engine backfire and loss of power

[neilbyrd]

I am a Operating Engineer also just a stationary type. hmmm small world

[Jeeperator]

Well times are tough for me right now. I been an Operating Engineer for over 20 years and never been out of work this long. Maybe when that HUGE solar project goes in up Lucern Valley I can get on that job and pay for the mjr membership. I have a bit of engine building,engine dyno and holley carb tuning experience. I dont mind sharing it with others.

[platnumb4x]

I am wondering why this is directed at me?

Maybe he saw when you joined and noticed how many posts you have and just thought he would mention the membership thing since its obvious you think this is a great site just like we do. Plus you aparently have quite a bit of experience and knowledge to offer to others.

[Jeeperator]

Beau,
You don't have to answer this post. But I wanted to suggest that if you can afford it, (it's cheap) you may want to become a paying member of MJR. I don't know if you are or are not, that's none of my business. No one is required to, but every little bit helps. It cost's some bucks to keep this website up and running. It think, as you just found out, this is the best Jeepin' website on the planet.

I am wondering why this is directed at me? Last time I looked theres alot of none paying members here. Why am I put in the spotlight? I am just trying to help this guy out with his issue. Is there a rule somwhere where only paying members can help a fellow jeeper out?

[neilbyrd]

Well I went up the canyon today and it was all well until I got to about 5000 ft and it started to pop in the headers. I got 1 good backfire out of it to. But I have to say it still ran alot better than before. I checked the spark plugs and they still look almost brand new, not white not tan not black, so I guess I can go down 1 more jet size and see what happens.

[neilbyrd]

Your other plugs could of just be shot from it being too rich before. Drive it up to high altitude again and see what it does.

Ya I was thinking that to. I am headed to High elevation in the morning and I will post how it goes. I really wanted to run The Hemet Jeep Trail every time I go by it but the jeep is usually not running that good by the time I get there so I just go to pine cove. Hopefully tomarrow will be my day to finally have some fun.

[Roger]

Beau,
You don't have to answer this post. But I wanted to suggest that if you can afford it, (it's cheap) you may want to become a paying member of MJR. I don't know if you are or are not, that's none of my business. No one is required to, but every little bit helps. It cost's some bucks to keep this website up and running. It think, as you just found out, this is the best Jeepin' website on the planet.

[Jeeperator]

Your other plugs could of just be shot from it being too rich before. Drive it up to high altitude again and see what it does.

[neilbyrd]

I took it out today and it ran soooooooo good. No backfire, spit or sputter, and plenty of power. When I got back I pulled the plugs and they look brand new still. I was driving for about an hour and a half on the road and up the canyon. So I guess I need to give it a full run to Idyllwild and back to see if there is any difference. So tomarrow I will do that and let you guys know. Thanks again for all the help. I am glad I joined this forum.

[neilbyrd]

Yes I have been taking baby steps. I fix computer controled machines for a living so I know how important it is to move one thing at a time. Yes, I have gotten alot of good information from all of you guys and I want to thank all of you for that. In the morning I will be taking it out to the canyon again and see if it all pays off. Hopefully the improper fuel bowl level was the last problem causing the richness.

[RAT]

You're getting a lot of advice here and that is a good thing. I just want to remind you to make one change at a time, and it helps to write down each change as you make it so if you need to go back you know where to go. I learned that from past experience in drag racing. Lists are a good thing...

[neilbyrd]

Well I checked the float today and as soon as I pulled the sight plug gas poured out, so I put the clear plugs in and adjusted the level to just under the glass. I checked the seat and it was clean. the secondary level was ok. I put new plugs in it and left the jets alone for now. I will take it up the canyon a bit tomarrow and see what the plugs look like after that. Then I will see if I need to jet smaller.

[chris142]

Ya check the float level. I've seen all kinds of stuff get stuck in the needle and seats.
Pieces of rubber hose is the most common.

[neilbyrd]

Last time I checked the float level it was at the bottom of the sight plug and the carb is only a coulpe years old and has external adjustments for the floats. As much trouble as this has been I am almost thinking I should just get a np435 and swap in the 318 mpi I have sitting around here.

[Russ Chung]

Make sure your floats are adjusted right also.

Good point. We know that the engine is running too rich. It might be caused by improper jetting, but it could also be caused by improper fuel level in the bowl if the float level is out of adjustment or the float valve is not closing tightly because of wear or age. I'm not familiar with the Avenger carb. Is there an external adjustment for the float level or do you have to take the carb apart to adjust it? Also check the float itself to make sure that there are no holes in it caused by corrosion. I would think that if the problem is due to the float level, the problem would occur at low and high altitude, but maybe it is running rich at low altitude but not enough to cause misfiring until you get to high altitude. But as Kurt said in an earlier post, just do one change at a time, whether it is the float, the jets, or different spark plugs.