My 02 Jetta Wagon Build
 

Hello all. Ive been a longtime lurker on the site but never really posted. Decided I'd try starting a thread on my most recent purchase. Its an 02 Volkswagen Jetta wagon with an auto transmission, 210,000 miles on the body and supposedly around 135,000 on the 2.0 engine. At the moment the only mod it has is lowering springs from the previous owner. Goal is to get as much MPG as possible as its going to be my new daily as well as being used for delivering. I'll try to update when I have time as I get some tank numbers and work on mods.

Welcome !
Looking forward to your build.

Does the car have a roofrack ?
That's an easy 1 - 3 mpg right there if you remove it.
They are usually made to come off easily, and any holes that may be there can be plugged with automotive grommets, and sealed with a dab of clear caulking. .

Would you spend more than you save for the bragging rights, or is it driven by ROI?

Cd- it doesnt have crossbars but it does have rails. I may look into removing them as i want to remove the antenna as well, just scared its gonna look bald without them lol.
Freebeard- im trying to keep this as a budget build for the sake of ROI, but me being me im sure I'll end up spending some if it gets me some good numbers.

Also, I'd like to run through at least one tank so I have some sort of baseline before I do any real mods. I believe epa ratings are 22/29. I'll try to figure out how to upload pics today as well. Im having weird issues with my scangauge since i swapped it over from my truck. The screen was blank at first, and when i got it to work it functioned as it should, then the next time i drove it it was showing i was getting 1200 average mpg. Is this just because i havent calibrated it yet, or could this be some sort of electrical gremlin since it doesnt have the original engine? Just please dont tell me my scangauge is dying lol

Some of the things that don't cost much:

Air up the tires to max sidewall or slightly below

Get an OBD adapter that will pair with your phone and download the Torque app or Dash Command.

Then you can look at rpm vs speed in top gear and keep the vehicle in the highest gear and the lowest speed possible.

Test to see if engine goes to idle when you put it in neutral at speed, if so, then that should help (note to rev match when going back to "D")

If you drive to where the transmission won't shift into overdrive due to speed and load, turn off the overdrive if possible, that will allow the torque converter to lock in direct (like the old days when you take a truck out of overdrive when towing)

Hope this helps, I did this with a 2005 Ford Focus Auto and consistently got 38-40MPG on a vehicle rated 29MPG highway

Hopefully these pictures upload correctly...
Edit: it worked! As you can see she sits pretty low, and I'm already thinking of how to cover the holes in the bumper where the fog light blanks should be.

Sharkmouth or chrome Dagmars?

Had to google that one... never knew thats what those bumpers were called :D looks like I could get the oem covers for cheap, but I think I can get creative with some sheetmetal and rivets for free since I already have those laying around. :turtle:
Also, what do the aero experts here think of that lower lip? Can I take it off, or maybe replace it with something with a bit more clearance? It was already broken and zip tied together when I got the car and it keeps scraping on certain driveways because of how low the car sits.

Low is relative. I had to raise my Superbeetle to 3 1/2" at the tow hook to clear bunp strips.

Air dams point downward and restrict air under the car. Splitters point forward and provide downforce.

Drifter's stitch:
https://ecomodder.com/forum/member-f...hlf3lbyhtg.jpg

Get a Scan Gauge II or Scan Gauge E; This will teach you where all your gas mileage drops come from and your mpg gains. Set the gauge up to show boost, instantaneous mpg, and trip mpg. Drive to minimize boost on cruise and accelerating. Run fast downhills to coast. I picked up 20% gas mileage gain just learning to drive with the Scan Gauge.

Leave a good gap in front of you so you can minimize using brakes in traffic.

Following a car 25' behind in the fast lane is the worst for mpg. Lots of acceleration pulses. You want superlight steady pressure on the accelerator.

Don't use cruise control unless its super flat.

Run max tire pressure or a few psi under it.

Check for emergency brake drag and wheel bearing drag. Your emergency brake tightens the rear disk calipers on a VW by rotating the caliper piston when using the e-brake for when the brake pads wear but every time it rotates a click there will be brake drag. I only use my emergency brake once a month or so unless needed on a steep hill.

Aeromods as needed.

Get good new injector nozzles. Old injectors waste fuel. Is your intake clean or gunked up from EGR?

I've never owned a euro car before so thanks for the VW specific tips! Brake rotors looked scored so I need to inspect everything brake related anyway. I do have a scangauge 2, but the instant and average mpg functions seems to work intermittently on this car, as noted in my earlier posts. I will check the intake as well and probably run some seafoam or something similar though it.

First morning of delivering at my new job! Things I learned:
 

- got a p0420 code yesterday. Previous owner gave me a new cat converter with the car, maybe I should install that?
- warm up times are kinda slow on these cold mornings, and coolant temps seem to settle between 200 and 210, per the scangauge. Would I be safe to insulate and raptor line the underside of the hood to keep things warmer? Anyone know the safe limits of this engine?
- 45 psi in the tires is noticeably harsher than 35 on the notoriously crappy roads around here. Gonna drop them to maybe 42 or 40.
- need to remove rear seat backs, partly for weight reduction but mostly because they dont fold flat and I need the room for the boxes I deliver.
- the cold made my knees hurt, and I'm only 23 :eek: glad I got an auto instead of another manual, even if it makes hypermiling harder.
- probably forgetting something, just excited to burn through this tank so I can get my baseline and start modding.
- the car does seem to use DFCO, but its hard to keep it there compared to my stickshift truck. Still, its something to keep in mind.

"P0420 Code: Meaning, Causes & How To Fix It | Mechanic Base
Mar 17, 2023The P0420 code indicates that the ECM has detected underperformance of the catalytic converter's efficiency on Bank 1. It can be caused by a faulty catalyst, or it can be a false alarm caused by a faulty O2 sensor. The engine control module (ECM) uses two O2 sensors, one in front, and one behind the catalytic converter to measure its efficiency."

I wonder why the owner provided a new expensive cat converter.......

Far as I can help, I own a TDI

Supposedly he got the converter, changed out an o2 sensor, and that turned the light off so he didn't install the converter... or something like that. He didnt have reciepts so I couldn't really verify any of the maintenance thats supposedly been done. Anyway...
Pulled the rear seat backs out! There's so much room for deliveries and picking up scrap metal now. I wish I had an accurate scale because it was stupid heavy, I swear the passenger side was at least 40 lbs. Also, not an ecomod, but I shampood the carpets to get some funky smells out.

I recently did some grille blocks on my civic, very cheap and easy mod to do. Very helpful for my city driving as the engine warms up faster. Probably helps with aero too, but I don’t do enough highway driving to be able to notice any difference

I have been contemplating how to build an upper grille block, preferably one I can easily remove in the summer if temps get too hot. Warm up times are awfully slow in this car which I know is going to kill my mileage come winter.

My Dasher came with a sliding fiberboard panel about 4x6" that had a choke cable control so it could be operated from the driver position. It was long gone before I acquire the car.

I have a picture squirreled away somewhere, but DDG can't find it today.

Ive read about other modders here building similar things. Im not sure how I could build one to be flush with the outside of the grille, I may have to dig around and find those old threads for inspiration. I am running up to autozone tomorrow to grab an oil change and hang out with some of my former coworkers so I'll take a look at the choke cables they carry.

Opportunity presented itself, so I struck!
 

Ok, so I know I said no mods until after my base tank, buuut the mod bug got me. While I had the headlights off the car to re-clear them, I discovered the Jetta has a cold air intake from the factory. And no, not the "cold air intake" we all put on our cars when we were 16. This is a proper snorkel that goes from the airbox to behind the drivers side headlight to draw cooler air from the outside. I went ahead and removed it since its best accessed with the headlight out. Now its breathing nice warm engine bay air, and I know plenty of others here have proven gains from warm air intakes. :turtle: Besides that, theres a mesh screen inside it that was completely clogged with dirt and debris.

I also discovered that the upper grille feeds at most MAYBE two inches of the radiator and core support, so I think I'm safe to do an upper grille block, at least in the winter.

Pics are attached.

Oh, and if anyones interested, I can do a quick writeup on refinishing cloudy headlights here, or on whatever subforum is appropriate.

The numbers are in and... they kinda suck.
 

Filled up today. 283.6 miles, divided by 12.43 gallons equals 22.81 mpg. :confused: Kinda disappointing, but under similar stop and go driving I'd be lucky to get 20 in my truck, so I guess I shouldn't complain too much. Still, seems kinda low. Time to start modding.

I had a 2003 Jetta Wagon TDI with a 5 speed. I did a grill block on mine on the middle grill opening. If I remember correctly it has 2 horizontal fins to make 3 openings and I blocked 2 of them. Popped out the grill, closed them off with black duct tape and popped the grill back in. I thought it might be an issue in the summer but I never had a problem and I lived in Alabama at the time.

I dub this... the lazy man's antenna delete!
 

Sorry I don't have anything more exciting, but I felt the need to post something here. Basically what I did was unscrew the oe antenna, took it to the hardware store to match the threads and picked up an allen head bolt and lock washer I found aesthetically pleasing. In hindsight a set screw would sit flush and look better, but meh. Looks fine to me and only cost me a dollar :cool: If I had an unlimited budget I'd remove the whole base, patch the hole, wash rinse and repeat for the body side moldings as well, fix dents, and repaint, but oh well. At least I can dream.

Needs a racoon tail. :)

I just bought two 1/4-20 shoulder bolts to solve a problem. They were $2.49 each!

Prices are crazy nowadays. I hate to complain but its just silly how one tiny bolt and one tiny lockwasher can cost a whole dollar. A lot of times I just buy the bulk hardware packs from harbor freight if I think I'll actually use them up. Why spend a dollar on a single bolt when you can get like 100 for what is it? Maybe nine or ten dollars?

Everything I make uses 1/4-20 for that very reason.

The shoulder bolts will accommodate my banana seat on the new bike. (I got the bike for $15)

Unfortunately, the gas engines in these cars aren't very fuel efficient. For good fuel economy from the factory, you'd have to get a TDI.

But since your fuel economy is fairly low, marginal utility will be your friend. For example, if you can get 5 more mpg from your car, the money you save will be greater than, for example, taking a 40 mpg car to 45 mpg. Since it's burning so much gas, every mpg you can squeeze out of it will make a difference.

That said, you might want to do a cost-to-benefit analysis of a more fuel efficient car vs this one. Figure out how much money you'll spend on gas in a year. Then compare it to how much you'll spend if the car had 40mpg or something like that. You might find that a 40mpg car will pay itself off in fuel savings after a few years.

That involes math, and that makes my head hurt :D I may do that one rainy day when I have some free time though. Speaking of numbers, my lastest fill up was 23.89 mpg. I'll attribute the gain over my last tank due to getting a new job with a pretty good commute for fuel economy. Its a few miles closer than my last job, with a lower speed limit (45mph) with long stretches between traffic lights. Still disappointed, but at least its an improvement.
I've also noticed a slight fuelly smell at the rear of the car after driving. Maybe its running rich and that's part of why my numbers suck?

Seems plausible. Any trouble codes?

I have a P0420 code I've been procrastinating on fixing. I have a new cat converter assembly that came with the car. Probably not related, but I'll probably throw in a new thermostat as well because it seems like it takes way too long to warm up. I really need to take a look at everything and see what's really been replaced by the previous owners and what looks crappy, and just replace everything related to fuel management.

The P0420 could be related to the gassy smell, but shouldn't affect engine management. The P0420 usually means the catalyst or the downstream O2 sensor is bad. The ECU doesn't use the downstream O2 for fuel calculations. It's basically just a "fix it" code.

To put things in perspective, my Prius also has the P0420 code. It has an aftermarket catalyst, and apparently the ECU doesn't like that. But the car still gets 60 mpg.

However, the long warmup times can definitely affect fuel economy. That would typically be caused by the thermostat sticking open.

After that's fixed, you could also try an upper grille block, for even faster warmup times. On the Mk4 cars, the upper grille is easy to remove and reinstall. So a grille block should be a piece of cake. Just zip-tie a piece of sheet plastic or whatever to the back of the grille.

Running rich can kill a catalyst.

Havent been on here much, and havent done any new mods. Been busy with work, side gigs, etc. Anyway, maybe about two weeks ago when I was driving to work, I noticed the transmission wasnt upshifting. Reverse and park are fine, but nothing will get the car to upshift. Took it to a shop and they say they heard noise from worn out bearings or something, I forgot exactly what they said besides that I need a transmission and the cheapest they can do it is 3400 :eek: Anyway, Ive already recruited a family member thats a mechanic thats willing to help me swap it for much cheaper, and I can source a transmission myself for much cheaper as well. Anyway, I'll keep the thread updated with anything new, and if anyone tells me the shop is wrong and all I need is a speed sensor or something I'd be very grateful lol.

Man, that sucks. Although I'm not really surprised. The automatic transmissions in these cars are notorious for being unreliable. Hopefully you get it back on the road soon.

Update: found a good deal on a rebuilt transmission on ebay, should be here by the end of the month. Anyway, thought I'd share these pics from Sunday.

I got the underside of the hood insulated and bedlined. Pretty much took the whole morning to clean it, it was pretty greasy and filthy. Should have taken a pic but didn't think about it. Then sand, scuff, and laying on boom matt. In hindsight, I should have bought a second pack as it didn't cover as much area as I thought it would, but at that point I could have just bought an oem hoodliner. Anyway, between that and the bedliner, I'm hoping it will insulate enough to speed up warm up times. I used herculiner that I had leftover from another project because it was getting old and I didnt want it to go bad.

(Yes, thats a pcv pipe holding the hood up. :cool: Im not gonna buy a strut thats gonna die again and I haven't built a real hood prop yet.)

Just noticed I haven't posted any updates in several months. My stepbrother and I are set up to swap the transmission this weekend. Was reading that the oem coolant to transmission cooler tends to either clog or leak and kill the trans, so I ordered a kit to get rid of that and put a regular air to trans fluid cooler. Besides that, havent done much. Been trying to shed some weight, and also trying to figure out if there's any manual steering racks that could fit. Hopefully I'll have some good news next week.

lower lip
 

I suspect that what is there was 'optimized' in VW's wind tunnel.
It's thermoplastic, and body shops have hot-air welders which could fuse the fractures back together. I used a low-power soldering iron to repair my friend's Prius front fascia which was in far worse condition than your Jetta's.
I don't know what's behind those openings. If you believe that your at no risk of cooking something, then blocking them closed has been demonstrated as a drag reduction technique so many times now, it would be a shoe-in for modification.:)

HI,

Did you ever remove the rails ? If so , any real MPG improvements?

My headliner is sagging so if I try to fix that , that would be the best time for me to remove the rack ....

Thanks

Andrew

The rails have minimal frontal area, act as vortex generators in crosswinds, and kill lift if you get sideways.

Regarding the front lip: That's a common issue on the Mk4 VWs. The front end hangs down pretty low, and can catch / scrape on stuff. RockAuto sells a replacement piece, for under $25. Part #VW1093104

Also, it's not uncommon for people to catch the front end on a parking curb, then tear off the lip and/or front bumper when they back out. On my Jetta, the previous owner's wife did exactly that: ripped off the whole front bumper. There's a filler panel available, that helps prevent that. (I also think it makes the front end a little more aerodynamic) VW part #1J5805301.

Unfortunately, it seems that part has been discontinued. But you can probably find some new old stock on ebay or something.