3500 Redline

Steve Owner Arizona Posted   Latest  
Unsolved
Driveability
2002 Volvo C70 2.3L (B5234T3) 5-spd (M56) — YV1NC53D82J028340
Vehicle Will Not Rev Past 3500
No Codes

On test drive vehilce is normal until you want to floor it, it gets to 3500 and then acts like a redline. No codes stored, timing is correct, timing adaptions are below 1 degree, does the same thing in park or neutral, any ideas

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Daniel Owner/Technician
Texas
Daniel Default
 

...Look at the PRNDL PID on scan data...maybe it never changes from Park or neutral (possible)...Dan H. ...South Texas...

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Steve Owner
Arizona
Steve Default
 

nope it changes

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Daniel Owner/Technician
Texas
Daniel Default
 

...Plastic grocery sack up the air snorkel and plastered on the filter media ??...seen that...Dan H....South Texas...

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Nate Owner
California
Nate Default
 

Sounds like a plugged exhaust to me. Do an exhaust backpressure test.

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Zachary Mobile Technician
Texas
Zachary Default
 

I agree with Nate about the stopped up exhaust. A quick initial check is to hook up a vacuum gauge and snap the throttle. If vacuum drops off and is slow to return, it's an indication of restricted exhaust. Definitely would still want to do the back pressure test but should give you a quick initial check. Chances are the manifold vacuum will be a bit lower than expected as well due to the…

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Steve Owner
Arizona
Steve Default
 

Vacuum is steady at 17.5 comes right back with snap throttle

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Zachary Mobile Technician
Texas
Zachary Default
 

Does this engine use a mass air flow sensor? If so you can do a volumetric efficiency test. That's going to give you an idea of how the engine is breathing. Ideally you'd want to be able to hit red line on this test but 3500 is essentially your redline right now. ATG has a good VE calculator on their website as well as an app you can download to your smartphone.

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Steve Owner
Arizona
Steve Default
   

At idle exhaust back pressure is less than 1 psi, on snap throttle it goes up to 5 but bounces between 0 to 5 and sometimes saw about 3 inches of vacuum, held at 2500 stayed under 1 psi, correction the vacuum at idle on the manifold was 18.5

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Zachary Mobile Technician
Texas
Zachary Default
 

When you say it bounces between 0 and 5 psi how do you mean exactly? Does it bounce there while holding the throttle or on different snap throttle events? Were you checking back pressure pre or post cat? Either way it shouldn't really get above about 3 psi in my experience. Graph the maf, iat, rpm, and baro pids on your scan tool and take this thing out and hammer it. Take a snap shot of the…

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Nathaniel Diagnostician
Ontario
Nathaniel Default
 

Nate is correct, an exhaust pressure test is required at this point. Tap in somewhere between the turbo and the cat. In a case like this, don't worry too much about finding out what normal back pressure generally should be. When the engine acts up, if it's the exhaust causing it, you'll see a clear spike in pressure.

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Douglas Technician
Maine
Douglas Default
 

Broken up catalytic converter. Pull an 02 and borescope the cats.

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Stuart Mobile Technician
Illinois
Stuart Default
 

What are the fuel trims.A restricted exhaust would be rich condition wouldn't you think?

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Zachary Mobile Technician
Texas
Zachary Default
 

I thought about that too but I don't believe it would show up that way on a single bank engine such as this. I may be thinking wrong, but I'm fairly certain the MAF calculation would be correct since the whole engine wouldn't breathe right. Now if it were a 2 bank engine with separate cats, the clogged bank would have negative trims and the other bank would have positive trims.

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Steve Owner
Arizona
Steve Default
 

1.2%

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Scott Mechanic
Arkansas
Scott Default
   

Look for a problem with boost pressure. The ECU will drop cylinders to prevent over-boost. I'd be surprised if that happened in P/N but it's worth looking at. Damn, let me edit that again. I don't think it will rev over 3500 in P/N.

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Nathaniel Diagnostician
Ontario
Nathaniel Default
 

If the ECU is taking action to deal with boost problems, I would expect it to set a code.

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Scott Mechanic
Arkansas
Scott Default
 

I'm not sure. You'll get circuit codes and it does check MAF against manifold pressure but I don't remember if it will set a code for over-pressure alone.

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Steve Owner
Arizona
Steve Default
 

Boost goes to 20psi at 3500 full throttle

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Douglas Technician
Maine
Douglas Default
 

Subtract your Baro pressure, 15 at sea level, you got 5 lbs Drop the exhaust before the cats and run it full throttle, you should get 30 psi, 15 lbs actual (- baro pressure)

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Scott Mechanic
Arkansas
Scott Default
 

It's been a while Steve but I'm just about certain that's too much. I'm thinking more in the 7psi max range. Have you tried easing up past 3500 rpm on the road? It's been a long time since I've run into this but I don't think even the HP turbo's put out that much. The LP turbo's are more about volume than pressure. If it starts actually "misfiring" (shutting cylinders down) I'd bet money on it…

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Douglas Technician
Maine
Douglas Default
 

Yes, sorry your probly closer. I'm high on my number for a stock Volvo I'm sure. I spoke without thinking of the specific vehicle in question. I work on 90% Ford powerstroke's that are tuned, and 15 lbs is common when actuating the turbo vanes 100%.

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Scott Mechanic
Arkansas
Scott Default
 

Maybe. :) Like I said I wouldn't bet more than $5.00 on my memory but it sounds very much like something I ran into that you could fix for cheap.

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Derek Technician
North Carolina
Derek Default
 

Are you sure the engine is really only going to 3500? Maybe the tachometer is wrong.

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Tanner Instructor
South Carolina
Tanner Default
 

Hi Steve, please do a ve test using this calculator and screen shot the results. The baro will be what ever your local baro reading is where you live. I would also like a screen shot of the maf pid and the absolute load pid merged together during a wot run. atgtraining​.​com/atg-volumetric…

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Steve Owner
Arizona
Steve Default
   

engine size 2.4l # cylinders 5 engine rpm 3500 baro pressure 30.1in/hg MAF 772lb/hr or 12.8 lb/min IAT 92 degrees all adds up to an awesome 119.31% ve and 118.35% theoretical load

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Tanner Instructor
South Carolina
Tanner Default
 

In my humble opinion you do not have an intake or exhaust restriction, maf is reading correctly or at least close and you also do not have a timing problem. Your manifold vacuum would be low if timing was off enough to cause the concern you have and ve is over 100% at what I consider a low rpm for a turbo car so the engine is breathing efficiently. In my opinion the ve you have also tells me the…

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Nathaniel Diagnostician
Ontario
Nathaniel Default
 

Using baro reading to determine VE can't work on a boosted engine. The metric has to be manifold pressure.

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