Forum:
My sportrak revs keep going up and down but it only is noticable when car is not actually moving. When driving along it seems OK. My husband fixes the problem each time by bleeding the bypass valve ??? Its OK for about a week then it all goes pear shaped again. Can anyone help as I dont want to sell/scape her cos I love her loads
idle speed vavle
not sure but my escort(ye ye i know keep it a secret)had a similar prob and it was the idle speed valve needing cleaned then eventualy replaced.
Nother Ford owner. Sorry.
Nother Ford owner. Sorry. Mondeo this time. When mine was doing a similar thing, it was just the throtel body was caked in crap on the inside. This was partialy blocking the butterfly bypass (alowing to little air to get through at tick over), and sometimes the butterfly wouldn't close properly (cousing the revers, too much air getting through). A dam good clean with white spirit did the job. Fantastic cloudes of white smoke for a min of so when I started it up afterwards. Did the trick.
Any veiws expresed in this thread by me are purely from my own experience, and (sometimes) falible memory. Hope my comments help, but please don't take them as gospel.
Hunting
Begin with the obvious, replace the fuel filter and chech the fuel pump delivery.
Check all the engine pipes, and those on the injection system, the most common problem is an air leak into the system from a worn, split, or badly seated pipe. Check the inlet manifold has all its bolts fitted and correctly tightened, and check all gaskets for obvious signs of degredation.
Work through the wiring connections on the injection system, ensure they are not corroded or wet, replace them and spray with waxoyl to prevent corrosion.
It will then be a process of working through the injection system components in logical order to find and problems, the best way is to have the system checked by an analyser, independant garages with the correct software will be able to do this. This will eliminate the working circuits, and identify the faulty ones. Most common faults are the temperature sensor, air flow meter, or the engine position sensors.
Mine always used to do this,
Mine always used to do this, its called "seeking", it would rev itself up to about 1200 RPM then drop back down to idling at 800 RPM in a 2-3 second cycle. Turns out either I hadn't filled the coolant up or there was an air lock in my sporty's coolant system.
Try this (waiting for the engine to fully cool first of course):
1. Drain the radiator by unscrewing the little valve on the bottom of it, then when it's empty close it up again
2. Fill it up SLOWLY with coolant, giving air pockets any chance to escape
3. When the rad seems full, start the engine, you'll probably see that the water level drops (as it draws the coolant deeper into the system. Top it up again as per step 2.
4. Go for a drive, pulling up (safely) every 5 minutes or so and see if the engine is still seeking.
I found mine would do it most noticably after the automatic choke had fully opened (as in, the choke isn't "on" anymore), but the engine hadn't fully warmed up yet. Maybe that can help a little with your diagnostic.
Good luck,
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Jason "Foxdie" Gaunt
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Jason "Foxdie" Gaunt