1986 Rough idle, and will only rev in park and neutral

Adobe reader is free.

Caleb, as you said, from driver seat looking forward, the A bank is always the right hand side and the B bank is the left. Regardless.

And for that filter Greg mentions just use a lawnmower fuel filter at the end of a couple feet of vacuum hose tucked over to the side of the engine bay. You just want to have clean fresh air into the distributor

Caleb. As Greg points out, Adobe Reader is a free app. You can read pdf files but not edit. Looking at Kirby’s book online at Jag-lovers is easy-peazy or you can download a copy onto your phone, laptop or whatever.

Check jagrepair dot com for some useful, and free, files

Take a lot of photos as you strip down the distributor. This is my final photo where i was able to give it a good clean after removing everything.

And check the vacuum advance as well.
It might have a bleed hole so don’t be surprised if it slowly bleeds.
There is also a vacuum advance kill on start up scheme that could cause problems.
Also check your FPRs.

FIY, unplugging the Coolant temp sensor makes the ECU think that the car is infinitely cold, so that implies that your engine is starving of fuel.

But before anything, read Kirbert’s book as already suggested.
Good luck!

thank you all so much. I’ve been busy over the weekend but I very very much appreciate all the help you have brought to me I’ll be reading the book for the next couple days getting a really good understanding over it before I hop back into working on the car i’ll post again after I check all the things y’all mentioned and go from there!!

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okay so i’ve broken down the distributor. now i can do a bit of cleaning to it but the weights that spring the button back but they seem to work well but are looking pretty dirty, any opinions if i need to clean them up? also what’s a good lubricant i can put in replacement after cleaning i’ve took a lot of photos for reference

I used brake cleaner on everything. As Book says, i used synthetic motor oil to lubricate.

okay great, thank you so much! everything looks great inside to me the weights snap back pretty strongly not any issues i can see but with how clean everything looks and feels i’d almost wanna say it’s been replaced before but i have no idea!


do i need to replace these parts the spring seems like it’s opened slightly but it moves back and forth when you touch it.

and also i tested the vacuum on this other part and it doesn’t stay open when blocking the air with pressure it drops the lever back down

The vacuum advance diaphram has a controlled leak so that a regulator in the line can work. If the diaphram mechanism works at all when vacuum is applied, it is probably ok. It won’t hold a constant vacuum but it will operate when vacuum is applied.

Jon

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IIRC the heavy spring is supposed to have some play.
Kirby’s book has all the details.

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sorry i thought i messaged back but i took the distributor out and cleaned it up well after taking the tedious time to rewire the spark plug wires back up to no avail the car still starts right up and starts to idle hunt, if i throttle the gas little by little i can get it to idle at a set rpm but is usually varies between 1,600 if i let it calm down and settle, and 1,900 rpm’s if i’m messing with the gas revving the motor. but it will only let me rev the motor very easily until i hit the gas to hard and it wants to sputter and try to die

any other ideas i could try out?

also i just tested the throttle position sensor and my green wire showed 4.7-4.8v yellow showed .3v and my red wire showed .3v - .4v (this is all at idle specs with car turned off) i turned the throttle open nice and slow the red wire was picking up a nice smooth voltage and as i did the same thing back down to idles and the voltage slowly creeped down but at about 2.8 it dropped to 1.5 ish then down to zero with the throttle still somewhat opened.

repeated what i just did and similar outcome again but when let off the throttle it wouldn’t pick up any voltage until i gave it throttle and slowly raised .1 .2 .3 .4v at about a quarter throttle

almost positive i need a new one but any tips on where to find a trusted new one or can it be generic from the auto store

The original black TPS is unreliable, should be replaced by the new and improved red TPS. (I believe they were used in Facelift XJS’s and newer)

But you’ll need a conversion kit, which is not sold anymore. I managed to get one from a used red OEM TPS that had the kit with it.

The new red OEM TPS is expensive, but I tried the aftermarket red TPS, and it was not consistent, I ended up throwing it away. I am still using my original used Red TPS, seems to work fine. One day I may spring for a new OEM one.

Plenty of talk about trying generic, but it seems quite fiddly and not perfect, so I didn’t try it.

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does it need to be year specific i found one for 2 years newer than my car

That’s it. Kinda expensive, and it doesn’t have conversion parts.

I got mine from Simply Performance in the UK. Cheaper, and they included conversion parts.

The true OEM red TPS is out of production…but there might be some floating around out there on Ebay or whatever.

If you order a new red TPS from Jaguar you’ll get the very same Brand-X part that all the usual vendors are selling. The only difference is the price. :slight_smile:

Cheers
DD

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