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Fan = Bad Idle?

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JSong

Probationary Member
10
0
Nov 1, 2008
Rock Hill, South_Carolina
Background:

I own a 95 TSi AWD. I'm new to DSMs and this would be my first one. Mods are on my profile. The day I bought it, it had an overheating problem because the radiator fan wouldn't turn on. Took it to my school's shop and the teacher came up with an easy solution. To hook the radiator fan to the AC fan wire. So I would have to turn the AC on and the radiator fan would come on (No AC in the car).

Problem:

After a clutch, pressure plate, and flywheel installation, I ended up with a bad idling problem. After warm up RPMs fluctuated between 300-900 and most of the time stalling out. So far I've replaced the ISC, throttle body, and BISS O-ring. I can hear air being sucked in every time RPMs get too low, I think its the ISC? So that would eliminate a bad ISC, correct? The coils were all good too.

My question would be what are the most likely possibilities causing my low idle? When I turn the radiator fan on, via the AC button, the idle seems to drop. I always have the radiator fan on after warm up. Could changing from a stock flywheel to an ACT flywheel cause this? Or a combination of both? I don't have a logger so I can't take a look at anything. Also, does the Valvoline complete fuel system cleaner work? I added it to a tank of gas before fill up.

I'm getting ready to take a look at the ECU. Will report back.

-Thanks for any info
 
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When you turn the power on to your AC motor or in your case your fan the ISC should automatically raise your idle it should not lower. I would suggest connecting a multimeter to your ISC and making sure the readings are correct.
 
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stevo911 said:
When you turn the power on to your AC motor or in your case your fan the ISC should automatically raise your idle it should not lower. I would suggest connecting a multimeter to your ISC and making sure the readings are correct.
Click to expand...

I think my ISC is only raising my idle when it gets below 500. I checked all the ISC coils and they were good.
 
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Doesnt that ECU already have a fix to keep the random misfire off?

Bottom right hand side of picture 86 around the black chips is that burnt or shadow?

Also alot of hacking goin on with that harness. Mayb take the tape off and make sure all wires are still connected?
 
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stevo911 said:
Doesnt that ECU already have a fix to keep the random misfire off?

Bottom right hand side of picture 86 around the black chips is that burnt or shadow?

Also alot of hacking goin on with that harness. Mayb take the tape off and make sure all wires are still connected?
Click to expand...

I don't know about the random misfire. You mean the tan colored spot next to the blue things? I was going to check all the wires but I was scared of getting electrocuted... So far I've gotten shocked by the battery, alternator, and someone elses radio LOL I'll just disconnect the battery and take a look at each wire.
 
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Yep thats what I was talkin about. Shes pretty fried. Check your wiring before you put it back in the way them wires are hanging chances are it was shorted.
 
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snowborder714 said:
I sent an e-mail to Tom Dorris so hopefully he'll be able to help out here.

Whatever it is, it doesn't look good.
Click to expand...

Who's Tom? Does it look repairable?

stevo911 said:
Yep thats what I was talkin about. Shes pretty fried. Check your wiring before you put it back in the way them wires are hanging chances are it was shorted.
Click to expand...

I would of never saw that. You got a good eye :thumb:

Heres a view of the back of it.
http://i688.photobucket.com/albums/vv244/j_song/DSC00994.jpg
 
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snowborder714 said:
Tom is one of the main guys at ECMtuning (makers of DSMlink). He repairs ECU's all the time so he should have a good idea of what is up with it and what needs to be done.
Click to expand...

Alright cool, thanks for your help.
 
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Thanks for the comment. Nothing really to it after blowing like 3 myself start to get a feel for it ;)
 
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The "black thing" in that one picture you labeled is a driver SIP. I can't tell you off the top of my head what that particular one drives, but I can tell you it needs to be repaired. It's most certainly blown. You can get a picture of a blow ISC driver here:

ISC driver repair

Thomas Dorris
ECMTuning, Inc.
 
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I've had a similar issue while using the K&N FIPK...

When I first put my car together I ran an upgraded SMIC with original route IC piping using the K&N FIPK, also running DSMLink.

When the fan kicked on during idle the air would "bounce" off the IC piping and hit the filter at some weird angle disrupting the flow across the honeycombs resulting in a "hunting" idle. Only "hunted" when the fan was on during idle...no other time did it do this. I searched the DSMLink boards and found several people with the same issue (only while using the K&N FIPK) and the fix was either to re-route the IC piping or just switch to a cone type filter. The only thing I did was switch to a different filter and the issue was fixed.

In stock form I only used a cone filter, it was during the first build that I switched to the K&N FIPK and had the issue. Dumped the K&N FIPK and haven't had an issue since.
 
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twdorris said:
The "black thing" in that one picture you labeled is a driver SIP. I can't tell you off the top of my head what that particular one drives, but I can tell you it needs to be repaired. It's most certainly blown. You can get a picture of a blow ISC driver here:

ISC driver repair

Thomas Dorris
ECMTuning, Inc.
Click to expand...

Yeah its blown. Is it repairable? And if it is, do you guys do ECU repairs? Rough estimate of the cost?
 
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FORMONTOYA said:
When the fan kicked on during idle the air would "bounce" off the IC piping and hit the filter at some weird angle disrupting the flow across the honeycombs resulting in a "hunting" idle.
Click to expand...
Yup, that definitely happens. The old-school HKS mushroom filters were the WORST for this.

We've also seen a few cases where just raising the hood will cause idle problems. Had a customer in the shop one day with this problem. He swore it idled fine before we installed DSMLink, so we kept poking around trying to figure it out and then realized we had been doing all his post-DSMLink testing with the hood raised. Closed that and his idle returned to perfectly normal like it was when he drove in (with the hood closed, mind you). :p

Thomas Dorris
ECMTuning, Inc.
 
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Hey Tom, I got a question for you: a while back (over 2 years ago) my ISC motor went out, and my idle began surging and getting ragged. I talked to my dad's mechanic (at my father's insistance) and he said "no big deal, it won't hurt the car's driving ability, just the idle." So I ran for all this time with a dying ISC. I finally replaced it with one from DSMISC (like 2 months ago), and it ran great for all of two days....then the CEL came on. Guess what? The code comes back as a bad ISC. The guys from DSMISC claim if you run with a bad ISC for too long, it will fry out a portion of the ECU board. Is this true? If so, can it (the ECU) be repaired, or does it have to be replaced? In retrospect, I should've seen this coming, when the original ISC started acting up the car (at a stop sign or red light) would start idling high...like to 2000-2500 RPM's. Then, after driving a bit, I'd hit another light, and it would be fine. I didn't really think anything of it at the time.

Ah well, shoulda woulda coulda....thanks for taking the time to read this.
 
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sarge281 said:
The guys from DSMISC claim if you run with a bad ISC for too long, it will fry out a portion of the ECU board. Is this true?
Click to expand...
Yeah, certainly. But I can't see how replacing that bad ISC with a good one would throw a code due to prior damage on the ECU board.

Thomas Dorris
 
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wow I'm Having the same problem right after I did a auto MT swap. Almost the same setup as you ACT2100 clutch and p-plate and ACT flywheel. And I have done almost the same things as you to try and get it running right. I replaced the ISC, throttle body gasket, Throttle body shaft seals and the TPS. I was going to try and do a block off plate on the Fiav but I didn't think about the ECU.

Are you having any boost problems? My car feels like a dog till 2500RPM then it hits full boost and runs great.

(have not done a boost leak but its next on the list of things before I waste more money.)
 
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BJ350hp said:
wow I'm Having the same problem right after I did a auto MT swap. Almost the same setup as you ACT2100 clutch and p-plate and ACT flywheel. And I have done almost the same things as you to try and get it running right. I replaced the ISC, throttle body gasket, Throttle body shaft seals and the TPS. I was going to try and do a block off plate on the Fiav but I didn't think about the ECU.

Are you having any boost problems? My car feels like a dog till 2500RPM then it hits full boost and runs great.

(have not done a boost leak but its next on the list of things before I waste more money.)
Click to expand...

Yeah, it runs great when boosting. I did a leak test and found 1 leak at my TB. Its the vacuum nipples that are lined up 3 in a row. I think the whole problem is my ECU. What I plan on doing is repair the ECU and leave the ISC unplugged so basically I'll just use my BISS screw to set my idle while the fan is on.
 
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If you are going to leave it unplugged I would suggest getting a block off plate for FIAV and ISC and completely eliminating whole lower TB.
 
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twdorris

Would running a block off plate on the FIAV and not fixing the bad drives on the ECU give me more problems or will the ECU still be okay to run? (Because there is no IAC for the ECU to play with at that point)

Or is this something that needs to be fixed so It does not do more damage to the ECU?
 
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The damage is already done at this point its not only the ISC driver that is shot whatever that leaked onto is now also gone.
 
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