P1174? Change your injectors.

[midnightbluS10]

Just got done putting injectors in my 2009 Envoy. It my have taken me an hour total to tear it down and get it back together after doing this job 4 times altogether. It's had this code for a couple of years at this point. By now, I changed everything else they recommend to change for that code and nothing fixed it.

Finally got to the point that it would barely run so I replaced the injectors. This thing purrs now and that stupid code hasn't come back in 4 days.

I knew it was the injectors but I was expecting it to take longer than 1.5 hrs to swap them out so I kept putting it off. There's also the fact that injectors were $125 each at O'Reillys. I got AC Delcos from Rock Auto for $35 each. $210 for all 6

Man this thing runs good.

And I haven't even gotten into the story about the POS shop I took it to. I was 95% sure it needed injectors but took it there for them to confirm my diagnosis before I spent all that money. At the time, I thought by injectors were still $100/each. They tell me I need valves and the engine should be replaced. The next sentence? Oh it has good compression on all cylinders.

Yeah? It ain't the valves then. Dumbazzes. I took my truck home and pulled the intake and replaced the injectors. I asked if they checked the injectors. The service manager started stumbling his words.. I Said you know... An injector balance test? I brought it here because I can't check that and I'm pretty sure it needs injectors. "Oh oh yea. They're good" is what he says. smdh. 100% sure they didn't check them.

This is exactly why I learned to fix my own vehicles at 15 yrs old. Shady, incompetent shops. I told them they're incompetent from the top to the bottom. From the POS parts changer that couldn't diagnose my truck to the service manager that was clueless about everything.

Anyway. If you have a P1174 code and a MAF and O2 sensor don't fix it, replace the injectors. It's a 2 hr job tops.

I ended up replacing the valve cover gasket at the same time due to my own stupidity. I blocked the port on the top of the valve cover with a rubber cap and it blew oil EVERYWHERE when I drove it lol. Out the back of the valve cover onto the firewall. Into 4 of 6 spark plug tubes. It sucked. The tubes were full of oil so I just pulled the plugs and let it drain into the cylinders, then thinned it out with Seafoam so it would drain into the pan. That was fun lol. Yes, I'm an idiot lol. I know. Had to clean the coils with MAF sensor cleaner. Replaced the plugs. This things runs immaculately now.

Why did I take it apart 4 times? I replaced 3 injectors the first time because 3 cylinders were misfiring. Had to pull it back apart for o-rings. Then had to pull it apart a 3rd time to replace the valve cover gasket when I blew oil everywhere. And a 4th time to replace the other 3 injectors. Replacing the last 3 injectors took an hour from start to finish. Lol I got pretty good at pulling the intake. For example, You don't even have to remove the alternator. Just move it to the side so you can reach the bolt behind it. I figured that out the 4th time lol

 

[mrrsm]

It's great that you were able to finally solve this issue. Your success has raised a few questions that would amplify the understanding of how you arrived at having such a smooth running Engine:

(1) When the P1174 Code appeared... did it also present as a "Flashing CEL Code" on the IPC Dashboard? Were there any other related Engine Codes also present in the PCM Memory?

(2) Did the Repair Mechanics at the Shops ever suggest or mention using the non-invasive technique of sampling the behavior of Secondary Ignition Wave Forms produced by the EFIs using a HV Induction Paddle Probe and an Inexpensive Oscilloscope?

This method greatly augments identifying not only any EFIs with marginal performances... but makes for easy comparisons with the adjacent, well functioning EFIs along viewing the bank of all six cylinders by observing them as an "EFI Parade" across the screen.





The RED ARROW below points out the Healthy Presence of this "Pintle Hump" as a subtle indicator that this particular EFI is functioning properly as the EFI Pintle Closes. If THIS artifact is ABSENT from the Wave Form... it would indicate either a Stuck or Failing EFI.



This Link describes how to perform these Lab Scope EFI Diagnostics:

Post #11, #12, #16, #17, #18 and #29:

How To Use PICO #2204A & HANTEK #1008C Oscilloscopes

You don't need a Huge Bag of Coins in order to obtain and use an Oscilloscope for performing In-Depth Wave Form Analysis in Automotive Applications on everything from Problematic Electronic Fuel Injection to obtaining accurate Compression Tests to Diagnose Internal Engine Conditions. HANTEK...

gmtnation.com

(3) Any chance that you took any Digital Photos to memorialize the repetitive Step-By-Steps you followed over the many times you worked on the Motor?

(4) Did you use any related Threads previously posted at GMT Nation to assist you with doing this work to link back to this one?

 

[midnightbluS10]

1. Nope. No flashing CEL with that code. It came later once the injectors got to the point that they were at, I assume. It started with a misfire on cyl 1. Then it was 1, 2, & 6. So I replaced those injectors the first time.

2. Oh no. I guarantee they didn't do that. They told me "the ignition system is good. But we think it's the valves. We did a compression test."

So I asked OK... What were the results of the compression test? Expecting that cylinder 1 had low compression since they said it needed valves on cyl 1. Nope. "it has good compression on all 6 cylinders".

At that point, I got quiet and said "so that's it? I just come get it?" and they said "yep. That's all we can do. You need a new engine or you can drive it until this one dies". So I said "yea, OK I'll be there in a minute" because I knew they didn't diagnose anything properly. Like I said, with my deductive reasoning and the tests I was able to do at home, I concluded it needed injectors.

It was only once I got there that I asked if they checked the injectors and the service manager said no. So I got physically agitated and went to bitching. So he starts stumbling..."oh oh oh well I'm not sure what he did. Let me ask this other guy..."

It was very clear they weren't car guys with any sort of repair experience. These 2 guys are the duo that bought the business from the original owner. Banking on using his good name to make money. They've turned that place into a crap hole.

3. Nope. No pictures. I was fighting the Louisiana heat so I was far too aggravated to spend time taking pictures lol.

4. I don't remember looking here for anything until after I was done and I figured I'd come and post about the fun I had lol!

By this time, I had already purchased a fuel injector cleaner and a thing to test them, also. I dumped the cleaner and fuel into the container, hooked up the air pressure to it and cleaned the injectors 4 different times with no change.

When I got it back from the shop, I bought a thing to power the injectors outside the truck so I could test the spray pattern. It was clear at that point I needed injectors so I bought 3...for cyls. 1, 2 & 6 since those were the only ones misfiring st that point.

When I got it back together, it started misifirng on 3, 4, & 5 lol. So I bought 3 more for those cylinders. After that, it was all smooth sailing. Well, I say that. Watching the misfire counter on the Torque Pro app, I get a single random misfire on random cylinders every so often. It only ever shows a 2. Never more than that.

Every time it does it, I tell myself it isn't an issue and it could have been doing this before these problems ever started. I don't know, though, because I didn't monitor the misfires until it was actually misfiring enough that I needed to watch it. It's never enough to set a code so I'm doubt it's anything I need to worry about.