87 Prelude Si warm start problem

[takemorepills]

My 87 Si (I guess we can just think of it as a 87 LX-i) has been having difficulty starting when warm. The symptoms are:

-starts perfectly fine when cold (as in engine fully cooled) and runs well overall, even when fully warmed up.

-if it's been sitting for anywhere between 10 minutes to 10 hours (which I'm gonna say is "warm") it takes extended cranking and when it finally fires off it stumbles to idle. Soon after the hard start it finds idle ok.

-after a hard start, it idled fine until I drive it in traffic. Prior to full warm up the idle will stumble when I'm stopped in traffic. The stumbling lasts 5-10 seconds then the car instantly finds a smooth, normal idle. 20-30 seconds later the process repeats. The difference between stumbling and good idle is like an on-off switch.

- sometimes the car will misfire (after the hard start) when I drive it, it's a full power loss misfire.

- following a hard start the exhaust reaks of unburnt fuel. The harder the warm start, the stronger the smell.

Things I've done:
- inspected TW sensor. Passed.
- no ECU codes.
- new Bosch cap and rotor, Denso wires, NGK plugs. No improvement
- inspected Main Relay. Passed. I am going to resolder anyway when I get a chance.
- cooling system flush and proper bleed of cooling system.

I'm at a loss. My opinion is maybe a distributor issue which in my estimation explains the raw fuel smell, and sensitivity to a not cold engine.

What do you guys think?
Hoping someone recognizes this issue and knows a solution.

[Jacques]

Not like I am an expert, but you might look into the idle control valves. My Lxi has two. One is hooked to wires that are part of the PGFI system. Should be on the front of the intake and has coolant running through it. The other one is on the back and also has coolant running through it. That one has a cap on the top. First thing on that one is to remove the cap and carefully tighten the ring in there with a screwdriver by tapping it around to tighten it with your hands only. The ring comes loose sometimes. Just snug, don't try to hard. Both of those have o-rings that seal then to the manifold. When the o-rings get old they leak and can cause issues too. Those vacuum leaks won't throw a code. There are several coolant sensors as well that all need to be functioning correctly. One near the thermostat, one in the bottom of the radiator. There is also a sensor for the air intake temp. that is on the manifold that also has an o-ring seal. Then you have all the vacuum hoses that go to the control box etc.
It can be a real bitch sometimes to figure it out. The fuel pressure regulator can go bad too. If you get it figured out, chances are the engine will last for a lot longer than you thought. Search the site here more. There is tons of really good info in here, it just takes time to sift through it all. Good luck to you.

[takemorepills]

Thanks man. I'll look into those suggestions.

The 1987 has a FITV, "Fast Idle Thermal Valve" that has the coolant lines running through it. There's a beeswax thingy in there that fails over time. I'll need to look at it too...

[Jacques]

Thanks man. I'll look into those suggestions.

The 1987 has a FITV, "Fast Idle Thermal Valve" that has the coolant lines running through it. There's a beeswax thingy in there that fails over time. I'll need to look at it too...

I know you said you checked the main relay already, but I will say the first time I had warm staring issues that was the problem. It would start but as soon as you released the starter it would die. Keep digging into the threads here and take care now. I have 333,000 plus on my 89 lxi and still runs strong. Yes, I have replaced many parts, but the engine and trans. are still solid.

[Dr_Snooz]

You might have a couple things going on. The warm start issue is a fairly classic main relay symptom. Most members here feel that resoldering it is sufficient, but the relays in mine had failed. It required replacement with a new unit. After that, some things you might check are:

- Fuel pressure
- Coil (p. 24-12 of the manual)
- ICM (p. 24-9)