Heres a wierd one

[Matt McClung]

Hey guys, I just reset my IAC and my TPS to .44 VDC and it idles great. But the wierd thing is when it gets to the temperature where the cooling fan kicks in, then it starts to idle rough. When the fan turns back off, it idles great again. I watched this cycle about four times before I dicided to come in the house and see what the board would say about this one. The only thing I can think of is maybe the fan is drawing too much from the coilpack/module, if this is the case maybe I can run a hotwire (fused) straight from the battery and use the fan relay as the switch (just like the fuel pump).
Any ideas?

Thanks again guys

Matt

 

[Dusty Bradford]

Alternator or battery problem???? The fan does draw lots of electricity, enough that if the alternator isn't up to it you could have problems.

 

[Dayton]

Don't mean to highjack your thread but i've been having the same problem. I posted the same question a few months ago and didn't get any replys. The car runs great till the fan kicks on. I have a new coil,module,and alternator and it still does it. I watch the voltage when the fan comes on and it will drop a little at start up but jumps right up to 13.2 to 13.9 sometimes 14+ while the fan is running but the idle is all over the place until the fan turns off and with the warmer weather the fan is on more often than not. I've even unplugged the fan relay and controlling the fan from inside the car because it got so bad. I checked all the grounds and their ok. I'm very frustrated hopefully some on can chime in and help us out with this very annoying problem. Oh, one other thing, while the fan is running 02 voltage is very low on the scanmaster. I also have an A/F gauge and when the fan is on it goes all the way to red which indicates lean condition and stays there until fan turns off then it will start bounce around like it should.

 

[Dusty Bradford]

Can either of you watch your MAF reading while the car is doing this. I'm wondering if somehow either the wiring or the MAF itself is picking up some interference when the fan is powered on.

 

[Dayton]

I will have to look into that tomorrow. Interesting, I never thought to look at the maf numbers. Thanks for the quick response. Keep the ideas comming!

 

[Dusty Bradford]

I'm sitting at work, this keeps my mind off of it :wink:

Since I can't look at a car I'm not sure but I thought the MAF wires and the fan wires were very close or maybe in the same loom together. I've also heard of some guys who had their air filter very close to the fan having some issues like this. It's like the fan was disturbing the air going into the MAF. I can't see this happening but have heard discussion about it. Something to think about anyway.

 

[Matt McClung]

Dayton, if anybody checks the maf numbers it will have to be you. I would check myself but only being an owner of a I/Ced car for only a week, and I have had a hotair for the past 9 years, I have not had a need for a scan tool. I guess I have to tell my wife that I need something else for the car. :biggrin: Let me know what you find.


Thanks

Matt

 

[Dayton]

LOL, I will definitley check tomorrow. I also have heard about the air blowing across the air filter screwing up the maf sensor. I will check out that theory also. I've been planning on moving the air filter out of the engine bay anyway, but until I get a new system I was thinking of putting a towel or rag over the front part of the air filter where the air from the fan could possibly be blowing across it, obviously I won't drive it like that the problem we are having is at idle anyway. I bypassed the resistor on the fan so it's always running at high speed so maybe this could be the problem. I will keep you posted.

 

[Quick6'n'-K.C.]

Guy here in town is having the same problem. I havent had the chance to look at it but same issue.

Get the car to where the fan comes on and is running bad, unplug the fan at that moment..This will let you know if the fan motor itself is the issue drawing too many amps.

If the problem exists, unplug the fan relays on the drivers side, if it still is the issue, check the diodes at the starter wiring that feed power to the relays.

If you unplug the fan and the issue goes away, its the fan, wiring to the fan ect.
Just a good point to start from.

BW

 

[pacecarta]

betting dimes to donuts if you check your fuel pressure while all this is going on you will find it drops off sharply as the voltage drops and the motor stumbles and maf drops

bottom line your alternator is not correcting fast enough for the demand and fueling is dropping big time , this is why most chips turn fans off at WOT

hook a fuel gauge to it and watch

 

[Matt McClung]

That is a good point with the fuel pressure, I had my 84 hotwired but I do not have the 86 hotwired yet. I will be getting whats left of my 84 back to my new polebarn within a couple of weeks. Even thought it burned the drivetrain and engine compartment went untouched. Even the wheels and tires are ok. Anyway, I will get the hotwire for the fuel pump off and try that too.

Thanks

Matt

 

[TurboDave]

It's been pretty well documented that in many cases, the fan air blowing across or near the filter can disrupt air flow and cause enough turbulance to generate funky maf readings. Causing strange fuel delivery issues.

 

[pacecarta]

yes, as dave says if your airfilter is in the airstream of the fan this will cause all kinds of erratic idling

 

[70-71-72]

Me too....

betting dimes to donuts if you check your fuel pressure while all this is going on you will find it drops off sharply as the voltage drops and the motor stumbles and maf drops

bottom line your alternator is not correcting fast enough for the demand and fueling is dropping big time , this is why most chips turn fans off at WOT

hook a fuel gauge to it and watch

I think you'd lose your dimes or donuts. That is what's happening but not for that reason.

I've got the same problem and what I've found is that when the fan kicks on the ECM readings go crazy. The miss is from the MPH readings going from nothing to over 200mph and back. It is contantly jumping around, a new MPH reading every second usually swapping sides of the ~124 MPH limit. I guess what is happening is that the ECM is cutting off fuel because it keeps breaking the governor limit.

The other thing I've tried is to unplug the fan and see what that does. In my case that makes it happen (miss; ECM go crazy) all of the time. This is exactly the opposite of what I would have expected.

I've got a few things to try that Bryan suggested above like check the diodes. I also want to check my voltage when this happens.

I have one question, though. I see that the A/C is on the same circuit as the fan. I know mine has been converted over to r134a. Any of you guys done the same? Didn't know if that could be a factor or not. It happened before I got the car. One of the few non-stock things on the car so it makes me suspicious.

I don't remember if TurboLink 2.13 has a MAF reading but I think it does and it goes crazy too so no help there....

 

[pacecarta]

I think your car is possesed
if your MPH readings are jumping at park then thats VSS related and something wrong in your wiring or VSS unit , ive never experienced vss spike with voltage drop

 

[70-71-72]

I think your car is possesed

I agree but it's like kids, you wanna kill 'em but you love them anyway

 

[VadersV6]

Fans blowing air on the air filter, throwing off MAF readings has been happening since the dawn of MAF controlled fuel injection. Do you have a translator? Sometimes the fan motor cause create a field that screws with the translator, but most people dont have it that close. But I will say that Ive noticed a BIG difference in idle quality and BLM's whenever I have the air filter too close to the air stream caused by the fan.
Also, unbolt the 2 fan relays from the drivers side inner fender, and unplug them, and tell us if the connectors and the bottom of the relays are filled with black hard goo. Youve got to get all that crap out, or you can start drawing ALOT of current to drive that fan, when the connections are poor. That could be causing major problems with the whole electrical system. It was on mine. It can cause your high and low speed fans to stop working right. My high speed was spinning the fan about half the speed that the low speed fan normally runs. Cleanning all that out fixed everything. Use ronsonol lighter fluid, an exacto knife, q-tips, rags and compressed air to get all that crap out. Make sure all the pins and sockets are CLEAN. It cleared up all kinds of issues I was having.

 

[70-71-72]

hard goo

unbolt the 2 fan relays from the drivers side inner fender, and unplug them, and tell us if the connectors and the bottom of the relays are filled with black hard goo.

I will bet that they are. I know the fan delay relay was. I replaced it from a junkyard pull but didn't clean the terminals as completely as I should have. I'll clean all three and get back with you. Thanks! :smile: I hope this is what I've been searching for.

Matt, Dayton? Do you have the same issue?

 

[Dayton]

70-71-72 ,yep same problem. I tried moving the air filter further away from the fan and that didn't help. Also watched maf numbers and they stayed steady at 5-6 the whole time the fan is running. I unplugged my relays and they are gummed up and dirty. I beleive that could be the problem, so I will clean them up real good and see if that helps. If not, possibly could be the fan it self like the others have said. I'm planning on getting a new dual fan setup anyway, so if the relay cleaning doesn't work I will just have to wait till I get the new fans.

 

[70-71-72]

70-71-72 ,yep same problem. I unplugged my relays and they are gummed up and dirty. I beleive that could be the problem, so I will clean them up real good and see if that helps.

Well, I did and it made the difference. It is running MUCH better and there is no problem when the fan comes on and I didn't clean them as well as I could still. I will go back and clean them more and I plan on cleaning all of the connectors around the car to be sure.

Such a simple thing for such a crazy problem. I hope it helps for you and I hope it is the same problem for Matt too.

:biggrin: Turbo Power :biggrin: