Need to figure out why LX9 runs poorly

[pocket-rocket]

Fuel pressure can play a HUGE role in how well an engine runs. My friend had one of those stupid Central Point Sequential FI 4.3 Vortecs in an S10 SS. When the fuel pressure was something like 8psi low, it ran like crap and was a complete dog. We cranked up the pressure to what it was supposed to be and instead of barely getting out of its own way I left ~30 foot number 11's on the road in front of his house. I would look into Dave's suggestion.

[Fastmax32168]

I cannot tell you the cause, but based on your symptoms it sounds to me like you are losing a cylinder which shows up more when the vehicle is placed under load. I would check to make sure you do not have a bad injector or bad coil. It is not uncommon for fuel to dry up in injectors when they sit open and render them inoperable. I would try pulling the injector wires one at a time and see if there is a cylinder that seems to not affect or affect the "vibration" less than the others.
Roy

[Schmieder]

I cannot tell you the cause, but based on your symptoms it sounds to me like you are losing a cylinder which shows up more when the vehicle is placed under load. I would check to make sure you do not have a bad injector or bad coil. It is not uncommon for fuel to dry up in injectors when they sit open and render them inoperable. I would try pulling the injector wires one at a time and see if there is a cylinder that seems to not affect or affect the "vibration" less than the others.
Roy

In that case, a bad spark plug wire can do that too. I had stock wires snap inside at the boot and don't even know it until I saw it arcing to the block. As it happens, it held idle okay, but any load caused heavy arcing.

I always test resistance on spark cables now when I remove them.

If your tuner has a cylinder balance test, I know HPT does, that can help isolate the offending cylinder (if that is the case). If pulling injector wires is too hard, try pulling spark plug wires at the boot. But don't pull any further then enough to disconnect. Or else YOU will become the path of least resistance and ZAP-ZAP-ZAP. GM HEI is quite strong and hurts, lol.....I know.

There is a cheap way to clean fuel injectors with carb cleaner, plastic syring, a switch, car battery and some wire. Look it up in youtube if you need to clean an injector for cheap.

Just some ideas, maybe one of them will lead you to find the problem.

[Fastmax32168]

That is all correct and good points. Just to add to that, if you do find a bad cylinder it is due to one of 3 things: spark, fuel, or compression.
After you have determined which cyl it is you can move things around between that cylinder and a known good cyl. For example if the problem moves when you switch a plug wire between cylinders you have found your culprit. If not you need to keep looking for the problem.
If you cannot get the problem to move around you need to do a compression test to determine if you have an internal problem.
Roy

[pocket-rocket]

In that case, a bad spark plug wire can do that too. I had stock wires snap inside at the boot and don't even know it until I saw it arcing to the block. As it happens, it held idle okay, but any load caused heavy arcing.

If your tuner has a cylinder balance test, I know HPT does, that can help isolate the offending cylinder (if that is the case).

He's OBD1, so no cylinder balance test.

Also the reason yours did that was because the the path to the block was of less resistance than what the spark plug was seeing because of the high cylinder pressures under load.

[jmgtp]

I've already tried to narrow it down to a specific cylinder. I did so by pulling a spark plug wire, starting it up and seeing how it ran. Shut it down, plug that one back in and unplug the next. In all cases it ran much worse. I can't really do that with the fuel injectors since they are under the intake manifold. The idle is steady, but it is unsmooth enough to make the Getrag rattle around and be noisier than it should be with the clutch engaged.

I have a compression tester but haven't check compression at each cylinder yet. It is a 100% stock LX9 with 52k miles, and while I know its plenty possible that it has bad compression in a cylinder it really shouldn't for its age/miles and prior life in a Malibu. The only thing I did was replace the LIM gaskets while it was on the stand. And of course that meant removing the pushrods but I was sure to put them back in the correct places (intake vs exhaust). Had I not I would have bent a valve and I imgaine I would hear some top end noises - and the top end runs silently. I also turned the motor over several times on the stand by hand and did not run into any interference.

[pocket-rocket]

I've heard a 3400 with pushrods in the wrong spots. Yes, you would for sure have heard some noises.

I almost want to mention Schmieders problem with dry cylinder walls not letting his build enough compression a while back, but I imagine by now yours should have had well more than enough oil on the walls to aid the rings. This sucks, I wish I had the answer for you, but without me being there to help troubleshoot I'm handicapped in helping :/ Maybe your car is pissed because it considers you a traitor now, lol. At least you didn't drop in "the engine that shalt not be named". That would make me consider you a traitor, but not an LX9 so much

[jmgtp]

Everyone,

I appreciate your responses. I will not be able to work on the car for at least a week and possibly longer but will revisit this thread once I am able to do so.

I ended up taking a small side job of replacing the radiator in a Chevy Truck, I was done in 45 minutes. Unfortuneatly, I discovered severly corroded and leaking brake lines throughout the truck which require replacement. Prebent tubing is unavailable (OEM or aftermarket) and I am going through the cumbersome process of bending, flaring and installing new line.

[pocket-rocket]

I never buy prebent. It's so much cheaper to bend your own.

Flaring and bending is cake, but then again, I've done it hundreds of times (if not thousands), literally. Not always on steel brake line, but copper tubing at work, and there isn't a single unit that I don't have to do some handy dandy hand bending.

The best advice I can give on bending is always support where you are bending, luckily the smaller the tubing, the more it resists kinking when hand bending. Don't just grab each end of the tube and bend unless you want to practice flaring new ends on the new piece after you remove the kinked piece. Also have a good quality flaring tool. Those $30 jobbies at the parts store are just shiny headaches in a package. I own this one:

http://www.grainger.com/Grainger/GENERAL-Double-Flaring-Tool-3ZH04?Pid=search

I've had 3 or 4 of those $30 ones from the parts store (thank God for lifetime warranties). One kit I got 1 good flare out of it before the press, I guess you would call it, started tracking sideways ruining every flare after that. This kit I have now might have cost more, but it's given me nothing but perfect flare after flare after flare, and I expect it will keep doing so for years to come.

I also suggest where lines run through enclosed areas (like between the frame rail and gas tank type of situation), seal the ends off somehow, be it tape or something. The last thing you want is a decent chunk of rust or dirt in your nice new brake lines.

[Schmieder]

He's OBD1, so no cylinder balance test.

Also the reason yours did that was because the the path to the block was of less resistance than what the spark plug was seeing because of the high cylinder pressures under load.

Ah yes, good ole physics. I love it. Somedays you'll catch me trying to calculate something crazy, like how fast steel at 190° will tranfer heat into gasket material, aluminum and then the air charge. btw, I still never found out the true volume of my plenum.....one of the values I was searching a ways back.

[Schmieder]

Everyone,

I appreciate your responses. I will not be able to work on the car for at least a week and possibly longer but will revisit this thread once I am able to do so.

I ended up taking a small side job of replacing the radiator in a Chevy Truck, I was done in 45 minutes. Unfortuneatly, I discovered severly corroded and leaking brake lines throughout the truck which require replacement. Prebent tubing is unavailable (OEM or aftermarket) and I am going through the cumbersome process of bending, flaring and installing new line.

When you get back........

You say there is a rattling that is greater with the clutch engaged? (pedal up) Maybe you have a loose rod cap or cracked connecting rod.

Are you getting excessive fuel/fumes from the oil dipstick port? Remove the oil dipstick and if you can SEE fumes puffing out, you probably have a compression issue. I can't say this is definate, but I noticed this when my rings were dry, excessive blow by. Any crack or loss in compression around the rings could do the same, and cause you problems.

If you haven't visually checked the injector spray, I suggest doing so. Remove the plenum and carefully remove the fuel rail with injectors still in the fuel rail. Remove the connectors to the ICM, specifically the power supply, we don't want sparking at this point.

Have a friend turn the engine over or do it by hand at the crank pulley. Your injectors will start firing off fuel (don't breath it in, please. it will burn for hours)

You should be able to tell if one injector is pissing instead of spraying. You will also rule out a leaky injector as well. It is possible to have an injector pissing while shut, and at 3-5% IPW, that is a lot of liquid fuel being dumped which in turn can cause a strong loss of power for that cylinder.

If you have a constant misfire, try disconnecting the battery and touch the (+)(-) terminal cables, not the battery. This discharges any remaining power and the PCM will reset fuel trims. It wont fix the problem but, a misfire can cause the PCM to skew richer fueling as the oxygen tricks the PCM into thinking their is a lean condition. If the car runs better after that (while cool) then your fuel trims were pegged.

But you are OBDI, I know next to nothing about OBDI systems.

Have you tried unplugging the MAF, O2 sensor (upstream).

[jmgtp]

This is a MAP only car, no MAF. I haven't tried unplugging the o2, it is a stock LX9 o2 sensor. I've heard it can switch too fast for the obdI ECM, but others that have done this swap report no issues using it.

Will injectors even spray without power to the icm? Were would the reference pulse come from since the cps feeds direct into the icm? Unless the ECM is able to pickup on that signal even if the icm isn't powered.

It doesn't have any blow by. I can run with the oil cap off and no smoke. It was ingesting a lot of oil through the intake at first. The stock lx9 setup doesn't use a PCV valve, it applies full vacuum to the front valve cover and this motor was just inhaling oil through it until I put a PCV valve inline. The motor has about a full tank of gas through it since the swap so any stuck rings I'd think would be free by now.

The getrag rattle calmed down a bunch as the idle improved over successive tunes. It's not that noticeable anymore, but it still a bit more rattly than I think it should be and that has to be due to the idle not being perfect.

Hoping to have the truck I am repairing done by the weekend, then I can delve back into the grand prix.

Thanks,
John

[Schmieder]

Yeah, keep in mind I am learning myself. You are probably right about unplugging the ICM. But anyway you can visually check the spray pattern can only help rule out the injectors or nail the problem. I just didn't want you turning the engine over, fuel spraying all over and a spark igniting the fuel drifting down a runner flashing up into your face. lol, very bad.

However you go about it, checking the injectors is a wise idea. Especially if the car sat for some time.

I once read you can hear a pissing injector through the throttle body once the pump primes the pressure, but engine isn't running. it should sound like a distant waterfall.

lol, see, I don't know OBDI and I just learned you run speed density fueling.

I had a HUGE problem recently with my GP. I was diagnosing everything up/down/left/right and it was a backwards wired crank sensor. Apparently the crank sensor can not be backwards even though it is a simple device that operates backwards. The PCM was dedicating #1 TDC at some other offset crank angle. Worth checking out, make sure the High and Low signal are wired properly. Or else the low is read as high and the high as low, causing the car to not run or run like utter crap.

[jmgtp]

The Grand Prix is finally back home in my garage. Replacing steel brake lines on a Silverado was just the beginning. Then I had a Trailblazer come in that needed a new steering rack, a Civic with bad brakes and then an Impala with a bad waterpump.... now that I've fixed everyone elses junk maybe I can get around to fixing my own car!

So, first things first... I have a new bin to try but it is made to run 3400 injectors (which I have) on 55 psi fuel pressure (I don't have! Mine tops out at 43-44psi). So I need to find a 3x00 fuel pressure regulator set at 55 psi. Information that I have is that any 2000+ 3x00 fuel rail will have the 55 psi FPR. Problem is that my usual source (ebay) doesn't have any for a reasonable price.

So anyone have a 55psi FPR or fuel rail w/FPR from a '00+ 3x00 for sale?

[jmgtp]

just found out that new FPRs arent that expensive at the parts store.

I guess the question is will a 55psi FPR bolt right into my existing fuel rail which currently has a 44psi regulator?