Low power

Car came to me with low power. It had been to a shop and they did some troubleshooting, but I don't know what the results were. I know that they disconnected the MAF and the intake at the EGR valve and the downpipe. I know this because this is how he drove it to me.

I found that the turbo vanes were seized, so I put on a good, used hot side and the actuator works when doing output tests with VCDS. So that means the N75 is good as well.

After I put the turbo back on, it still had no power and it wouldn't rev past 2500 RPM. I don't know if it would have before the turbo.

MAF specified and actual are hitting 850.

I got to wondering about the downpipe and I sat in the parking lot with the pedal on the floor. Slowly the RPMs would climb. Eventually I was hitting 3700 RPM and she was spewing blue smoke.

I think I need to pop that downpipe back off and see if we have a restriction. It's like sitting there revving it has help blow out the crap in the exhaust.

So, lets say that we do have a restriction there. Other than modifying the exhaust system, how do you clean out the exhaust other than a Tony tune-up?

Clogged cat perhaps? If so...fixing the restriction is easy.

That was my thought once I saw the rmps start to climb when holding it in the floor. I didn't pull the downpipe today because it was still hot and I didn't want to. That'll be the next thing I do.

N75? Could it be in chronic limp mood?

MarsBar said:

N75? Could it be in chronic limp mood?

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Cycling the key doesn't return power. Also limp mode wouldn't allow the RPMs to slowly climb.

Vince Waldon said:

Clogged cat perhaps? If so...fixing the restriction is easy.

Click to expand...

.......or possible restricted intake?

MAF readings are good.

Exhaust not plugged.

Logged 3, 4 and 11. MAF was reading fine, Boost was reading fine.

Timing would go inverse of what it wanted. At one point, it was requesting +9 degrees advance, but I was getting -10 degrees.

Um, what?

It would kinda help if we know what engine we are talking about here.

I never mentioned that? Sorry. It's an ALH.

checking the case pressure would be a good direction to go, then.

whitedog said:

Timing would go inverse of what it wanted. At one point, it was requesting +9 degrees advance, but I was getting -10 degrees.

Um, what?

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-10?

Where is the timing set at warm idle? What is the duty cycle?

The car should trip a code for the timing being that far off shouldn't it?

Wow. I'm just watching is all.

Check for rags in the lower portion of the intercooler...

oldpoopie said:

Check for rags in the lower portion of the intercooler...

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Done that, but I should pop the hose off the EGR just to be sure. Why the -10 on timing under load? At idle, timing is perfect.

I can check my logs for what duty cycle was at idle and under load.

Hello "White-Dawg".
I recommend taking a vacuum reading.

Connect your vacuum gage at item #9 (small nipple). At idle you should be reading 30" of vacuum. The vacuum pump on my ALH was reading near 20" and caused me considerable problems. I repaired my vacuum pump and and now get a reading of steady 30" of vacuum and solved my problems.
I had already replaced the vacuum lines, MAF sensor and the N-75 while the whole time the problem was a weak , leaking vacuum pump.

One other item you should check is the vent hose on the vacuum system.
Last year I made a dumb mistake while replacing the engine air filter.
I had pinched the vacuum vent hose between the lid of the filter box and the lower box.
This "pinched" hosed caused me some serious problems.

In Basic Settings at idle isn't pump at it's fully retarded position? I didn't think it could go backward from there?

It seems to be temperature related. Cold start (45ish) and it wouldn't rev to 1500, but as I kept on it, it would rev higher and higher. Just sitting in neutral and revving it, the Actual timing was retarded when it was asking for advance. Let it go to neutral and it sits very close. Duty cycle was 94.7%

I am pretty sure that the problem doesn't lie with air flow. If there was a restriction, my MAF readings would be off and they are not - they follow requested right on. I pulled the relief valve and it was all intact - out maybe 1/16' so I tapped it back in. I haven't checked pump pressure yet. I want to, but if the pressure is low, how would that cause the timing to go opposite?

Revving in neutral. You can see that the RPMS are starting to slowly climb.



I do have very low vacuum. Like 13 inches at idle. The piping is also hacked together. I think I will start there to eliminate that problem, but that won't effect the timing, will it? I just can't see how.

whitedog said:

Let it go to neutral and it sits very close. Duty cycle was 94.7%

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What was the request/actual timing at idle?

The 94.7%, was that at idle, at full operating temp?

It's starting to sound like an N108 problem...which could be a wiring problem, or a problem in the start of injection plunger/bore...dirt or debris, plugged screen, burrs, etc. Low fuel pressure...plugged pick-up in the tank, etc...

Is the car throwing any codes for not being able to meet requested timing?

At idle, they are close, but not exact. Something like 2.2+/- for req. and 0.0+/- for actual.

I am going to talk to DFIS tomorrow. I could be wrong here, but if there was a sticky timing plunger, I don't think that it would be moving exactly opposite of what it is told to do.

Same with the N109 --- I think.

whitedog said:

I am going to talk to DFIS tomorrow. I could be wrong here, but if there was a sticky timing plunger, I don't think that it would be moving exactly opposite of what it is told to do.

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Well...that's what it might do. The timing plunger is spring return (spring pressure to retard) so if N108 isn't supplying enough fuel pressure to push the plunger for advance, the spring is automatically pushing it to retard the ignition.

I dunno. I'm no expert...just thinking out loud of why the timing might not be able to meet requested.

Of course there could be something else wrong, but that sounds like one issue at least...

Rembrant said:

Well...that's what it might do. The timing plunger is spring return (spring pressure to retard) so if N108 isn't supplying enough fuel pressure to push the plunger for advance, the spring is automatically pushing it to retard the ignition.

I dunno. I'm no expert...just thinking out loud of why the timing might not be able to meet requested.

Of course there could be something else wrong, but that sounds like one issue at least...

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I was in the middle of looking at my junk IP to get a better picture and think about this when I had to go move a couch.

I am thinking about spring pressure and fuel flow and other stuff. I think I need to review the operation of the pump in regards to timing adjustment.

Here is something else to mull over. You know how when you switch to basic settings, if the timing is on, the engine sound doesn't change? This one doesn't change at all. I don't know if that means anything or not.

whitedog said:

I am thinking about spring pressure and fuel flow and other stuff. I think I need to review the operation of the pump in regards to timing adjustment.

Click to expand...

Some good reading here with a nice cross sectional picture that shows the spring return in the injection advance/retard plunger.

http://www.dbwllc.net/app/uploads/2014/09/Advance_Solenoid_Replacement_Procedure1.pdf

That was the picture I was looking for. The N109 bleeds pressure off of the piston and the spring pushes the piston to retard. For the piston to move towards retard, the pressure has to drop on that side. So why does the pressure drop when under load? Or, to look at it the other way, why is there more pressure on the spring side? The spring side bleeds pressure to the suction side of the low pressure pump so why would pressure build?

How about this? We know that a pump only creates flow and pressure and comes from resistance to flow. So what if there is blockage after the spring and before the suction side? As the N109 opens to bleed pressure from the piston side to spring side the fuel should flow back to the suction side but if its blocked, pressure would build, pushing the piston towards retard.

That was the picture I was looking for. The N109 bleeds pressure off of the piston and the spring pushes the piston to retard. For the piston to move towards retard, the pressure has to drop on that side. So why does the pressure drop when under load? Or, to look at it the other way, why is there more pressure on the spring side? The spring side bleeds pressure to the suction side of the low pressure pump so why would pressure build?

How about this? We know that a pump only creates flow and pressure and comes from resistance to flow. So what if there is blockage after the spring and before the suction side? As the N109 opens to bleed pressure from the piston side to spring side the fuel should flow back to the suction side but if its blocked, pressure would build, pushing the piston towards retard.

Lug_Nut had a problem like this, and it turned out to be a restriction in the intake. I don't recall if he checked the MAF readings though.

Simple test... unplug the MAF, remove the charge air pipe going to the intake, and see if it revs.

-J

Lug_Nut had a problem like this, and it turned out to be a restriction in the intake. I don't recall if he checked the MAF readings though.

Simple test... unplug the MAF, remove the charge air pipe going to the intake, and see if it revs.

-J

Did that and no change. I think Luggys problem was the intake manifold. He had to remove the intake to get it to rev. I don't recall his MAF readings either.