V8S misfire/ hesitation
Discussion
My V8S has picked up a misfire/ hesitation. It is not always there, but then can be there for the day.
Accelerate and she pulls normally, and then hesitates like I lifted off the throttle and then slapped down the accelerator again, and she pulls like normal. A passenger does be thinking WTF are you doing as their head snaps forward and back!
Here she is running on a constant throttle on the motorway, and I could feel the miss. But then I noticed that the tacho needle jumps forwards and backwards during these misses.
This is on a constant throttle, and the engine's actual rpms are not jumping around. But I can feel the miss. Any ideas of first port of call to check? Electrical issue I would guess.
Accelerate and she pulls normally, and then hesitates like I lifted off the throttle and then slapped down the accelerator again, and she pulls like normal. A passenger does be thinking WTF are you doing as their head snaps forward and back!
Here she is running on a constant throttle on the motorway, and I could feel the miss. But then I noticed that the tacho needle jumps forwards and backwards during these misses.
This is on a constant throttle, and the engine's actual rpms are not jumping around. But I can feel the miss. Any ideas of first port of call to check? Electrical issue I would guess.
Edited by Beast Master on Monday 13th March 16:27
That sort of intermittent miss could come from anything affecting the tune. If it tends to happen around cruising speed, a worn throttle pot is a well known cause. That won't cause the tacho to misread though. That could be a distributor pickup / amp / coil problem, or a wiring fault. Have you removed the dreaded yellow connector yet?
It seems to always be between 2500 to 3500 rpm. Outside of that it seems fine. And some days will be fine, and then others can be worse. If it were leads etc. I would expect it to be across the full rev range. Throttle pot? I'll do some reading on that.
No, I didn't remove the yellow connector. Is there a thread on here to teach me more about that?
Thanks for the reply.
No, I didn't remove the yellow connector. Is there a thread on here to teach me more about that?
Thanks for the reply.
I had a similar problem on mine once and it turned out to be a loose HT lead which was intermittently touching the exhaust manifold. When the insulating cover burnt through it would short out on the manifold causing the same problem you describe. Back left in my case, aft the AFM and tricky to see.
Beast Master said:
No, I didn't remove the yellow connector.
There is a big yellow connector inside the steering column cowl which joins the ignition switch to the rest of the loom. By now it's probably a corroded piece of junk. Symptoms include the ignition circuit browning out or momentarily disconnecting.
I used an Anderson connector but that was massively over engineering the solution. Many long term 'S' owners have used a simple terminal block. There is a type of connector block which pulls apart and can easily handle the current going through that wire if you get one heavy enough. Here's an example CLICK.
Edited by v8s4me on Tuesday 14th March 17:59
Check the engine running in the dark,checking for any sparks to earth from the leads. After you are happy all is in order with the ht leads and the wiring to the coil and distributor, check out your afm, remove the cover and clean the interior with alcohol and cotton bud finishing off with a blade of fine emery drawn through the points.
GreenV8S said:
Join the wires together directly.
Disagree! All the other connections to the steering column are through multiway plugs/sockets.So taking the column out (a fairly routine job, unfortunately) becomes impossible.
I made up a 5-way block from these : pretty straightforward.
The two halves of the column cowl come apart quite easily. Getting them back together can be a bit fiddly.
If the wires to the yellow connector are long enough you might not need to remove the cowl but getting it out of the way does help.
When re-fitting the upper part be careful not to overtighten the screw as this can crack the plastic.
If the wires to the yellow connector are long enough you might not need to remove the cowl but getting it out of the way does help.
When re-fitting the upper part be careful not to overtighten the screw as this can crack the plastic.
mentall said:
Disagree! All the other connections to the steering column are through multiway plugs/sockets.
So taking the column out (a fairly routine job, unfortunately) becomes impossible.
I'd question this being a fairly routine job. Don't remember last time I needed to take the column out, but it wasn't within the last 25 years. If I do need to at some point, I'll cut the wires and install a connector when I refit. It won't be any harder to do then than now. Same goes for the fan override switch, telltale lamp, remote boot release, alarm flashy light and so on.So taking the column out (a fairly routine job, unfortunately) becomes impossible.
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