Lude Generation

had a new (used) engine put in my 99 Prelude and the mech sez it starts & runs good til it warms up then if you allow the rpm to drop below 1500 it will die and not restart.
he can't figure it out so the car will come home on a roll-back and I get to try.
what should i look at ?
tommyt

Which prelude/engine/gearbox was it originally? And what engine was put in it (Which donor car? or engine from the shelf?)

For Idle issues i would look at the temperature related bypass valve on the throttle body (Check it is plumbed in and circulating warm coolant).

Scott560 wrote: ↑

Thu Jan 20, 2022 8:39 am

Which prelude/engine/gearbox was it originally? And what engine was put in it (Which donor car? or engine from the shelf?)

For Idle issues i would look at the temperature related bypass valve on the throttle body (Check it is plumbed in and circulating warm coolant).

exactly this. had my FITV go on me many times causing these issues, could be blocked or bust or plumbed in wrong as scott says

I've never had any real trouble with mine (except maybe it is a little old and probably wants flushing out / cleaning).

Essentially it's a thermostat bolted to the bottom of the throttle body. Coolant flows over it, and it opens a channel within the throttle body to let more or less air through to bypass the butterfly.

Remove it and check the throttle body orrifice is clean (they can get gummed up with oil breathed in), and check that coolant is flowing well. The coolant is fed from a couple of hard pipes which feed some rubber pipes. It would be quite easy for the hard pipes to get kinked/bent or perhaps even furred up with old coolant, which would stop it working properly.

A healthy dose of carb cleaner into the TB whilst its running won't hurt tbh.

It may also be worth checking that the engine, if unknown, has good compression when cold. A marginal engine will run , but issues are highlighted at idle.