Chasing a slightly lumpy idle...still

[AllHailKingVolvo]

More work done today...fitted the new four-hole nozzle injectors! They didn’t make a huge amount of difference at first impression, perhaps a little smoother under power. The EZK etc obviously has to tweak itself to accommodate (did the customary Fuse #1 pull of course) so perhaps more benefits will reveal themselves over time.

If anything, they perhaps flatten the torque curve a little bit-a touch more at the bottom and top at the expense of the midrange. That’s fine by me.

A good test for me is to drive from my hometown of Sherborne to Yeovil, then turn around and drive back, this time up the rather fallaciously named Babylon Hill. Babylon Hill (or “Babs ‘ill” as it’s known by some!) is a long, steep bugger of an incline that isn’t particularly NA Volvo friendly. When I bought my 744, it wouldn’t climb it at more than 40mph in third. After the ignition system rebuild it would motor up it at 50, but today, with the new injectors onboard, I cruised up at 60 and was able to put it in fourth for the last third of the climb without disappearing backwards into the pack of following cars!

Progress...just the in-tank pump and shocks to do now. Not looking forward to the former!!

[AndyV7o]

Nice!
A 20mph increase up a steep hill is a good show of significantly more power since you got it.

[AllHailKingVolvo]

Originally Posted by AndyV7o

Nice!
A 20mph increase up a steep hill is a good show of significantly more power since you got it.

Yeah I’m pretty happy with that! It had been a bit neglected when I bought it and did need a good going through, but it’s a really up together car now from the mechanical perspective. It’ll never be a rocketship unless I go +T (which I don’t intend to do!) but I like the stately performance.

The cosmetic stuff is next...nothing fancy, just lots of touching up and polishing to do. I’m not hipster enough to call it “detailing” but that’s what’s required!!

[Laird Scooby]

Good work well done Phil!

I'd be interested to know how the economy fares with the 4-pintle injectors?

Also, do you have a part number for them please? Such as 0 280 abc xyz?

Out of interest, has the idle improved with the new injectors?

[AllHailKingVolvo]

Originally Posted by Laird Scooby

Good work well done Phil!

I'd be interested to know how the economy fares with the 4-pintle injectors?

Also, do you have a part number for them please? Such as 0 280 abc xyz?

Out of interest, has the idle improved with the new injectors?

I’ll be interested to see how the economy shapes up too...the part number for them is 0280156045. The only difference fitment wise is that the four pintle units don’t have a recess for the clips that snug the yellow ones into the fuel rail-the new ones have a different shaped nozzle end so they butt up to the intake manifold apertures with no lengthwise movement whatsoever, so the clips aren’t required-they fit perfectly between the rail and the manifold.

I noticed that there was a fair bit of black gunk in the intake manifold, I cleaned up as much of it as possible with carb cleaner but I’ll have to take it off at some point and give it a good clean.

Oddly enough, the injectors smoothed out the idle by a VERY small amount but it’s still slightly uneven.

A friend of mine posited the theory that the head gasket might be leaking a smidgen of coolant into one of the cylinders which was causing the occasional shudder, but the car doesn’t seem to lose any coolant to speak of and it comes up to temp like a champ, with the gauge sitting at halfway come hell or high water, so I’m not convinced by that theory!

[AndyV7o]

It could, however, leak compression/combustion into an adjacent cylinder, causing no effect upon the oil or coolant. Have you had a compression test? (I dont recall, I know it was mentioned earlier)

[Laird Scooby]

Thanks for the part number Phil - i might have to hunt down a set for my beastie as well. Thought of doing it for my Jeep but that was on gas most of the time and wasn't ever planned as a "keeper".

If you're losing coolant into the combustion chambers, wave goodbye to your Lambda sensor! Coolant tends to kill them in short order!

I doubt the head gasket has gone, if it's pulling better now with the other improvements you've made, then the potential head gasket fault would be emphasised - the symptoms have decreased which points away from the head gasket.

[AllHailKingVolvo]

I’ve not done a compression test yet-I don’t have a compression tester at present but would be a useful thing to have in the toolbox. My plan is to replace the in-tank pump first off (as I know it’s weak) and drive it for a while with the new injectors etc in place to let the ECU etc get its head around the new gubbins...I’ve found that any significant changes usually take the ECU around 80 miles to adapt to, at which point it all settles and everything gets quicker/smoother/generally better.

I suspect that having a fully fresh pair of pumps will optimise steady fuel pressure at the rail and help join the last few dots with it all. If not, I’ll do a compression test and delve a bit deeper. I don’t really fancy having the head off, but I could do it if need be...skimming heads and blocks isn’t in my skill set but it wouldn’t be a problem to do rings, a hone and lap the valves in. A bit of a faff compared to the light tinkering I generally prefer though!

Dave, I tend to agree about the HG-the Lambda system seems fine, I may put a fresh sensor in at some point but by choice not necessity. The car is drum tight in terms of oil and coolant, it hasn’t used a drop of either since I did the oil change and coolant flush when I bought it!

[Laird Scooby]

Originally Posted by AllHailKingVolvo

If not, I’ll do a compression test and delve a bit deeper. I don’t really fancy having the head off, but I could do it if need be...skimming heads and blocks isn’t in my skill set but it wouldn’t be a problem to do rings, a hone and lap the valves in. A bit of a faff compared to the light tinkering I generally prefer though!

Dave, I tend to agree about the HG-the Lambda system seems fine, I may put a fresh sensor in at some point but by choice not necessity. The car is drum tight in terms of oil and coolant, it hasn’t used a drop of either since I did the oil change and coolant flush when I bought it!

Have i suggested adding some synthetic ATF to the engine oil Phil? It might be worth a try, it will help revive oil seals and keep them supple (not too much of a problem with yours if it's not using/leaking oil) and also gently but very effectively clean the engine internals, including any slightly sticky piston rings.

The other thing that might be worth a try is Seafoam spray, i've not used it but have seen some very good results on YouTube :

https://www.ebay.co.uk/itm/SEA-FOAM-...y/252942048128

There might be something cheaper but i can't find it on ebay, i made a basic water injection kit on my Rover but couldn't get it to work on any of my Volvos - this basically steam cleaned the engine internals (as well as giving more power and economy!) and decoked the engine as i drove. The emissions were cleaner year on year so i know it worked on the Rover, just couldn't get it to work on a Volvo!

[mocambique-amazone]

You will need a pressure lost check to find a fault at the head gasket between cylinder 1 and 2 or 3 and 4.
A compression test isn't precise enough.
The head gasket is prone to fail between two cylinders.
Thank you for the number of the nozzles
Regards, Kay