mk4 jetta down on power.pls help

Models manufactured from 1999 to 2004

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mk4 jetta down on power.pls help

Postby olson1990 on May Tue 31, 2016 12:41 am

Ok so I have a 2002 jetta with Big valve ported head, 276, cam, race header, ram intake, and c2 motorsports tune. I had my car dynoed last week because I fealt she's not pulling like she should. And as suspected it dynoed at 59hp and 75 trg. my afr wot is 12.4and tapers to 11.9 At 6000. Now this lack of power started when I had the head ported and did the tune. Before head work I was running big valves and dual springs with the 276 cam and I could hit 120mpg120mph no problem. Then few months ago I had head ported and tuned it threw c2 motorsports. my compression is good. Fuel pressure is good. I think it may be either the tune. Or a bad 02 sensor. idle is rough cold. And little bit of stutter/ hesitation between 2-3k rpm. Other than that she sounds good. Idles lean. I'm not running any check engine lights. I'm hoping someone in the billings area can help me narrow this thing down. Because I should be sitting about 140hp not 59. I'm good with the mechanical aspect just lacking on the electrical side. So if someone could help me check the maf sensor and o2 sensor. ide appreciate it. Also any other advice would be greatly appreciated. Also is there any one in the state of Montana or billings area capable of tuning. Personally I don't like take mine to vw because they tell me my whole car is wrong lol
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Re: mk4 jetta down on power.pls help

Postby Mikewire on May Tue 31, 2016 1:00 am

I'd check timing first, from your description, it sounds like it's off. Plus you had the head off for porting, and would have had to check/set timing post install, and that's when you say you started having issues.

If you unplug the MAF the ECU will use a default value that will make it run. But you have a C2 tune, so I would question that. Exactly what tune did you get from them? You say it idles lean, what are the values?

If it's not timing, I would see what C2 can do for you.

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Re: mk4 jetta down on power.pls help

Postby MT-Getto on May Tue 31, 2016 6:32 am

Do you have a vagcom? Almost necessary if you want to be doing heavy mods.


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Re: mk4 jetta down on power.pls help

Postby olson1990 on May Tue 31, 2016 7:05 am

My tune is just a n/a cam tune with Sai delete and rear o2 delete. If I unplug the maf. It runs leaner. C2 said my idle should be around 14.7. And afr wide open should be a little leaner. I also do not have a vag com. I have a buddy that dose and all he knows how to do with it is check codes. My idle current is 16.7 afr. And my timing is dead set. I'm just trying to make sure everything is good on my end. Before I mail c2 my ecu
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Re: mk4 jetta down on power.pls help

Postby olson1990 on May Tue 31, 2016 7:30 am

Just got off the phone with c2 they verified I'm running rich. And to send ecu if I want. But ide like to checkmaf And o2 first. Witch is were I need help.
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Re: mk4 jetta down on power.pls help

Postby MT-Getto on May Tue 31, 2016 11:08 am

Might consider just replacing the o2 sensor. If you do, I'd suggest avoiding the "universal" type. Bosch OEM type for sure. If possible, I'd try to swap MAF with someone that has a known good one or get one from someone parting something wrecked. Or again. New OEM Bosch. My opinion is to not skimp or compromise on these important components and don't try cleaning them.

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Re: mk4 jetta down on power.pls help

Postby olson1990 on May Tue 31, 2016 12:24 pm

I only run Bosch or oem. The maf I replaced less then 10k miles ago. It's bein down on popower ever since the tune. Are you local and could u possibly look at my ignition timing and injection. I'm hopen to try and figure out if it's my tune or my car but I doubt it's the bar because I'm not throwing any codes...
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Re: mk4 jetta down on power.pls help

Postby olson1990 on May Tue 31, 2016 1:26 pm

Got lots of spair 2.0 parts or can pay for someone else to help make sure everything is 100%
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mk4 jetta down on power.pls help

Postby MT-Getto on Jun Wed 01, 2016 6:32 am

Track down your buddy with a vagcom. Start playing with it. They are not hard to use. Spend a few minutes at Ross-tech.com looking at tutorials. If you want a heavily modded car, you need the right tools or deep pockets. I don't know any vw "tuners" around here.
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Re: mk4 jetta down on power.pls help

Postby olson1990 on Jun Wed 01, 2016 7:11 am

That's funny that's what I did last night. His vag com showed my lumbada out of ranger
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