Car still idles rough/runs rich after 2 months work - I'm at a wall

(Michael Garcia) #264

aim high,
when you saddle it up
it will feel like an extention of your family
it will be there for you
until the day you expire

(Greg) #265

good point…while he has it in his hands, maybe pay a bit extra for tuning? I have already opened up the air intakes to 2.5". And my eventual exhaust improvement will be the icing on the cake.

(Michael Garcia) #266


…here in Albuquerque
we need the slip every two years

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #267

Oh, man, there is nothing better than a set of tires you need to get rid of!

(Greg) #268

So you’re saying while burning plenty of rubber off the tires, I’ll burn plenty of carbon off the inside the engine? Seems to me the outside of my car would now become covered with black powder!

(Robin O'Connor) #269

just an excuse to give it a wash :slight_smile:

(Michael Garcia) #270

…cant find that thread l started about a month ago…
just wanted it to be known
after a tank of gas, no problems
after changing the fuel filter.
lt would appear
you were correct, Greg

(David Jauch) #271
(Michael Garcia) #272

Thanks David…
earlier in that thread
l noted how the po replaced the fuel pump and tank.
How or why he wouldnt have replaced the filter is beyond me.

Didnt even have to cut it open,
just turned it and saw it trickle,

(Michael Garcia) #273

…it would be nice
to see a picture
of your exhaust manifold ports
when you get around to it Greg…
and one of the segment that ties into the mufflers near the tires

on a different note,
anyone notice more vapor
from the bank B exhaust?

1 Like
(Michael Garcia) #274

happy groundhog day

here is to
standing behind
our words…

(Trevor Beckwith) #275

Hi Greg
Not much I can add to these very educated responses… suffice to say that I had a similar situation a couple of years back. Overrevving idle and what appeared to be a rich mixture.
Out come… there was a faulty PCV valve that was allowing a vacuum drain on idle hence overrevving. The gumming up of the plugs was not so much a rich mixture but simply because I switched the motor off before it got up to temp each time due to the concern with the over revving resulting in a build up of carbon that is usually burn off at the higher temps during a run. It was Richard Dowling who said if he started the motor he would always run it up to temp before shutting down otherwise the plugs will gunk up after a few starts (paraphrased) . I have found this the case. My whole problem was the PCV valve. Trev

(Robert Laughton) #276

I just had some luck with my rich-running V12. I made reference to it in one of the many posts above.

Anyway, cleaning the ground bunch of wires, under the bolt that grounds the battery NEG terminal to the inner fender, worked! There was think grease between each eyelet, and bolt heard and the body.

Before, the engine would belch black smoke, not rev, and needed a plug change after every start.

It still won’t pull cleanly to redline, but almost, and it’s huge step forward.

I hope this works for you!


(Greg) #277

Thanks for that, I actually did check those, no change.

I’m pretty sure it’s my ECU causing this, just waiting for the guru Roger Bywater to fix my ECU. He’s super busy, so it’s been sitting at AJ6 Eng. for a few weeks now. But I wouldn’t trust anyone else to touch it.

Belt types - Continental or Gates
(Philip Lochner) #278

Does it pull cleanly at all? If so, to what Rpm?

What ignition system do you have?

(Robert Laughton) #279

Hello Philip,

It’s winter here, and just had a break in the weather to road test the car after fixing/mostly fixing the rich-running.

The car has the Lucas system typical of a mid 80’s V12.

It seems to pull cleanly to about 3500.

I don’t want to hijack this thread, so I’ll start a new thread later that contains all the pertinent data, and testing I’ve done. The engine finally runs close to how it should, just needs tuning, or I’ve overlooked a vac hose etc.



(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #280

That’s the standard symptom of the secondary coil being NFG – or, if there’s only a single coil, it’s either the wrong type coil or it’s going bad. Of course, there are zillions of other possibilities. First, tell us if your car has one ignition coil or two.

(Robert Laughton) #281

Kirbert, I have the 2 coil system.

I only had a brief drive, but the car would rev to 5000 or maybe more,if I accelerated slowly. It felt more like lean running to me. But, I’ll check everything again.

Here’re are some pic’s.

I’ll start a new thread, when I have had a chance to try the car again - weather permitting.



1 Like
(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #282

Yeah, check that coil out front. Also, have you modified the fuel pickup scheme to make sure the pickup screens don’t plug up?

(sloth) #283

Hi Greg:
I will keep it simple…concesus says not the ECU…tell me where is the best place to test fuel pump pressure.? It may be weak…