Club 80-90 Forums

Hi guys,

I was wondering if you could weigh in on this if you have experience with digijet overfuelling.

I have a 1988 van with a 2.1 DJ.
The van idles rough and lumpy and is incredibly rich both cold and hot. grey smoke and smell of petrol, sooty plugs.

Here is what we have tested/changed:

We compression tested it and the compression is good.

It has a new blue ecu coolant temp sensor which we tested, the values are good, bought from Brickwerks a few weeks back.
We checked the plug for it and the wiring to the ecu, all good.

We checked the timing, all good.

Checked and cleaned the ISV, tested the wiring etc, all good.

All the earths are good.

No vacuum leaks

New plugs, cap and rotor.

All plug leads are good.

Just serviced, oil, air, fuel filter.

Cleaned the throttle body and tested the idle and wot micro-switches and wiring.

The idle relay behind the tail light looks ok, the idle control unit beside the coil is plugged in too. If I use the timing light without disconnecting these I can see the timing fluctuate so it seems as if they are working.

The only thing we are suspicious of is the AFM. The plastic lid has clearly been off before because it is siliconed back on. I am wondering if the previous owner may have readjusted it to try and cure a previous issue?

An important thing we noticed is, we can greatly improve the idling issue.
To do so, we get the hose that runs from the S shaped intake boot to the ISV, and disconnect it. So we are introducing a massive air leak after the AFM. The S shaped intake boot is now sucking a large amount of unmetered air, and the ISV is now sucking in lots of fresh air too.
When we do this the idle is lovely and smooth and the exhaust is alot less fumey and smokey.

So what does this mean? With the hose connected the engine is getting far too much fuel for the air it is receiving. Allowing the engine to get a lot of unmetered air seems to improve the AFR considerably. Has the AFM been messed with maybe?

P.s. The air intake hose for the airbox isn't collapsed, restricting air flow, we checked, its good.

Unplug the lambda sensor and see how it runs

davidoft1 wrote:Unplug the lambda sensor and see how it runs

Its a 2.1 DJ, it doesnt have one

Check the fuel pressure regulator.

bigherb wrote:Check the fuel pressure regulator.

+1

Im not a petrol expert, but found this:
https://siradventure.files.wordpress.co ... nj_ign.pdf" onclick="window.open(this.href);return false;

ZsZ wrote:Im not a petrol expert, but found this:
https://siradventure.files.wordpress.co ... nj_ign.pdf" onclick="window.open(this.href);return false;

Thanks very much, thats a useful document

937carrera wrote:

bigherb wrote:Check the fuel pressure regulator.

+1

bigherb wrote:Check the fuel pressure regulator.

Ok I'll set myself up with a pressure tester and verify the FPR, will report back when I have findings. thanks

Or this even: https://www.youtube.com/watch?v=6Tn8dyzn9a4" onclick="window.open(this.href);return false; Wish I'd seen it earlier as I still have a puzzle with my DJ.
Under what circumstances did this problem arrive or has it been that way since acquisition?
BTW I assume you have run the CO adjustment to both ends of range to see whether that makes any difference.(Granny sucking eggs alarm sounds)
E D I T:
Forgot to mention that after years of blindly taking my vehicles to the MOT fingers crossed on the emission pass I recently bought a Gunson G4125 Digital gas tester for a bit over one hundred pounds to sort out my DJ idle problems. It seemed to work as described and met the approval of my (don't say I said it!) somewhat pedantic ex mechanic mate. From the symptom description I should imagine this would be well off the scale of measurement but when you get it closer...

Mr Bean wrote:Or this even: https://www.youtube.com/watch?v=6Tn8dyzn9a4" onclick="window.open(this.href);return false; Wish I'd seen it earlier as I still have a puzzle with my DJ.
Under what circumstances did this problem arrive or has it been that way since acquisition?
BTW I assume you have run the CO adjustment to both ends of range to see whether that makes any difference.(Granny sucking eggs alarm sounds)
E D I T:
Forgot to mention that after years of blindly taking my vehicles to the MOT fingers crossed on the emission pass I recently bought a Gunson G4125 Digital gas tester for a bit over one hundred pounds to sort out my DJ idle problems. It seemed to work as described and met the approval of my (don't say I said it!) somewhat pedantic ex mechanic mate. From the symptom description I should imagine this would be well off the scale of measurement but when you get it closer...

The van has been like this since I got it, I'm not sure what the previous owner may have tweaked or adjusted.
I have tried adjusting the co screw on the afm but it had no affect, so I set it back to where it was (2.5 turns out)

That video is very useful, thanks for that.

We have been meaning to get one of those Gunson testers for the garage, glad to hear some positive feedback on them!

Don't know if you have a Bentley's manual but Mine has been a godsend at times. Sadly it covers all sorts of stuff on the American vehicles which is of little interest to me of course. But there is a whole bunch of very usefully tucked away info in there if you delve. Wouldn't be without mine.

Hi,

Just to follow up and close off the discussion. I solved the issue. It turns out that the AFM was completely out of calibration. The van has an LPG system. The previous owner had mentioned that they changed the AFM at some stage. I suspect the replacement AFM had been fiddled with or was from a different vehicle. I recalibrated it by adjusting the wiper arm back in the lean direction until the van ran nicely. It now starts and idles nicely both cold and hot, no more rich smell and smoke.