Club 80-90 Forums

I've got a Multivan with a 2.1 water cooled motor (3 spd Auto box) and it's recently started to run very erratic. Mainly when I slow down at a junction for example. Pick up can be slow and sluggish (not all the time though). Also, at speed (say 50-70mph) you can sometimes feel the engine surge forward and pull back a little.
My first thought is that it could be down to a duff Idle Control Valve.
Not sure really where else to check. All sparks are good. leads, dizzy cap and plugs are all recent. Can be a bit erratic on idle. Will sit at about 800-900 then shoot up to 1200-1400 then down again.
Air Filter is new and clean.
Everything else is ok. (I think!)

Any ideas are welcome as I maybe barking up the wrong tree.

If you're sure it does it at speed, doubt its the idle control valve..
sounds liek the AFM could be playing, check the movemetn of the vane and the condition of the tracks and its wiring.

As usual with these, also check and remake all earty connections (even double up alternator earth with a fixed thick wire to bodywork) as well as the T2 sender plug and wire.

Is it an MV or DJ engine?

Thanks for that. I did get the AFM checked by a local garage last week. (Also got them to do a head gasket leak test as trying to elliminate everything!)
TBH, it's been no better since it came back and they were uncertain about the state of the AFM.
It's more noticable from start but it does do it sometimes at speed. Like I said, it seems erratic. You could be driving about 10 miles and everything is fine, but then, for the next 2-3 miles it will feel juddery at speed and sluggish on start up.

Is it a DJ? or has it an O2 (lambda) sensor in the exhaust, a late model.. (MV)

suspiciously like one of the main 'vanagon syndromes'..

check the T2 sensor wiring really thoroughly - stuff is bouncing about in the engine bay, almost everything inclusing wiring - checkit or re-run it.

clean the ISV with carb cleaner if its hasn't been already - when idling from cold, move the T2 senders wiring and that of the ISU about - does the idling change?

check the state of the ISU behind the r/h rear light cluster - does that compartment show signs od water ingress, damp, rust and corrosion around the isu mounted on the front wall of that compartment near where the fuel filler hose steel sleeve goes through to the inner wheel arch?

visually inspecting the AFM tracks and general assembly for wear and general condition is not that difficult...

How many miles on the vehicle and what year?

etc.

It's a 1987 model.
The engine was rebuilt by Laurie Petit some 40,000 miles ago.
It's only recently started to happen. Looks like I've got a bit to be going on with today at least!
Cheers for the help and advice. I will let you know the result!

Yes lots

Mileage on vehicle (which determines wear on AFM) ?

Air leak checks on all vacuum pipework and I have even seen an inlet manifold to be rusted enough to leak (and I haven't seen many of these atall)

OK, update:

It seems there is an intermittent fault going to the injector on no.2 cylinder.
When removing any other injector, there is a major difference, but on removing no.2, there is little difference to the running (i.e intermittent missing). Have swapped over injector and problem persists on no.2, therefore the injector is ok, but the feed to it isn't!

What we need to know is where the wire runs to/fed from so we trace it back and check the feed to the wire and also to maybe run a seperate wire from the live feed to the injector to see if the wire is the problem.

This a white wire going to Pin 11 on the ECU(Fuel control Unit) (via the ecu's multi-plug/engine loom)

Cyl No. 1 ~ Pin 12
Cyl No. 2 ~ Pin 11
Cyl No. 3 ~ Pin 24
Cyl No. 4 ~ Pin 23

The other side of the wiring from all four injectors is star-joined (White) and then to one side of the Aux. Air Regulator and the fuel pump relay where the circuit is presumably energised from.

Temp Sndr II ~ Pin 2

This is the diagram I have from bentley Digijet 1985 on

I would definitely check the star earths (left side of crankcase top face) and remake with electrical contact cleaner and a Nocrode grease.
Check and clean all ecu plug contacts too...

Done everything possible and still runs like a bag of spanners!

It's probably something simple and obvious but whatever it is, it's confused me something chronic!

? Is the idle stab switch on the throttle body operating correctly ? Switching at idle and full throttle ?
If DJ then also check vacuum pipes from throttle body to disi carefully and check vacuum advance unit operating ok

It is an MV engine. Have come across a few problems whilst hunting for this problem but nothing has cured it. Like a supposed set of new leads which had bits of a broken dissy cap in the end of one of them. Work carried out by a so called reputable specialist as well.

Ahhhh! So it is an MV with a lambda sensor...

Vanagonitis old mate Well, remember the longest thread ever? - going round in circles until someone re-checked the lambda sensor and found it duff... when it had already be checked and given the OK.

So, in the first instance, just remove the lead from the exhaust lambda sensor and drive it for a while like that - see if any of the symptons go away - then report back. Some never re-connect it.

PS Has it had a replacement lambda sensor (O2 sensor) lately (non-OEM)