Tragic DSM Help Please..

[Seraphix]

So my dsm has become more of a lifelong problem then a mode of transportation...

From a general diagnostics point of view, my car is stock. Free mods done include hacked air can, removed silencer, cosmetic- relocated battery to rear (0 gauge stinger 12.9v off, 14v engine on) current is not a problem.

I have an idle problem. a week ago it used to run fine until it hit normal temp, the fan kicks on and it drops from 800rpm sputters and backfires and hangs around 500.. dies occasionally at stops. I have tried 4 different ISC, new CAS, Replaced the injectors with known good from a buddy, tried multiple ecu's.

yesterday i popped the throttle, replaced the shaft seals, and the FIAV as i noticed coolant residue inside the intake side of the throttle, thought this would resolve my problem, to no avail, it still lobes. I leak tested a week back and found the shaft seals leaking. I have yet to retest, however everything is sealed with silicon, new gaskets, etc (i'm getting very good at making leak free connections)

Somewhere in the middle of this i developed a gnarley misfire. I found a loose connector on the #4 injector wire , resoldered a new injector connector (thx slowboyracing) Still missfires.
Found a bad plug wire on another cylinder (makes me wonder how it was running-the connector had jammed up inside the wireplug and wasn't even making contact with the plug) . Replaced that. Still misfires. Now i have great spark at all 4 plugs, new injectors and still am misfiring like crazy, almost like i'm missing a cylinder. I've examined all plugs, none fouled, none blackened, none whitened.

I have 12+v at all injector wires with key to on. All injectors test 3ohms.

The car will idle somewhat, Put it in gear, and it's pretty apparent i'm missing a cylinder. Around 3-4000rpm the tach goes crazy and starts jumping around. Ran fine a week ago, with the exception of the idle lobing problem.

I'm aware the lobing problem is probably just a silly air leak i have yet to find, but the sudden misfiring is keeping me from getting to that. Next plan of action is to test the harness and grab a noid light, then it's back to plugging the turbo pipe and testing for leaks again.

Just curious if anyone else has as any insight, or personal experience. Am i going about this completely wrong?
I have yet to add any mods until i can get stock to run right. Car is in pristine condition, no body rust, 19in lcd custom fiberglass in dash(not installed yet, no wiring done). =P

Tell me i'm going about this the right way, throw out some ideas, i've read hundreds of threads on idle problems, leaks, BISS resetting, ISC check/test, TPS adjustment, etc, i feel like i've tried em all.

Frustrated and tired....

 

[doggo]

Missing on one cylinder could be an injector problem. Did you check for proper injector cycling with a stethescope? It may be injector, bad wire or coil if the injector isn't cycling. Even if injector ohms read ok, it could be something else like a bad coil connection

 

[Rex2342]

Check the caps in the ECU. My car was running perfect one day and the next day it just sputtered and died on my way to work. Turned out to be the ECU caps. Also check to see if the coil pack is working properly. Any service manual will tell you how to do this. Good luck.

 

[sadsm]

You state that you have the free mod "hacked air can" and I assuming that you are referring to the honey combs in the mass. When you started this thread, how long had you hacked the air can. This could be your problem. Try reinstalling the honey combs to see if that is the problem.

 

[toybreaker]

It's a proccess of elimination, and your methodology is sound. It can get confusing when/if there's multiple issues at once.

It's probably time to see if we've got a single cylinder issue, or a generical issue affecting all four.

Doggo's suggestion to listen to the injectors in action is an excellent piece of advice. . They can check good at rest, and have issues dynamically.

I'd say pulling and inspecting the plugs will tell the tale, as far as mix and spark quality.

Look very carefully at the tip and ceramic with a 10x magnifying glass for where/how the spark is occuring.Look at the ground strap and the ceter electrode for the tell tale grey spots where the spark is actually occuring. Are they even from cylinder to cylinder? Is there any tracking down onto the ceramic insulator?

Most ignition problems show up under idle and high rpm conditions. I've had some plug wire into the coil issues show up like you describe. Make sure the wire connector goes all the way into the coil, and the coil terminal is clean and corrosion free. I strongly recommend using silicone di-electric grease on the boots at both ends of the plug wires. It'll make things a little happier by allowing the boots to slide all the way on to the plugs/coils, and will make the wire way easier to remove in the future. This prevents having to put force on the wire to remove it, potentially damaging the wire...the next time you have to service the system...(and there will be a next time )

Checking for spark with the plugs outside the motor won't necessarily reveal a weak spark, as there's no load on the system. Under compression, it's a whole different ball game. The temperature and pressure of compression increase the firing voltage requirements significantly, and what looks good on the valve cover may not work inside the chamber.

An amazing amount of problems are actually created by yoking on the wires to get them off. Most of the plug wires for these cars use carbon covered stringish conductors, and any force will make a kerbillion teeny tiny tears in the conductor, rendering them less then servicable due to the increased resistance as the spark current has to cross all those little tears in the conductor.

The o.e. wires are way better than anything else for most people in that regard, as they'll take a bit o' abuse. The spiral wound wires are what I use, but understand, you get what you pay for in the plug wire department, and they're somewhat more spendy than the ngk or sumitomo oe style. With the proper care, plug wires can live thru quite a few plug changes. Without care, they can be killterfied in one careless moment. As you remove the wires, try not to bend them excessively. I usually leave them bundled together, and just rest them off to the side. They take a "set" in service, and bending them unnaturally can focus all the flex at once spot, stretching/tearing the conductor.

If you have any doubt as to their health, I'd replace them now, along with the plugs. Please use ngk plugs.

It's a simple, and often overlooked first step in troubleshooting misfires.

The chain store wires should be avoided, lifetime warranty and all, imho.

While the plugs are out, a compression and leakdown would be helpfull. We may have a valve sealing issue or some such.

I've been having an intermitent cas issue that has somewhat similiar symptoms. After a comprehensive diagnostic of my 92 tsi's secondary system, I've found a problem with the connectors at the cas. Using a little radio shack cleaner/contact enhancer has alleviated the problem for now....(errrr...was that the kiss of death?...)

In your case, the tach hopping suggests looking hard at the cas/coil/transistor connections. A little cleaning with the radio shack cleaner/contact enhancer may do the trick, if there's corossion/intermitent contact occuring on the pins/connectors. Performing the resistance and power checks as suggested in the factory service manual is a very good use of your time as well.

Occuring while warm only suggests a potential coil problem.

Again, it's a proccess of elimination. Try not to skip any steps at the beginning. Deal with the most likely causes first.

EDIT: as Sadsm has noticed, a hacked air can can degrade the idle significantly as well. Good call!!!
Good luck, and let us know what you find.

 

[Seraphix]

Thx for the advice.. here's an update. With the new ignitor it now seems to have resolved the 2 cylinder misfire, Now It starts up fine, idles high and strong but the closer and closer it comes to operating temp, the more it starts to misfire. First it's just one little pop/sputter now and then but as the FIAV drops closed it picks up to about once a second. As soon as the fan kicks on, boom.. it eats it for the first time. My engine hits the floor and never comes back. 300-500rpm and maybe firing 2/4 at most, as random as can be. The iac seems to be functioning better also, i rebuilt it with a few other known good coils i had around. When i start the car, idles real high, 2500+ and in the first 5-10 seconds it slowly and steadily drops to 1600ish. Real nice like the iac is spinnin out. Today i'm going to check wiring/ connections/ temp sensors, cas, injector wires. etc, as well as a leak and compression if i have time. I use ngk plugs stock temp. I can deal with a pop/sputter here and there, but this is way past that. I'll post my results as well as some pictures of the plugs tonight. Thanks again!

 

[Seraphix]

No Ecu codes. Compression hot 1-4 = 155,145,175,174
My misfire is still happeneing on the 2/3 cylinders. I can pull either plug wire and the eraticness stops. Checking injectors tick/coolant sensors next. Only happens once it warmed up.
Plugs appear normal. not too dark/ slight whiteish on back of ground arm. even across all 4. Lighter grey ring around edge of electrode as well on ground arm directly above. Appears to be firing normally. No burns/tears etc on the plug wires. Plug wells clean and dry.

 

[Seraphix]

So I finally figured it out...Started checking the harness... 2nd thing i checked.
No voltage on closed throttle switch wire. tapped in at ecu, 1.4v tested the wire...no continuity ... must be a break somewhere. Grounded out the tap.. the rpms dropped to 900 and sat still.. Reran the wire thru the firewall and hooked it back up right.. runs like a dream. Tiny tiny lobe occasionally..I've counted a total of 3 misfires, since. waaay better than twice a second. I am going to check the passages thru the firewall to make sure the harness isn't rubbing thru, i imagine i just pulled it too hard when i was tussling with the ecu. That specific wire seems to be one of the shortest straight thru wires.. not much room to pull/flex at all in the harness. It still idles a little high, I have the biss all the way in... so i must be leakin bad somewhere. throttle plate might be pushed open a little by the closed throttle switch.. but it runs like a dream none the less...