Studder problem around 2400 rpm coming on boost help

H

Hotrodbuick

Member
Joined
Apr 17, 2012
I'm new to these cars and the turbo aspect as well. I bought the car a couple months ago with turbo off and intercooler off. What I know is it has a cam (don't know what size) and it had twin pumps with a 66 ball bearing turbo on it at one time. Now it has a walbro fuel pump and a turbo not big but I don't know what it is but it's aftermarket. When you stop and go to take off as soon as it makes around 4 pounds of boost and 2400 rpm the car spits and spudders like it has a rev limiter in it but if you can get it to go past that part it will come on boost fine and drive fine, but when you stop and start it does it all over again. Oh one other thing it starts when the fuel pressure hits 40 lbs. I have adjusted the fuel pressure up and down but when I can get the car to not do it it runs too lean and the plugs are white as can be. I don't know what size the injectors are or what chip is in it but the chip says 55 rev LC don't know what that means. I am running out of ideas with trying different things any ideas or help would help a lot.

Thanks
 
It's hard to say since you don't have a lot of information, but it sounds like your turbo is going into rotating stall a.k.a. surging. My car does the same thing at part throttle when it's at around 8 to 10 psi. The engine starts to rapidly buck, I can hear the repeated sneezing sound in the intake, and the boost gage flutters up and down. As soon as I either give it more throttle or let off the throttle, it goes back to normal. This means that at that exact condition, the turbo is operating at a speed that is generating too much pressure ratio for the amount of air that the engine can swallow. Technically, it means that condition is asking the turbo to operate to the left of the surge line of the compressor map (look that up on the Garret web site).

Assuming this is your problem, it's not a big deal, other than being annoying.

Mike
Sent from my HTC Droid Incredible using Turbo Buick
 
Surge may be it. But when I give it more throttle it does not change at all and when I give it less it goes away until I go back to that certain rpm. I have to give it less than quarter throttle and get up to around 45 mph and it makes boost just fine and has a little lag but not bad. Also I put a blow off valve on it because I thought the turbo was pushing too much air through the intake but I don't think that's it either. At first it was the down pipe was messed up so I blocked the waste gate off and it helped but still had the same problem. Im not too sure which one the cam sensor is, meaning the sensor goes into the timing cover looks like a mini distributor? I thought that was for the fuel injection or i could be mistaken. Thanks for the replies it's helping, I just dont know what other information to give
 
Yep, that's the cam sensor. When you unplug it the CE light will come on. Don't worry about it. Go for a quick spin and see if there is any difference.

RL
 
Ok I will try that tomorrow. I believe you set it 25 degrees after tdc. I used the tool to set it with so I'm assuming it's correct. Would it being out of time cause this type of problem?
 
Generally if the car starts and runs the setting is ok.

A wore out cam sensor, loose wheel, broken tab or a bad cap will cause drive-ability issues like you described. It's a quick easy test.

LMK

Rick
 
I just tried the cam sensor and it seems like it does better. I have a question though, the downpipe has two holes one for the turbine wheel from exhaust and one for the waste gate. Can you take any turbo and make it have external waste gate or does it take a certain exhaust housing may be a dumb question but I'm not sure. Because the gasket I have between the turbo and downpipe the gasket fits good on both holes of the turbo but on the downpipe the wastegate hole is off about half a hole? The exhaust wheel hole fits good to the downpipe but not the wastegate hole. This is the second downpipe I've had on the car and both downpipes the wastegate hole does not line up. With the other downpipe I blocked the wastegate hole off from the turbo and it still sputtered but it at least made boost. I can see where it's leaking exhaust from.
Thanks for everyones help thus far!!
 
For the most part the pipes should be interchangeable. Why are you using a gasket? Are your flanges jacked up?

Snap a picture of your pipe and post it up. Lets see what you got.

Rick
 
image-2337179565.jpg

It is a new downpipe the flange is good not messed up just thought u had to put a gasket between it
 

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Well was gonna try the rtv and take off cam sensor but broke off bolt in turbo. So will be a day or so before I can get it out. Will keep up with tread after bolt is out.
 
It is the cam sensor that went out in the car. Tried unplugging it and it helped but also just got a scanner to check everything in the car and threw a code for the cam sensor. Will have to look and buy a new one.
 
Um, when you unplug the cam sensor the code is set. To clear the code unplug the orange wire by the battery for a few seconds.
 
I unplugged the orange wire and cleared all the codes ( thanks because I could not figure out how to clear them in my snapon scanner) and ran it for about 10 mins. No codes came up and still doing the same thing. My tps v is at .40 idling and looked that up on the forum from another posting and that's good an wide open is over 4 so good there. My o2 is saying it's running lean then rich then lean then rich and the car smells and burns your eyes so you know it's running rich. My o2 mv is 430ish running. But it also says open/closed loop and it is in the open loop shouldn't it be closed running or am I reading the manual wrong for this thing? My spark advance degree idling says it is 38. Also have another thing that says prom id is 394. Do any of these numbers sound good?
 
For the most part things sound normal. Do you have a cat converter on the car?

The chip determines when it goes closed loop. Some chips are programmed for open loop idle. The cars idle better that way.
If you press the gas and hold rpm's 2000-2500 does it go closed loop? What chip?
 
It might help to state all mods that the car has..... i.e. alky? translator? etc.....
 
I can't get it to go into the closed loop maybe I will try holding it around 2500 like you suggested. I have no idea what chip it is, it says 55 rev lc on both sides and that's it. I bought the car and it was already in it. The injectors I dont know how big they're either gonna pull one out and look for numbers on them. The only mods I know the car has done is a cam (don't know size or anything) the turbo is aftermarket. Says Garrett on compressor side with a/r 60 and the exhaust says precision on it. Also has some old hooker headers and I just bought a new dp for the car. It does not have the cat on it, long gone before I bought the car. The maf is stock and I put a front mount intercooler on it. Transmission is as good of a guess as mine, it shifts fine and doesn't seem like it has a big stall.
 
Will a vss sensor cause this type of problem? I have aftermarket autometer gauges in the car (in there when I bought it but also have factory digital dash) and driving down the road about 15 or 20 mph it's showing about 35 to 40 so the speedometer is way off. Just a thought
 
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