Strange P1174 issue

[Ajaxzem]

I keep getting a P1174 code on my 08 H3 3.7, 170k mi. If i ride back roads at 55-60 it never sets a code. If i get on the interstate i can ride all day long and never get a code, but if i hop on the interstate when the rig is still cool (not warmed up) it sets a code. after a few miles. I've also noticed if i hit a bump like railroad tracks or a big pothole it will set off a CEL almost immediately.
I got a downstream O2 sensor code a few months back and replaced both sensors with bosch sensors, no O2 code since then, I also got the thermostat code P0128 i think? anyway i replaced the thermostat and no problems there. it's running a bit warm though, around 211-216 on scan gauge. I also replaced the plugs with ac delco, and #2 coil because i got a P0302 once but not since replacing the coil.
Also cleaned the MAF and throttle body, and checked for vacuum leaks everywhere. I checked the intake manifold bolts (all were loose) but i still get the P1174 code. I ran a few tanks of Techron gas and used techron additive along with a few others here and there. Code still comes back but only under the conditions mention above. So what gives? What should i do from here to solve the code issue?

 

[a0128]

P1174 references possible fuel injector issues. Take a look at this document. Hopefully it will be of some help.

https://www.autocodes.com/uploads/gmc/03-06-04-030F.pdf

 

[Ajaxzem]

I think i read that somewhere a while back. Not really wanting to bring it to a dealer and get that done. I'm kinda low on cashflow at the moment. Are there any other options on cleaning the injectors that may by a DIY?

 

[deserth3]

Get some Techron injector cleaner. Basically what the dealer will use

Sent from my LG-H700 using Tapatalk

 

[a0128]

Get some Techron injector cleaner. Basically what the dealer will use.

Try two bottles and a full tank of tier-one fuel (Chevron, Union 76, Texaco, etc). Once you have filled the tank, make sure you run it almost empty to get full benefit out of the Techron.

When cash flow improves I would consider replacing your injectors verses a cleaning at the dealer. These things eventually wear and the fuel atomization will suffer. At 170k you probably have some worn injectors. Rockauto.com carries AC Delco parts @ $75.79 ea (yikes!). Cheaper than the dealer though. Might even be cheaper than the dealer's injector cleaning service.

 

[rascole]

Or replace all of the injectors for under $100.

 

[Ajaxzem]

Really don't want to replace all the injectors, although i guess it's not too expensive. Whats all involved in removal and replacement? it looks like I'd have to remove the intake? I'm not even 100 percent sure that's the problem. I've run a lot of cleaner through it already. Im also not sure what the highway speed while still warming up or bumps have to do with it.

 

[alrock]

The only way to "know" the problem is to begin troubleshooting. Sounds like you've done the first step, which is injector cleaner. The next step is probably replacement. You could rig up something like on Wheeler Dealers to test each injector, but it's probably easier to replace them all. There are injector cleaning services, like the dealer or BGs, but in my opinion that's at best a 50/50 chance. And if you lose, that's a chunk of money to put into a gamble with 9 year old injectors with 170K miles.

 

[a0128]

Or replace all of the injectors for under $100.

Where do you get injectors for $20 per? I'd love to know. Cheapest I've seen is a remanufactured unit for $35.

 

[deserth3]

Never mind

 

[rascole]

Where do you get injectors for $20 per? I'd love to know. Cheapest I've seen is a remanufactured unit for $35.

Amazon.