 back firing and kinda missing, Now what? |
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| Elliot_Cannon |
 Jan 21 2004, 01:42 AM
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#1
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Senior Member  Group: Retired Members Posts: 1,922 Joined: 26-March 03 From: Orange County Ca Member No.: 480 Region Association: None  |
Hi,
Cruising down the feeway and everything is fine. Doing about 80 running like a top. Then...feels like it's missing a little and it is back firing, spitting through the carbs. The thing is, it accelerates fine as though nothing is wrong. Only time it happens is at a steady RPM. I'm thinking a carb problem. Could it be a clogged jet or something? Any thoughts or ideas would be greatly appreciated. It's a 73 with a brand new 2.2 with webers. Only about 500 miles on the new engine. Very frustrating but then what is life without a little 30 year old German sports car?? (IMG:style_emoticons/default/headbang.gif) Cheers, Elliot |
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| seanery |
Jan 21 2004, 08:01 AM
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#2
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waiting to rebuild whitey! Group: Retired Admin Posts: 15,854 Joined: 7-January 03 From: Indy Member No.: 100 Region Association: None |
it's probably a fuel related problem, but you knew that already.
When my motor was given to me, it did that quite a bit, even died a couple times at the Ramble. I just kept cleaning out the jets. By the time I got home whatever it was (probably crap in the tank, car sat for long periods without use) was gone. |
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| Gint |
Jan 21 2004, 08:20 AM
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#3
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Mike Ginter Group: Admin Posts: 16,083 Joined: 26-December 02 From: Denver CO. Member No.: 20 Region Association: Rocky Mountains  |
I assume this fresh motor has decent carbs? Rebuilt or something? Clean out the jets.
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| Steve Thacker |
Jan 21 2004, 08:42 AM
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#4
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UMMMPH Yea Baby Yea ! UMMMPH Group: Members Posts: 1,089 Joined: 8-January 03 From: Pickerington, Ohio Member No.: 113 Region Association: Upper MidWest |
I know that some may disagree with my method of cleaning out carbs, when something appears to be stuck. I usually hand rev the engine up momentary to a blister rpm (pulse) and then place my hand over the carb intake as I'm stabbing the gas, then pull my hand away at the moment of strong vacuum. This usually clears out small blockages that need a nudge.
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| Elliot_Cannon |
Jan 21 2004, 02:34 PM
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#5
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Senior Member Group: Retired Members Posts: 1,922 Joined: 26-March 03 From: Orange County Ca Member No.: 480 Region Association: None |
Hi,
Thanks for the replies. I also think it is a fuel problem. I don't know how it could have gotten clogged. Brand new engine, carbs, fuel pump and filter, fuel line and cleaned out fuel tank. Cleaning out the jets seems to be the easiest to start trouble shooting the problem so that's where I will start. Cheers, Elliot |
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| J P Stein |
Jan 21 2004, 03:40 PM
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#6
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Irrelevant old fart Group: Members Posts: 8,797 Joined: 30-December 02 From: Vancouver, WA Member No.: 45 Region Association: None |
QUOTE(Elliot Cannon @ Jan 21 2004, 12:34 PM) I don't know how it could have gotten clogged. Brand new engine, carbs, fuel pump and filter, fuel line and cleaned out fuel tank. Heh, that's when it happens. I had problems with clogged jets on my 2.7.....2-3 times in a few months after getting it running. None in the past 18 mos or so. Little pieces of fud ...or FOD, if you prefer, nesting in the idle jets. |
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| URY914 |
Jan 21 2004, 03:49 PM
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#7
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I built the lightest 914 in the history of mankind. Group: Members Posts: 121,070 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
Also check the nuts on the manifolds and carb mounting hardware. They can work loose and you'll get air getting sucked in. Happens on mine form time to time.
Paul |
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| redshift |
Jan 21 2004, 05:26 PM
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#8
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Bless the Hell out of you! Group: Members Posts: 10,926 Joined: 29-June 03 Member No.: 869 |
I know with Fords, and Shelbys, I'd have someone stand on the gas, and dump a gallon of hot soapy water down the carbs, slowly.
Fuel filter. M |
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| SirAndy |
Jan 21 2004, 06:35 PM
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#9
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Resident German Group: Admin Posts: 41,679 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(Steve Thacker @ Jan 21 2004, 06:42 AM) then place my hand over the carb intake as I'm stabbing the gas ever seen flames coming out a carb during "backfire"? i wouldn't want my hand anywhere near that. (IMG:style_emoticons/default/wink.gif) Andy |
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| 914ghost |
Jan 21 2004, 06:44 PM
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#10
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BOB Group: Members Posts: 406 Joined: 25-November 03 From: Wenatchee Washington Member No.: 1,387 |
It could also be that they just aren't synched right. Y'know you leave a little jamb nut loose on one side and the linkage changes length / position.
AT steady throttle the vacuum difference between the cyl's can cause running like that- one cyl' bank wants to push harder than the other, causing more vacuum on the side with the thottle plates not opened far enough, then that side can run rich. It's just another thing on the list to check, likely on engines what's had some work done recently too. Also, timing on my car does that- if timing is off it pulls great as its advancing but when the springs in the dist. pull back (retard) when you let off- or constant thottle- it get all rough, worse at lower rpm. Whatever it is it prolly aint too bad. Robert O |
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