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View Full Version : GT2871R with Unitronics tune problems



danphines
01-20-2010, 10:20 AM
Hey guys im trying to help my brother get his car running still it has been a few months since we started the install and it still is having problems. First off the car is a 99 1.8TQM with a 2871R, unitronics tune, apr exhaust, raceteck front mount, and 415cc injectors. its 034 motorsports stage 2 kit. there was a major exhaust leak at the manifold that we got fixed and the car will start up fine but after 5 to 10 minutes it will go into limp mode for no reason at all. there are no longer any misfires but it still somehow goes into limp mode. Any help would be greatly appreciated i really wanna get this car onto the street!

adr3naline fix
01-20-2010, 10:21 AM
Is the MAF original?

Any other symptoms?

lowandslow4now
01-20-2010, 10:31 AM
You might be over boosting I think the Unitronic tune calls for 21 psi of boost. How are you regulating it? MBC, N75 or EBC.

danphines
01-20-2010, 10:42 AM
Is the MAF original?

Any other symptoms?

its the original internals from the maf but its in a metal maf housing that came with the kit.

There was a misfire in cylinder 4 but that was because there was a leak from the injector missing an o ring. the o ring was replaced and there doesnt seem to be a misfire anymore.

danphines
01-20-2010, 10:44 AM
You might be over boosting I think the Unitronic tune calls for 21 psi of boost. How are you regulating it? MBC, N75 or EBC.

Its not able to hit boost cause when it goes into boost it gets a flashing cel, also that 24 pounds of boost in my sig is for my car, the car i am trying to help fix is my brothers. Thought i should clear up that confusion.

lowandslow4now
01-20-2010, 10:49 AM
thats cool I am glad you cleared that up. I would do a Vag com scan and see whats coming up. also check for boost leaks.

danphines
01-20-2010, 10:55 AM
thats cool I am glad you cleared that up. I would do a Vag com scan and see whats coming up. also check for boost leaks.


The car is at the shop right now where they fixed the exhaust leak. it had a misfire on cylinder 4 last time but they think they fixed that they are going to call me in a few hours and see if any codes popped up. they already fixed all of the boost leaks as well.

Thanks for the ideas. + repped. keep them coming please!

Seerlah
01-20-2010, 11:02 AM
My thought is you are running lean and it is placing you in limp mode. You need to find out where and why you are running lean. And yes, an exhaust leak can make you run lean.

lowandslow4now
01-20-2010, 11:04 AM
No problem I know how these issues can get frustrating. On my Uni 440 file I am using a VR6 3" external diameter maf and I am pretty sure the inner diameter is 2.75" inch I would also look at that. You may be bringing in more air and running a little lean.

danphines
01-20-2010, 11:24 AM
well he does have a wideband sitting on the floor of his room. im debating getting the car towed back to my house since the exhaust leak was fixed and installing the wideband so i can see if it is indeed running lean.

Seerlah
01-20-2010, 11:32 AM
^That would be the best route. And by best, I mean cheap[;)]. Plus it gives you guys an opportunity to install what should have been installed with the BT setup to begine with. This is one reason an A/F ratio gauge is very important with BT installed.

If it is running lean, simply look at the common cuprits. That mainly being the MAF and vacuum leaks (this can be observed via hg/in readings). If those check out, then investigate the fuel pressure (an fuel pressure gauge will also come in handy) in accordance with the tune.

danphines
01-20-2010, 11:36 AM
just called the shop apparently its getting random misfires in cylinders 1 and 3. may have to play musical coilpacks. gonna head up there with the wideband and ill let you guys know what happens

danphines
01-20-2010, 11:38 AM
everyone has been repped for the help!

dcampana
01-20-2010, 11:44 AM
you also might want to check the n75. i had issues with mine when i swapped over. i ended up going with out the n75 and just running a Hallman MBC. have not had any issues goign into limp since.

i do recall initially i ran into issues with the ecu flash. i had to resend in... if he has an additional ecu you can put that in to see if the issues persists or if its the ecu.

Seerlah
01-20-2010, 11:46 AM
just called the shop apparently its getting random misfires in cylinders 1 and 3. may have to play musical coilpacks. gonna head up there with the wideband and ill let you guys know what happens

This sounds more like a MAF issue.

20vpower
01-20-2010, 11:58 AM
Was the maf sensor installed in the correct position (arrow facing toward turbo inlet pipe). If misfires continue after swapping coil packs, check ICM

djwimbo
01-20-2010, 03:32 PM
This sounds more like a MAF issue.

... could be a number of things

First priority, see if the misfire moves if you move the coil packs around. CHECK your plugs and plug gap. With that setup, .025" is where I would start.
Second, if you have a donor part/car, try swapping Ign Control modules(ICM).

MAF issues usually cause misfires across the board, not just on 1 & 3. Failed coil packs are typuically #2 or 3, BUT the ICM on an AEB will almost always misfire on #3. The #1 misfire can be a result of the crankshaft "twist" caused by the misfire on cyl #3.

danphines
01-20-2010, 04:21 PM
but why would the issue of a bad icm happen only after the turbo install. I never had a problem with the icm with the k03.

djwimbo
01-20-2010, 04:40 PM
but why would the issue of a bad icm happen only after the turbo install. I never had a problem with the icm with the k03.

increase in power = increase in electrical demand on the ignition system. Plus, I didn't say that it was 100% certain to be the problem, just a step in diagnosis.

It's merely an observation, and a suggestion. I used to repair Audi's for a living, there's always something that will catch someone (incl me) off guard, my suggestions thus far are from my personal experience.

danphines
01-20-2010, 04:54 PM
increase in power = increase in electrical demand on the ignition system. Plus, I didn't say that it was 100% certain to be the problem, just a step in diagnosis.

It's merely an observation, and a suggestion. I used to repair Audi's for a living, there's always something that will catch someone (incl me) off guard, my suggestions thus far are from my personal experience.


Thanks for the suggestion i am convincing my brother to get it towed back home so i can go ahead and diagnose the problem cause he still has it at the shop at the moment. i will be sure to check the icm but i will probably play musical coil packs first. + repped for you

Tifun
01-20-2010, 08:49 PM
I don't know how I feel about the .025 gapping personally. I tend to stay at .028. Have you guys pulled the plugs out and physically looked into the cylinders with a flashlight? Check to see if there is some massive build up. I ran into this issue. My gt28r had somehow loosened itself up enough to create a leak so my car actually ran super fat and bloated up the entire system. Seafoamed the intake and a real engine flush(not a seafoam flush) made a ridiculously huge difference and I lost my miss fires. Other than that the bentely has a method for testing the icm. I did it a few weeks ago. you'll take your VOM and do an ohm check on it with the key turned on. I had a buddy(99.5blackA4) shoot me over the info. It's in the book though and worth looking into as well.
-Keith

EDIT: My system got bloated up in a matter of about a week of short driving back and forth to work.

djwimbo
01-20-2010, 08:56 PM
Keith - I agree with .028", BUT it's not like running .025" would cause a misfire. It would just make jumping the gap easier.

Tifun
01-20-2010, 08:58 PM
Keith - I agree with .028", BUT it's not like running .025" would cause a misfire. It would just make jumping the gap easier.
I can agree with that. It would at least make the car have a sure fire...fire if the ignition system will allow it to do so. I now run a bosch side fire plug like a lot of the vast s4 cars do. so far they have been promising.

djwimbo
01-20-2010, 09:52 PM
word, just please, please, please, NEVER run Bosch Platinum plugs.

Tifun
01-20-2010, 10:15 PM
The side fires are an interesting plug. I've been very pleased with them so far.

danphines
01-21-2010, 06:47 AM
Well along with the install we did NKG BKR7E's gapped at .28 and I have only had misfire problems in the past with .32 gap. I myself run the Bosche FR7LDC+ plugs and love them. I was talking with my brother last night and we think that the car is leaning out because when you spool the turbo up it gets a flashing CEL and goes into limp, however he is informing me that he needs to get an EBC cause he is running to off the stock n75 which I don't think will be able to react in nearly enough time for that turbo causing it to lean out. My theories will be confirmed when the wideband gets installed. The shop is welding the bung in for us and then i think it will be towed back to our house so we can do the install of the EBC cause its a complete waste to have a shop do it for you, and then I should have an easier time tracking down the problem.

Seerlah
01-21-2010, 07:05 AM
The Unitronic tune is written to be run off the n75. It is more of a personal option if you want to add a boost controller. So, the misfires stopped? And you guys are simply being placed into limp mode?

It's the n75 that places you into limp mode. If you guys opt to bypass the n75 and run off the EBC, be sure your A/F ratio is correct or you run a very high risk of detonating the engine. If you can confirm that the MAF is not the issue, and you have no leaks, I would maybe look into tweeking the fuel adjustements if it needs be. But only do that if you can not find any leaks, MAF is confirmed 100% (you may want to source a VR6 MAF) and all your other issues are gone. But you are being placed into limp mode due to running lean. That's what it is there for. To protect your engine from detonation.

I would actually put my trust in the mapping being on point with the Unitronic tune and lok for a different answer. But the upping of the fuel pressure is always an option (recommended you actually find why you are running lean, though). Then you may have to worry about the fuel pump, unless he already upgraded that.

Sales@RAI
01-21-2010, 07:06 AM
are you running off the N75? Sorry if I missed it

danphines
01-21-2010, 10:03 AM
yeah its running off the stock n75 still and i have a vr6 maf sitting in my garage i want to try out as soon as i get the car back. from what i was told by the shop, it will go into limp mode when the turbo is spooled up, and if the turbo is not spooled up it will simply have misfires during idle. i want to get the car back in my driveway so i can know exactly whats going on and not take someones word for it.

dougyfresh
01-21-2010, 10:27 AM
word, just please, please, please, NEVER run Bosch Platinum plugs.

Care to elaborate on that please?

Fink_tha_Audi
01-21-2010, 03:16 PM
I got back my tune from RAI 440cc file on Eliminator Gt2871r recently, plugged the ecu in, installed the FPR, and injectors, and it started right up, a little rough. The ECU needed to "learn" the car etc. Try changing your fuel filter. I changed mine about month ago and man was it dirty.

By the way. Thanks you guys at RAI , Ray, Clint and Zack, awesome guys. Ill make a trip to RAI once it gets warmer to see if we can squeeze some more power out of her and fine tune her.

GetBoosted84
01-22-2010, 07:37 PM
Do you have access to a wideband? If you do, log the car and post it up here. If not, pull the plugs and see what color they are. That will tell you if you are running to rich or too lean. After that I would log the MAF then if the numbers are low, clean it. You could have just fouled the plugs due to another issue (MAF, vac. leaks, etc.) which is now causing misfires. I've had that happen to me anyway.

Post up some logs of the wideband.

Sales@RAI
01-23-2010, 09:11 AM
I got back my tune from RAI 440cc file on Eliminator Gt2871r recently, plugged the ecu in, installed the FPR, and injectors, and it started right up, a little rough. The ECU needed to "learn" the car etc. Try changing your fuel filter. I changed mine about month ago and man was it dirty.

By the way. Thanks you guys at RAI , Ray, Clint and Zack, awesome guys. Ill make a trip to RAI once it gets warmer to see if we can squeeze some more power out of her and fine tune her.

Thanks man, I'm glad you made the decision to come down, I know it was a drive but it's always a good time at the shop [up]

djwimbo
01-23-2010, 10:05 AM
I was talking with my brother last night and we think that the car is leaning out because when you spool the turbo up it gets a flashing CEL and goes into limp, however he is informing me that he needs to get an EBC cause he is running to off the stock n75 which I don't think will be able to react in nearly enough time for that turbo causing it to lean out.

Quite the contrary. The bigger the turbo, the slower the spool. A K03/K03s/K04 goes from vacuum to boost almost instantaneously in comparison. The N75 can control the K0x turbos, it can control the 28xx.

The problem with the N75 is that you can't just tweak it like a MBC/EBC, and using it to control 25+psi is difficult without tuning the wastegate.


Care to elaborate on that please?

I can just about name all the customers that I've had (Euro or Jap imports) that I've pulled out Bosch Platinum ("+2" or "+4") plugs and replaced them with an NGK or Bosch Iridiums, because the look on their faces when I tell them it's a $30 fix, not $300.

Personally, I've pulled them (the two or four tip) out of a number of A4/S4/A6's with anywhere from 500mi-15K miles on them, and there was a noticeable difference in performance and even MPG.

This of course is my experience ... there's only one thing that I've found that actually LIKES Bosch Plat +4's. Isuzu's.

$teady$upreme
02-01-2011, 09:58 PM
Wonder if you can post up the instructions on how to test the ICM?


I don't know how I feel about the .025 gapping personally. I tend to stay at .028. Have you guys pulled the plugs out and physically looked into the cylinders with a flashlight? Check to see if there is some massive build up. I ran into this issue. My gt28r had somehow loosened itself up enough to create a leak so my car actually ran super fat and bloated up the entire system. Seafoamed the intake and a real engine flush(not a seafoam flush) made a ridiculously huge difference and I lost my miss fires. Other than that the bentely has a method for testing the icm. I did it a few weeks ago. you'll take your VOM and do an ohm check on it with the key turned on. I had a buddy(99.5blackA4) shoot me over the info. It's in the book though and worth looking into as well.
-Keith

EDIT: My system got bloated up in a matter of about a week of short driving back and forth to work.