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Engine bucking while cruising

 
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ThomasJoseph315  
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PostPosted: Wed Jul 17, 2013 11:20 am    Post subject: Engine bucking while cruising Reply with quote

So this maybe an obvious answer, but my fuel injectors are leaking and I have ordered new ones, but I wanted to see if leaking injectors can cause this. It's to the point now to drive it I got to hold down the gas to the floor to get it to run normal, but I can't to this for long as I. Increase in speed.

Is there anything else that can cause this?
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11733
Location: PacNW

PostPosted: Thu Jul 18, 2013 1:42 am    Post subject: Reply with quote

Air leaks. . .smoke your intake.
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  • WeiBe (1987 924S 2.5t) - 931 S3
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Harm  



Joined: 02 Apr 2009
Posts: 1378
Location: Holland

PostPosted: Thu Jul 18, 2013 2:14 am    Post subject: Re: Engine bucking while cruising Reply with quote

ThomasJoseph315 wrote:
Is there anything else that can cause this?


Read: Lurching (Judder, Studder) Motion in 924
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ThomasJoseph315  
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PostPosted: Thu Jul 18, 2013 5:27 am    Post subject: Reply with quote

it ended up being the timing advance kicking in with an improper fuel mixture.

Thanks for the help.
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ThomasJoseph315  
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PostPosted: Thu Jul 18, 2013 5:23 pm    Post subject: Reply with quote

It's baaaaaack,....

Grr on the way home tonight it came back with the colder air. Why would this change the conditions so much?
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scm924s  



Joined: 22 Oct 2010
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Location: Gloucester UK

PostPosted: Fri Jul 19, 2013 12:48 am    Post subject: Reply with quote

have you tried cleaning the lift pin in the fuel distributor? had terrible trouble with the martini bringing it back to use after about 15 years storage, continually bucking at about 2000 revs, cleaned mine several times, seemed to get gummed up from old fuel.
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1984 n/a Ruby Red Metallic
1988 924S Guards red- sold
1986 924S Guards Red - sold
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1980 n/a Le Mans#1 - sold
1980 n/a Le Mans#2- sold
1977 Martini - sold
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Rasta Monsta  



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PostPosted: Fri Jul 19, 2013 1:38 pm    Post subject: Reply with quote

Air leaks. . .smoke your intake.
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ThomasJoseph315  
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PostPosted: Fri Jul 19, 2013 6:39 pm    Post subject: Reply with quote

I've cleaned the pin in the dis and even wet sanded it down so it glides nicely. and I have sprayed the intake-vacuum system with brake cleaner, if there was a leak I would have found it.

Maybe it is the injectors leaking, not sure at this point.

Also, the EGR isn't connected and is plugged off. The AAV is not opening all the way, but t does close. This thing is hell to start atm, but after it does it purrs like a kitten. It's just when I feather the gas driving down the road.
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ThomasJoseph315  
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PostPosted: Sat Jul 20, 2013 5:07 pm    Post subject: Reply with quote

Looking over on the A/F gauge going down the road tonight I noticed the A/F was bucking in the lean when it kicked. Still thinking injectors,.. but would this also be a sign of fuel pump going out?
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Sat Jul 20, 2013 9:37 pm    Post subject: Reply with quote

Might also be worth making sure there's no vacuum leaks at the throttle body itself, on the throttle shafts...
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scm924s  



Joined: 22 Oct 2010
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Location: Gloucester UK

PostPosted: Sun Jul 21, 2013 2:30 am    Post subject: Reply with quote

I'm getting the similar problem back on the Martini, starts by missing a little under load at about 50, then gets worse to the extent when pulling away from lights, it's as though it cuts out intermittently, repeatedly. When you stop at lights you can hear the pump revs suddenly rise as though it is sucking air, then it cuts out immediately. Restarts straight away OK then repeats. The pump also seems to become very noisy. Symptoms are as though there is a fuel blockage from something being sucked up when used a bit enthusiastically.

I find the small right angled filter between the pump and tank gets full of rusty crud and needs blowing through, penalty of being stood for 15 years, pump then runs quietly for a bit then starts getting noisy again.
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1984 n/a Ruby Red Metallic
1988 924S Guards red- sold
1986 924S Guards Red - sold
1984 n/a Black - sold
1980 n/a Le Mans#1 - sold
1980 n/a Le Mans#2- sold
1977 Martini - sold
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Rasta Monsta  



Joined: 12 Jul 2006
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Location: PacNW

PostPosted: Mon Jul 22, 2013 1:16 am    Post subject: Reply with quote

924RACR wrote:
Might also be worth making sure there's no vacuum leaks at the throttle body itself, on the throttle shafts...


Brake cleaner don't lie, Vaughan.
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924RACR  



Joined: 29 Jul 2001
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PostPosted: Mon Jul 22, 2013 5:00 am    Post subject: Reply with quote

Oops, sorry, missed that bit, was scanning too quickly... am too busy these days!
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Vaughan Scott
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'79 924 #77 SCCA H Prod racecar
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ThomasJoseph315  
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PostPosted: Tue Jul 23, 2013 5:38 pm    Post subject: Reply with quote

Problem solved! See this...

http://www.924board.org/viewtopic.php?t=38759
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