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Old 10-02-2021, 11:32 AM   #1
Bqd1997
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Default 940 turbo stutter in boost

https://drive.google.com/drive/folde...-EpTfaBn04d8FH

^ video of issue. IÂ’m at a loss. Any input will help.

Any idea what causes this?

1994 940 turbo.

Idles perfectly, sounds fine, fine when easing on the gas, just stutters when you hammer the gas pedal.

140-145 compression across the board, entire ignition system is new, new fuel pumps and filters, new relays, new maf sensor, new CPS, new o2 sensor, new intercooler hoses, new turbo inlet hose (minus the sensor in the hose, had to reuse old on because new one didnÂ’t come with it).

I do know the previous owner had someone mess with the Ezk to remove the CEL due to EGR removal. Could the ezk be bad? If so does someone near Sacramento have one I can plug in and try out / test?


If anyone wants to come get a second set of eyes on this thing too I’ll buy you a beer
Located in Sacramento CA

Last edited by Bqd1997; 10-02-2021 at 12:46 PM..
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Old 10-02-2021, 12:21 PM   #2
Janspeed
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video not visible. Google is asking for permission.

Is the car giving EZK error codes? (check code reader box near driver side strutt tower)
What kind of fuel are you using? If the octane rating is not high enough maybe the knock circuit is detecting knock and the EZK is pulling timing?
How are the spark plugs? What type/heat range? are they gapped to spec? If the gaps are too wide it could cause spark blow out under boost. Try 0.6mm
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Old 10-02-2021, 12:48 PM   #3
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Quote:
Originally Posted by Janspeed View Post
video not visible. Google is asking for permission.

Is the car giving EZK error codes? (check code reader box near driver side strutt tower)
What kind of fuel are you using? If the octane rating is not high enough maybe the knock circuit is detecting knock and the EZK is pulling timing?
How are the spark plugs? What type/heat range? are they gapped to spec? If the gaps are too wide it could cause spark blow out under boost. Try 0.6mm
No codes, 91 octane, spark plugs gapped to stock spec.


I reuploaded the link and changed the permission to everyone. Thanks for calling that out, totally forgot about that haha.


I had almost felt like the intercooler hoses and turbo inlet hose were getting sucked shut, and the problem is better than it was before that, but still not wanting boost
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Old 10-03-2021, 12:52 PM   #4
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Anybody in Sacramento have a good working turbo ezk that would work with my car I can borrow to plug in and see if mine is toast?
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Old 10-03-2021, 01:08 PM   #5
dl242gt
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Have you checked for any codes? Some codes don't turn on the check engine light. I read that you set the gap but what did you set it to? Turbos like the smaller range of plug gap at .028".
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Old 10-04-2021, 10:25 AM   #6
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For reference, here is an overview of how to retrieve the codes from LH2.4.
http://www.volvoclubofbc.com/technic...codes.html#rfc
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Old 10-04-2021, 01:38 PM   #7
gsellstr
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Yeah, I've got a couple boxes with various tunes, also have a factory non-EGR box you can throw in for testing purposes. I'm over off Power Inn and Fruitridge.

Low boost levels when it's doing it kinda rules out fuel cut, different rpm when it does it after it shifts, kinda seems odd. I've got a little time in the evenings this week if you want to swing by.

Have you checked the clocking of the distributor? Should be ballpark middle of the slots. If it's all the way to one end or the other, the spark event may not line up right with the rotor/post timing.
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Old 10-04-2021, 02:06 PM   #8
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Quote:
Originally Posted by gsellstr View Post
Yeah, I've got a couple boxes with various tunes, also have a factory non-EGR box you can throw in for testing purposes. I'm over off Power Inn and Fruitridge.

Low boost levels when it's doing it kinda rules out fuel cut, different rpm when it does it after it shifts, kinda seems odd. I've got a little time in the evenings this week if you want to swing by.

Have you checked the clocking of the distributor? Should be ballpark middle of the slots. If it's all the way to one end or the other, the spark event may not line up right with the rotor/post timing.


I’ll shoot you a pm to get in touch.

I’m not sure about the distributor, previous owner did that. I feel like if it was clocked incorrectly it would cause rough idle no?
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Old 10-04-2021, 04:16 PM   #9
gsellstr
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Not necessarily. Given the timing changes under load, when you roll into boost your timing will retard a bit, plus more voltage/current is required for the spark event. At idle, minimal is required compared to high load, so it can be more forgiving. It's worth taking a look, takes a 10mm, a mirror, and about 2 minutes to check/fix.

Got your pm.
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Old 10-04-2021, 06:21 PM   #10
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I had a misfire under boost issue that drove me nuts for a while that ended up being a coil wire going bad. Low boost 5-10psi no issues, 14-21psi it would misfire. Slowly over time the lower the boost the more I would see the issue. After going over everything I finally swapped the coil to a spare I had and when swapping coils the wire came apart.
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