First timer

[rockola1971]

Ok lots of great replies.

The truck is tuned for the cam, it’s only a stage 1 cam so modification of injectors wasn’t necessarily required. But I dis do some springs in the heads to help ease valvetrain.

It used to run very great, hot off the line and steady through all gears it would pull hard.

The issue slowly became worse so that’s why I felt slowly other issues brought problems.

The fuel pressure at static KOEO was 40 on my gauge but I tried another it was like 45. Then when I’d pull FPR and receive 50 I immediately replaced the FPR because with it connected under load the pressure would fall off. Now that to me was a sign of possible weak pump as well or a clogged filter. So I’m gonna change the filter today. Then re test with gauge on it.

One thing I noticed last night as I thought about it, my spark plugs are a hotter plug than what I necessarily would have wanted when it was running E85 and that lead to a spark plug diode over expanding the gap and blowing the plug. Which it then allowed the truck to develop the initial stumble which I will be checking the cylinder isn’t fuel washed but I also will be checking the tune as I never had one misfire code so I’m wondering did the tuner stupidly turn off misfires in the tune. Which as I find out more I’ll report

A simple scanner will show you your fuel trims and show if you are running lean. That fuel pressure aint gonna cut it. How many miles on the Fuel pump? They typically die miserable death between 100k-125k. Ive seen some just die with no warning, usually right after the tank is filled and ive seen plenty that just make the vehicle hard to start for well over a year until they finally just die. If you have to replace the fuel pump, I suggest to plan on replacing the wire harness plug that feeds power to the fuel pump assembly(Chassis side). They typically get hot and deformed at the plug and/or corrosion on contacts.

 

[Mudsport96]

Are you trying to run e85 with this combo or just premium?

Stock flex injectors with a cam on E85 is going to be in the top range of their duty cycle. Even just on 93 octane you are pushing them. A stage 1 truck cam from btr is worth 45hp on a 5.3 on gasoline.

Second if you got a plug hot enough to damage it, you probably should do a compression check of that cylinder. Just to verify you didn't hurt the piston. And while you are at it, check them all.

Third injector circuit open means those injectors are likely not firing. That can also be part of the problem.

And lastly, not knocking your build, we all do things different. But why did you decide you needed 11:1 compression for a SUV build? That narrows the oops window when dialing in your setup. You can get into detonation real fast and hurt things quick.
I built a 12:1 Chevy 301 using a 327 with a 283 crank. Octane is your friend, colder plugs are your friend. And high compression in a heavy vehicle can cause trouble.

Get a scanner that sees live data and check the following things.

1. Knock counts
2. Fuel trims
3. Throttle Position through the whole pedal travel. ( this can be done with the engine off)
4. Since it is a flex vehicle, check the alcohol content sensor. If it is reading wrong, it will fuel wrong.... and jack timing up for alcohol. So if you don't have enough Octane and it thinks you do it will cause problems.
5. O2 sensor switching to make sure they are reading right.

Those will be a good start.

 

[BigBackHoe]

A simple scanner will show you your fuel trims and show if you are running lean. That fuel pressure aint gonna cut it. How many miles on the Fuel pump? They typically die miserable death between 100k-125k. Ive seen some just die with no warning, usually right after the tank is filled and ive seen plenty that just make the vehicle hard to start for well over a year until they finally just die. If you have to replace the fuel pump, I suggest to plan on replacing the wire harness plug that feeds power to the fuel pump assembly(Chassis side). They typically get hot and deformed at the plug and/or corrosion on contacts.

My fuel trims which I logged on go tuners were reading as rich prior to replacing the injectors as the ones I had were reaching the end of their capabilities and 2 were over fueling.

The fuel pump is maybe 6-7k miles old

 

[BigBackHoe]

Are you trying to run e85 with this combo or just premium?

Stock flex injectors with a cam on E85 is going to be in the top range of their duty cycle. Even just on 93 octane you are pushing them. A stage 1 truck cam from btr is worth 45hp on a 5.3 on gasoline.

Second if you got a plug hot enough to damage it, you probably should do a compression check of that cylinder. Just to verify you didn't hurt the piston. And while you are at it, check them all.

Third injector circuit open means those injectors are likely not firing. That can also be part of the problem.

And lastly, not knocking your build, we all do things different. But why did you decide you needed 11:1 compression for a SUV build? That narrows the oops window when dialing in your setup. You can get into detonation real fast and hurt things quick.
I built a 12:1 Chevy 301 using a 327 with a 283 crank. Octane is your friend, colder plugs are your friend. And high compression in a heavy vehicle can cause trouble.

Get a scanner that sees live data and check the following things.

1. Knock counts
2. Fuel trims
3. Throttle Position through the whole pedal travel. ( this can be done with the engine off)
4. Since it is a flex vehicle, check the alcohol content sensor. If it is reading wrong, it will fuel wrong.... and jack timing up for alcohol. So if you don't have enough Octane and it thinks you do it will cause problems.
5. O2 sensor switching to make sure they are reading right.

Those will be a good start.

I actually just had a spare engine sitting around when my original was gonna get rebuilt so I decided to just swap them out and use the one getting rebuilt for a Monte Carlo build.

So the engine is 6k miles in now. Which is why I was stating it ran great prior, but I understand heavier vehicle more lord on the engine but for 5-6k it drove like a champ even up to Vegas multiple times.

Being I ran e85 I’m sure colder plugs would surely be my friend but now it’s on 91.

Within the tune short terms are turned off so I can only log long terms and I can check the log from yesterday for knock count.

I can surely see the injectors being at end of range but I didn’t state a 3rd injector code it simply says injector circuit which could be in the harness or within the ecu to my knowledge.

 

[Mudsport96]

Few things here.
Long term fuel trims are calculated using short term trims over a longer period of time. So if short terms are disabled, your long term trims are just a guess.
Being an older flex vehicle you should check with the scanner what the computer is "seeing" for alcohol content. If that is off, it will be fueling wrong. So throttle response will be poor, mpg poor. And that doesn't always throw a code. So it could have been part of your initial idle and tip in problem. And then changing the injectors could have caused the open circuit code. As crazy as it sounds, I've had to do this before, unplug the coils so they don't have power and pull one fuel rail at a time. Then have a helper crank the engine to see if all injectors spray. The replace and repeat with the other side. A bad injector coil can cause an open in the circuit.

After rereading the post about spark plugs, typically you want the same temperature or slightly hotter plug not cooler for e85 than gasoline, as the higher ethanol content takes more to light off. And when you say blew a plug, do you mean the center electrode and porcelain? And did it go into the cylinder?

Something easy to check that can also cause a problem without necessarily throwing a code is the maf. Just unplug it to put the truck in fault mode and see what happens with the shifting. A bad maf can possibly make the transmission shift goofy.

 

[Mudsport96]

He is probably referring to the electrode which is the little tip(Center electrode) the spark jumps from to the bridge (ground electrode). There is no diode in a spark plug.

Correct, some have resistors, but that is a whole different subject

 

[BigBackHoe]

Few things here.
Long term fuel trims are calculated using short term trims over a longer period of time. So if short terms are disabled, your long term trims are just a guess.
Being an older flex vehicle you should check with the scanner what the computer is "seeing" for alcohol content. If that is off, it will be fueling wrong. So throttle response will be poor, mpg poor. And that doesn't always throw a code. So it could have been part of your initial idle and tip in problem. And then changing the injectors could have caused the open circuit code. As crazy as it sounds, I've had to do this before, unplug the coils so they don't have power and pull one fuel rail at a time. Then have a helper crank the engine to see if all injectors spray. The replace and repeat with the other side. A bad injector coil can cause an open in the circuit.

After rereading the post about spark plugs, typically you want the same temperature or slightly hotter plug not cooler for e85 than gasoline, as the higher ethanol content takes more to light off. And when you say blew a plug, do you mean the center electrode and porcelain? And did it go into the cylinder?

Something easy to check that can also cause a problem without necessarily throwing a code is the maf. Just unplug it to put the truck in fault mode and see what happens with the shifting. A bad maf can possibly make the transmission shift goofy.

Yes I meant the electrode and the porcelain.

I had the injector code prior to replacing the injectors. Tested each connector with noid light all were pulsing. So I went with the injectors. But after when it still seemed to start stumbling under load I decided drive a while with a fuel pressure gauge on it. After about 30 mins pressure was slightly dropping while it sat took it on a drive and after about 10 minutes it started to see under 40psi on the gauge.

I’m gonna actually retest with a different gauge to make sure of accurate reading. I’m currently letting it sit so I can test pressure before koeo and with koeo so I can see if it rises in pressure. I’ll also be checking my intake for a possible crack or anything or anything with the IAC as the truck has a brand new MAF with less than 3k on it. Most things were replaced on this truck, engine, trans, ckp/cmp, ect, oil pressure, etc. So recently the only things that were being double checked IE injectors, FPR, and fuel filter are items I hadn’t replaced.

The truck never did the loss of power as I’m driving then cutting in and out of revving and having throttle response issues to where I had to go in and out of the throttle to keep it rolling. But even if I didn’t touch the throttle car would not die it would just not give any throttle response with accurate timing as if it had to get the pressure built up to even load the injectors possibly it was odd.

 

[Mudsport96]

Yes I meant the electrode and the porcelain.

I had the injector code prior to replacing the injectors. Tested each connector with noid light all were pulsing. So I went with the injectors. But after when it still seemed to start stumbling under load I decided drive a while with a fuel pressure gauge on it. After about 30 mins pressure was slightly dropping while it sat took it on a drive and after about 10 minutes it started to see under 40psi on the gauge.

I’m gonna actually retest with a different gauge to make sure of accurate reading. I’m currently letting it sit so I can test pressure before koeo and with koeo so I can see if it rises in pressure. I’ll also be checking my intake for a possible crack or anything or anything with the IAC as the truck has a brand new MAF with less than 3k on it. Most things were replaced on this truck, engine, trans, ckp/cmp, ect, oil pressure, etc. So recently the only things that were being double checked IE injectors, FPR, and fuel filter are items I hadn’t replaced.

The truck never did the loss of power as I’m driving then cutting in and out of revving and having throttle response issues to where I had to go in and out of the throttle to keep it rolling. But even if I didn’t touch the throttle car would not die it would just not give any throttle response with accurate timing as if it had to get the pressure built up to even load the injectors possibly it was odd.

You need to borescope the cylinder that plug came from. With an 11:1 engine there isn't room for that to not hurt the piston.

Secondly, you need use a scanner to check for linear readings of the tps.

Rechecking the fuel pressure is a good idea. If you replaced the Regulator make sure you used a flex fuel one not a standard one, they have different pressure ratings.

If the void light is working on all injectors, the circuit is functioning, but that doesn't necessarily mean the injectors are.

 

[Mudsport96]

Something else I just thought of before falling asleep. Is this a cable throttle? Or is it one of the oddball early electric throttle bodies? I think in 02 they tried something before the 03 ecm change.

 

[Matthew Jeschke]

TUNE:

This reminds me of spark and idle air control routines need adjusting in the controller. You said you did a tune, was it a mail order tune? What did he adjust in the controller?

When I did my cam I had to tune:

- Spark overspeed, & underspeed tables
- Idle Airflow Table for Park and gear
- And adjust the setscrew on my throttle body (not sure if you're cable or wire)

TIP: I also have a pretty mild cam as well. If these are not tuned properly the truck will stall when weather changes. Especially the Idle Airflow. If the temp, changes your truck won't run right till it's warmed up. If you replace injectors don't mess with the 24# ones they are REALLY close to the limit of their flow. Get the flex fuel injectors from the L59 motor. You can get them used fairly cheap. I spent $100 on 8 used ones. If you buy new they're the same price. You do have to do some spacing on the fuel rail but billet IAT sells the spacers and you can get the harness adapters on eBay.

What year is your vehicle?

PUMP:

37 PSI is lower than both flex fuel L59 (48PSI) and gasoline LM7 (58PSI) spec. Researching pressure regulators I see they do sell them that low for the 5.3L. If you're not careful you may have snagged one of those. Did you recently change the regulator? Otherwise likely a bad pump.

I had my junction block go out. It was TOTALLY random and would do odd stuff like that. You could probe it and it was fine... but it wasn't. There was a cracked trace inside the block for the pump. REALLY hard to diagnose and unfortunately, I destroyed the block confirming the problem. Probably only indicator externally was the fuel pump relay and fuse area was getting really hot.

Do you have a Wideband AFR meter? I monitored mine while the problem happened. It felt like a lean condition and I could quickly confirm that with the WB meter.

Loss of power makes me think it might be a lean condition.

FYI ~ fuel trims especially if your truck isn't well dialed in won't tell you much. I had a rich condition where the trims always reported lean from the PCM. Never did figure out why it did that. I had to re-baseline the PCM so I don't much trust the PCM unless I can confirm with my wideband now.. I also was told to turn of LTFT, not sure if you can turn of ONLY the STFT? I know software will allow it. I turned back on all my fuel trims once I got the VE table better calibrated.