Our ’03 Jetta Gets A Clean Intake and 33 More Ponies

Well we’ve had just about all we can take of driving a bone stock, 2003 Volkswagen Jetta TDI. After 5,000 miles of parts running, traveling to events, and getting passed by everything with wheels under it, it’s time to give the little V-dub a kick in the pants this month in the form of a programmer. But before we break out the power adder, we’ve got a major house cleaning item to tackle: cleaning the intake manifold and EGR valve.

Stealing Our Thunder

Thanks to their exhaust gas recirculation system, gummed up or clogged intake manifolds are a very common problem on the ALH Jettas (’99.5-‘03)—especially on cars that are subjected to a lot of short-trip driving or extended periods of idling. This kills performance, hurts fuel economy, and takes a lot of the fun out of driving these cars. We’ve even seen engines so plugged up they couldn’t accelerate without holding the go pedal to the floor…

Dyno-Verified Tuning

Following the aforementioned housekeeping duties, we’ll be strapping the car to Scheid Diesel’s Mustang chassis dyno. Once we’ve collected a stock baseline, we’ll flash the ECU with Kerma TDI’s Q-loader programmer and re-dyno to measure our horsepower improvement. After that, it’ll be time to hit the road, log all of our trips, and see if we can beat the car’s current 48-mpg average. DW

Parts Required

Part: Part Number:
Exhaust manifold to lower EGR pipe (metal) 038131547A (OEM)
EGR Cooler to EGR Valve Gasket (paper) 069131547D(OEM)
EGR Valve O-ring N90521604 (OEM)
Victor Reinz Intake Manifold Gasket 71-28781-10 (Aftermarket)
Thermostat 044121113 (OEM)
Thermostat Housing 038121121 (OEM)
Volkswagen 1.9L ALH engines are equipped with an exhaust gas recirculation (EGR) system which will require a periodic (or eventual) intake manifold cleaning. When it’s overdue, you’ll likely know it, as performance and fuel economy will suffer.
In addition to cleaning the intake manifold, we planned to change out the engine’s thermostat. So the Jetta was placed on a lift and raised high enough to clear a bucket. From there, the engine’s coolant was drained (and reused later on).
With the rubber intake manifold elbow out of the way, the EGR valve’s vacuum lines and anti-shudder valve line disconnected, and the intake side of the EGR cooler’s flex pipe unbolted, the EGR valve was removed from the engine. Care should be taken during removal of the plastic vacuum and anti-shudder lines due to their age and potential brittleness.
When exhaust gases (soot) mix with the oil vapor from the close crankcase ventilation system for 200,000 miles, a ton of carbon buildup is the result. Take it from us, a lot of elbow grease is involved in the removal of this stuff, you can’t simply throw the components in a parts washer and walk away. We got started cleaning the EGR valve by digging out the gunk with a pick.
Once the majority of the carbon buildup was removed, the EGR valve was treated to a long round of compressed air. Then a combination of brake cleaner and more compressed air was used until the valve came clean.

This should give you a good idea of just how much carbon buildup can occur in the TDI engine. After an intense, 15-minute cleaning, you can see how clean we were able to get the EGR valve (thanks to a pick, flat head screw driver, compressed air, and brake cleaner).
Digging back into the engine, the six factory intake manifold bolts were hit with penetrating oil (to avoid any stripping issues) and pulled. The intake manifold bolts require a 6mm Allen.
With all bolts removed, the intake manifold was slowly lifted off of the cylinder head. While some Jetta owners opt to avoid downtime by buying a brand new intake manifold (roughly $350), we didn’t find the process of removing it extremely drastic or time-consuming. An experienced VW mechanic can have the intake manifold off within an hour’s time.
While we’ve seen worse, it was definitely time to clean the intake manifold on our Jetta. The general consensus in the TDI enthusiast community dictates that it’s time to perform this job once 5-to-10mm worth of carbon buildup is present around the perimeter. Up to 2mm worth of buildup is thought to be normal, and not detrimental to the performance and efficiency of the ALH engine.
Here you can catch a glimpse of what the intake ports looked like. If the intake ports on the cylinder head are clogged to the point of nearly being sealed shut, removal and cleaning of the cylinder head is warranted. Thankfully, we weren’t at that point.
Although some folks use heat (torch) to burn out the carbon buildup (we wouldn’t recommend that due to possibly compromising the manifold’s metallurgy and the obvious inhalation and potential fire hazards), we stuck with the same cleaning methodology that was employed for the EGR valve: digging and scraping, followed by compressed air and loads of brake cleaner. Pressure washing is also a viable cleaning option, along with letting the manifold sit in a tub of solvent cleaner overnight.
Throughout the cleaning process, the EGR cooler was allowed to hang against the firewall. After seeing minimal buildup in the EGR cooler tubing, we didn’t opt to clean it at this time.
After roughly a half hour of labor and a mess of oily grime left behind, the intake manifold was clean enough for our liking. While the majority of our buildup was at the inlet of the manifold, the ports responsible for feeding air into the head shouldn’t be overlooked (even if only a slight buildup is detected).
Turning our attention to the thermostat replacement, the two 10mm bolts that hold the thermostat housing (also referred to as the coolant flange) to the block were removed, followed by the thermostat housing and thermostat. All remaining coolant was then vacuumed out with a shop-vac.
Upon removal of the thermostat housing, we noticed its plastic locking pins were missing (right), which is very common. The locking pins present in the new housing (left) are used to secure the thermostat in place (the thermostat goes in and turns to the right in order to be locked solid).
We decided to replace the engine’s thermostat due to not knowing exactly how old it was (just like the timing belt replacement, performed in the Sept., 2016 issue). The OEM thermostat (PN 044121113) came with its respective O-ring included. Using a small strip of paper towel wrapped around the 10mm head of the housing bolts (so the bolts don’t fall out of the socket) helped tremendously when the new thermostat and housing were installed.
With everything clean and the new thermostat in place, it was time to ready everything for reinstallation. Here the refurbished EGR valve has been fitted with a new O-ring seal (PN N90521604).
A Victor Reinz intake manifold gasket was used (PN 71-28781-10) to properly seal the intake manifold to the head. The easiest way to install the intake manifold and gasket is to position the center two bolts in the manifold, allowing them to hold the gasket in place while the other fasteners are threaded into the head.
From there, it was a matter of reinstalling everything removed during disassembly (crankcase ventilation hose, hard air intake tube, vacuum line, radiator hoses) and topping off the engine with coolant. At the end of the intake manifold R&R process we had roughly $90 involved (with several cans of brake cleaner factored in).
Using Kerma TDI’s Q-Loader programmer is very straightforward, provided you follow the step-by-step instructions the company lays out for you. It requires you to download the Q-Loader console PC interface software onto your computer, use it to set up the programmer for your specific car, and then use the programmer to pull the stock ECU file.
The process of reading the stock ECU file took roughly 12 minutes. Once the stock calibration was saved to the Q-Loader we reconnected it to our PC, saved a copy to the desktop, and emailed it to the folks at Kerma TDI. Shortly thereafter, a modified file was sitting in our Inbox. We promptly threw that file onto the Q-Loader and made our way to the dyno.
After trekking over to Scheid Diesel’s Effingham, Illinois location, the Jetta was strapped to their Mustang chassis dyno for a stock baseline horsepower number. After three runs—all of which were made in Fourth gear, from 40 mph to 90 mph—the car laid down a best of 72 hp. If you look close, you’ll notice that the front recovery hook had to be utilized (accessible via the passenger side lower pop out panel) in order to strap the front end of the car down.
Being that the ’99.5-’03 Jettas were rated at 90 flywheel hp from the factory, our 72 hp at the wheels seemed legitimate (given a 20 percent driveline loss), so we went ahead and uploaded the modified Kerma TDI tuning file to the ECU. We were subtly impressed to see a 33hp gain once the rollers stopped turning. And as you can imagine, a 45 percent increase in horsepower is very noticeable on the street. Now the car is much more responsive down low, pulls strong throughout the rpm range, and while the accelerator is touchier, power comes on in a smooth and linear fashion. One thing is for sure: Kerma TDI’s tuning feels extremely refined—and as far as a back-to-back comparison on a chassis dyno is concerned—it adds considerable horsepower to the ’99.5-‘03 Jettas.

Mileage Log

Being that we just tuned the Jetta this month, no fuel economy data has yet been collected in the car’s current 105hp state (in fact, we haven’t even had to fill up yet). However, the first eight fill ups with the Jetta in 100 percent stock form yielded an average of 48.1-mpg. Now that the car is tuned, and because Kerma TDI’s ECU tweaks are known to provide a mileage bump, we hope to improve these numbers by 1-3 mpg. We’ll showcase this in our next installment. Stay tuned.

Date: Gallons Used: Trip: Tank Average:
4-28-16 11.235 570.1 50.7 mpg
5-11-16 5.807 255.0 43.9 mpg
5-18-16 11.344 585.6 51.6 mpg
5-20-16 11.226 553.6 49.3 mpg
6-2-16 11.459 556.5 48.5 mpg
6-24-16 9.541 448.1 46.9 mpg
7-13-16 11.410 537.8 47.1 mpg
8-3-16 10.830 486.3 44.9 mpg
Overall Combined Average: 48.1 mpg


Kerma TDI

Scheid Diesel

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