engine miss
 

My LS1 swap has been great running for around 5 years. Yesterday I took it for a ride, and it developed a miss on acceleration and at all speeds. Got my mechanic coming by to place on a computer. The gas is probably 6 months old. Thinking of adding a additive the see if it is bad gas. Any suggestions on a additive? My guess is coil. donor car was a 2002 Firebird trans am

Re: engine miss
 

i'd bet a dollar to a donut if the fuel is that old it has a stuck injector. a quick ODB2 scan will tell you whether it's ignition or fuel related

Re: engine miss
 

Thats why I am thinking an additive may unstick it. Thats what I get for not driving it more.

Re: engine miss
 

It's all speculation until you scan the computer.
An additive is unlikely to work unless the injector works partially, as it will never reach the injector.
Let us know what the scan identifies.
The self-diagnosis is way better than the earlier cars.

Re: engine miss
 

perhaps loose plug wire or bad connection on a coil pack or injector.....with a seldom used vehicle, make sure mice have not been eating and peeing on your wires

Re: engine miss
 

Check first to make sure it's getting fire to each cylinder. I do this with an inductive timing light, just to see if it flashes on each cylinder.


Also check the connectors for both the coils and the injectors. When you turn the key to run position, they all should have voltage on them.

If all that checks out, then more than likely, you have a stuck(sticky) injector.

I first started my LS1, it had a dead miss, turns out it was a stuck injector.
My buddy also had the same issue with his 5.3, we pulled the injectors and two were gunked up and stuck.

Re: engine miss
 

Determined the issue is a bad injector. figure remove and replace/clean all of them??? NOW the question. New or clean them? Been looking back at this forum and most say rebuild/clean them. Mine are gray and I think org Delco. Thoughts.

What was the OEM Brand? Bosh

Wilie, I owe you a donut

Re: engine miss
 

If it was me I would send all your injectors out to get cleaned and rebuilt. Good shops will supply a print out showing the flow rates on each injector.
Or just replace the bad injector with a OEM injector and then a bunch of injector cleaner?

Re: engine miss
 

My plan is I bought a oem rebuilt cleaned injector with a flow rate test included. Once I get it installed if all good, I will send out my org 8 for the same cleaning and then have a replacement one for backup.

Re: engine miss
 

I've had good luck cleaning them myself. I run them thru my cheap Chinese ultra sonic cleaner filled hot soapy (dawn) water then "flush" them with a can of injector cleaner, a large livestock/vet syringe, a short piece of rubber hose and fire them with a 9 volt battery. Only ones I've ever had that didn't come back to life were because the solenoid was dead, not because they were dirty or gummy.

I have also used the plastic handle of a screwdriver to tap on the sticky injector while the engine was running to "persuade" it to unstick. Works better than you think. ;)

Re: engine miss
 

well replaced injector still missing. Put additive and some fesh gas no change. Back to square one, Dang.

Re: engine miss
 

Do you have a scanner? If not I would take it down to a parts store that scans for free and see what codes if any come up.

Re: engine miss
 

my mechanic has one. He is going to come by the house and take a look. We did check the power to one injector we thought was bad, It had constant strong power as the test light lit bright and it had a pulse on the other wire but it was weaker in brightness. I assumed that was normal. I will keep you posted.

Re: engine miss
 

Factory ECU or Holley?

Re: engine miss
 

factory type. bought it on ebay about 8 months got vats deleted. Ran great till now. My original oem lost its rad fan turn on off temp function. I am going to put the oem back in as it worked great even after the fan function went out to see if maybe my replacement went bad,.

Re: engine miss
 

Definitely give that a shot and report back. The OEM ECU's are very robust, plus they can communicate with a scan tool to help diagnose themselves. Can't hurt to swap the coil to another cylinder and see if the problem moves.

Re: engine miss
 

I installed my original ECM and still missing. So I rule out ecm. So now I got to decide to get my mechanic out here or just go buy 8 rebulit Fuel injectors and try that. I know sounds like a lot of money but if i get my mechanic out here that will be his recommendation, and I can pretty much buy the FI for what his service charge will be.

Re: engine miss
 

Go for a drive and unplug one injector at a time until you find one that does not make the miss worse when unplugged?

Get an injector buzz box and an inline EFI fuel pump and start testing injectors?

How did you narrow the problem to an injector issue?

Re: engine miss
 

My mechanic unplugged cyl 3 said it didn't make a difference in rough idle. I will go disconnect each fi and see what results I get. The scan showed nothing. We pulled the plug on three and it was bone dry. Figured it was the problem. <maybe more than one plugged up

Re: engine miss
 

With all due respect to those involved... If your mechanic can't diagnose this simple problem, you need another mechanic. All he has done is narrow the problem to that particular cylinder (or maybe not)... Hint, but not intended as a diagnosis: A burned valve and/or bad camshaft lobe will produce the same symptoms.. Simply unplugging a certain injector that produces no change in the run quality does not necessarily mean that injector is bad.

Re: engine miss
 

I agree . All respects. Hé's a good young mechanic. I really been trying to solve the solution on my own. I will have him take a more detailed look as I am starting to think internal problem not FI. He already mentioned bad lifter. Has suggested a compression test.

Re: engine miss
 

did you ever test spark? disconnect coil packs one by one to see if the miss is only cylinder 3.

compression test would be next.
A bad lifter could be the culprit, but it would be making some noise if it was so bad as to cause misfire

Re: engine miss
 

Checked spark on cyl 3 . it is getting spark. Need to give my mechanic a real opportunity now, as I was trying to trouble shoot it on my own.

Re: engine miss
 

Well, let me say, Never had and never will consider myself a smart person, but I think I am a better mechanic then most mechanics out there. I am just venting, I don't really mean that, I think. Just had a second highly recommended mechanic come take a look at my miss fire. Drove the truck for 10 miles at all speeds, with computer hooked up, miss is there. He says no codes other then o2 sensor on bank 1 and 2. I explained there is no cat and no second o2 sensors and maybe that is throwing the o2 codes. Will bad o2 sensor make it misfire? He recommends changing coils. He unplugged them one at a time at my request and they all were sparking whatever that proves.
My question is when they removed the vats and redid my wiring harnesses does that stop the ecm from giving codes?
There should be a mis fire code showing up somewhere.

considering replacing the coils, buying oems. I hate doing the replacement parts route, but I give up. Unless I find a real mechanic, who knows how to diagnose a transplant, until then I am on my own. Frustrated.

Re: engine miss
 

"o2 sensor on bank 1 and 2"

sensor 1 or 2 on each bank? If we assume your ECU was setup for no cats then the code for sensor 2 should be disabled.
If sensor 1 on both banks is complaining you need to check long term fuel trims. If the O2s have failed then the ECU may be making it too lean or too rich. What does the exhaust smell like, make you eyes water maybe?

Both o2s fail at same time seems a little coincidental, check wiring, make sure engine grounds are really good.