- Thread starter
- #21
Sounds like a solid plan! Thank you sir!
3FE Discouraging tale (valves, oil galley, and knocking)
- Thread starter TheWhitefox
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- 3fe knocking power loss
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- Thread starter
- #22
UPDATE:
Rechecked valves after second adjustment and they are spot on. After driving it some more it seems after each adjustment the power gains that were achieved disappeared after a few starts. Throttle response and power do not slowly go away it is literally, wake up next day and it is totally different. Symptoms both times are lack of power, poor to almost no throttle response and very poor mileage 4/5 miles per gallon. In terms of throttle response, it will reapond better to how fast you move the petal rather than the position of the petal.
On the positive side after the second valve adjustment and a full tank of 87, the knock is gone, engine runs smooth, idles well, and valves sound very normal and smooth.
Its just that the power disappeared. This is beyond bad even for 3fe. Example, accelerating out of a stop going up slight hill and you have to floor it to get to 30. Also if you hit the hill around 40 miles (usually in 3rd, low 2000rpms) and you slowly add full throttle to maintain, the rpm will only go up by 100 and I will lose speed. Basically zero throttle response. Conversely after the first valve adjustment I would put in a quarter to a half throttle going up a slight hill and it would maintain and actually gain speed.
Next thing im going to check is the throttle position sensor and see if the voltage increases as it should.
Rechecked valves after second adjustment and they are spot on. After driving it some more it seems after each adjustment the power gains that were achieved disappeared after a few starts. Throttle response and power do not slowly go away it is literally, wake up next day and it is totally different. Symptoms both times are lack of power, poor to almost no throttle response and very poor mileage 4/5 miles per gallon. In terms of throttle response, it will reapond better to how fast you move the petal rather than the position of the petal.
On the positive side after the second valve adjustment and a full tank of 87, the knock is gone, engine runs smooth, idles well, and valves sound very normal and smooth.
Its just that the power disappeared. This is beyond bad even for 3fe. Example, accelerating out of a stop going up slight hill and you have to floor it to get to 30. Also if you hit the hill around 40 miles (usually in 3rd, low 2000rpms) and you slowly add full throttle to maintain, the rpm will only go up by 100 and I will lose speed. Basically zero throttle response. Conversely after the first valve adjustment I would put in a quarter to a half throttle going up a slight hill and it would maintain and actually gain speed.
Next thing im going to check is the throttle position sensor and see if the voltage increases as it should.
- Thread starter
- #23
Couple videos where I manually moved the throttle. Not sure if it helps, everything sounds good to me but.... Maybe those with more time listening to the engine might hear something im not.
Thanks guys for your help!
It is extremely strange that the power comes back when you adjust the valves but is then gone the next morning if the valves are in fact spec'd out correctly.
The only way in my mind that that can happen is if the seals and guides are bad and causing oil and sludge to sit on top of the valves causing the newly done valve job to go out of wack again. But again like I said before one night seems a little extreme so the fact that it had to do with the valves the last two times must just be an incredible coincidence.
Could you update the post for everything you have and haven't checked that people have suggested so we can all be on the same page and not suggest things you've done already.
The only way in my mind that that can happen is if the seals and guides are bad and causing oil and sludge to sit on top of the valves causing the newly done valve job to go out of wack again. But again like I said before one night seems a little extreme so the fact that it had to do with the valves the last two times must just be an incredible coincidence.
Could you update the post for everything you have and haven't checked that people have suggested so we can all be on the same page and not suggest things you've done already.
- Thread starter
- #25
Timeline:
Bought with follo
Timeline:
Purchased with following conditions;
1) major power loss, poor to nil throttle response
2) running ultra rich, gas coming out the exhaust system
3) leaking gas tank, leaking filler neck
4) knock under heavy load (uphill etc)
5) exhaust pipe rusted off the front of stock muffler and rusted off of one of the high flow cats.
6) black oil (yes I know this is sludge. Slowing working it out with 1 qt marvel per change, and do changes at 500 mile increments)
7) gas mileage around 5/6 miles per gal
fixed gas filler neck and gas tank. Performed 2 oil changes at 100 mile increments to get the oil color to stabilize at a dark brown
no other issues resolved themselves
replaced and upgraded exhaust system (dual highflow cats already installed, from there back see pics. Pic of cats was at time of exhaust system overall. both cats had similar flow that was within normal limits even though the right cat which is for cylinders 4 thru 6 had more carbon buildup)
no other issues resolved themselves, truck started dripping gas out of the exhaust tip. Running ultra rich
Immediately changed plugs ( see picture in second post, original plugs in pic far left is #6 far rt is #1) no major problems found
no other issues resolved themselves
Reset ECU/EFI by pulling fuse for 5 mins (with @GLTHFJ60 guidance)
immediately solved the problem of running ultra rich, no more gas coming out exhaust tip. Still some carbon buildup occurring along exhaust tip
At this point only issues were knocking, major power loss/poor throttle response and super poor gas mileage
switched to 93 gas, knock disappeared
power loss and poor gas mileage remain (gas mileage increased to 7/8)
Some time later...
Performed first valve adjustment. Found sludge (see picture on second post) was moderate but not terrible.
instant power gains, incredible throttle response, much less full consumption.
Next day! after adjustment, Oil galley plug blow up. Repaired many weeks later myself ( with assistance from @GLTHFJ60 on the reassembly).
power gains from valve adjustment held.
Changed oil and filled up tank with 93 again after oil galley fix. Upon this engine light starts to come on every time I accelerate and then extinguishes and all power gains lost. Took off positive lead to batt. for 12 hours in attempts to reset code. Might have worked but issue came right back when i accelerated away from my driveway, engine light on & same power loss that I has when I bought it.
Taking into dealership to pull codes. Codes (OBD 1, no one understood them, 2 codes - one was O2 sensor, second was something about speed) They thought bad wiring harness coming out of trans. but never replaced any wiring harnesses. Instead did another valve adjustment (Bob, 25yr tenure at Fred Anderson completed work) and stated 4 valves were too tight.
Power gains/throttle response achieved at first adjustment came back and engine light stayed off.
After about 4 starts power gains disappear. Drove one day and all is fine, wake up next morning and all gone. Try resetting ECU/EFI by pulling lots of fuses for 30 mins (all fuses in manual that state fuel injection system, 4 in all). This helps very little if at all. Fill up with 87 for the first time in a year and knock has disappeared!
Only 2 problems remaining, very poor gas mileage and power loss/throttle response
Return to dealership. They state they cracked the valve cover again and that all the valves are in the right position. Now give me the BS of the aftermarket floor mat is causing the petal to catch up. Right....
TODAY, Tried resetting ECU/EFI by removing positive lead and touching it to negative terminal for 2 minutes (recommendation of the mechanic I trust the most in town and has lots of experince with the Chevy 235 engine). This did nothing for the power loss/throttle response issue or gas mileage.
Problems remaining: Power loss/throttle response and gas mileage around 5/6 per gal.
Sorry for note outlining better before handed. Owned truck for one year.
THOUGHTS?!?!?!
- Thread starter
- #26
Timing.
- Thread starter
- #28
That was going to be my next ask from ONSC members! Have just started to read how to accomplish that adjustment.
check the timing and add it to your list
Trans cable....
Have you checked the trans shift cable? It could be stretched or slipping. It would have to come off each time you pull the valve cover and the initial drive might be enough to reseat the cable, then goes back to pot.
Have you checked the trans shift cable? It could be stretched or slipping. It would have to come off each time you pull the valve cover and the initial drive might be enough to reseat the cable, then goes back to pot.
- Thread starter
- #32
Genius! Will let you know!
- Thread starter
- #33
Timing as been added but after some more thought this weekend decided to order couple of these. They look rather old...to my untrained eye. Figured it couldn't hurt to have some fresh O2 sensors on board. Especially since one of the codes that kept coming back was for that. @GLTHFJ60 know of anyone in the club that is wrenching this weekend? Pretty sure I can handle it though. What is everyone's favorite way of resetting the ECU? Ive been told about 5 different ways of doing it.
- Thread starter
- #34
Pictures, O2 sensors .
Maybe @jonheld can chime in and give an opinion. @TheWhitefox if Jon does chime in, listen to what he says, and do everything he asks, exactly the way he asks it, even if it's a repeat of something you've already done. He is the smartest man I've ever met when it comes to the 3FE computer control system and associated diagnostics.
- Thread starter
- #37
Wilco!
Gimme a break. I'm really just some guy.
The 3FE has very little "magic". It is first generation fuel injection and the system is very very basic.
The O2 sensors, AFM, and TPS are the 3 major feedback sensors that the ECU uses for fuel trim and fuel delivery. If any of these sensors is not working correctly or is outside of the ECU's programmed "tolerance window", it will go into "limp" mode. This appears to be happening to you.
Remember, the ECU is not "smart" and can only work properly within a limited range for all the sensors.
That being said, it is absolutely crucial to make certain that all the mechanical adjustments are done FIRST and need to be within spec according to the FSM. Again, the ECU and sensors can only operate within a narrow window. If the basic mechanicals are out of spec, the ECU doesn't have the range to pull things back in.
If the O2 sensors or O2 sensor wiring is compromised, fuel delivery will not be correct for any given throttle position.
If the door in the AFM can't operate smoothly of if the electrics internal to the AFM have been compromised, fuel delivery will not be correct.
If there's an air leak ANYWHERE in the top of the motor, it will allow unmetered air into the system and she won't run right.
The air intake plenum MUST be sealed. They typically tear at the bellows.
If the temperature sensor on the thermostat housing that feeds the ECU (not the dash gauge) is compromised, the fuel delivery will not be correct.
Again, the mechanicals must be within spec before any electrics are touched.
You can also simply remove the 15 amp EFI fuse in the underhood fuse box rather than disconnect the battery. It does the same thing and is less invasive.
- Thread starter
- #39
Jon where in NJ might you be? Im going to be in tereboro sometime this week. Drinks on me!! Thanks for the advice, definitely agree with your assessment.
No worries. I'm booked in the city all week, so that's probably not going to work, but I do appreciate the offer.