trying to understand L Jet...

vwfye · Post by **vwfye** » Wed Dec 19, 2007 8:29 am

if you have any air leaks in the system up stream from the AFM, does this promote a full rich issue in the system? i've replaced pretty much every hose that the system has and can't find any leaks, but i'm still getting 9mpg. i've replace fuel lines, checked voltage to the FI and replaced the head temp sensor... i've a new 1.8L ECU coming this week... if this doesn't solve the issue, i'm not sure where to turn next. the car runs fantastic, doesn't seem to have fuel in the oil, but gets 9-11 mpg no matter what speed i drive. Guys, i'm already going bald, i don't need to keep pulling my hair out! help! i want to keep the car and give it to my mother (she can't drive a stick) but i've listed it again on the samba because of the MPG. who can afford to drive one at these #s. anyway, thanks for any more help!

raygreenwood · Post by **raygreenwood** » Wed Dec 19, 2007 6:58 pm

Ok for the sake of conversation, upstream of the AFM would mean between the AFM and the throttle body. Yes...no air leaks allowed in this area.
Critical things to check......runner to plenum boots, injector seals, cold start injector, valve cover gaskets and the o-ring between TB and plenum. There are no air leaks allowed downstream either (meaning on the engine side of the TB).

Also check that your throttle cable is not too tight and keeping theTB cracked open. Also, check that the seals on the throttle shaft of the TB are not shot. If you need new ones I believe they are the same seal as the clutch bearing throwout rod on any five speed golf. Little blue shaft seals...about $3 each.

Also....you need to know what your fuel pressure is at idle and at WOT. If you have a very fine vacuum leak either at the TB or on the plenum....or if the vacuum line to the fuel pressure is connected to the wrong place...you will get too much fuel pressure...and lousey milage.

It should be low...like 32 psi at idle and up to about 42 when teh throttle opens (check the book...going off memory).

Whats the rest of the engine like? If the cam is too wild in overlap/lobe center the vacuum signature could mess you up too.
Make sure your valve adjustment is spot on and the timing is right and advance is working. Ray

vwfye · Post by **vwfye** » Sat Dec 22, 2007 7:49 pm

this is a bone stock 1.8L... if i can get a dry day it will go in the air and i will follow every line (again). the throttle isn't too tight as it will drop right off to whereever i set the idle at. i will have to get a pressure gauge to test the Fuel pressure.

Post by **Piledriver** » Sat Dec 22, 2007 8:29 pm

The biggie is the hose that controls the regulator.

Even a small leak there can cause your fuel pressure and thus mix to be way high almost the time.

Of course the reg could just be buggered... Only a gauge will say.

vwfye · Post by **vwfye** » Mon Jan 07, 2008 9:56 am

if i disable the cold start valve, will this help with a full rich issue if the valve is bad?

Post by **Piledriver** » Mon Jan 07, 2008 11:09 am

vwfye wrote:if i disable the cold start valve, will this help with a full rich issue if the valve is bad?

If the valve leaks, unplugging it won't help.
(Is that what you meant?)

Post by **david58** » Mon Jan 07, 2008 11:22 am

http://manuals.type4.org/ljet/

vwfye · Post by **vwfye** » Mon Jan 07, 2008 11:25 am

yeah, i guess it was... thanks! i'm ready to rip this stuff out if i can find some shorty Dellorto manifolds to fit my 40s under the lid. 8mpg sucks! literally

Post by **david58** » Mon Jan 07, 2008 11:29 am

David58bug wrote:http://manuals.type4.org/ljet/

You could fix the problem if you have a look at this site, it has alot of good info and trouble shooting charts, wiring diagrams etc......and the people posting here are all giving you good info don't give up.

vwfye · Post by **vwfye** » Mon Jan 07, 2008 8:12 pm

this was interesting today... 30F and cold engine = major surging. 30F and warm engine = slight surging...

oh, and telling someone with an electrical phobia they can fix it is like telling someone afraid to fly that if there is trouble, put on the parachute and jump!