Alh turbo boost control question

Jakub

Veteran Member
Joined
Mar 30, 2014
Location
Chatsworth
TDI
2000 Vw golf tdi
Ahu turbo boost control question

Hi
I converted a 93 suzuki sidekick gas engine to a 1997 VW Jetta TDI alh. I had a code jump up and noticed that when I’m driving my boost stays constantly high as if the actauator never kicks in to let it out when it reaches to high and puts me in limp mode . The actuator moves freely and has no obstructions and seems to be set properly. What can I adjust to allow the actuator to open to allow boost out? Or do I need to get a manual boost controller ?
 
Last edited:

Jakub

Veteran Member
Joined
Mar 30, 2014
Location
Chatsworth
TDI
2000 Vw golf tdi
For some reason the code I get on vagcom is 000625 vehicle speed signal
27-00 implausible signal
 

Mongler98

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Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
So it was working before right? Boost control is controlled by vacuum on the ALH and the n75 valve. Check your vac lines and pull a vacuum on the turbo actuator and check the n75 valve. It sounds like its the n75 or the controller within the ECU or some value its getting improperly and not letting it open to dump the exhaust waste gate open.
 

Jakub

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Joined
Mar 30, 2014
Location
Chatsworth
TDI
2000 Vw golf tdi
Yea it was working before or it appeared to be bec I didn’t get the code.
I was thinking n75 valve but it appears to be clicking away working.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
get a vacuum tester tool and test the actuator for leaks and im asuming that the vtn ring and blades are freely moving from your description. You go into limp mode so i would say most likly you have a vacuum leak or boost leak and its not closeing or its getting stuck open
 

Jakub

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Location
Chatsworth
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2000 Vw golf tdi
I only go into limp mode on the highway going up a steep grade
I’ll check things
 

Jakub

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Mar 30, 2014
Location
Chatsworth
TDI
2000 Vw golf tdi
Well when I installed them with the engine everyting was new but I will check
The car makes boost just something doesn’t let the boost off it just continues to climb
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
what lines did you use? OEM lines like supplied from IDparets.com lasts a a while, the hoses you get a auto stores last about 4 months if your lucky, ESPECIALLY in diesels.
the silicone high quality hoses on amazon last for near close to forever.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
sounds like a bad actuator, ripped diaphragm, thats easily the 2nd likly issue. Have you checked the line going into the ECU? there is a small part of vac line inside the ECU.
 

jimbote

Certified Volkswagen Nut
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Jul 10, 2006
Location
spiral arm, milky way (aka central NC)
TDI
Tacoma 4x4 converted to TDI
if your engine is from a 97 jetta it's an AHU not an ALH. ... AHU uses boost (not vacuum) through the N75 to control the wastegate, so if you've plumbed it to vacuum that's a big problem...
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
OH good point lol, i missed that one. HAHA, well it was working before, i think he is confused and does have a AHU so yea boost lol

OP can you elaborate for us what turbo you have on it and what engine please.
 

Jakub

Veteran Member
Joined
Mar 30, 2014
Location
Chatsworth
TDI
2000 Vw golf tdi
Right I acccidnetly wrote alh and tried to edit that but I guess it didn’t work.
Yeah it’s the Ahu.

The actuator seems to hold air
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
yea, its all boost, 99% sure if your lines are good and your still having issue, take the ECU out, open it up and CAREFULLY replace the hose inside it.
 
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