Rough Idle

porcha42 · 03-01-1999, 09:15 AM

I have a 71 914. The problem is it has a rough idle that I can't seem to find the cause of. I tried to adjust the idle screw by the throttle body, but to no avail. I'm close to replace the accelator cable. Guys, do you have any ideas? Please advise, thanks.

JP Noonan · 03-01-1999, 10:06 AM

1. Ignition system
2. Ignition system
a. Ignition system again
3. Vaccuum leaks
4. Look at the D-Jet article on the 914 fan's web site.

Look at the plugs and do a compression check to see if there is one bad cylinder or all are bad. See if each plug is getting a good spark. If the ignition system looks old or you know it is old change the plugs, wires, cap, rotor, points, condensor, set the dwell then the timing. I haven't had a coil go bad but I replace them anyway, they are the most expensive part($50-60) so use your own judgement. Then replace all the vac hoses if they look old. This is really just maintanece stuff that should be replaced anyway, but once it is done any problems (there probably won't be any left) with the FI system can be properly diagnosed and fixed. Whatever ANYONE tells you, don't start replacing FI parts (well, maybe if you have extra parts laying around) until you are POSITIVE the ignition and vac lines are up to par.

John Rogers · 03-01-1999, 12:25 PM

I agree with JP with one addition: Is the engine stock and was the idle okay yesterday/ last week? If a stock engine, then the guides will help, otherwise get the references for any nonstock items such as MSD ignition, etc and use them. If the roughness started suddenly, look for something that has changed or broken or come loose. Especially the hoses. As a matter of routine I cut off the last 1/4 inch on each end at least once a year and it prevents leaks and I only do one hose at a time. The 914 fan's web site is down right now due to a hacker, but if you pull up all the past BBS articles from here, there are several about rough idle and what was done to fix it.