120,000 miles. 5.4 L CNG.
My problem started 2 months ago. Shuddering whn I accelerated and hills. Read that I need cop's. Changed them and the plugs. Yes I had a plug blow out on number 5 and helicoiled it. Problem persisted so I took it to Ford fleet service.

Changed O2 sensors.

When I took the truck out friday and saturday it ran nicely. Flew all round own for 300 miles in a day. Sunday it started to lose power after 40 minutes into a one hour trip. Hills. Had to pull over and get a ride. When I returned I was able to get it home with power loss on and off.

NOW it will only do 15-25 mph tops.
They now say i need catyliic convertors. They want 1600 per cat. I do not think that is gonna happen.



Brought the truck today to my mechanic. Told him to change the O rings.

 

Sorry but my computer made me continue the posting.

I have read many posts here about ignition problems on this engine.
From what I have read here I am led to believe that what I have is an ignition problem. This is why I am having the O rings changed.

Does anyone have any input on :

1) need more information on the truck to help
2) taking the catylic converters off the truck and changing exhaust
3) eliminating the catylic converters all together
4) what to do to make this thing stop shuddering

Thank you for your help.

 

CNG tends to build up oil in the fuel system. The oil is from the compressor lubrication needed to protect them during the pump cycle to reach high PSI needed to fill your tank. Usually the seat that seals the HP stage on the regulator is also worn. Repairs and cleaning usually take care of the fuel problem. CNG drops off rapidly in power with the malfing regulators. If you have never had the CNG system maintenance look to this area soon. It will get to the point it won't pull itself up a little hill.

 

I have not found a CNG mechanic here in Los Angeles.

What does the system maintenance include and what should I expect to pay?

Yes, it will not go flat more than 25 mph right now. I would have a hard time against a person in a walker when hitting a hill.

 

Compressed natural gas fuel system are used mostly in industrial situations, also Bus. Most of the Fuel Regulators are no longer rebuildable, you have to bolt on a new one. CNG can be dangerous ( is dangerous ) out of containment. A leak ( like a split fuel tube) can cut or severly damage skin. I can't express how important having the fuel tank shut off and the fuel psi drained from the line is. The huge power loss is most certainly the fuel system. It's safety feature shuts down the fuel flow. The V8 neads a gushing huge quantity of gas flow to run with good power. You also get into the area of the tanks safety date. It should be stamped on it. At that time the tank needs to be recertified, PSI tested and valve replaced. It's very easy to get your eye brows burnt messing with this stuff, due to its extreme flamibility and rate of flow if not containted. Your fuel supplier/wholesale delivery may point you to a qualified/certified technician. If you have a technician of LPG fuel systems probably CNG is also offered. You may have to call Ford to find a regional Certified Tech. Good Luck and stay safe. Remember if it is shut off at the tank, it is probably safe, but you don't know for sure until the fuel line is off/unhooked. Running the Tank empty of fuel is a good option, then being drained of fuel psi, it can be tipped up and the oil let drain out of it. That helps with the contamination. The rest of the fuel system is replacable. HP-LP ( low pressure regulators ) and fuel lock valve, and safety PSI valve. I haven't been around this since 2009 now so the systems have changed. They used to use a HP regulator like you would find on a Gas Cutting Torch ( using different seat materials designed for CNG ), + a modified Impco fuel regulator ( to pass the huge quantities of fuel vapor flow) to a carb fuel mixer. Getting them running on cold mornings and the huge power loss, due to wear of the HP seat, the secondary regulator woud over pressurize and stop fuel flow, were the most problems. The seats were mounted on a square and could be rotated 3 more times before the HP regulator was completely trashed. The seats lasted 24/30,000 miles before needing rotated. Otherwise better than gasoline fuel systems on the life of the motors. Now the system is higher in injection pressure to fuel injectors that stay on and are turned off by the PCM. A lot more PSI control sensitive sensors and better filtration. The less time there is to get the fuel in due to amount needed, the PSI injection pressure increases. The injection PSI still stays in what can be termed low pressure values around +/- 12 psi. If it wandered upward the system would start shutting down. There were only a couple of manufactures of the systems in the world then.

 

Ford Parts - Genuine OEM Ford Auto Parts at FordPartsGiant, Lake Forest Air Conditioning, Laguna Hills Air Conditioning Repair, Laguna Niguel Air Conditioing Services, in Orange County, CA, attn. Tony Dispoto 800-937-7227 ext. 6803 general manager of CNG. may be able to get more info.

 

check out HOME CNG conversion kits cylinders tanks and DXATC - Dixie Applied Technology College for more info. Scroll down the list, the 2 day course is $250.

 

The best thing you can do is to get rid of it. People buy CNG vehicle to try to save on fuel, because CNG is less expensive as a fuel. The reality however, is that they are high maintenance. CNG vehicles are common here in Utah, and almost every person I know who has bought one hates that they are stuck with it. The maintenance costs totally defeat the purpose of buying the vehicle. Factory CNG like yours is less problematic than aftermarket conversions.

Any misfire, even a partial one can damage the catalytic converters. This is especially true of CNG.