Missing

GeorgeZ · 25th September 2007, 06:48 PM

Hi all,

Here is a curly problem.

Car is a 1993 RR, 3.9 ZF

When driving at cruising speed on 100kph, and with a significant electrical load, i.e., air con, full fan, rear demister, head lights, radio, in fact all that is practical that can be turned on, the car shudders/misses like its running out of petrol. Runs perfectly on gas. As I turn of the electrical load, air con off etc, the shudder/miss stops and car runs fine. What could be causing this problem?

TIA,

George

**landyfever** · 25th September 2007, 06:52 PM

Could be the Throttle position switch mate. You can test it with a ohm meter, you might find it to be open circuit in one position.

**loanrangie** · 25th September 2007, 06:57 PM

Alternator not keeping up or battery on its last legs ?

I had a similar prob 1 winter years ago in my old TA23 celica, driving home from NSW the lights got dimmer and dimmer till the car would barely run, had demister/stereo/high beams/wipers on as well. Had to get my little bro to hang his head out the window to clean the screen so we could see while driving at night with just parkers on.

**PhilipA** · 25th September 2007, 07:07 PM

Bosch alternator?
If so move the wire from dizzy to coil away from the alternator, or shield it with shielding which is earthed at both ends.
The electrical hash from a Bosch under load interferes with the signal from the dizzy to the coil.
Regards Philip A

GeorgeZ · 25th September 2007, 07:30 PM

Just did a check,

14.27 volts at the battery at revs, 13.5 at idle with all electrical items on. Miss occurs at high revs, roughly about mid throttle. When gunned, engine sounds sick. Perhaps starved for fuel?? Runs perfect on gas under all conditions.

Checked throttle pot and its OK at that point. Resistance goes up smoothly against one terminal and reduces against the other until at full throttle where there is infinite resistance.

George

**Blknight.aus** · 25th September 2007, 07:37 PM

whats the fuel pressure doing if you can check it?

googe · 25th September 2007, 08:10 PM

An earth fault in the gas/fuel setup'does it idil ruff on gas and smooth on fuel ?

**Scouse** · 25th September 2007, 11:05 PM

I'm leaning towards the alternator like PhilipA but for a different reason.

Try running the car without the alternator belt & see what happens.

Years ago, when your car was new, we had a similar problem that we chased for weeks. It turned out to be the alternator interfering with the injectors affecting the pulse rate (and it wasn't a Bosch alternator).

**Blknight.aus** · 25th September 2007, 11:15 PM

hey thats nice... I can see that happening....

how goods your multimeter, can you read AC with it or have acess to a crow to check it out?

GeorgeZ · 26th September 2007, 03:52 PM

Hi all

I did a few more tests. I would say that when high electrical load that the motor is missing at 2500 rpm on petrol, but does not miss either side of those revs. When gunned between 3000-4000 rpm, no probs even with all the items on, but still is missing at 2500 +/- 100 rpm.

I tried to see if a particular appliance is causing the grief but no, it does not matter what is on, lights, air cond, same symptoms.

So its a miss at a particular rev range and only with a high power load. What gives?

I would have thought that this test would exclude the fuel pump from being faulty.

TIA

Thread: Missing

Thread Tools

Missing

More Info

Missing - More Info

Bookmarks

Bookmarks

Posting Permissions