Wobbly idle

[Juular]

KJet fitted 1988 B230E.

I've had a sort of wobble from the idle since I first got the car. From outside the engine would sound perfectly even and smooth, but sitting in it you could feel that something was a bit off. It's like an occasional miss / pop / stumble every 4-10 seconds.

Car runs and pulls well, but I have noticed an occasional hiccup maybe once a day that feels like a misfire. Usually at low throttle low load.

I just changed the engine mounts which has made this much more noticeable. It seems like a misfire.

So far I have replaced HT leads, Distributor Cap, Rotor, Spark plugs are new genuine Volvo.

I've tested the coil and all of the wiring that feeds the coil, impulse sender and ignition module. Fixed a couple of borderline connections but no change.

The KJet system has been completely stripped and rebuilt, tuned to spec. All seals and filters have been replaced and the 4 injectors are brand new. System pressure is a steady 5 bar.

I wonder if there's anything else I can try or something I may have missed?

[Moomoo]

In my ‘79 ,244, if you looked under the bonnet while the engine was running, you’d swear it was hung in there on strings, it wobbled so much. Never touched it, all seemed ok though!

[BicycleBoy]

Genuine injector seals? Have heard the aftermarket ones notsogood in the sealing department.

(Which is the first place I'd have suggested looking if you hadn't changed them).

[Juular]

Originally Posted by BicycleBoy

Genuine injector seals? Have heard the aftermarket ones notsogood in the sealing department.

(Which is the first place I'd have suggested looking if you hadn't changed them).

Actually I think you're onto something.

So the injector seals have been replaced twice now as, to me, it really does feel like an air leak. The second time was with genuine seals, although to be honest there was not much difference, at least visibly, between them.

I ruled that out as a cause of the problem a while back, but last night I went in with some carb cleaner and properly drowned the injectors. I noticed that it took a few seconds, but spraying #1 and #2 definitely gave a change in idle. I also noticed that these two are quite loose in their plastic holders.

I took them out, cleaned everything up and refitted them, again with new seals to no change.

It looks to me like the plastic holders themselves are the culprit here. The groove that the fat o-ring sits in appears to be quite worn.

I've ordered some replacements from Brookhouse and will update when I change them over.

[Juular]

Ok, this is a strange one.

The new injector holders arrived from Brookhouse. These were fitted with yet another set of new seals, so the whole unit; injector, holder and seals are new.

No change, idle still lumpy. Carb cleaner on the area of #1 and #2 injectors is still causing a change in revs.

I changed the intake manifold gasket as it's right next to the area, but that made no difference.

I can't see anything else that would let air in. Spraying on #3 and #4 caused no response. There's no leaks around the spark plugs, inlet sock, or any of the vac lines (which have all been replaced anyway).

So it does seem that the injectors are still at fault here. I am almost tempted to RTV them in place, if nothing else just to eliminate them as the issue.

Here's what it's running like currently.

https://youtu.be/WSye1wH09Vk

[Bob Meadows]

Maybe stating the obvious here:~

Seating area for the injectors clean, engine block & fittings.
Seals lubricated prior to fitting.

K.Jet has a slow/fast adjuster- (round black plastic top) just below the throttle body.

These can be removed carefully by unscrewing and pulling away, the spigot has an "O" ring to aid the seal: again lubricate when replacing.

Good Luck.....Bob.

[Juular]

Originally Posted by Bob Meadows

Maybe stating the obvious here:~
K.Jet has a slow/fast adjuster- (round black plastic top) just below the throttle body.

Didn't realise this could be a source of air leaks. I will check this!

Injector ports in the head are perfectly clean. I have tried fitting a thicker O-ring around the holders without success. If it is still the injectors, I think it may be the small fat seal that is letting air past.

[Chris1Roll]

You can make a DIY smoke tester from a big jam jar, a cheap soldering iron, some tubing and some baby oil and rags. I used a stirrup pump to provide the air, no need for a compressor although that would make it quicker.
I didn't have much luck spraying stuff about on the V70, but the smoke tester showed it up quickly.
If you are testing the injector seals you would of course need to make sure the inlet valve is closed on each one in turn (or perhaps make them open and add smoke via the spark plug hole).

[Juular]

Ok, it's definitely the injector seals, but it seems to be the thin ones on the outsides of the holders.

Tried it again with soapy water and could clearly hear the air rushing in around the edges of the holders on #1 and #2.

Going to try, yet again, a set of new genuine Volvo seals.

[Bob Meadows]

A descent hydraulics shop are generally good for quality "O" rings.
Engineering supplies are another:~

The last time I used ours they measured the items precisely- it also gave the opportunity to alter the diameters if required.
Regards Bob.