# Propane Camry with P304 fault **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [February 24, 2016, 1:24am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610 "2016-02-24T01:24:04Z")\ **Posts on this page:** 19\ **Page:** 2
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [March 5, 2016, 7:06am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/21 "2016-03-05T07:06:21Z")
@“Propane Car” Well, congratulation on fixing P0354 Good luck on P0304 ---
**Author:** ![knfenimore](https://avatars.discourse-cdn.com/v4/letter/k/9fc348/32.png) [@knfenimore](https://community.cartalk.com/u/knfenimore)\ **Post date:** [March 5, 2016, 5:35pm UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/22 "2016-03-05T17:35:38Z")
More than likely it’s carbon build up on the back of the valve. Tom and Ray liked this stuff. > **[Amazon.com: BG 44K Fuel System Cleaner: Automotive](https://www.amazon.com/BG-44K-Fuel-System-Cleaner/dp/B00DDVU6EI)** > > This fuel system cleaner, added to gasoline, quickly and effectively cleans the entire fuel system, including fuel injectors, intake valves, ports and combustion chambers. Because it provides efficien ... ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [March 6, 2016, 1:45am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/23 "2016-03-06T01:45:18Z")
@knfenimore I see no harm in trying that product . . . it’s worth a shot Now here’s a few questions Are you thinking the carbon deposits are causing #4 low compression? If so, why is the compression normal on the other 3 cylinders? If OP used it, how long should he wait before performing another compression test? ---
**Author:** ![knfenimore](https://avatars.discourse-cdn.com/v4/letter/k/9fc348/32.png) [@knfenimore](https://community.cartalk.com/u/knfenimore)\ **Post date:** [March 6, 2016, 5:25pm UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/24 "2016-03-06T17:25:47Z")
I’d run a couple bottles through and try it after each tank full. If it’s working, you should notice a difference. Carbon on the back of any valve will cause low compression if the valve does not seat properly. It’s a cheap fix if it works. ---
**Author:** ![nbpt100](https://avatars.discourse-cdn.com/v4/letter/n/9f8e36/32.png) [@nbpt100](https://community.cartalk.com/u/nbpt100)\ **Post date:** [March 6, 2016, 8:14pm UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/25 "2016-03-06T20:14:40Z")
What would a used engine cost to install vs. rebuilding? I would think that the Camry engine is pretty popular and you could get a decent used one. Just a thought. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [March 6, 2016, 9:10pm UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/26 "2016-03-06T21:10:17Z")
@knfenimore Please tell me why carbon buildup on the valves would only lower the compression on #4 cylinder ---
**Author:** ![knfenimore](https://avatars.discourse-cdn.com/v4/letter/k/9fc348/32.png) [@knfenimore](https://community.cartalk.com/u/knfenimore)\ **Post date:** [March 6, 2016, 11:31pm UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/27 "2016-03-06T23:31:36Z")
There are intake and exhaust valves in each cylinder. Any valve in any cylinder can cause low compression in that one cylinder. It does not have to be in all cylinders. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [March 6, 2016, 11:54pm UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/28 "2016-03-06T23:54:29Z")
@knfenimore What you are saying is not news to me I’d just like to hear your explanation as to why carbon buildup would cause low compression in one cylinder only, and the others have absolutely perfect compression I agree that using that stuff is worth a shot But I’d like to hear your explanation as to why only the valves in one cylinder are affected to the extent that the compression is drastically lower than standard, while all others are perfect? I thought maybe you’d tell me that it’s due to the design of the intake manifold, or something like that, but I’m not hearing anything concrete No offense intended, I’m just curious I would be more inclined to agree with you, if cylinder 1 was 150psi, 2 was 145psi, 3 was 150, and 4 was 120psi But that’s not the case If if were the case, I might think carbon buildup had caused lower compression in all cylinders, but #4 was the most affected ---
**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\ **Post date:** [March 7, 2016, 6:56am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/29 "2016-03-07T06:56:32Z")
Assuming carbon buildup on a valve can eventually cause the valve to not close all the way, I can see how one valve would be the first to be affected. To me it would be very coincidental for all the valves to fail to close at the same time. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [March 7, 2016, 7:08am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/30 "2016-03-07T07:08:33Z")
And for me it’s very coincidental for the other 3 cylinders to have perfect compression ---
**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\ **Post date:** [March 7, 2016, 7:41am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/31 "2016-03-07T07:41:44Z")
Why would they not have perfect compression if the carbon buildup weren’t preventing those valves from seating? ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [March 7, 2016, 7:57am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/32 "2016-03-07T07:57:03Z")
If carbon buildup were a problem, and was causing drastically low compression in #4 cylinder, I would expect less than perfect compression in the other 3 cylinders ---
**Author:** ![insightful](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/insightful/32/2732_2.png) [@insightful](https://community.cartalk.com/u/insightful)\ **Post date:** [March 7, 2016, 8:06am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/33 "2016-03-07T08:06:09Z")
To me, carbon would build up slowly on all intake valves, not causing any valve to hang open. Then at some point, one valve would, by chance, be the first to fail to seat which would drastically lower compression in only that cylinder. That’s the only way I know to explain it. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [March 7, 2016, 8:16am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/34 "2016-03-07T08:16:07Z")
Well, I’ll believe that when/if OP posts pictures of massive carbon buildup on the valves No offense to anybody, but I believe I have a right to be skeptical ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [March 7, 2016, 8:49am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/35 "2016-03-07T08:49:44Z")
I don’t think it is carbon build up either, but I would not be surprised if it has a burnt valve, most likely the face of the exhaust valve burnt off. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [March 7, 2016, 10:06am UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/36 "2016-03-07T10:06:42Z")
I am more inclined to believe it’s a burned valve, versus carbon buildup ---
**Author:** ![Propane\_Car](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/propane_car/32/6561_2.png) [@Propane\_Car](https://community.cartalk.com/u/Propane_Car)\ **Post date:** [March 7, 2016, 8:53pm UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/37 "2016-03-07T20:53:18Z")
Thanks for all the comments. I have read them all. This car ran exclusively on gasoline from miles 0-100k. At 100K I added a sequential injection propane system. From miles 100K to 240K the car has run \>90% of the miles on propane. You will not get the carbon buildup while running on propane. For the past 5K miles since I have had the check engine light I have been running on gasoline. I will try the cleaner but I am very skeptical that it is buildup carbon. I have taken apart a few propane engines over the years and I have never seen any carbon buildup on the internals. I suspect that I have a burnt exhaust valve. To remove the intake, the air box and throttle body has to be removed. My inspection camera is broken so I will have to get a new one to see inside the intake port. The exhaust side should be fairly easy assuming no stuck bolts. As far as getting a different engine, I am on the fence of doing this. The car is already high mileage and it maybe the case that the transmission, CV shafts, etc will start to fail. So basically, I could spend $1500 on the car and be up and going or i could use that $1500 + what ever I could sell the car for + 6-8K and get a decent used car with fewer miles. I may just wait and look for something else out there and continue to drive my truck or motorcycle around while a good deal comes along or I have the time to remove the engine and get a rebuild kit. I have never rebuilt a small 4 cyc car engine before but I have rebuilt dozens of V8’s and motorcycle engines. The funny thing is that if this was one of my V8 trucks, I would have already fixed it. If this was one of my motorcycles, I would have already rebuilt the engine. Not sure why I am being such a wuss with this car. I am lucky that I have alternative transportation while I decide and or fix this car. ---
**Author:** ![Propane\_Car](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/propane_car/32/6561_2.png) [@Propane\_Car](https://community.cartalk.com/u/Propane_Car)\ **Post date:** [March 7, 2016, 8:59pm UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/38 "2016-03-07T20:59:39Z")
I just had an idea at how to blow some cleaner into the intake port without taking everything apart. I will just squirt some B12 through the propane injector port on the intake manifold. [![](http://pic.photobucket.com/bwe.png) ](http://pic.photobucket.com/bwe.png) ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [March 7, 2016, 10:12pm UTC](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610/39 "2016-03-07T22:12:16Z")
You can get carbon build up in a propane fueled engine, just not from the propane. All modern engines have a PCV valve and if the engine develops enough blow by, the oil vapors sucked into the intake manifold will cause carbon build up on the intake side. Its more of a sticky very thick sludge rater than the hard gritty carbon you see on the exhaust, but it is carbon none the less. I suppose after a while, enough of this would be sucked into the combustion chamber that it could build up the hard carbon on the exhaust, but I haven’t seen that myself…yet. [Previous page](https://community.cartalk.com/t/propane-camry-with-p304-fault/92610.md?page=1)