Fan relay

[1Gab Laser]

I've sorted out most of the bugs in my car by now but there's one left...

When I go on a "long" trip (30 minutes or more usually) my car starts running/idling funky. I've traced the problem to be something with the cooling fans. When I pull up to a stop, idle drops down to around 500 RPMs and it sounds like it's barely staying running. If I'm driving kind of slow, keeping it around 1000-1500 RPM, it acts like it stops running for a second then fires. I can't really explain it, I'd have to take a video or something.

So trying to figure it out I've let the car just idle for a while until it acts up. I've noticed that only the passenger's fan comes on. After a while, it'll start running crappy, then the drivers fan will kick on for a second, both of them will shut off immediately, and it'll run great.

I've tried replacing the little aluminum box on the fan and the mini harness, and tried a whole new fan, it hasn't changed anything.

Hooking power up to them DIRECTLY from the battery, both fans run fine, no problems.

So I'm thinking it might be some sort of relay that's gone bad or something? Does anybody know where I can find this or maybe know if that's not the problem at all?

Oh, and the temperature never gets past dead center.

 

[1Gab Laser]

Please refer to http://www.dsmtuners.com/forums/newbie-forum/351669-fan-relay.html#post152011546 rather than bumping the thread (which is against the rules here). You still have a lot to do before there is any thing else to look at.

The BISS and CAS need to be set correctly for a good idle. That's a basic step.

Sorry, it had been a few days and I figured it got lost and forgotten on the 3rd page.

I searched through the manual for "BISS" and "base idle" and didn't come up with any results for either one. Is it just as simple as adjusting it until you get a smooth idle ~750RPM? Or is there more to it than that?

The thing is it idles fine when it's cold/warming up. It's once it gets up to temperature and that second fan comes on, it starts to surge. We're still convinced it has something to do with the fan, because it's fine until that fan tries to come on.

I'm being told by multiple mechanics that that fan runs off the AC. The AC is totally dry, and shut off (its not even 40 degrees out, why would you need the AC? ). So then shouldn't that fan not be trying to start in the first place?

 

[steve]

I searched through the manual for "BISS" and "base idle" and didn't come up with any results for either one. Is it just as simple as adjusting it until you get a smooth idle ~750RPM? Or is there more to it than that?

Page 14-48 and 14-49 of the 1G Engine Chassis Body manual. Section 14 is on the fuel system of the car and also contains the diagrams for the MPI wiring (pretty much everything under the hood dealing with the engine.

Which fan is the second one? I understand driver side and passenger side and will sometimes assume people know what they mean when they say radiator fan and AC fan.

Your still working with some questionable parts (like the ECU) and I haven't asked about the throttle body, FIAV, or the coolant lines to it.

Reading the 1G technical manual might help you get a better feel for how the various pieces interact.

Remember I'm not interested in providing quick answers to people. I'm interested in teaching people how to be able to solve their problems.

 

[1Gab Laser]

Page 14-48 and 14-49 of the 1G Engine Chassis Body manual. Section 14 is on the fuel system of the car and also contains the diagrams for the MPI wiring (pretty much everything under the hood dealing with the engine.

Which fan is the second one? I understand driver side and passenger side and will sometimes assume people know what they mean when they say radiator fan and AC fan.

Your still working with some questionable parts (like the ECU) and I haven't asked about the throttle body, FIAV, or the coolant lines to it.

Reading the 1G technical manual might help you get a better feel for how the various pieces interact.

Remember I'm not interested in providing quick answers to people. I'm interested in teaching people how to be able to solve their problems.

I'll take a look at those pages. Hopefully tomorrow I'll have a chance to get the car in the garage. Thanks.

By "second fan", I mean the AC one. I meant second in order of coming on (but to my knowledge, which maybe I'm wrong, it shouldn't be coming on at all?). What's happening is the cooling fan comes on, then after a while the car starts idle surging. Eventually (minutes) the AC fan will kick on real fast, then they both stop and the idle smooths out.

 

[steve]

My AC fan spins for a second as the radiator fan kicks off. I always assumed it was from a inductive kick when the radiator fan shuts off that triggers the AC fan relay.

 

[1Gab Laser]

It seems to be running fine now. Could it have just taken a while for the ECU to get proper readings from the new ISC? Or maybe it has something to do with the cold weather?

I drove it 20 miles then let it idle for about 20 minutes and it didn't surge anymore. I might try again today if I have time just to make sure.