p0174 454 vortec

[dirtautoguy]

this morning my dad and I went hunting, we took his truck because mine is having alternator issues. when he picked me up he said it was running great. when he got to my house it started running really rough like it was miss-firing.

we tested it out around town before we left debating on if we should take it or not. when it was up to speed it smoothed out but still did not have the power that it should have. we drove it about 20 miles and came back that afternoon on our way back it had smoothed out a lot and was running much better but it sill had a shake to it. I was condemning the distributor because it felt similar to my truck when it got moisture in the cap.

I plugged my scanner into it and only found one code p0174 bank 2 lean. I then went to live data and looked at bank 1 and 2 pre cat sensors. when compared to bank 1 it switched about twice as fast as bank 2 with bank 2 having a lot of small plateaus. with the idle raised they were about the same.

then I looked at the fuel trims.

stft both stayed around + or - 4%
ltft bank 1 5%
ltft bank 2 8%

I did a quick check for any vacuum leaks but didn't find anything obvious. I hadn't thought of doing a fuel enrichment to see if the o2s responded until later.

my dads had the truck for about 8 years and has only but about 35000 miles on it so it doesn't get drove a whole lot, it is a 1997 rclb with the 7.4l and it has about 160000 miles on it.

I would think that if it was the MAF or MAP it would effect both banks
I didnt find any exhaust leaks
it has had new plugs, wires, and cap done fairly recently
it has had intake gaskets done in the last 2 years as well

what do you guys think? am I on the right track? am I missing something? I just dont want to throw an o2 sensor at it and find out it wasnt the issue.

 

[dirtautoguy]

Well I looked at his truck for him over the weekend. I checked really hard for any vacuum leaks or any other issues and didn’t find any.

I cleaned the throttle body and that did seem to smooth it out a little bit there Is still a minor shake or miss at idle.

It’s been raining a good bit recently so we will see if it starts acting up with the moisture

 

[Schurkey]

Misfire creates a false lean O2 sensor signal. What are the cylinder-by-cylinder misfire counts?

 

[81nascar]

Usually with something like Besides checking misfires and the graph. I like to double check all of the ignition parts. Loose plug wire, loose plug backing out, wires rubbing thru ,wires snug on cap, cap solid on it's base . You would be suprised at how that one can get you.. Then kind of go from there..

 

[dirtautoguy]

We’ll time to bring a thread back from the dead…..

My dads truck hasn’t had an issue since I cleaned the throttle body. (He doesn’t drive it much either) but he went on about a 200 mile road trip he said it ran great most of the way there. Then he got a check engine light and he said it was way down on power and consumed a lot of gas.

When he got home he said he filled up with gas and the check engine light went out and it ran much better not like it should but much better.

When I went over and scanned it and checked it out it again had P0174 bank 2 lean, it also had a code for insufficient temp for closed loop fuel control, and p0157 bank 2 sensor 2 voltage low.

The truck ran fine, felt pretty smooth, of course it was at high idle because it was cold. My dad said that it seems to run good when it’s cold but after it warms up is when it acts up. That makes me think closed loop has something to do with it which makes me think O2 sensor which would only affect bank 2.

They are stock O2 sensors so I’m sure they are due for replacement but he doesn’t want to spend more money than he has to. I told him if you pull them out he may as well just put new ones back in.

I do want to check the cap, plugs, rotor etc. I would think if it were the cap/rotor it would affect both sides but I’ll check anyway it could be something stupid….

I’m also gonna see about just bringing it to my house and driving it for a while so I can learn more about what’s going on

 

[454cid]

Check the engine coolant temperature sensor.

 

[stutaeng]

We’ll time to bring a thread back from the dead…..

My dads truck hasn’t had an issue since I cleaned the throttle body. (He doesn’t drive it much either) but he went on about a 200 mile road trip he said it ran great most of the way there. Then he got a check engine light and he said it was way down on power and consumed a lot of gas.

When he got home he said he filled up with gas and the check engine light went out and it ran much better not like it should but much better.

When I went over and scanned it and checked it out it again had P0174 bank 2 lean, it also had a code for insufficient temp for closed loop fuel control, and p0157 bank 2 sensor 2 voltage low.

The truck ran fine, felt pretty smooth, of course it was at high idle because it was cold. My dad said that it seems to run good when it’s cold but after it warms up is when it acts up. That makes me think closed loop has something to do with it which makes me think O2 sensor which would only affect bank 2.

They are stock O2 sensors so I’m sure they are due for replacement but he doesn’t want to spend more money than he has to. I told him if you pull them out he may as well just put new ones back in.

I do want to check the cap, plugs, rotor etc. I would think if it were the cap/rotor it would affect both sides but I’ll check anyway it could be something stupid….

I’m also gonna see about just bringing it to my house and driving it for a while so I can learn more about what’s going on

I know O2 sensors are not cheap, but @Schurkey has stated that they do wear out and become slow to response. I do agree with that.

However, in this case, the O2 codes you are getting are likely the result the lean condition. I highly suspect that changing O2 sensors in your case would not solve the problem.

Example: My 1500 swapped 5.3 right now is running about 11% LTFT on both banks (pretty much stay the same if idle, or revved up.) The problem is my injectors are not matched to the flowrates of the tune. I have lean codes on both banks, exactly the same percentage. I also got O2 sensors codes, but I know the problem is not there, because the problem started after my engine was swapped. I need to fix the lean condition, and the O2 codes will go away I'm positive. All O2s are original, and truck has 260k

Can you do an injector balance test? I thought the injectors going bad were kinda of a common problem on these, no? Sometimes they only act up once the engine is warm.

To test the vacuum leak question: Once in open loop, look at fuel trims under idle. Rev the engine up to 1,000, 2,000, and 3,000 while watching the fuel trims. If the fuel trims percentage stay the same, likely a fuel delivery problem. If the fuel trims get smaller with increase in RPM, more likely a vacuum leak.

What does your scanner say is the temperature? If the temp. fuel sender is bad, ECU thinks engine is still too cold and keeps it in open loop. I understood that's what one of the codes was saying?

If you want to replace O2 sensors, Rockauto is the place to get them cheaper. I've had good luck with Denso brand.

 

[dirtautoguy]

The O2 code was for the downstream sensor after the cat so I’m not real worried about that code.

If it was more of a injector issue wouldn’t it be a problem all of the time not just warmed up?

I’ll have to look at the the fuel trims. When I looked at it last bank two was at 6% short term I don’t recall what the long term was.

The scanner I’m using is called a blue driver. I don’t believe it can do much in the way of commanding the computer to do things but it does have a mode 6 operation though I haven’t quite figured out how to use it yet…. It comes up with just pid numbers


I thought the coolant temp code was a little suspicious. As I believe fueling is affected by engine and coolant temp. I know it has a relatively new thermostat though new doesn’t mean good.

 

[stutaeng]

Yes, start with coolant temp. sender. Easy to check on your scanner. But I think that would affect BOTH banks, equally. I think you may have more than one problem.

 

[dirtautoguy]

I spent some time looking at his truck today. It did not run terrible but it did run with a noticeable stumble.

I scanned it again and came up with the same lean bank 2 code. And my dumb butt didn’t look at the freeze frame data before I cleared it.

While warming up the coolant sensor gave some bizzare readings. It had 3 spikes. The first time it was about 100 it spiked to 198 for a sit second, again when it was about 140 it spiked to 357! And then last when it was about 160 it spiked to 259. The cooling system is full and hasn’t been opened for quite sometime so I really think there is a issue with the coolant sensor.

In watching the fuel trims and temps it seemed the truck ran smoother when cool and got rougher as it warmed up. When it went into closed loop the stumble was more noticeable (still not running as bad as it was)

I checked it all over again for any vaccum leaks and revved it up while watching the trims they did. Not seem to indicate a vacuum leak. However the truck was not acting up as bad either.

We went for a drive and at times ltft would hit around 11% on both banks with stft would hang around 8% on both. It’s really odd the computer only throws codes for bank 2?

While it is stumbling rpms are still around 620-700 at idle.

I’ll keep working on it when I can but my dads real skeptical about spending money on it. I told him he had 3 options

Take it somewhere and have them diagnose it

Drive it untill we can catch it acting up (he doesn’t want to drive it for fear of hurting it)

Or try replacing some parts. Obviously the coolant sensor IS a issue.

I’ll keep reading any more suggestions you guys have and if we come to a fix I’ll update this thread along with any updates I find out.