93 EX AUTO... so ive been driving around with this problem for a while now, but its been more prominent since the warmer weather started. the car is idling extremly low, but it had idled low with the past 2 d16z6's ive had in the car so i thinking its a sensor. i think i can rule out the IACV and the FITV both have been cleaned recently. The head is also running extremely hot like no coolant is getting to it. hot enough that the valve cover can literally burn after the car has been idling for about 3-4 minutes with no other driving. also its been eating up some coolant over long trips. it really got bad after my car was sitting for a month when i did the front end swap... also when i took the valve cover off, the lost motion assembly over cylinder 4 was locked up, it was stuck down, the other ones were up and had a "spring" to them. i might be using the wrong terminology for this part ill post up a pic of what im talking about in a few minutes.... but heres the Tach in drive sitting at a stoplight... the car will stop shaking when the car gets down this low... i have energy suspension motor mounts which cause the car to shake.

 

Your main concern should be the engine overheating not the low idle.

Have you replaced the thermostat and radiator cap and properly bled the cooling system? Can you detect a coolant leak? Is there white smoke in the exhaust?

 

im gonna replace the t-stat tomorrow, im gonna go get an oem honda one, i replace one from oreillys but i think it has failed, ill pull it and test it tomorrow... ill look over the whole coolant system tomorrow, i wasnt sure if the low idle could be a tell tale sign of a blown headgasket or not.

 

It could be, but rule out the simple possibilities first.

 

alright. would you recommend getting a t-stat from a honda dealership? also ill flush the coolant system tomorrow too. i did it about 6 months ago after my coolant hose blew off on the highway. Also, there is no visible white smoke coming out of the exhaust, so hopefully its not the headgasket. also it just recently really started getting really hot when i put my magnaflow cat on. i dont see how this could really cause it though.

 

You already replaced the T-stat, so replace the radiator cap instead. OEM would be best.

Next bleed the cooling system:


1) Park the car on an inclined driveway with the front end higher than the rear.

2) Push the dash heater lever/**** to MAX heat.

3) Follow the directions in the diagram below (hint: the bleed bolt is located where the upper radiator hose connects to the engine):

 

i replaced both the cap and the t-stat today. i also bled the coolant system. unfortunately im still losing coolant. i looked for leaks, and couldnt find any. whats the next thing to look at replacing? is there a good way to test the radiator itself? i dont know if some sparks from welding/ cutting off the radiator support hit the radiator and burnt small holes in it? is that possible even?

 

That's a headgasket at this point. I've gone through two and the the low idle happened to me too...

sorry dude. depending on mileage I would use it as an excuse for an engine swap.

 

Alright I'm gonna attempt as head gasket swap tonight. Is there any thing I should really inspect while doing so? Are there any coolant lines that run below the IM that are frequent culprits of leaking? I have a new z6 head I'm putting on with a comp cam in it... Anything ill need to watch for? Should I change the oil too?

 

You will likely end up spilling water into the oil (if it's not there already) taking the head off, so change it.

Inspect everything for external leaks first. There are a lot of lines on the back of the engine and intake, they are much easier to see from underneath. If you can get access to a pressure tester (basically an air pump which puts the cooling system under pressure while cold), that is very useful in finding leaks.