Steady speed motor miss

[robert blanchard]

Iv'e been sorting a miss for some time and have corrected the worst of it ,but for at a maintained speed over 3800rpm. Car starts to spit from air box. Get's bad as rpm climbs.Runs fine if increasing speed through rpm range. Is fine with wide open throttle.

Problem started with motor shutting down after 5 min. at speeds over 70 mph. Loss of all power than would pickup again at about 50 mph.Reset floats. New fuel pump and filter,new distibutor. Thought it was running out of gas. Then replaced spark and coil wires and plugs. No progress. Replaced coil and car then ran strong and held speed's over 100mph. Timeing set at 18 degrees at 4000rpm. Iv'e gone through the vacum lines at distibutor and carbs. Checked disributor for bad diaphram and all checks out. Cold start fluctuates from 950 rpm to 2800rpm randomly.I don't know if that has any bearing.Iv'e hit a wall but for the cold start and am not familiar with that system.Please, ANY ideas?

Bob

85 turbo

[USAndretti42]

Usually, when an engine spits back out of the airbox, it's running lean which would also reduce power. Have you tried cleaning all the caburetter jets? My boss when I firsts started at Jaguar used to say how, when he worked at MIRA, they could not get a Marcos (or TVR, I can't remember now) to respond to all jet changes to improve its emisions over the test cycle. Turns out it was running on the idle jets the whole cycle. Perhaps the Turbo is still on the idle jets and it's on some intermediate jet at 70 mph.

What happens if you pump the throttle as this squirts extra fuel into the engine?

Edited August 22, 2005 by USAndretti42

[Guest teigan]

i'm perplexed. your symptoms are all over the map. i'd check the regulator on the alternator, and even your battery.

[robert blanchard]

i'm perplexed.  your symptoms are all over the map.  i'd check the regulator on the alternator, and even your battery.

<{POST_SNAPBACK}>

Thank's, Battery is good and charging fine. I'm very perplexed.

Bob

85 Turbo

[WayneB]

Methinks you have a timed vacuum leak.

One of your vacuum lines is off or leaking.

Go through them all until you find the culprit.

There is a diagram on your rear hatch.

If they are still the colour coded(striped ) originals they are due for a change(20yrs old)

[dglotusltd]

Robert

Do check the vacuum lines as has been suggested.

Have you baseline tuned the carbs and check the balance between them? I had some of your symptoms on my normally aspired S1 engine (missing and lean spitting). After baselined my Dellorto 45s' air bleeds, mixture and airflow balance it all smoothed out.

DomG

77 S1

[robert blanchard]

Robert

Do check the vacuum lines as has been suggested.

Have you baseline tuned the carbs and check the balance between them?  I had some of your symptoms on my normally aspired S1 engine (missing and lean spitting).  After baselined my Dellorto 45s' air bleeds, mixture and airflow balance it all smoothed out.

DomG

77 S1

<{POST_SNAPBACK}>

I have a Carbtune and set the carbs when the shut down problem was most glareing. Atually was about to try that tonight, but the misquitos were bad so I came in.Switched my seats over and now have a nice tight fit.I actually passed emissions last year after using the Carbtune.Will hook it up when back from LOG in St Louis.Thank's for your help.

Bob

84 Turbo

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