No engine power after 20 minutes of driving- solved: brakes dragging

[Shawn]

After finally fixing the cooling issue, It stayed 172-174 for about 10-15 minutes of driving. Was feeling pretty damn good driving it again. Then I started to lose power. Hard to explain but it felt like it was going up a steep hill with no power left in the engine but this was on level roads or going down hill. Stopped, let it cool off for 20 minutes. Checked all the vitals- oil, antifreeze, trans oil, tune, etc. No shavings in oil. Everything looked good.

Got back in it, drove for another 3 miles. Was normal at first then it happened again, no power. Struggling just to drive down a street that was slightly downhill. So weird. Was in 3rd, lost speed, then I downshifted in 2nd, still losing speed. Finally pulled over in a neighbor hood a mile away from house. Temp was 190. I have a 160 thermostat.

Walked home, let it cool off for an hour, then went back and it drives fine going back home for that 1 mile. Definitely something to do with heat. Oil pressure is normal at 35psi at idle. Goes up with RPM.

Specs:
Freshly built 406 SBC, Dart block, AFR heads, Edlebrock PF4 EFI, 4L80 with manual valve body. Engine should have plenty of power with the mods.

Possible causes:

-Edelbrock PF4 still not dialed in. Could be something there in the tune that I'm missing. Something to do with the pump? I forgot to look at the fuel pressure when this happened. Its normal now in the garage when at 190 temp. Fuel filter is new.

-Something in the engine. Valves too tight? rings expanding too much? bearings?

-4L80 trans acting up, could be overheating. Need to put a temp gauge on it. Could be built wrong.

Has anyone had this happen on a new engine build or transmission?

 

[rampage]

Sounds like it’s going into limp mode after it heats up. Have you tried pulling codes?

 

[eric67camino]

Sounds like it’s going into limp mode after it heats up. Have you tried pulling codes?

Also might check fuel pressure when hot. Sounds like vapor lock.

 

[ZooMad75]

Any chance the brakes are dragging and locking it up when they get hot? Let it cool and it drives ok until they lock up again? I would think if it was a fuel delivery issue the engine would run lean, possibly pop and run like it's running out of fuel. Meaning the engine would not be smooth running.

Just throwing an idea out but it's worth checking.

 

[bp71k5]

190 is a totally normal temp, maybe a bit cool as 195 was somewhat standard for early injection models. The 170 thermostat only controls the minimum operating temperature and does nothing for max temp. The maximum temp is controlled by the radiator and cooling fans.

It does sound like it’s heat related though. With a customized injection system, it sounds like there’s a tuning issue. Sounds like it runs ok in open loop and then falls on its face when it heats up and goes into closed loop.

 

[Bent77]

Shawn I’d call Edelbrock tomorrow and get their .02

If there’s something wonky in there, they can probably find out faster than you. If not you know to look elsewhere

 

[Shawn]

Sounds like it’s going into limp mode after it heats up. Have you tried pulling codes?

No codes or limp mode on Edelbrock PF4 that I know of.

Also might check fuel pressure when hot. Sounds like vapor lock.

I'll check that next time.

Any chance the brakes are dragging and locking it up when they get hot? Let it cool and it drives ok until they lock up again? I would think if it was a fuel delivery issue the engine would run lean, possibly pop and run like it's running out of fuel. Meaning the engine would not be smooth running.

Just throwing an idea out but it's worth checking.

Brakes seem OK but the master and HB are new. I think it's more engine related. Possibly PF4 going closed loop with wrong parameters or fuel issue.

190 is a totally normal temp, maybe a bit cool as 195 was somewhat standard for early injection models. The 170 thermostat only controls the minimum operating temperature and does nothing for max temp. The maximum temp is controlled by the radiator and cooling fans.

It does sound like it’s heat related though. With a customized injection system, it sounds like there’s a tuning issue. Sounds like it runs ok in open loop and then falls on its face when it heats up and goes into closed loop.

I agree. I will call Edelbrock tomorrow

Shawn I’d call Edelbrock tomorrow and get their .02

If there’s something wonky in there, they can probably find out faster than you. If not you know to look elsewhere

Agree!

 

[ktmoutfront]

Any chance the brakes are dragging and locking it up when they get hot? Let it cool and it drives ok until they lock up again? I would think if it was a fuel delivery issue the engine would run lean, possibly pop and run like it's running out of fuel. Meaning the engine would not be smooth running.

Just throwing an idea out but it's worth checking.

If the brakes were dragging that bad, he would smell them when he stopped. Ask me how I know.

 

[ZooMad75]

I've seen hydroboost issues that could cause the brakes to lock up fairly quickly. If the wrong pushrod is used between the booster and master it could be holding pressure on the master cylinder, which would increase with the engine running and fluid moving through the booster. That's my theory at least.

Granted I don't have any experience with an Edlebrock system, but I've been around GM EFI systems for a long time and I haven't seen many situations that would kill the power and then come back after cool down. A weak fuel pump is one. At the pressures even the Edlebrock system uses, vaporlock is unlikely. But a pump getting hot and dropping output is entirely possible. Should be pretty easy to watch with a fuel pressure gauge. But normally when a pump drops pressure like that the fuel trim will go lean. If you can watch the fuel trim data while it's running, you should be able to see it go that way. GM systems will typically set lean fuel trim codes with a weak fuel pump, not sure what the pro-flo does in that situation.

Another situation that would slow an engine down is when the cats start melting down. I'm not sure if cats are on the truck, but I'm guessing there are since you are in Denver and the truck has to pass emissions. Typically the cats have enough flow right after start-up but will lose flow after they start taking on the heat of the exhaust. Sometimes blocking flow enough to stall the engine out completely. Pretty easy to confirm. Put a hand over the exhaust when it's down on power and see of the flow is decreased. Or uncork the headers ahead of the cats and take a quick run to see if the engine continued to loose power

I'm just throwing ideas out there. I could be way off base too.

 

[Shawn]

I've seen hydroboost issues that could cause the brakes to lock up fairly quickly. If the wrong pushrod is used between the booster and master it could be holding pressure on the master cylinder, which would increase with the engine running and fluid moving through the booster. That's my theory at least.

Granted I don't have any experience with an Edlebrock system, but I've been around GM EFI systems for a long time and I haven't seen many situations that would kill the power and then come back after cool down. A weak fuel pump is one. At the pressures even the Edlebrock system uses, vaporlock is unlikely. But a pump getting hot and dropping output is entirely possible. Should be pretty easy to watch with a fuel pressure gauge. But normally when a pump drops pressure like that the fuel trim will go lean. If you can watch the fuel trim data while it's running, you should be able to see it go that way. GM systems will typically set lean fuel trim codes with a weak fuel pump, not sure what the pro-flo does in that situation.

Another situation that would slow an engine down is when the cats start melting down. I'm not sure if cats are on the truck, but I'm guessing there are since you are in Denver and the truck has to pass emissions. Typically the cats have enough flow right after start-up but will lose flow after they start taking on the heat of the exhaust. Sometimes blocking flow enough to stall the engine out completely. Pretty easy to confirm. Put a hand over the exhaust when it's down on power and see of the flow is decreased. Or uncork the headers ahead of the cats and take a quick run to see if the engine continued to loose power

I'm just throwing ideas out there. I could be way off base too.

Appreciate everyone's input on this! Its SO frustrating to have spent so much time and money on this build making sure everything is perfect and I finally get it so it cools correctly now this.... Has me wondering if I did something wrong somewhere. Did I use the right part, did I use the right setting, should I have gone a different route.

As for the brakes, I'm not going to deny this happens. I was able to push 6" more after I got it back in the garage since I did not pull up enough. I would think if the brakes were locking, it would not allow me to roll it while running. I made sure to get all the right parts including brake pedal, spring and rod for it.

I think I need to get a video log of the PF4 and see if anything stands out. Until then I want to dump the oil and filter and look for any signs of metal contamination. Give it some fresh oil (still has break in oil). Also want to get a temp gauge on the transmission and make sure thats ok. The fuel pump and filter and new. Walbro 450lph so its definitely delivering the fuel but its always possible I got a bad pump. The PF4 has a fuel pressure gauge built in. Just need to look at my display. I don't think PF4 has codes but I wish they did for times like this.

No cats on mine. Just a dual 3" exhaust so should be unrestricted unless someone managed to break in my garage and shove some big ass bananas up my tail pipes. (old eddie murphy movie)

Thanks for the advice!

 

[Fordum]

Sorry you don't have a cat. Until you said that, it was really sounding like some kind of exhaust restriction. Do you have any kind of a port on the exhaust that is not being used? Like an extra oxygen sensor? If its easy to get to, you could pull the plug, and either rig up a pressure gauge with any hoses or the gauge far enough away to prevent heat problems. Failing that, if you can reach it, on the street, try pulling the plug, putting some antiseize on the threads, and putting it back finger tight. When the truck starts acting up, switch it off, pull the plug with some vicegrips or something, and recrank it.
You will hear some noise, but a plugged system will be obvious.
Bad ignition will usually cause some roughness. Either a skip or misfire or quit completely. Low fuel will also usually cause erratic engine stuff. An air restriction would tend to cause black smoke. EGR opening wrong or not closing right might do it.
Dragging brakes would tend to smell, but if all four were dragging a little, it might take a while for them to get hot enough.
Next time it does it, carefully feel the center of the wheels for heat.
I think you would be smelling a banana by now. That only works if the exhaust is completely blocked.
Do look under the truck for something wrapped around the drive shaft, or a Graboid.

Those are all the "good" ideas I can come up with right now. Now for the bad one: Transmission trying to apply two clutches or bands at the same time. Next time you check the fluid, sniff it carefully. If you have a dragging band or clutch, it should be starting to get hot.
Also, when it starts, try kicking it into neutral and see if it coasts OK. If so, then most of the drivetrain should be OK. Rear diff, transfer case, etc. Any drag will cause the truck to slow down real fast.

 

[Shawn]

Sorry you don't have a cat. Until you said that, it was really sounding like some kind of exhaust restriction. Do you have any kind of a port on the exhaust that is not being used? Like an extra oxygen sensor? If its easy to get to, you could pull the plug, and either rig up a pressure gauge with any hoses or the gauge far enough away to prevent heat problems. Failing that, if you can reach it, on the street, try pulling the plug, putting some antiseize on the threads, and putting it back finger tight. When the truck starts acting up, switch it off, pull the plug with some vicegrips or something, and recrank it.
You will hear some noise, but a plugged system will be obvious.
Bad ignition will usually cause some roughness. Either a skip or misfire or quit completely. Low fuel will also usually cause erratic engine stuff. An air restriction would tend to cause black smoke. EGR opening wrong or not closing right might do it.
Dragging brakes would tend to smell, but if all four were dragging a little, it might take a while for them to get hot enough.
Next time it does it, carefully feel the center of the wheels for heat.
I think you would be smelling a banana by now. That only works if the exhaust is completely blocked.
Do look under the truck for something wrapped around the drive shaft, or a Graboid.

Those are all the "good" ideas I can come up with right now. Now for the bad one: Transmission trying to apply two clutches or bands at the same time. Next time you check the fluid, sniff it carefully. If you have a dragging band or clutch, it should be starting to get hot.
Also, when it starts, try kicking it into neutral and see if it coasts OK. If so, then most of the drivetrain should be OK. Rear diff, transfer case, etc. Any drag will cause the truck to slow down real fast.

Thanks for the suggestions. I'll take a look at those. Not ruling out the transmission. It is a new build so you never know if something was missed or done wrong. Trying to see if anyone with a manual valve body transmission has had this issue before. I have another one thats full auto, freshly rebuilt but will take some more work to get it installed with the computer and different adapter is needed.

 

[centexk5]

I'd be looking at the fuel pump. Had one that acted the exact same way as your symptoms. Replaced it and never had another issue.

 

[Shawn]

I hope thats all it is. If I have to pull this motor AGAIN, I'll be really bummed.

 

[diesel4me]

This might sound far fetched as far as what fixed it,but my friend had a car at his shop that lost power after it was driven awhile--it would feel like it was not getting enough fuel,it wasn't sputtering or lurching,it just wouldn't respond when you floored it,it just labored along like it was only getting enough fuel to hit a certain speed and stay there..

He spent quite a few hours on diagnosis and found a few things he thought was the trouble--one steel fuel line above the tank was rotted enough to be weepy,so he fixed that,but the car still had the same problem..tested fuel pressure,it was within specs..cleaned the throttle body,noted slight improvement,but was still not "fixed"..replaced the air filter,as it was original and severely filthy,but it still ran the same..
He even dropped the front pipe off the manifold and drove it to see if it had a clogged converter..nope!..

He doesn't dive too deep into problems with ECM's and assumed it had a bad one,so he told the customer to take the car to a dealer,and returned the next day--said "they fixed it in 10 minutes--all it needed was a new gas cap !"....evidently the original was defective,or maybe someone lost the original,and just put "any" gas cap that screwed on ?...

It wasn't letting enough air into the tank,so the pump couldn't deliver enough gas--they told him the tank looked like it was collapsing some after being driven long enough for it to start acting up,and they heard a suction noise when they took the cap off to test it..
After a new cap was put on it would accelerate normally again and got all its power back..

I thought the fuel tank would get air in thru the charcoal canister or try too,if the cap got blocked up,but I guess they have check valves --I'm not that familiar with newer cars emissions so I'm guessing..
My friend still feels they found some other issue and just didn't want to admit it...the dealer charged $150 for diagnosis and a new gas cap!..

I've seen bad ignition coils,modules,and pick up coils do weird stuff like this in the past...bad distributor cap or rotor can do it too,but being temperature related I'd suspect the first 3 things,not the cap & rotor,those "should" be bad right from a cold start..

 

[Shawn]

Thats one thing I was going to test as well. Make sure the tank has enough ventilation with this new setup. I might loosen the cap up. I have my canister removed right now but might check to see if its venting correctly. Will check those other items too.

Speaking of tanks, I need to replace the current one. The baffle is knocking around. Could be causing some kind of blockage with the pump.

Thanks!!!

 

[Wes Harden]

Baffle CAN do this.

Also for future sake, if running p30 hydro and master, check brake fluid lvl. Keep it at least 1/4" below the top.
It will expand and apply brakes if to full.

 

[6.2Blazer]

First thing I would look at it are the feedback loop to the EFI. Assuming the EFI system is getting feedback from the O2 sensors. Generally when cold the system runs open loop, meaning it's runs off of preset parameters regardless of what exactly is going with the engine and being read by the sensors. Then when warmed up enough it switches to closed loop and looks for sensor input thus adjusting the fuel trim. On a factory setup most generic OBD tools will show you when it switches, and also show you the fuel trims. If the fuel trim numbers (long term and short term) are large it means something isn't right. Either the engine itself it running bad and the O2's are trying to adjust, or the O2 reading is bad and giving the EFI setup wrong values. On my 2500HD 6.0L truck I had an issue where it ran fine when you first started it and started driving, but as soon as the engine warmed up it ran really bad. Also, if you did wide open throttle it would run fine. That is because when the engine was cold or when you went wide open the engine was running in open loop, or not relying on input from the O2 sensors. Otherwise one of the O2 sensors was giving it a bad signal and trying to say it needed a lot more fuel, the engine was running way rich on one bank.

 

[Shawn]

Baffle CAN do this.

Also for future sake, if running p30 hydro and master, check brake fluid lvl. Keep it at least 1/4" below the top.
It will expand and apply brakes if to full.

Yeah that tank needs to go. Looking at them now.

I'm running the GM hydroboost with the Wilwood master. I'll double check on my fluid level and make sure its not too high if that might affect it like it does with the stock cast iron.

First thing I would look at it are the feedback loop to the EFI. Assuming the EFI system is getting feedback from the O2 sensors. Generally when cold the system runs open loop, meaning it's runs off of preset parameters regardless of what exactly is going with the engine and being read by the sensors. Then when warmed up enough it switches to closed loop and looks for sensor input thus adjusting the fuel trim. On a factory setup most generic OBD tools will show you when it switches, and also show you the fuel trims. If the fuel trim numbers (long term and short term) are large it means something isn't right. Either the engine itself it running bad and the O2's are trying to adjust, or the O2 reading is bad and giving the EFI setup wrong values. On my 2500HD 6.0L truck I had an issue where it ran fine when you first started it and started driving, but as soon as the engine warmed up it ran really bad. Also, if you did wide open throttle it would run fine. That is because when the engine was cold or when you went wide open the engine was running in open loop, or not relying on input from the O2 sensors. Otherwise one of the O2 sensors was giving it a bad signal and trying to say it needed a lot more fuel, the engine was running way rich on one bank.

I'm going to turn off the closed loop option for now. It seemed to struggle even at WOT but fine again when it was cooled off for an hour. I believe I have another wide bad sensor I can throw on but need bung welded in.

Tried to call Edelbrock tech support at lunch and they finally returned my call 3 hours later and I was back at work but it was not a tech. He will have a tech call me later. In the meantime, their support forum is telling me to maybe change my map to 5030 so I may try that. He thinks its a fuel tank issue or possible pump.

Started it in the garage over lunch. Let it warm up to 172 and it sat there for awhile. No change in fuel pressure. I will take it another spin when I get home.

 

[Shawn]

OK gentlemen... found the issue. It was the brakes locking up. Never noticed it when I was driving yesterday but damn! Fuel pressure fine and gas cap loose. My k5 won't even roll back on a hill in neutral. At least its not the engine or trans. Time to let it cool off... walking home once again....