Poor MPG since rebuilt KR head... Any Suggestions???

[slugmaster100 0]

Hi,

 

About 2000 miles ago, my engine decided enough was enough and started running on just 2 cylinders. I have had the head off and it had burnt through the head between cylinders 3 and 4. I think this has been slowly happening over the course of the last year, and in all that time my MPG was around-about 28-35mpg (depending on what kind of driving obviously). The only thing that i was experiencing was a bit of trouble starting now and then.

 

I have had my head repaired and skimmed (but not really anything extra shaven off i believe). I have re-ground all my valves and fitted new oil seals. I have set my CO to approximately 1-1.2%, and my ignition timing to 6 degrees. My idle is around 950-1000rpm. (this is all the same as before I took it all to bits i believe).

 

In the 2000 miles since its all been back up and running, I haven't really felt much of a difference in performance, however my MPG has plummited to 22-26mpg! I have rechecked my CO and ignition timing which all are still ok, and there are no fuel leaks etc.

 

Does anyone have any idea why my MPG has dropped so significantly???

 

Thanks!, Rich.

[raddo_tom 0]

Engine will need bedding in fella. Although after 2k it should be....... I'll shut up now... :ignore:

[davidwort 0]

head recon won't make any difference to performance, by that I mean negative, as it doesn't need to be run in like a bottom end rebuild. I reckon you've got dodgy injectors, you need to pull them, disconnect the dizzy and crank it over lifting the air plate in the metering head, spray each injector into a jar and see how much fuel and how good the spray pattern is.

The cold weather kills economy on the 16v too, especially the 1.8.

 

Edit: Actually far better to remove the fuel pump relay, bridge the main terminals for it on the fuse board and run the fuel pump like that, then there's no need to crank the engine and you can switch it on/off by connecting and disconnecting the battery negative, with one 1L bottle strapped to each injector you'll get about 250ml of fuel in each in a minute with the metering flap wedged fully open, that should give enough time for you to clearly see how good the spray pattern is on each injector and also compare output from each injector, the amount in each bottle should be identical.

[slugmaster100 0]

Hi again....

 

I am still suffering around 22MPG from a pretty much standard 1.8 16v KR. I used to get at least 30MPG as mentioned above.

 

I'll say what I've done, and welcome any further opinions etc. (I'm getting a bit fed up now!):...

 

checked bottom pulley to top pulley timing marks - ok

checked when timed up the cam positions (with the 2 'o' marks on the cam shafts) - ok

checked ignition timing - 6 degrees

checked CO content at idle - around about 1%

checked resistance's of temp senders on back of head - all read the same and one is brand new

replaced, and now unplugged cold start injector and thermo-time switch - so cannot be an issue injecting all the time

re-wired the UFO shaped vacuum thing next to the air box as it had no live feed

set up the idle micro-switch on the throttle flap so that gets pressed when it should

replaced spark plugs and dissy cap (previously leads too)

when I unplug the ISV it cuts out so thats seems to be working

none of the injectors appear to be leaking externally

I've run through some injection system cleaner

 

it has also taken up the habit of spluttering to start in the morning as though a cylinder starts one after the other (only for a few seconds before its idling fine again). When it has been stood from warm for a couple of hours, it also misfires as though running on 3 cylinders for 30 odd seconds before it recovers and runs ok.

 

Its not seeming to use any coolant or oil

 

My mate said that when I pulled into the car park the other morning that it smelt as though it was running very rich (which would explain the fuel consumption) but I don't know how to test that, what is causing it to do it, and how to cure it or what to adjust!

 

I hope someone knows whats up, cos I've run out of ideas and am rapidly running out of enthusiasm!

 

many thanks, Rich.

[Jim 2]

Sounds like leaking injectors.. I'd do what davidwort said before to test the spray pattern. New injectors for the 1.8 16v aren't too expensive.. or if you're on a shoe string budget, you could get yours removed and sent off for cleaning.

 

They won't leak externally - they'll just have an incorrect spray pattern, and they'll also dribble fuel into the cylinders when the car isn't running as they won't close properly. This could account for the lumpy start / smell of fuel when starting the car from cold.

 

Assuming the 1.8 16v works the same as the 2.0 16v, there is also an ECU temperature probe in the block which monitors coolant temperature - I believe this is used to control the fuelling and may well cause a drop in fuel economy.

[aide 0]

am a bit rusty on valver set up, been a few years :D

 

if the co2 is ok at idle then it must only be running rich off idle, the mixture screw is located within the metreing head, you'll see a small access plug at the front which can be removed to adjust the screw beneath *carefully* with an allen key but this seems ok in your case

 

i wouldn't put too much stock in the mpg reading we're talking 20 year old technology here, are you sure your actually filling up more? :D

 

there's really not much to go wrong with valver fuel supply and it seems you have most the bases covered, defo worth doing the spray pattern tests suggested by david

 

the only other thing i can think of is the the warm up regulator, on start up this reduces the control pressure in the metering head thereby allowing more fuel to pass to the injectors..... these can be purposely adjusted for a mild power gain, yours may be completely foobarred :scratch:

[Toad 0]

You don't have any vaccum leaks since disturbing the pipework to take the head off?

[slugmaster100 0]

Sorry to re-bring this old one up again, but I keep going in phases of trying to fix this, cos I just lose interest now and then! :|

 

As suggested, I have removed all the injectors and checked the spray patterns which all looked good and all squirted pretty much the same amount of fuel in the same amount of time. - So that all seems ok.

 

They also don't seem to leak out when left for a while (overnight) either.

 

I've checked for vacuum leaks and found nothing of concern there.

 

In regards to the warm up regulator, what do I need to check on that? I have done a resistance check across it and have got virtually no resistance at all - about 0.03 ohms I think - so short circuit. This is both at hot and cold so I'm not sure that it's doing much.... but I don't know! If you have a KR engine that runs properly with good MPG, would you check the resistance across your warm up regulator and let me know please... thanks!

 

I have also checked the fuel pressure and have about 3.5bar reading all the time. From what I have read and discussed with people, I think that the higher the pressure on the gauge, the less is being injected. I also heard that the gauge reading should increase from around 1 bar to 3.5 bar over about 10 minutes as the engine warms up. If this is the case, then I suspect that low fuel pressure would cause the start-up spluttering, but I cannot work out how it would be using the fuel it is doing if it was running at 'lean/warmed up' pressure at all times! :? But I'm not sure what would be causing this either.

 

I appreciate all your input to my problem,

 

Rich.