Need help diagnosing erratic idle on alh

Atcfan

Active member
Joined
Sep 23, 2015
Location
Central square ny
TDI
2003 jetta 5 SPEED
My 2003 Jetta 5 speed started to develop an erratic idle today. Idling it will go from 903 rpm to 882 rpm momentarily and then jump back to 903. When i raise the idle with my foot to say a steady 1100 rpm the idle fluctuates down momentarily as well. Ive tried this with the A/C both off and on. I have vagcom so is there any measuring blocks that I can look at to help diagnose this?
 

Franko6

Vendor , w/Business number
Joined
May 7, 2005
Location
Sw Missouri
TDI
Jetta, 99, Silver`
There are EGR settings to reduce the usage, which can smooth out idle from too much EGR usage.

However, it also can be overfueling injectors. Aging injectors tend to leak and run rich.

The more likely is to raise your injection pump's Injection Quantity (IQ) with a 'Hammer Mod'. Loosen the pump lid and move it to a higher I.Q. number. That would mean you move the pump IQ toward the passenger side, while watching the IQ numbers on your VCDS. This is done with all fans, a/c or other load on the engine turned off.

It takes a special triangle tool to loosen the front passenger side screw in the lid of the pump. The other screws are about a 20 torx bit. We don't like the tool that is sold for about $39 around the club. Instead, we use a 1/4" drive 7mm, 6-point socket and cut three of the flats 120 degrees apart, into the triangle shape with a 'christmas tree' shaped carbide cutter. Cut and test.. when it fits snugly onto the security screw, it's a good, cheap tool. You can't do it? We make them for $9 plus shipping.

Then, moving the lid toward the passenger side of the engine will make the pump's IQ rise, which lowers fuel usage.

This is our method of testing for 'optimized fueling'.

Basically, you raise the IQ until you lose performance. We run in 3rd gear, starting at 35 mph. Go to Wide Open Throttle (WOT) and when you reach 40 mph, count three seconds on a stop watch (or your Iphone), look at the speedometer.. Raise IQ incrementally until you lose MPH. Reset IQ to the previous number that preserved speed.

Questions? Feel free to call.
 

Atcfan

Active member
Joined
Sep 23, 2015
Location
Central square ny
TDI
2003 jetta 5 SPEED
I should have mentioned that i have a stage 4 malone tune with dynamic egr and when i checked the egr reading on vagcom it was showing 4.8% when the motor is fully warmed up. Injection quantity bounces around between 4 and 4.8.
 
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