Multiple idle and drivability problems...

[5150DSM]

This is gonna be a book so please bear with me.

Car:92' Talon TSi
Mods: Stock turbo, stock bottom end, mildly ported head. 2 1/2" intake, 3" turbo-back exhaust, MBC @ 15psi, heavily ported exhaust mani, ported EVOIII O2, 550's, Walbro 255, SX FPR, SAFC-II, 28 X 9 X 3" FMIC W/2 1/2" aluminum pipes.

SAFC settings: Low: -10% across High: -15% across (same settings from before rebuild)

Recently, I lost the BS belt, which took out the timing belt, which took out all 8 exhaust valves. I purchased a used head and rebuilt it with stock components, including 3G lifters and a mild port job. (unshrouded the valves a bit and polished the combustion chambers) I installed the new head with a new Fel-Pro head gasket and did timing and BS shaft belts(oem belts). Initially, I screwed up the cam timing and had the intake advanced a tooth and the exhaust retarded a tooth, the car idled like ass but it pulled like mad up top, even over 7K rpm it was still pulling. I decided to redo the job correctly and with a little effort pulled it off. As soon as I got everything back together correctly the car started idle surging like crazy and wouldn't go above 4500 rpm without bogging and popping.

I started by shooting the base timing and bringing it back to 5* BTDC, it had been at 15* BTDC. I then proceeded to set the base idle via the VFAQ and Chilton guide but the idle wouldn't hold steady , it would either surge from 1500-1800 rpm or idle at 450-500 rpm with about 5hg of vacuum. I went through the idle surge VFAQ piece by piece starting with the BISS screw and o-ring, which were in good shape. The ISC was next, I tested resistance between the pins, which showed 40.3 ohms across the board. Next, I moved on to the EGR valve , which was caked with carbon and resistant to air being pumped through it, I suspected the plunger was stuck so I soaked the EGRV in carb cleaner and got everything clean and moving freely again. I put everything back together, re-shot the timing and again tried to set the base idle to no avail. Now, the car just idles around 450-500 rpm and belches black smoke(definately unburnt fuel) until the BISS is adjusted about 3/4 of the way out and then it starts surging again, sometimes the "idle" will hold steady arouns 2500 rpm but the car is undrivable at that point because it completely bogs out above 3K. Even with the low idle the car still bucks and bogs at anything above 3K and just belches clouds of black smoke. Worst of all, I have been thorugh every vacuum line and induction/exhaust point on the car and I can't find any leaks, except for a little bit of exaust gas spilling out of the hole where the wastegaste arm attaches to the manifold.

I finished the 2nd timing belt job a week ago and have not been able to figure anything out in that time so any ideas are welcome at this point, I don't care how off the wall. If you have anything constructive to offer, please do, right now I'm so far past the WTF point that I might not come back. Thanks in advance for any help or ideas you guys can offer.
Aloha

 

[andymoraitis]

You've really checked out a ton of possible causes, but the one thing I didn't see mentioned was the FIAV (fast idle air valve). I'd check that next before completely ripping your hair out since a faulty one can give you fits when it comes to setting timing and holding a steady idle.

Le us know what happens.

Andy

 

[5150DSM]

Yeah, the FIAV... Is there any other way of testing it, besides just blocking it off? Also, the 40.3 ohms I got from the ISC is slightly out of spec but being that it was consistent across all the pins, I disregarded it. Was that a mistake? I'm going to try and pressurize the system again tomorrow and re-check for leaks, even though I didn't find one before, my instincts still say boost leak. Thanks for the idea, keep em' coming.

 

[5150DSM]

Ok, I tried to pressurize the system today and found a torn hose at the wastegate so I replaced that and moved on. I blocked off the turbo on the intake side and looped the MBC lines but I couldn't get any pressure in the system. I was trying to push air throught BOV line and then through the wastegate line but the system just wouldn't pressurize, my boost gauge didn't move during the entire procedure. Was I doing something wrong? Are my leaks just so major that the system won't pressurize? I'm confused.

After the failed leak test, I re-shot the base timing and found it at TDC... WTF Anyways, I reset the base timing and tried again to set the idle via the VFAQ. Things worked out a little better but the idle is still unstable and low with low vacuum or surging. I then moved on to the fuel... After screwing around with the SAFC for a while I settled on some ultra-lean settings, because that's the only way I can get the car over 3K rpm. Now my low settings are at -20 to -25 and the highs are at -30 across. The car runs and will accelerate to redline but the boost builds real slow and then hits all at once about 4K.

Using speed as a gauge... Previously the car would go to about 50-52mph at the top of second now it hits 60-65 at 6700 rpm in second gear, only a little knock from the super-advanced timing.

I'm really at a loss here, I've tried everything I know to do and nothing is working.

 

[5150DSM]

I posted this in the general problem diagnosis forum because my problems are all over the map. If the mods feel that this needs to be in a more specific forum please feel free to move it at your discretion.

No real progress has been made but I did notice that my Karman reading at idle is astronomical even with the idle fluctuating between 550-800rpm. When I say astronomical I'm talking about a 300% increase over the previous idle readings. Previously, at idle my Karman frequency showed 35-40Hz on the SAFC display and 0 counts on the pocketlogger. Now, my SAFC shows 105-125Hz and the pocketlogger fluctuates between 1-2 counts.

I'm going to add a valve to my pressure tester tomorrow and try again to pressurize the system and look for leaks. Also, I plan to pull out the ECU and inspect it for leaking caps, damaged connections, burns, etc... If anybody has any other ideas, just add them to the list, I'll check anything at this point.
Aloha

 

[andymoraitis]

I really wish I had better answers for you, but you're doing ALL the right things. To answer your question about the FIAV, I'm not sure if it can be tested in any other manner than blocking it off. You may want to try one of the wisemen like Steve or GTM and see what they say to be sure. I've also Pm'ed Oldman to jump in here since he's great at tracking down nagging issues. The FIAV could certainly be the cause of the idle surge and I've seen it be the culprit more times than not.

I also have to agree with the boost leak idea. A 4K spool on a 14B is pretty late and that reeks of boost leak. I think once you address that and look at the ECU caps, that should tell you where the problems lie. Even if I have no new ideas, know that a fellow DSM'er is keeping his fingers crossed for you.

Keep us posted and stick with it!

Andy

P.S. Looking at your Karman information, I'm almost tempted to point to the MAS next or even the knock sensor.

 

[oldman]

Let's take a couple of steps back and start with the basics.

1. Complete that leak test, you're not finished until system is able to hold 20psi. Open the oil cap and listen for leaks into the crank case.

2. Have you done a compression test yet since the re-built? If not, do a dry and wet test.

Post back results and we will take it from there.

 

[5150DSM]

Thanks for the replies.
I am going to do the leak test right now so I'll have results later on today. I did a compression test after the first timing belt install and got 165-170-170-165(dry) I haven't re-tested since then but I will add that to the list.
Thanks again.
Aloha

 

[urinmysights]

About your ISC reading 40.3 ohms consistent across all the pins. Here is my story, my original ISC died on me, one of the pins didnt read any ohms anymore and my idle was erratic but it didnt surge. So I'd decided to kill two things with one stone and purchase the bigger 60mm throttle boby with an ICS that can with it. It read 40.7 across the pins. I'd rebuilt the throttle body and used the 40.7 ISC it came with. Once installed I had idle surge between 1500 to 2000 rpm from what I can remember. I'd switch bewteen the two ISC many times and still could get my car to idle right. I didn't have any problems about acceleration above 3k rpm. I'd tried everything suggested on vfaq and this forum about idle surge except for getting a new ISC. So I finally replace the ISC with a rebuilt one from ebay for $100 bucks and magical my idle surge is gone and no more idle problems. The rebuilt ISC reading was 29.9 ohms and worked prefectly for my car. When I swap it with the 40.7 ohms ISC just to see what would happen my car idle surge even when I tinker with the biss to adjust it. My suggestion is to borrow someone ISC that you know works and has the ohms in the proper range and test it on your car to see if it work. If it works, problem solved....goodluck.

 

[5150DSM]

Andy gets a cookie.
ECU was good. Compression was good. The system still wouldn't pressurize so I pulled the throttle body and cracked it open. I don't know what a functioning FIAV looks like but mine was definately non-functional. There was just a couple of fibers smeared around the inside of the TB, it looks like the wax pellet disentegrated. I blocked off the FIAV with a Pepsi can cut into a block-off "plate" and things got much better. The car idles with decent vacuum and I'm able to run hard above 3K. It's still a little erratic but definately better. Unfortunately, it was way past dark when I finished the FIAV so I didn't get to run another leak test but I'll do that today and hopefully all will be good.

urinamysights: It's a good point about the ISC, I would have liked to see the readings actually fall within spec but I hoped consistency would make a difference. However, I think I will take your advice and swap out for a good ISC and see if that gets things perfect.

Thanks for the help, it looks like we got it.

 

[andymoraitis]

Thanks for posting your results and I'm really glad that all of us could help. I just love it when something gets fixed and there's a happier tuner out there. I think swapping the ISC next would definitely bring you where you want to be. Also let us know how that boost leak test comes out.

Now, excuse me while I Snoopy dance on your behalf.

Andy

 

[oldman]

Andy is the man. I think we can all retired now.

Make sure you finish the leak test though. Disable the mbc during pressure test, most of them leaks. If you still can't pressurize the system, post back, there must be something wrong and you must find it. Also I didn't read that you re-routed the coolant line after you block off the fiav, make sure you do so.

 

[andymoraitis]

Actually, I'm just a mini-man. What's sad is that I can often come up with the fixes, but if I had to do them myself, I'd be lost.

And back down to earth I come!

Andy

 

[5150DSM]

Been working the last few days so I just got to redo the leak test today.
First off, I found that the wastegate flapper was stuck open from the extension on the rod being too far out. That was an easy fix that eliminated some of the vacuum issues but the car still bucks on crossover and is laggy until about 10psi when it comes alive. Next was the leak test, which I expected better results from; at this point, the intake system still won't pressurize at all. That's right, 0 psi, even after ten minutes of pumping air through the intake, I got 0 psi. I can hear air rushing through the turbo and what sounds like the exhaust manifold but I'm sure the wastegate flapper is securely closed so I don't know why the air seems to rush out or where it's leaking from. Not being able to generate any pressure in the system makes it kind of hard to listen for air leaks so I'm wondering if I'm doing something wrong? I have a coupler with a PVC cap pressed and clamped in one end, the cap has a valve stem(which is airtight) and the other side clamps onto the turbo inlet. I pressurize the compressor and start pumping in air at about 20-25psi but the air just rushes straight out. Am I missing something?
The car is running much better but overall it's much like venting the BOV without a MAFT, it's too rich, it's boggy, it wants to stall on decel and right now the SAFC settings are so lean that I get like 30* of advance at WOT.

Ideas anyone, as to where the leak is?

 

[oldman]

1. Disable your mbc, bcs...etc. during pressure test.

2. If you're using a bike pump , borrow an air compressor or the likes.

3. Open the oil cap and feel/listen for leaks into the crank case. If air is leaking into the crank case then read through this thread. http://www.dsmtuners.com/forums/showthread.php?t=174682&page=1&pp=25

Post back results.

 

[5150DSM]

Oldman:
BCS is long gone, MBC was disabled, I am using a compressor and the air never makes it into the induction system, I think it's just rushing out of the exhaust.
Right now my SAFC settings are -25-35%(Low) and -30-35%(High) which is way too lean for 550's, it's the only way the car will run but the settings are wrong for my set-up. Thanks for the article, extra knowledge is always welcome.
Aloha

 

[oldman]

If you're sure the air is leaking right out of the exhaust then I can only think of three things.

1. Through the turbo seal.

2. EGR valve.

3. Your intake and exhaust valve are both open, bring #1 to TDC and repeat test see if it helps.

You must find out where the air is going to, there's no question you have a huge leak and probably bunch of little ones that's waiting to be discovered when you're able to pressurize the system better. I went back and read your original post again and I think your idle surge and 5HG can very well be connected to the fact that you're unable to pressurize the system. My suggestion is to focus on completing the leak test. Good luck.

 

[5150DSM]

So I am thinking to myself... if my leak is so big that I get zero pressure in the system, maybe I can find it if I rev the engine from under the hood and listen for air rushing out. Not exactly scientific but I was getting desperate. Revved the motor up high and sure as shit I get a windstorm in my face, look down and I can see my J-pipe flexing as I rev the motor. Seems the little tin heatshield I wrapped around the coupler didn't do it's job and the coupler melted. I went and got a silicone "ultra-temp" coupler, clamped everything down and what do you know, I have a new car.

System pressurizes to 25psi and held for over 45 seconds, idle is steady and pulling 20Hg of vacuum, spool up is quick(20 psi by 3500 rpm) and she just pulls and pulls all the way past 7K.(Head porting seems to have an effect)

Thank you to everyone who hung in there and kept throwing ideas, especially "oldman" and Andy. Thanks to you guys my DSM lives, runs better than it ever has and should propel me to an "official" 12 second pass this weekend. Learn from me, don't be an asshat and "ass"ume anything without double and triple checking it.
Aloha

 

[oldman]

You're welcome, glad it worked out.

And back down to earth I come!

I think Andy is still recovering from the fall.