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2000 Camaro Z28 LS1 engine, 6-sp manual transmission. Engine…

2000 Camaro Z28 LS1 engine...
2000 Camaro Z28 LS1 engine, 6-sp manual transmission. Engine has been modified. 2200-7200 Compcams cam, 60 lbs injectors, 80mm Edelbrock throttle body, ported heads, ported exhaust manifolds, 2 1/2" y-pipe to 3" pipe to Magniflow... Engine ran great 35,000 miles, until today. At idle, engine started to run very poorly, like misfiring cylinders. All ignition coils are working fine. At idle, on 4 cylinders, when the fuel injectors are unplugged, there is no change. With engine running, using a multimeter, on those cylinders, the connectors have 14.26V from (+) wire to ground, 8.91V when multimeter is connected between the 2 wires at each connector. So there is no electrical issue, injectors must be no good on those cylinders. Engine has been dynotuned to those 60lbs injectors. I plan on replacing all of those injectors with better quality ones. Are all 60lbs injectors the same? Will I have any issues by simply changing out those injectors with better quality ones?
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Answered in 55 minutes by:
1/2/2016
Gary
Gary, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1,644
Experience: Senior Technician
Verified

Hi there,

Can you tell me which cylinders the engine is misfiring on?

Can I assume that your modified engine has a non-AFM camshaft?

I would always recommend to replace injectors with the same type from the same manufacturer.

If other injectors are also rated at 60lb, then they are probably ok, but there could be subtle differences.

Then the tuning will be off, some rich some lean etc.

Gary

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Customer reply replied 2 years ago
Cam is Compcams K54-428-11 kit. Cylinders 3,5, 2,4. The current injectors are Siemens Deka, paid $229.00 for set of 8 of eBay. Ran great for 35,000 miles. I was considering going with a FAST 306008 60lb set. But if that is going to throw the tune of then I won't. Should I still stay with the Siemens Deka? If so, it shouldn't have to be re-tuned then right?

Hi again,

I am happy that you have used a kit from a cam manufacturer, especially Comp Cams, top marks.

Are you quite sure it is the injectors for those four cylinders, all failing at the same time?

The cylinders you have mentioned are adjacent to each other, 3 and 5 on bank 1, and 2 and 4 on bank 2.

Have you done a compression test with all spark plugs out?

Have you measured the injectors resistances, all 8 for comparison?

You should be able to stay with identical injectors and no further programming should be needed.

I would ask the programmer what the maximum duty cycle is at the moment, maybe you need larger injectors.

Gary

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Customer reply replied 2 years ago
100% sure all 4 of those injectors failed at the same time. I did not see a reason to do a compression test. It does not burn any oil, no smoke in exhaust, not even an engine code. If compression was off, cylinder would still fire. If there were no compression, I'm sure there would be smoke in the exhaust. With engine running at idle, disconnecting the injectors involved has no impact on idle quality at all, not even a momentary drop in rpm. This happened at idle.

Hi Brian,

Ok, I would class it as extremely odd to have 4 fail at the same time, but if you are sure it is the injectors, then go ahead with replacing them.

Strange that is also does not have an engine code.

But maybe the program ignores misfires, since misfire detection is more important for emissions as far as OEM is concerned.

It is possible that the offending injectors have become blocked with fuel system debris etc, I would take the rail and injectors out for a flow test by an off-car injector specialist.

I have seen injectors block up or go open circuit (no fuel), and have seen injectors stick open, flood the engine and then bend rods. It only takes one to do that.

I bet your car goes well prior to this.

Gary

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Customer reply replied 2 years ago
I agree with you that it is extremely odd. On the 4 that work, the idle changes when the injectors are unplugged. The 4 that I am referencing do not. Like I said this happened at idle. Can the fuel rail be cleaned without taking it to be tested? The injectors that are in it are out of warranty. I don't really have a lot of time, would rather just purchase a new set, and clean the fuel rail. Yes, my car is quick.

Ok, another test to do.

Have you had a noid light on the injector plugs to see if the pulse is there?

Another thought is the offending cylinders are 2,3,4,5.

Coincidence?

Is it a programming issue for antitheft or something?

You can remove the rail, remove the injectors, blast some carb cleaner through the rail, to make sure it is clean, fit the new injector set, etc. Replace your fuel filter.

I like to read the new injectors ohms first, just in case one is faulty out of the box.

Gary

Gary

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Customer reply replied 2 years ago
I don't have a noid light, just know that there are no broken wires, no electrical issues. The system must have had debris in it some how. That is the only explanation I can fathom for 4 injectors failing at once, at idle. Fuel filter is prob has 12 months on it. I wil definitely changing it. Can the fuel pressure regulator in the fuel rail be cleaned with carb cleaner too? How is it cleaned? Would the regulator have any debris caught in it?

Hi Brian,

If your system is like ours, then you only have the feed line going to the fuel rail.

The regulator is in the tank pump assembly.

You may find nothing in the rail, but you need to take it off for inspection.

If you are really keen, I would swap the 4 injectors with the other 4 and see if the fault does go to the other 4 cylinders.

Gary

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Customer reply replied 2 years ago
There is a valve in the fuel rail. What is that? Does it need to be cleaned? The fuel rail has to come off to change to change the injectors anyways.

It may have a damper within the rail.

It also has a schrader valve for fuel pressure measurement, and pressure relief prior to disassembly.

A blast of compressor air as a final check to make sure all is clear.

Blast into a rag etc, to check for what may have been in there.

Gary

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Customer reply replied 2 years ago
The valve is part of the rail, does not separate from it. Should I blast it from all sides?

It really depends on what if any comes out of the rail.

The injectors have their own filters, so as you pull each one out, look into the top of the injector for debris.

That will give you idea of what might still be in the rail.

It could well be clean inside, a blast out of air in every direction should suffice.

Gary

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Customer reply replied 2 years ago
Is it possible that the injectors involved just need to be cleaned? Or are they no good once debris get's in there?

Hi Brian,

I have seen many injectors come back from the dead after a clean.

Get them out for an off-car injector flow test and clean.

Could be worth your while prior to buying a new set.

Gary

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Customer reply replied 2 years ago
Do they have to be taken somewheres or can I clean them myself with air compressor/carb cleaner?

Injectors are best cleaned by an ultrasonic cleaning machine, and then flowtested to ensure they flow within a tolerance of each other.

Normally the tech would flow them first to see the errors.

Gary

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Customer reply replied 2 years ago
Where would I find a place that has 1 of those machines?

Hi Brian,

You need a service that comes to you like this:

http://electronicinjectorservices.com.au

Do you have anybody like this where you are?

It would cost you more to buy the necessary equipment than to buy many sets of injectors.

Gary

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Customer reply replied 2 years ago
This was addressed in the other thread we had today. Thx.

Hi Brian,

I hope I have given you some guidance with your car.

Gary

Gary
Gary, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1,644
Experience: Senior Technician
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Customer reply replied 2 years ago
Thanks you for your assistance.

Thanks very much Brian.

Hope you get your car running fast again.

Happy New Year to you and your family.

Regards

Gary

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