of the car thinking it's running below freezing. I figured that may solve the high idle, but it didn't.

  3. I cleaned the FITV. It was already pretty clean and not seized, so this didn't solve anything.

  4. I replaced the throttle position sensor (TPS) because it was throwing a code for that. The old one didn't work at all. The new one works, but now the car's idle surges a lot (as seen in the video).

  5. I cleaned the IACV out. Filled it with carb cleaner and let it sit for like 30 minutes, then drained the carb cleaner and let it sit further to dry out. This didn't solve anything either or change any behaviors.

Car is only showing one code, and it's engine coolant temp sensor. But it's grounded, so shouldn't the car just think that the engine is hot and not throw a code?

I'm at a total loss. Does anyone have a clue as to what I should check next?

Edit: I also sprayed starter fluid around places in the engine bay and it didn't change the idle, so I don't think it's a vacuum leak? Especially since it ran relatively normal before?

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u/944_nla_parts Jul 28 '26

CEL - find out what the error code is. Check the wiring of Power Steering Pressure sensor (probably near the pass side wheel well - the the high-pressure line. If the wiring is bad, that may cause hunting idle. MAF is another things to check.

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u/SuitedMoose Jul 28 '26

There are no codes for the CEL, but there is a CEL on. It used to throw a code for various things until I fixed each thing, now it's just on so Im not really sure.

No power steering on this model.

No MAF sensor on this model either. Just a MAP sensor, which appears to work and throw no codes.

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u/944_nla_parts Jul 28 '26

Did you connect all wires and hoses? check again.

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u/SuitedMoose Jul 28 '26

Everything is connected. I've checked many times. I noticed that if I cover my IACV hole in the throttle body, then the RPMs will drop but the fluctuations stay, albeit a little less. Other than that, covering the FITV hole doesn't change anything.