Lost power

**Pogust** · 05-07-2011, 11:58

I have a motorhome from 96 that only done 20 000 km (12 000 miles). Only driven it 4 000 km myself since bought it last autumn. It suddenly start loosing power, estimate around 20% less. But that is much on a heavy motorhome. I replaces air and fuel filters, lift pump is working well. There is no smoke from exhaust. I got codes P0236 and P0237 suggesting a turbo/wastegate problem. But there is no black smoke or other sympthoms that should show if I have low pressure. Turbo is fine, wastegate seem to work. Still have to get a way to measure the pressure to confirm that. Don't think it's a blocked exhaust system.

Any thoughts?

--
P-O

**Robyn** · 05-07-2011, 12:32

welcome

When was the last time the fuel filter was changed ???

Fuel flow constriction can really chop the power and in a hurry.

Missy

**Pogust** · 05-07-2011, 23:02

Hi Missy,

I changed fuel and air filters 2 days ago, that was the first thing I thought of. I will try find a gauge to measure turbo pressure this week. A loose part in the silencer could cause the same problem, but don't feel like crawling under to take it apart...

Could there be a dried and cracked bellow in the waste gate actuator? The rod is feeling very sloppy when engine is not running, but seem to work when I start. Vehicle has been sitting unused for most of it's life.

--
P-O

**Robyn** · 05-08-2011, 07:17

Check the vacuum to the waste gate actuator, it should be about 16" HG with engine running.

Check the vacuum at the vacuum pump too, it should be 26"hg and steady. If the needle wobble wildy then the pump is shot.

Keep us posted

Missy

**Pogust** · 05-09-2011, 02:19

Made a temporary connection to a pressure gauge. When starting with cold engine pressure is going up to 0,5 bar around 1900 rpm and drops off above. After driving 5 km and engine reaching operating temps, pressure suddenly drops to zero. Looks to me like an electric fault in a component when it gets warm. The drop was instantly from pressure to zero when I was watching the guage.

Don't have a vacuum guage near to test, but is that nessesary now?

I been reading the service manuals, 2 heavy books. Not the easiest to follow, especially when I don't have the diagnostic tools. Any further suggestions appreciated.... I'm going for a 1 000 km trip in a few days and don't fancy limping along without turbo pressure

. I have taken the MAP sensor off and measured resistance. No change when putting a bar pressure on it.

--
P-O

**JohnC** · 05-09-2011, 06:53

Originally Posted by Pogust

I have taken the MAP sensor off and measured resistance. No change when putting a bar pressure on it.

--
P-O

That's not a valid test. Apply 5 volts to the sensor. The output is voltage proportional to the pressure.

If you're going to fire the parts cannon at it, change the wastegate solenoid first. before you do that, though, check all the connectors

**Pogust** · 05-09-2011, 07:06

Tried the MAP sensor better. Applied 5 volts to it and checked what came out. There is 2,4 volts without pressure, and 3,5 volts with 0,5 bar on it. Took the vehicle for a test run and same thing happened, only earlier this time when engine was warmer. Sudden drop of pressure.

Update: bypassed the solenoid, still no turbo pressure. So pump or actuator bad. Will go to town buy a vacuum guage tomorrow. And throwing parts at it is not a valid option. I'm in Europe and parts here usually comes through GM importer at a price I wouldn't consider... So parts are a week away from US dealers like RockAuto. That means I have to make sure I really order the right part.

Anyone taken a pump apart? What could cause this intermittent failure... Really don't fancy crawling under the motor home trying to get that pump out.

--
P-O

**JohnC** · 05-09-2011, 14:30

After it drops out, if you let off the throttle then come back in gradually, does it make boost again or not? When it drops out, is the boost increasing or decreasing right before?

I cannot imagine a failure scenario for the actuator where it would work until hot.

**Pogust** · 05-10-2011, 03:20

Found it! Was the solenoid after all. I didn't manage to bypass it properly first time, there must have been a leak. Now with the vacuum gauge I could see what I was doing. Pump is doing 24" Hg steady.

Thanks Guys for the support!

Now, should I go for the turbo master instead? We have similar emission control as California, would there be a problem if I also do the Heath computer upgrade too?

--
P-O

**anp4god** · 05-10-2011, 03:51

Originally Posted by Pogust

Found it! Was the solenoid after all. I didn't manage to bypass it properly first time, there must have been a leak. Now with the vacuum gauge I could see what I was doing. Pump is doing 24" Hg steady.

Thanks Guys for the support!

Now, should I go for the turbo master instead? We have similar emission control as California, would there be a problem if I also do the Heath computer upgrade too?

--
P-O

I'm dealing with the same issue and believe the solenoid is at fault on my rig as well. I have also considered going with a turbomaster and computer work but the computer isn't in the budget right now so I'll probaby just change the solenoid. Let me know how it works out. Oh, I just passed a smog check here in California. If I get a chance I'll stop back by the shop and ask if the computer programming will cause it to fail.

**6.5 Detroit Diesel** · 05-10-2011, 09:21

Originally Posted by anp4god

I'm dealing with the same issue and believe the solenoid is at fault on my rig as well. I have also considered going with a turbomaster and computer work but the computer isn't in the budget right now so I'll probaby just change the solenoid. Let me know how it works out. Oh, I just passed a smog check here in California. If I get a chance I'll stop back by the shop and ask if the computer programming will cause it to fail.

how did you pass a smog check with a gutted out cat?

**JohnC** · 05-10-2011, 18:57

Originally Posted by 6.5 Detroit Diesel

how did you pass a smog check with a gutted out cat?

The test probably doesn't look for NO2

**DmaxMaverick** · 05-10-2011, 21:09

Originally Posted by JohnC

The test probably doesn't look for NO2

It doesn't. The test consists of a visual inspection (all listed components according to the VIN must be present and "appear" to be working) and a happy computer. Smoke will fail.

**anp4god** · 05-11-2011, 03:21

Originally Posted by 6.5 Detroit Diesel

how did you pass a smog check with a gutted out cat?

It's mostly a visual check and check for computer codes. $50.00

I'm also wondering if anything did get done to the cat when the engine was changed 50K ago. I had mentioned doing it but I think we ran out of time. Nothing looks disturbed at the cat. I might wait until I move back to the midwest before doing any mods or upgrades just so I don't have to worry about it. Hopefully a move will come in a year or so.

**Robyn** · 05-11-2011, 05:59

If you go wityh the Computer upgrade, you need a free flowing exhaust system.

The turbo master and the computer upgrade (reprogram) allow for more boost and more fuel (more power) and the stock exhaust system will be way to restrictive.

If your up and going OK now, wait until t\you can add the exhaust upgrade.

You can do the exhaust without doing the TM and computer, then add afterwards.

check to be sure these components will not violate Cali Smog Laws.

**DmaxMaverick** · 05-11-2011, 07:36

Originally Posted by Robyn

If you go wityh the Computer upgrade, you need a free flowing exhaust system.

The turbo master and the computer upgrade (reprogram) allow for more boost and more fuel (more power) and the stock exhaust system will be way to restrictive.

If your up and going OK now, wait until t\you can add the exhaust upgrade.

You can do the exhaust without doing the TM and computer, then add afterwards.

check to be sure these components will not violate Cali Smog Laws.

They will. Any of the above. The visual inspection requires all of the OEM emission system equipment to be present and working (or appear to be working). Computers are more complicated. The best option is to obtain a core PCM and have it programmed (for testing, diagnostic, or off-highway use only. It is unlawful to modify or disable emission system equipment in any way). Swap in the OEM during the test. The converter must "appear" to be present. The actual function (exhaust gas composition) isn't tested.

**a5150nut** · 05-11-2011, 19:47

DMax,

Which counties are they testing in?? I'm in Santa Clara County and have a 94 and haven't had to test so far. Knocking on wood. . . . Maybe I need to register in Lasen County to be safe. Or am I out of the year range or 8600 gvw get me clear ?

**DmaxMaverick** · 05-11-2011, 21:22

So far in CA, it's for 1998 models and later. Nothing for earlier models.

**rameye** · 05-12-2011, 04:28

No cat for 8 years..passes every time. CT's test is not a joke either.

**Pogust** · 05-16-2011, 03:04

I have done 500 km since bypassing the solenoid. Manifold pressure stay around 3-4 psi when full vacuum on the wastegate. Haven't felt any difference in driving, and fuel economy is exactly the same.

--
P-O

Thread: Lost power

Thread Tools

Display

Lost power

Posting Permissions