Rough running 7.4 Vortec

[TexasAggie]

I was hoping that you'd say the scanner could help pinpoint which cylinder was acting up. Are these things fairly intuitive to use, or will I need to study up on how to read the findings? I looked on Amazon and there are a lot to choose from.... Anyone have one they particularly like and is easy to use?

The cap I used was ACDelco so should be exactly the same as original.

 

[454cid]

I actually have a fuel pressure gauge already, so I'll check that out tonight. What should it read at idle and under load?

The reason I'm thinking ignition is because it's doing it all the time - barely noticeable at idle, but very noticeable when revving in neutral. Doesn't get worse under load (almost gets drowned out by the road noise).

I don't' recall what the spec is. I think its a range. I'd want to see at least 50.... 55-60 would be better.

 

[Supercharged111]

I don't' recall what the spec is. I think its a range. I'd want to see at least 50.... 55-60 would be better.

Should jump over 60 when you crack the gas good and hard too.

 

[TexasAggie]

Good to know. I picked a scanner on Amazon and it will be here tomorrow, so I'll do some testing tomorrow evening and let you know what I find!

 

[stutaeng]

Any preference on which one?

Not really. I bought a basic Innova from Amazon, but didn't have live data, just freeze frame.

There's so many models out there on Amazon, and seems like the reviews are skeptical, i.e., fake.

I bought my second from the local parts store. Innova 5610, which is almost like first, but has live data. Kinda expensive, but quickly helped me diagnose my 5.7 spider injectors as faulty. Has paid for itself diagnosing my vehicles and friends' vehicles. Has also saved me a lot of money from just throwing the parts cannon at my vehicles.


Some are happy with the device that works with your phone. Members have posted screenshots and it looks pretty good. I think it's around $100. Torque App, I think? Someone please chime in on this...

Then there's the Tech... something, which was the original GM diagnostic tool. There's also clones. Don't really know much about those.

I'd say get whatever is cheaper and has full featured live data.

Edit: Sorry, it looks like you already something picked up. Typed this up on my phone last night, didn't hit the reply button.

 

[C30454]

ASSUMING the scanner you ordered is fairly capable, there should be a section for misfire data. I don't know what machine you have ordered or how it is laid out, but that data should be fairly easy to find if it is there. One thing that you will possibly want to do is drive it and watch the misfire counter for the faulty cylinder. For example, if it only misfires at idle but is good going down the road, you could have an intake gasket leak, or a plug with almost zero gap from being dropped. If the miss is always there, check the basics, fuel, spark, and compression for that cylinder.


Tom

 

[TexasAggie]

I went out this morning to move her out of the way and now she won't stay running at all. Fires right up, but then dies. I'm thinking Idle Air Control valve (because I've changed them out on several vehicles over the years). I was hoping to confirm by giving her some gas during start, but no luck their either. It's either the IAC, or something fuel related (and harder to fix).

Thoughts?

 

[TexasAggie]

I bought my second from the local parts store. Innova 5610

This is the same one that I picked up. I also have a BlueDriver unit on the way (I had it in my Amazon cart and got notified that it went on sale for $30 off). I'll do a compare and keep the one I like better.

As far as the Innova, I need to play with it a bit, but it isn't quite as user friendly as I was hoping. I plugged it in but couldn't figure out how to diagnose my recent no start issue. Hard to run tests when the motor doesn't run!! haha. I picked up a fuel pressure gauge from the parts house and will be hooking it up this afternoon to at least check what it is before startup. More to come... I need this thing running by Friday!

 

[TexasAggie]

No luck on the IAC. Same results... runs for a half second and then dies. Checked fuel pressure and it shoots up to 60 as soon as the key is turned on. Turn the key off and it slowly leaks down but goes right up to 60 again when you try to start it or turn the key back on.

Feels like a sensor to me.... I forgot to mention that this happened on Saturday morning after I changed the cap and rotor. I cranked it up to test out the cap and rotor, backed it out of the garage and shut it down. Went inside to grab my wallet and what not and came back out and it didn't start. After about the 4th try it fired up and away we went. Didn't act up again until this morning.

 

[TexasAggie]

More updates - went out to try and run the diagnostics again and left the key on for a long time while I fiddled with the scanner. Turned it to start and it fired right up and stayed running. Went and drove around for 20 minutes to try and collect data and now I can't figure out how to read it from the scanner app. Turned the truck off and started it again with no issue.

Checked fuel pressure before my ride and it was a steady 52psi at idle and jumped up to 60 when I would hit the throttle in the driveway.

No idea what caused the no start condition all day.... need to figure it out though before it leaves me stranded.