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While you are running it idle to get rid of all the gas, consider adding this additive to the gas. It has PEA in it and helps remove deposits along the way
Well looky here what's at the end of the fuel rail:
I'm ordering a fuel pressure test kit. Unfortunately have to wait until delivery to test. In the meantime, I walk. Maybe I should get my bike up to snuff.
A clogged fuel filter might cause these symptoms - stalling on demand for fuel - so I will check it out with the fuel pressure test kit before draining the gas. If the fuel pressure drops precipitously when I stab the throttle, there it be.
imo the fuel pressure test kit is a must have for the GL.
I was able to verify it is not a fuel pressure problem by monitoring the pressure as the fault happened.
I also used the Schrader valve adapter that came with the kit to rig up a drain hose to the fuel rail. It didn't take too long to drain all the fuel, and was far easier than crawling underneath with a drain pan and a death wish.
One problem was the adapter goes to a quick disconnect, which shuts off both sides, so I had to remove the Schrader valve core. The Autel I have was able to turn on the fuel pump, but it was easier to insert the jumper to bypass the relay.
I ***think*** this solved the problem; the stalling still happened a little bit on a test drive after some time idling. One mistake I made was to not leave the drain hose connected to purge the lines with fresh gas. I could have run the drain line around to the filler neck and let the gas recirculate. It has a full tank of fresh fuel now, and I'm leaving it idle for a while to deliver a final verdict.
Edit: It seems to be solved. Will take for a real road test and update if it is time to go ECU shopping.
Last edited by eric_in_sd; 12-05-2021 at 08:03 PM.
Maybe from the same guys who do third party valve body programming?
Don't know about them. Who is this?
I got in touch with the guys at Pressertech.
On the minus, they are questioning whether it is the ECU at all - and speculating that if it is the ECU, it is the processor inside and not repairable. Hence I am in for a replacement, which they will help me with for a cool $1050.
Who knows, maybe they will be able to repair it.
I really am having a hard time imagining what could be the issue besides the ECU. The fact that turning it off and back on again resets it screams electronics, particularly, as the fellow said, a cpu. I even flushed a couple of gallons of gas through to ensure it was not residual fuel causing the issue.
Last edited by eric_in_sd; 02-09-2022 at 11:46 AM.
Well, I mailed off my ECU to Pressertech. The guy I chatted with about the situation seems very knowledgeable. Again, he seems skeptical it is the ECU, but if it is not, I truly do not know what to do. The motor even stalls now during warmup, without stabbing the gas pedal at all.
I double checked the fuel pressure. While it is slow to come up without the engine on, it promptly goes right to 55 psi and stays there, solid, with no change when the failure occurs.
I have never in my life wished so hard for a $1,000 part to be bad.
Unfortunately my wishes were not granted. After an amazing series of snafus, my replacement ECU from Pressertech exhibits the exact same issue.
I ordered a throttle body in hopes this is somehow connected to the throttle plate being sticky. The values move around roughly as expected (watching via the ECU, on my scan tool) but I cannot easily tell what the proper values would look like.
Canceled the throttle body order - out of stock - then discovered the right catalytic converter is plugged.
1) The post cat oxy sensor on the right side provides wildly swinging voltage while the left side is steady.
2) The manifold vacuum is low (280 hPa = 8") (Edit: Unclear whether this is pressure, indicating high vacuum, or vaccum itself.)
3) Tapping the exhaust near the right cat, stuff can be heard rattling around.
The guys at Pressertech guided me to look at cat blockage.
Anyone who can comment on how terrible the cats are to remove, let me know. Just like to know how much fun I am in for.
Since I already have become good buddies with the guys at Pressertech, I might simply core out the cat and reinstall. Decent cats range from $400 to $700+, and I am only using this vehicle "off-highway" now. Hopefully there are not too many chunks lodged in the mufflers.
Last edited by eric_in_sd; 02-09-2022 at 11:45 AM.
The exhaust bolts, being stainless, are shockingly easy to remove. I made it through the point of needing to drop the rest of the exhaust to get the clearance to completely remove the right cat. I can almost get the cat pipe out of the inlet to the exhaust but not quite. Since the garage is a nipply 25 degrees right now, I will probably only try to drop the right cat for now.
I had ignored the possibility of catalyst breakage because the cats are well protected from banging on the ground. Perhaps this is connected to the oil consumption problem, though that is hard to believe considering the worst the oil consumption got was a quart every 600 miles, and the valve stem seal leak is almost certainly on the intake side.
Pressertech agreed to modify the code on the ECU for a very reasonable fee. I believe they feel sorry for me considering I just spent a grand on an ECU that did not solve my problem. They are good guys; highly recommended if you have a potential ECU issue or wish to pursue modifying the ECU.
Performance improved with right hand cat deleted, but still suffers. Proceeding to the left hand now. This is quite a bit harder, with more stuff, such as the driveshaft and steering column, in the way. Also these bolts holding the cat to the exhaust header are frozen on. This would indicate overheating.
Some of the chunks of catalyst pulled out of the right side had actually melted. There are literally globs of ceramic (I think) amid eroded sections of the catalyst substrate.
Melty cats are usually caused by lean burn cycles or more likely; continuing misfires where the unburned fuel is combusted in the cat itself…did you ever have a history of blinking CEL or codes to indicate persistent misfire?
it’ll be interesting so see if gutted cats make it run better but you still have an underlying fuel/spark issue.
Melty cats are usually caused by lean burn cycles or more likely; continuing misfires where the unburned fuel is combusted in the cat itself…did you ever have a history of blinking CEL or codes to indicate persistent misfire?
There was one period in which I limped for a few miles with a misfiring cylinder (#5). However, this melting occurred on bank 1, which is cylinders 1-4. Nothing that I know of that would have hit bank 1. Conceivably the intake oil leak is on bank 1, but still - a quart of oil over six hundred miles, that would be a quart in 30 gallons of gas - enough to cause a difference? No one of the spark plugs was all hot or anything.
Never any misfire codes besides the one period I was struggling with diagnosing the #5 coil.
When I changed the plugs, they were sooty. However, this was after struggling with the current issue, so ... ?
They say that a failing cat can bring the whole thing into a downward spiral. I was getting 410 / 420 cat insufficiency errors for quite some time. There is a bunch of fiberglass in there, so I could see it coming loose and partially clogging the cat, forcing the exhaust through a small area of the honeycomb, causing that one area to overheat ...
Originally Posted by Max Blast
it’ll be interesting so see if gutted cats make it run better but you still have an underlying fuel/spark issue.
tbh I'm kind of running out of fuel/spark issues. This had better fix it!
Pulled the driver side cat. Wow, what a pain. This one, the bolts holding the cat pipe to the exhaust manifold were frozen, but a night soaking with PB Blaster fixed 'em. The bolts are also both harder to get to, because for some reason there is more shielding in the way.
This cat was not heat damaged, at least not obviously so. A few plugged channels, but more or less okay. Changed the upstream oxy sensor, which was overdue (I had already changed all the others, but driver side is wedged in there impossibly tight.).
A cold garage is not conducive to extended work, so I quit for the day before reattaching the cat pipe to the manifold. The clearance in there is a nightmare. Almost feel like it would be worth making a jig to hold the flange up and in place from above. It's tough, and WIS (which I just acquired via Ebay) is no particular help. You literally have to maneuver up a stainless bolt held in a wobble socket on a 18" extension.
WIS did, however, help make it clear you do not need to pull the center-front driveshaft to get the cat pipe out.
The exhaust hardware is clever: Stainless bolts and copper nuts. Those two metals don't like each other and so don't fuse. At least not much.
I don't think the rest of the exhaust is impeding anything. The channel through is fairly clear; we appear to have left some fiberglass in the passenger side cat, and it was amusing to see it blow out the back when we started up the motor. The two center mufflers are straight-through resonators, which are helpful for verifying that chunks of cat matrix have not tumbled down the pipe and gotten stuck.
Reinstallation of the bank 2 cat was a nightmare, but it's over now. You need a wobble socket; I jerry-rigged one wrapping rubber bands around the u-joint type. Plus three layers of electrical tape on the bolt head to hold it in the torx socket while it is being maneuvered up from below.
While the problem is not fixed, at least the exhaust sounds better now, and the cats needed "replacement".
Next step, the throttle body. Ordered a reman unit (Cardone) from Rock Auto. Hope it's not too hard to install.
One issue with having an older vehicle is there is typically a bunch of deferred repairs that all need to be eliminated as a possible cause. It is a tradeoff between "if it ain't broke don't fix it" and "fix it before it breaks".
Man, it must be frustrating trying to figure this out.
Sending best wishes your way and I hope you can figure it out soon.
what can one do to prevent these kind of exhaust clogging?
Man, it must be frustrating trying to figure this out.
Sending best wishes your way and I hope you can figure it out soon.
what can one do to prevent these kind of exhaust clogging?
Thanks for the good thoughts. Much of what I am doing is deferred maintenance and repairs, so it is not a total loss. I'm out $1200 for the ECU and a battery, the former not being a total loss as I kinda wanted a tuned ECU anyway, and the latter being my own ignorance - apparently it is normal for a battery's voltage to sag under load when it is cold. Anybody in southwestern Idaho want a nearly new battery, hit me up in DM.
I sure am glad I checked with the ECU guys before placing the order for the $400+ cat.
I do not know for a fact that the bank 1 cat was clogged. Yes, pieces were rattling around, but clogged - don't know. And I really do not know why that side cat melted and broke apart. If you want to do a preventive repair, change the cats when the 420 and 430 errors first come up - but this is a costly and laborious repair, and the perennial struggle is risking doing an expensive repair only to have the vehicle get hit by a rock from the sky the day after.
Changed the throttle body, on the thinking it was sticking and/or the position sensor had gone bad. No luck.
Got to thinking maybe it is carboned intake valves, because I had been doing a bunch of cold (Idaho November) starts and short trips, plus maybe put bad gas in. The symptoms include stalling when cold plus hesitancy on the throttle, which match up to carboned intake.
I put a can of Seafoam spray in the intake. I ran it in to the vacuum line, which enters the manifold just fore of the throttle. No real help. The engine tilts back a lot, though, so it probably only went into cylinders 4 and 8. I left the rear up on stands and lowered the front, unplugging the air compressor to squat down the front all the way, but still the engine is tilted back. If I had a steep driveway I'd do that, but I'm on a flat plain. I tried a second can (Napa has them on sale for $8bux; why not?) but still no help and enormous white smoke clouds to show for it.
I'll try pulling a fuel injector and a spark plug, inspecting the pistons and valves for carbon. I could spray Seafoam in the fuel injector holes directly onto the valves, and through the spark plug holes directly into the pistons. After I do that I would run the engine at idle with a heavy concentration of Seafoam fuel treatment, hopefully to help wash away the carbon that's been turned to sludge.
I'm even thinking of walnut blasting the valves if necessary; I have a sandblaster and strong air compressor. Shouldn't be too hard to pull the intake manifold.
Does anyone have an idea of the typical spark timing at idle? I'm wondering if mine is in spec. Thinking about carbon raising the compression ratio, forcing spark retardation.
Last edited by eric_in_sd; 01-12-2022 at 08:09 PM.
The saga continues. Pulled all the injectors and cleaned. Some improvement, but it is difficult to tell - there have been many false hopes in this saga.
The back sides of the intake valves are nice and shiny. A bit tan but not crusty with deposits, not by a long shot.
The piston tops are covered with bubbly carbon:
Crummy picture, but that is what you get with a cheap borescope.
The resolution is good enough to show clean intake valves:
The research I read indicates that about the only way to clean carbon out of combustion chambers is with water injection. PEA and similar will help, but only very slowly. The other issue is the motor won't run strongly enough to endure hard driving which would knock loose or burn up the carbon. The problem is that the primary vacuum fitting is on the back of the motor, which is angled down to the back. Seems to me injecting water there will be near useless, at best getting cylinders 7 and 8.
I tried running a heavily concentrated solution of Gumout Regane, which is high concentrations of PEA and naphtha, but am getting concerned it may degrade the o-rings on the injectors, that sort of thing. The above piston photo is from after the Regane (and Seafoam) treatment. It does not seem to be doing much.
However, there is a vacuum fitting at the front. I believe it goes to the manifold absolute pressure sensor. I will try routing the MAP vacuum line to the PCV vacuum line, and see if I can drip water into the front. This should work well with the engine being angled up to the front.
This is still all based on the hypothesis that the carbon makes the ECU go off into la la land, due to spark retardation and/or mixture enrichment, but does no self diagnosis or reporting of the condition.
Figured out that attempting intake manifold injection of anything is a waste of time and actually dangerous. There is a huge well between the cylinder heads to accomodate the variable length runner system. Pretty sure it fills with whatever you are attempting to put in the intake, and then dumps into the cylinders all at once when you throttle to activate the tumble flaps.
Since it is 35 degrees during the day, too cold to attempt anything major like swapping the motor, I am tempted to remove the intake manifold and tap 1/16 NPT threaded holes to allow injection directly at the intake ports. Fill with NPT plugs when done. Have to remove the intake manifold; I am not confident in tapping the holes without aluminum chips falling in.
Could be useful to have this feature on an intake manifold anyway.
It's been a while since I've been on here. What oil are you running? Asking because it seems some oils are better at keeping carbon build-up at bay, it seems.
I swear by Mobil1 Synthetic. I used 0w40 in a 1.8T VAG engine for 20 years. That motor was rock solid till the day I donated the car a few months ago to a local high school.
We have a Sonata which was being filled with Quaker State dyno oil under warranty. By the dealer. Since the warranty expired, I've used Pennzoil Synthetic twice so far, to be followed with at least the next two oil cycles with Pennzoil Platinum. Both are made with natural gas so their cleaning properties are better than most synth oils. This is all in an attempt to remove any carbon buildup gradually. The GDI engines seem to be notorious for carbon related problems. Not to mention that my wife complained about the car losing some pep. She also used to fill gasoline without techron additive. I use almost exclusively Mobil/Esso gas stations for the detergents (techron primarily) to keep the injectors semi clean and also help with the carbon prevention. In the states there are several chains which have techron.
On the GL I jumped straight to Mobil1 0w40 when I got it two years ago. I figured that it would have mostly been run with half decent synthetic oil, so no need for gradual transition.
11-30-2021, 06:19 AM
