Stumbling and hesitation and engine note has changed. Advice sought.

[decampos]

The car (stock ignition) has developed a very noticeable hesitation which appears to occur at any speed and there is a general loss of power. Also, the sound of the engine has changed; it now sounds weird. It sounds like two engines and kind of 'drones'. Is particularly noticeable under load.

Any ideas of what to investigate? I've done some searching around the forums and the search results have been a little overwhelming so am hoping for advice that will help me filter the results a little.

Any help enormously appreciated.

 

[61porsche]

Carbs? FI... what version?

 

[OZCSi]

These can really send shivers down your spine if you arent experienced with this kind of problem, but they are almost always 99% easily fixed.

Most common problems with hesitation are simply spark,fuel or vac hose related.

If i had to guess, I would think spark plug leads would be my first bet.

Then fuel filters( not common unless its been run dry) if it has all of a sudden started

Then close attention to all of the vac hoses for cracks.

At idle i used to spray small amounts of crc near possible problem areas and see if engine note changed.

On the second round, try distribuor rotors and cap or if FI, the contact trigger points which are located in base can get oily if the lower distributor shaft seal fails.

Just my opinions anyway.

Cheers

 

[MMercury]

The car (stock ignition) has developed a very noticeable hesitation which appears to occur at any speed and there is a general loss of power. Also, the sound of the engine has changed; it now sounds weird. It sounds like two engines and kind of 'drones'. Is particularly noticeable under load.

Any ideas of what to investigate? I've done some searching around the forums and the search results have been a little overwhelming so am hoping for advice that will help me filter the results a little.

Any help enormously appreciated.

It appears that you have both stock ignition and stock DJet Fuel injection.

Loss of power and strange sounds may indicate a universe of symptoms - from the very simple to something major. It might be more helpful if you would set forth a more detailed description of your symptoms. This includes when the issue was first noticed, e.g., after recent maintenance? Does loss of power mean rough running or misfiring, or a smooth running engine that is bereft of power. There can be a difference. It would also be helpful if you could elaborate on the sound. "Two engines" and "droning" could be an exhaust leak or even the failing bearings of a water pump, alternator or power steering - or all of the above. It could also be your valve train screaming that it is starving for oil the proper weight oil. Along those lines, locating the general source of the noise, be it from the top, bottom, front or back of the engine could be helpful too.

Some of the archives may seem daunting and/or unintelligible, but since you mentioned “stumbling" and "hesitation," see if these threads help you better describe your symptoms:
http://www.e9coupe.com/forum/showthread.php?t=7232
http://www.e9coupe.com/forum/showthread.php?t=4439
http://www.e9coupe.com/forum/showthread.php?t=1520

Given your vague description, the problem/s could be something as simple as a loose fastener as can happen with the screw fixing the ignition points, or the distributor hold-down clamp. Either situation could affect ignition timing and could be easily addressed as normal maintenance (tune up).

Symptoms could just as easily be fuel-injection-related. If, for example, the wiring from the throttle position sensor was inadvertently bumped loose, you would have an engine that is very unresponsive and seemingly without power. Similarly, a plugged fuel filter could account for a power loss, and a laboring or failing fuel pump could account for poor running and noise.

Hth.

 

[decampos]

Thanks for the replies. All helpful stuff, I now have a checklist. Tomorrow I'll have a chance to thoroughly investigate.

These can really send shivers down your spine if you arent experienced with this kind of problem...

Tru dat, was fighting through the worse kind of London rush hour traffic and it felt as though the car was going to die. I'm still fairly unfamiliar with the workings of these cars, would have been a disaster.

On the second round, try distribuor rotors and cap or if FI, the contact trigger points which are located in base can get oily if the lower distributor shaft seal fails.

Great tip, thanks.

Loss of power and strange sounds may indicate a universe of symptoms…

Indeed. As demonstrated to me by the mountain of search results in the forum. Sorry for the vagueness, I'll try and be a bit more specific.

… a smooth running engine that is bereft of power

Yes, that's it. Combined with the noise.

"Two engines" and "droning" could be an exhaust leak…

Yes, it does sound like an exhaust leak. The exhaust is only a couple of years old and is a fairly expensive stainless steel type (as verified by a receipt in the history file). I discounted that idea for that reason and the coincidence that the noise appeared just as the car began running terribly. I will investigate though as that is what it sounds like.

… the problem/s could be something as simple as a loose fastener as can happen with the screw fixing the ignition points, or the distributor hold-down clamp. Either situation could affect ignition timing and could be easily addressed as normal maintenance (tune up).

Symptoms could just as easily be fuel-injection-related. If, for example, the wiring from the throttle position sensor was inadvertently bumped loose, you would have an engine that is very unresponsive and seemingly without power. Similarly, a plugged fuel filter could account for a power loss, and a laboring or failing fuel pump could account for poor running and noise.

Great suggestions. I'll post up any useful findings.

 

[nealf]

I had a similar issue a few years back

As it turned out the linkage came off one carb it made
For a real mess driving wise.