HOW TO DO AN ADVANCED SEARCH.

Mon Jul 08, 2013 3:56 pm by Admin


For the benefit of 944Hybrids users there are two search functions available for you to use.
The purpose of this sticky is to explain the "Advanced Search" function because it is much more powerful and is the best choice when researching information.

When you log on to the site a list of options is shown in a line at the top of the page. One option is labelled "Search", use this option (NOT the search box lower down on the right).

After you click on the upper search option, a drop down box appears. At the bottom of this box is a radio button marked "Advanced …

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Cranks, but nothing else (Surprised? no)

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Re: Cranks, but nothing else (Surprised? no)

Post  Bridar on Mon Sep 13, 2010 10:06 am

I don't think that the VSS would do that, since many people don't run it at all. VSS is mainly to keep the engine running smoothly on rapid decel, like comming in hot to a stop sign.

Could it be a fuel issue? Just sitting still and revving, an engine doesn't require much fuel as commpared to when it is at partial or even full load (defined as brake-specific fuel consumption for you aspiring engineers out there). So I'm thinking while you may have ample pressure, if your pump cannot deliver the required GPM's of fuel, the engine will starve under load. Check fuel filters and if they are ok, then disconnect a fuel line and time the flow into a bucket (in a safe manner, of course). These same symptoms can occur if a spark is not hot enough or if plugs are really dirty, though that is less likely on modern computer controlled engines like the LS1. You could also try driving at speed down a hill, without accelerating and then seeing if the engine runs smoothly above teh 2000 rpm mark. That would definately tell you if it is VSS or not.
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Re: Cranks, but nothing else (Surprised? no)

Post  spence on Mon Sep 13, 2010 10:10 am

How old is the gas in the car? Has it been in the tank for a long period of time?
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Re: Cranks, but nothing else (Surprised? no)

Post  Luke714 on Mon Sep 13, 2010 10:20 am

How old is the gas in the car? Has it been in the tank for a long period of time?

Embarassed

probably too long, since thanksgiving last year. Would that cause to only run like $#** under acceleration? I've got the pressure, but I'll test flow rate next weekend. What kind of numbers am I looking for? I put in a new fuel line to the engine and the only filter I have is the filter/regulator from a corvette. That's new. The plugs look fine, but I have not changed them.

Is the MAF suspect? Are there any sensor inputs that I could be missing that would cause this?

I won't worry about the VSS then. I bought the cheaper sensor pn: 24225896. Will I be able to plug this directly into the harness and have it work exactly in the same way as pn: 15547452 which is like $88
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Re: Cranks, but nothing else (Surprised? no)

Post  Bridar on Mon Sep 13, 2010 10:44 am

The Stock 944 Bosch fuel pump has a minimum delivery rate of 850cc in 30 seconds. If it is lower than that, the pump is bad. My pump went bad, THe Bosch units are very susceptible to low voltage operation, so if your battery is very low when you try to turn the engine over, it could burn out the pump motor, as mine did. I replaced it with a Walbro GSL392, which also has better output.
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Re: Cranks, but nothing else (Surprised? no)

Post  Dawgz83948 on Mon Sep 13, 2010 10:50 am

Or for those of us that want a bolt in that isn't a million bucks.

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Re: Cranks, but nothing else (Surprised? no)

Post  Luke714 on Mon Sep 13, 2010 11:02 am

so people really think it's the fuel pump? Aren't most people using the stock 951 pump? Is there anything else I should check? Could the computer causing a lean condition that is doing this? I'll check the flow this weekend, what should I be looking at for gpm?
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Re: Cranks, but nothing else (Surprised? no)

Post  Bridar on Mon Sep 13, 2010 11:33 am

850 cc/30 sec. or .45 GPM
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Re: Cranks, but nothing else (Surprised? no)

Post  944-LT1 on Mon Sep 13, 2010 12:26 pm

You HAVE to buy a scanner. I do agree thats its not VSS. I do agree it could be the fuel. But I have to mention that the O2 sensors could be junk, not hooked up correctly, intermittant, etc. And then again, it could be due to MAF, TPS, bad coils, bad spark plugs/gapping, wires, airflow into the TB, injectors, fuel pump/regulator.....

Theres many many things that cause this. Have it scanned to make sure its not something within the engine controls.

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Re: Cranks, but nothing else (Surprised? no)

Post  Luke714 on Mon Sep 13, 2010 4:38 pm

Ok, I just ordered all the stuff to wire in an ALDL port. Does anyone have an old junk harness you can sell me cheap for the wire? I'll pay quick so that maybe I can receive it by Friday. My feeling is that my problem isn't the fuel pump so I want to explore other options first. I want to check how my O2 sensors are hooked up. The plugs on the O2 sensors that I bought and the plugs on the harness matched so I didn't really bother double checking but I should.

The plugs are the same that came with the engine, the wires are new. The filter and regulator is a new unit from a corvette. The prime suspects right now in my opinion is the MAF and the O2 Sensors. I just thought that a problem with either of those would show up when it was revving without load.

Thanks,
Luke
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Re: Cranks, but nothing else (Surprised? no)

Post  Wild Bill on Mon Sep 13, 2010 10:24 pm

Awesome progress!! If I recall you need at least 42 PSI for it to work properly.. Porsche oil pressure gauge.. Original sending unit I just drilled and tapped it down the center of the little hole for 1/8" NPT and reused it.. with all the machines you have you can probably dress the threads off so it looks normal. I can't see an O2 sensor fail limiting you to 2000 rpm. Doesn't sound like limp mode to me?
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Re: Cranks, but nothing else (Surprised? no)

Post  Luke714 on Tue Sep 14, 2010 9:11 am

Thanks! Yeah, I got the OP working a while ago. I threaded it into the oil filter adapter, just used a VDO sending unit and gauge. Works great and I love the gauge! I mounted it along with a water temp in the center console.

I want to at least check my O2 sensors, I have to admit I just plugged them into two plugs by each header that fit the plug on the sensors I bought. I couldn't find any other plug on the harness that fit and they were in the position by each bank so I just lengthened the leads on the sensors I bought and plugged them in, I didn't even check that they were right by chasing the wires back to the ECU. Thinking back on this it was pretty stupid. What do the plugs on the O2 sensors look like for you guys? Mine were square four pin.

I was thinking that the rear O2 sensors would only be used for emissions, and if I had emissions removed the computer wouldn't even recognize those sensors. So if I have my two front sensors plugged into where the rear ones go they won't be doing anything. If that's the case the ECU won't know to richen the mixture under loaded acceleration. My symptoms are similar to an over lean condition (maybe??). I don't think it would be a MAF issue, because the engine runs fine without a load and the mass air flow is solely dependent on temperature (density) and engine rpm (volume flow). The amount of air being sucked into the engine at 2000 rpm under load is exactly the same as 2000 rpm without a load. But if the O2 sensors aren't there to pick up on a need for more fuel then the computer won't richen the mixture under loading.

That logic is probably flawed, but it's a place to start. tongue

Which bank are the front sensors again? Bank 2, right?

Cheers,
Luke
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Re: Cranks, but nothing else (Surprised? no)

Post  Luke714 on Tue Sep 14, 2010 2:46 pm

Ooch, completely ignore what I said about the MAF. I'm embarassed I ever had that train of thought.

That means the MAF is suspect as well, I was just hoping wouldn't be the problem Sad

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Re: Cranks, but nothing else (Surprised? no)

Post  Porch on Tue Sep 14, 2010 5:14 pm

Couple points:
1). you can't tell rich or lean by the seat of your pants. Don't assume either!
2). Looking at your maf setup, i wouldn't be surprised if that was the problem. Disconnect the maf sensor and take it for a drive before you make any other changes. It will run on the base maps (so it won't make a ton of power), but it will fix the problem if that's what it is.
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Re: Cranks, but nothing else (Surprised? no)

Post  Luke714 on Tue Sep 14, 2010 10:17 pm

I know I can't guess the Fuel Air ratio, I'll probably end up putting in a wide band O2 sensor and getting it tuned.
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Re: Cranks, but nothing else (Surprised? no)

Post  Porch on Tue Sep 14, 2010 10:36 pm

Well, you'll definitely need to get it tuned one way or another. I do think you should try unplugging the maf first just so you know where to start!
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Re: Cranks, but nothing else (Surprised? no)

Post  Luke714 on Tue Sep 14, 2010 11:03 pm

I'll do that for sure!
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Re: Cranks, but nothing else (Surprised? no)

Post  Porch on Wed Sep 15, 2010 11:06 am

BTW, not saying anything is wrong with your MAF setup, it looks good! It looks like you went to an aftermarket housing or a different style MAF, though. Stuff like that can really throw the computer off! Even de-screening the stock MAF requires a retune. They're finicky little things!
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Re: Cranks, but nothing else (Surprised? no)

Post  Luke714 on Wed Sep 15, 2010 1:19 pm

yeah, I know. I think I'm going to have to narrow it down to the MAF and then trailer it to Portland so that it can be put on a rolling road. I will have to buy two wideband O2 sensors, right?
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Re: Cranks, but nothing else (Surprised? no)

Post  Porch on Wed Sep 15, 2010 3:11 pm

You mean because of dual exhaust?
Generally, no... You just kind of assume (but verify) that the exhaust is the same on both sides. As long as the engine (injectors, spark plugs, wires, rings, etc.) are all in good shape, it shouldn't be an issue.
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Re: Cranks, but nothing else (Surprised? no)

Post  Luke714 on Sun Oct 03, 2010 10:49 am

See:

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I still plan on having it tuned in the spring to make sure everything is running as efficiently as possible though, although I'm pretty darn happy about how it's running currently. I just have to get the stupid cooling problem fixed Evil or Very Mad I may be posting a new cooling scheme in the near future.

Thanks for all the help guys,

Luke
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