Knocking when turbo is redlined

tbanks3

New Member
I recently bought an 86 GN and the other day when I floored it, the engine knocked and sputtered. It seems to do it only when the pedal is floored or pushed 3/4 of the way. Any ideas? I am new to the forum and the world of the GN! Thanks
 
try some race gas and see if it stops doing it. until you get some high octane in there i recommend you dont floor it either...
 
Stop doing it till you can get the car tuned, it's detonation and you will wind up replacing headgaskets, if you keep doing it. Also run the highest octane gas you can find, Do you have a boost gauge?
 
Get a Scanmaster and tune the car first. The last owner may have adjusted the boost way up and you may not be getting enough fuel. Which means running lean and blowing the motor up.
 
come on guys ... HAMMER that baby!!! then when it goes "KABOOM" you can see what happened and fix it :cool: "Search" feature is your friend :p
 
Thanks a lot for the help folks. In reply to a few of you: The car is all original, 82,000 miles, original turbo, (has a cat converter), and I do not boost gauge yet. Based on reading the posts it sounds as though the best place to start is getting her tuned up properly. I drove the car today to make sure I do not hear it at any other time and I didnt. Definitely only when floored. Also, the previous owner has the idle set pretty high on this thing. I asked him about that and he said it would stall out sometime when it was lower?? Thanks again for the help guys, Im happy there are knowledgeable people in regard to this type of car.
 
Start with 1/2 throttle blasts until you can address the detonation. These cars love/need octane.

Is the rod on the little canister below the turbo threaded? If it is, then it's an adjustable wastegate. The previous owner may have had the boost turned up without supporting modifications.

Read, read, read. Best advice I can give. We are here to help.
 
Check your wastegate hoses for incorrect hookup and integrity as well as the wastegate diaphragm. Probably hooked up wrong or full of holes since it is probably over 20 years old now. If you disconnect the wastegate solenoid it should only go to about 10psi. It will throw a code but its no big deal since you are trying to isolate the overboost situation. It should be 13.5-14psi in 1st-3rd and 10psi in 4th if the stock chip is in it and the wastegate is in good shape.
 
Hey guys, sorry for the delayed response. I took a look today at the parts around the turbo (turbos are new to me) and I looked for the rod under the turbo. It did not appear to be threaded. I did find a small hose disconnected from the turbo setup. It appeared to be a vacuum line (not sure) that ran from the turbo setup towards the block to a junction of vacuum lines. It was on the right side of the setup near a larger metal tube that runs to the intercooler. I hooked it back up, but have not been able to see if that had any impact on the problem as the weather is not so good.

To answer the question regarding where I am located; I am located in Central Virginia and can certainly set aside a few bucks for some oat soda and I always have some Yeungling on hand! Thanks again for your knowledge and replies.
 
is that what yours looks like? That is an adjustable wastegate. Shorten the rod = more boost, lengthen it and you get less. Try to dial it down to 15 psi. If I remember correctly a half turn is a pound of boost.
 
tbanks3;2128273I did find a small hose disconnected from the turbo setup. It appeared to be a vacuum line (not sure) that ran from the turbo setup towards the block to a junction of vacuum lines. It was on the right side of the setup near a larger metal tube that runs to the intercooler.[/QUOTE said:
:eek: :eek: :eek: That is one of the wastegate pressure lines. Those hoses need to be replaced and zip tied so they cant ever blow off.
 
If its all original it still probably has the stock chip which is not good for todays gas formulations.
 
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