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Discussion Starter #1
After a few weeks of hunting down an exhaust leak, Im starting to think it is a blown head gasket. I recently got a wide-band and at idle im bouncing all over the 12s. I am going to try and get a datalog later today. Does a head gasket leaking to the outside sound similar to an exhaust leak?

Ive gotten lean codes before and figured it out but this time seems different. Same tune ive had for years no new mods. My coolant water is brown and rusty, definitely needs a flush. Exhaust is normal, no gray or white smoke at all. I was told my iats would be high if its a head gasket, let me know what you guys think. Appreciate it
 

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I've never heard a head gasket leak like an exhaust leak.

A true test for a head gasket is a hydro carbon test
 

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I guess in theory it could make a sound similar to an exhaust leak. But very doubtful. I have not heard any doing that over my 25+ years in the Lightning world. Dusten mentioned hydrocarbon test. That would confirm or reject the theory. But more likely a vacuum issue is the issue.


Jim.
 

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Discussion Starter #4
Like the guy in this video? Skip to about 2 minutes in. So he does the test and it doesn't change color, but then he notices bubbles and says there is a problem. haha probably not the best example to use. Is this a real accurate way of testing? If it was a head gasket I would see smoke out the exhaust right?



Ive checked over all my vacuum lines multiple times, I had a minor exhaust leak that I thought was the problem. I fixed that but I can still hear a slight tisk and its not wanting to get in boost at all. Very hesitant especially at low rpm
 

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If it is a ticking sound, check your plugs. A loose plug can make noise before spitting out. The drifting and lean A/F reported made me think unmetered air.


Jim
 

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Discussion Starter #7
Here are the plugs from the drivers side. Tips were white, meaning lean right? All of them looked like this. I also got two lean codes on both banks on the way home from the shop. Cruising around 55-70 the wideband was normal 14-15. When I started getting into 5lbs boost it leans out, stutters and does not accelerate well

Last time I got the truck tuned was by Jim at Jdm in houston. I had obx headers on the truck that I found used in the forums and had a local shop weld new midpipes. I didnt know but at the time the pipe they installed was 2.25 not full 2.5. So Jim had set up running a little rich, once I got the real 2.5 midpipes it should lean back out. That was 4-5 years ago and the trucks been running great for the most part. Recently Ive added a accufab tb, metco upper idler and a bigger intake filter. Do you think these parts are having an impact on the lean condition? Im not sure what else it can be, maybe header gaskets? I replaced those a few years ago
 

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Discussion Starter #10
My tuner recommended me getting a fuel pressure gauge. I do have 2 walbro pumps. So now Im starting to think its a fuel delivery issue. Ive been reading older threads on similar issues, should I jump the hi/low relay first? What about this fuel resistor by the intercooler pump, could that have something to do with my issue?
 

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Slevin
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Your pumps should be on 100% all the time IIRC with 255s
It could be that way if it was tuned that way. Jump the relay and see what happens. But you need an adjustable fpr for that
 

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Discussion Starter #12
Your pumps should be on 100% all the time IIRC with 255s
It could be that way if it was tuned that way. Jump the relay and see what happens. But you need an adjustable fpr for that
A fpr for what? A pressure gauge? I thought the gauge can tie into the stock rails?
 

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Slevin
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Fuel pressure regulator.
At idle you should be around 40 psi.

I guess checking fuel pressure through the Schrader valve would be my first check.
 

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Discussion Starter #14 (Edited)
Fuel pressure regulator.
At idle you should be around 40 psi.

I guess checking fuel pressure through the Schrader valve would be my first check.
At idle I should be at 40 or at WOT? I saw another thread saying idle should be 20ish, wot around 50-60psi.

So I had the wideband on fuse #30 for power. I was thinking maybe fuse 30 had something to do with the issue since it also controls the ignition coils. So I swapped the fuse to another location. Now it will read the A/F at idle but under any throttle it maxes out the wideband and doesnt read anything. Still having the same issue with it not wanting to get into boost. Ive ordered a fuel pressure gauge and hope to get that hooked up soon and see what it reads.
 

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20 in of vacuum is about -10 psi, so 30 psi is your fuel pressure target at idle. What are your long term and short term fuel trims at idle?
 

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Discussion Starter #18
20 in of vacuum is about -10 psi, so 30 psi is your fuel pressure target at idle. What are your long term and short term fuel trims at idle?

Awesome thank you. I should get the pressure gauge installed this weekend hopefully. Im not sure whats going on. I was looking at the log I sent my tuner a couple weeks ago and looking at a new one I did this morning.

The one I sent my tuner at idle and my A/F avg was 14.9
Short term avg 1.01
Long term
B1- 1.23
B2 - 1.19

I took another log today, my wideband is maxed out. A/F avg was in the 18s at idle
Short term avg 1.0
Long term avg
Bank 1 - 1.19
Bank 2 - 1.16


I didnt change anything or even work on it between those two logs so im not sure how thats possible. Should I send my tuner this second log? Fuel trims didnt seem to change much but the A/F changed. My tuner was leaning toward a fuel pressure problem but now im lean at idle so Im not sure if that changes his outlook or not
Appreciate the help
 

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When was the last time you calibrated your wideband?

LTFTs typically have a min/max range of 0.75 and 1.25 respectively. LTFT above 1 means it is adding fuel, below 1 means it is removing furl. So if you're at 1.23 or even 1.19 then you're getting close to the limits of your system to be able to add fuel to maintain a 14.7 A/F during idle and cruising (closed loop operation).

For your wideband to be 18s and super lean but for your LTFT and STFT to be within bounds at idle leads me to believe that either your wideband needs to be calibrated or that you have a leak between your front O2s and your wideband. If your idle A/F was really in the 18s, then your long term fuel trims would probably be maxed at 1.25 since it is unable to provide any additional fuel beyond 1.25 which would cause it to indicate it was running lean. This LTFT ceiling of 1.25 is dependent on how your tuner set up your time file of course.

Fuel pressure being low will cause a lean condition at idle and cruise and may indicate why your LTFT is so high. May also show up as lack of fuel volume... So under load you may be VERY lean.

Definitely do a fuel pressure test as recmmended by your tuner as this may correct your issue, but also calibrate your wideband and check for any exhaust leaks between your front O2s and the wideband.
 

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Discussion Starter #20
When was the last time you calibrated your wideband?

LTFTs typically have a min/max range of 0.75 and 1.25 respectively. LTFT above 1 means it is adding fuel, below 1 means it is removing furl. So if you're at 1.23 or even 1.19 then you're getting close to the limits of your system to be able to add fuel to maintain a 14.7 A/F during idle and cruising (closed loop operation).

For your wideband to be 18s and super lean but for your LTFT and STFT to be within bounds at idle leads me to believe that either your wideband needs to be calibrated or that you have a leak between your front O2s and your wideband. If your idle A/F was really in the 18s, then your long term fuel trims would probably be maxed at 1.25 since it is unable to provide any additional fuel beyond 1.25 which would cause it to indicate it was running lean. This LTFT ceiling of 1.25 is dependent on how your tuner set up your time file of course.

Fuel pressure being low will cause a lean condition at idle and cruise and may indicate why your LTFT is so high. May also show up as lack of fuel volume... So under load you may be VERY lean.

Definitely do a fuel pressure test as recmmended by your tuner as this may correct your issue, but also calibrate your wideband and check for any exhaust leaks between your front O2s and the wideband.
Thank you for that explanation, very informative! That makes sense, my wideband is probably out of whack. I just installed the wideband a couple weeks ago along with some vband clamps on the midpipes because I was sick of those shitty slip on clamps leaking.

I did not do anything for wideband calibration so I will definitely look into that. I got the pressure gauge today but seems im going to need a couple more pieces to install it. I will keep you guys posted. Really do appreciate the help, thank you
 
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