Well, yesterday I took off my UIM to replace a failing air intake thermosensor. I was done and the car started right up perfectly as it had always. I took it out and when it hit 80 degrees I went WOT in first and second gear. It felt fine so I drove back home and parked the car.

About 15 mins later I started it up to go to a friend's house and it had no trouble starting but instead of reving to about 1500 rpm it went to about 500 rpm (i start my car in gear so the AWS doesnt affect startup). It felt like it was going to stall out but didn't. I didn't really think anything of it.

Well, ever since then, it's been doing it every time I start the car when it's warm. I know "hard starts" are a symptom of low compression, but what exactly do people mean when they say hard start? Does it mean it takes a long time of cranking to get it to catch? Because mine starts after about 4 cranks, just as it did when it was new. It has no trouble starting, it's just that when it starts, it only goes to about 500 rpm then builds up to 800 rpm after about 30 seconds.

I plan on doing a compression anyways, but I hope my engine is ok. It is a reman with 5k miles.

 

I have had the same issue before... and even do now off and on... I feel my issue is electrical related possibly a bad ground. Since I have had ground issues in the past. So tomorrow I plan on installing my HKS ground wire kit.. I'll let you know if that helped at all.

 

I added about 10 grounds so I don't think that's the problem. I am pretty sure the motor is very healthy, it starts after about one crank when it's warm, it's practically like it starts as soon as you turn the key. If i start it with the gas pedal pressed in a tiny bit, it revs up to normal rpm (~1500) then slowly drops to a rock solid 800 rpm. I've searched and some people said this can be a problem with something to do with the fuel system.

 

What kind of ECU are you running? I have a PFC, and I've noticed a problem similar to this on warm startups. I do notice, however, that air temps tend to be really high from heat soak, so the idle is a bit rough, bouncing up and down for a while. After a while it calms down back to normal. Even if you're running a stock ECU, I would imagine that warm startups with rough idles has something to do more with the air temp sensor being too hot.

 

I have a M2 Stage 3 ECU. What you are saying makes sense, because my old intake temp sensor was not working, so if it was giving no signal at all, it wouldn't take into account the heat soak that occured, and now with the new sensor, it tell the ECU that it is extremely hot?

 

Sounds about right. Something I would suggest that I'm also gonna do pretty soon is set the base idle so that even with the idle control solenoid completely closed, the engine won't rev below 800 rpms. You can search for the procedure, but basically I think you put a jumper wire between the "Ten" and "Ground" terminals in the little black diagnostics box and use a screwdriver to set the idle (located right below the intake elbow).

Good luck!

 

I would agree on this.... I've noticed when its warm reving the engine a bit getting things circulated seems to help. Since I too feel my engine is pretty damn solid... I'll check out that sensor you mentioned.. perhaps Im in need of a new one. =)

btw.. installed the kit and it seemed to help some but not on this issue.. just on others.. =)

 

Okay I was reading through the FC-Datalogit manual, and it covers correction values for air temps, and I believe the stock computer retards the timing when air temps are higher than 60 degrees. Maybe that's why we get such weird idle properties on warm startups?

 

I guess that sounds about right.
I have never driven an FD without a broken IAT until I just replaced mine. Is it normal for it to rev up on startup to like 1000-1500 rpm then settle to normal idle rpm on a warm start? Or do they all start with a low idle then build up to normal idle rpm?

 

A sign of low compression would be your car cranks forever before starting up, and usually ends up not starting but just flooding out, had that problem in my FC

 

Well that's a relief. My car starts in about 1-2 cranks when it's warm and 4-5 when it's cold.