Discussion
My wedge (1988 350i) is driving me mad! Please help!
It idles like an old american muscle car when cold, very lumpy and the idle is very low. It's also a bit stuttery when driving but only for the first half a mile. It runs perfectly when you're driving, revs cleanly, etc. But when you stop sometimes it stalls and strangly other times it will idle for a few minutes before stalling (but does hunt when idling).
So far I've replaced the Air Flow Meter and the pipe between the AFM and the plenum.
I've had it tuned twice now and it will run perfectly for about a day but will eventually start to deteriorate until it becomes the same as above.
Now the only other things that I could think of is:
1. Disconnect the cold start injector (don't know if this would help or not)
2. The exhaust has a hole in the centre pipe (but I've had this on cars in the past and it hasn't affected the running)
3. Maybe trying some injector cleaner?
I've checked the connection to the ECU and it's fine but I'm beginning to think that the ECU itself maybe knackered.
Any ideas guys?
If anyone lives close and wouldn't mind swapping over ECUs to see if it makes any difference then it would be appreciated (I'm in North London/Hertfordshire).
It idles like an old american muscle car when cold, very lumpy and the idle is very low. It's also a bit stuttery when driving but only for the first half a mile. It runs perfectly when you're driving, revs cleanly, etc. But when you stop sometimes it stalls and strangly other times it will idle for a few minutes before stalling (but does hunt when idling).
So far I've replaced the Air Flow Meter and the pipe between the AFM and the plenum.
I've had it tuned twice now and it will run perfectly for about a day but will eventually start to deteriorate until it becomes the same as above.
Now the only other things that I could think of is:
1. Disconnect the cold start injector (don't know if this would help or not)
2. The exhaust has a hole in the centre pipe (but I've had this on cars in the past and it hasn't affected the running)
3. Maybe trying some injector cleaner?
I've checked the connection to the ECU and it's fine but I'm beginning to think that the ECU itself maybe knackered.
Any ideas guys?
If anyone lives close and wouldn't mind swapping over ECUs to see if it makes any difference then it would be appreciated (I'm in North London/Hertfordshire).
the garage should be able to tell you what they found wrong while tuning - presumably same thing twice. definately disconenect the cold start injector, mine was way to rich on start up when connected,this had the engine very rough when cold , fouled plugs and passes unburned fuel down the bores into the oil. another problem i found was a faulty extra air valve which was jammed half open, try blocking or clamping the extra air valve pipe when the engine is hot and see what happens. one other thing i found was the vac pipe from the back of the plenum to the fuel pressure regulator had fallen off - lots of popping and banging but way to much fuel on tickover and over-run.
there is a lot of info on the TVR Wedge Pages a great website i would have spent a lot of money without it. good luck
there is a lot of info on the TVR Wedge Pages a great website i would have spent a lot of money without it. good luck
Coolant temperature sensor on front of inlet manifold (there are 2 - the one nearest the car is the thermotime switch).
Mine would cough and stutter when cold, as this had gone,and the previous owner had shorted the loom plug out.
replaced the CTS and setup the mixture (also disconnected cold start injector after following advice on this forum).
Running pretty well so far (don't want to tempt fate though!)
Cost me £10 and took 15mins to fit (10 of then 're-shaping a 3/4" spanner to go past thermotime switch)
Might be worth getting one, and just connecting it without fitting it to the manifold. try to run engine from cold and see what you think.
Someone had obviously bridged mine out and then fudged with the mixture / idle to make it run.
Mine would cough and stutter when cold, as this had gone,and the previous owner had shorted the loom plug out.
replaced the CTS and setup the mixture (also disconnected cold start injector after following advice on this forum).
Running pretty well so far (don't want to tempt fate though!)
Cost me £10 and took 15mins to fit (10 of then 're-shaping a 3/4" spanner to go past thermotime switch)
Might be worth getting one, and just connecting it without fitting it to the manifold. try to run engine from cold and see what you think.
Someone had obviously bridged mine out and then fudged with the mixture / idle to make it run.
Throttle pot: if not ok, idle not ok, but rest of the rev range not too bad. Perhaps they set it up twice during the tune up. If the throttle pot is worn/damaged, tune-ups won't help and replacement is required.
ECU.If you think about ECU, when mine had problems it was the other way round: idle ok, but acceleration caused rough running or stalling. First thing with ECU is to have someone resolder the thing (that knows about electronics to not melt some of the internals). Very often (like in nearly always) the ECU is fixed (mine is).
Rob
ECU.If you think about ECU, when mine had problems it was the other way round: idle ok, but acceleration caused rough running or stalling. First thing with ECU is to have someone resolder the thing (that knows about electronics to not melt some of the internals). Very often (like in nearly always) the ECU is fixed (mine is).
Rob
borat said:
Cheers guys,
Throttle pot sounds a definite possibility.
So the cold start injector is in top of the plenum on the drivers side then? I'll disconnect it tommorow and see how it goes...
Throttle pot sounds a definite possibility.
So the cold start injector is in top of the plenum on the drivers side then? I'll disconnect it tommorow and see how it goes...
You could try that. But most standard 350's work well with it on. I'ts the larger engines that have them disconnected as they deliver more than enough fuel on startup. The thermotime switch only allows it to fire for about 12 seconds anyway. If it does run better with it off (for more than 12 seconds) then you could pissibly have a leaky cold start injector causing over fuelling but I doubt it would affect it that much.
I would start with either changing the temp sensor or shorting it out with a 170Ohm resistor to simulate a warmed up engine.
I know that the throttle pot was adjusted last time it was tuned. Maybe it be worthwile getting it replaced. Is it a standard Rover part?
Do you think the car is ok to drive though? It's just that I'm supposed to be going to kent this weekend and thought it would be ideal weather to take the wedge
Do you think the car is ok to drive though? It's just that I'm supposed to be going to kent this weekend and thought it would be ideal weather to take the wedge
Get the efi pdf from the tvrwedgepages site and read it. Follow the fault finding procedure and that will hopefully improve matters or at least eliminate possible causes. There does seem to be some variation on the throttle pot wire colours though.
We have done the efi diagnostics, cleaned all connectors, checked the solder joints on the ecu, checked for air leaks, disconnected the cold start injector, adjusted the overrun air valve, replaced the engine temp sensor, fuel filter, spark plugs, leads, coil dizzy cap, rotor arm, distributor with ignition amp (it died one day) and the coolent thermostat.
It is better but is still rough for up to a minute from cold start, the idling sometimes hunts a little (+/- 100 rpm maybe) and it can stall. What I have noticed is that if you blip the throttle on the 2nd to 1st down change just before stopping the car has a tendancy to stall on idle. If you slow in 2nd and down change to 1st without throttle it generally dropps to a steady idle. My theory is that excess fuel hangs around in the plenum/trumpets and causes an over rich stall if the throttle is touched. I think the next step is a rolling road tune with a possible ecu upgrade at Austec.
Does it stall if you blip the throttle from idle?
We have done the efi diagnostics, cleaned all connectors, checked the solder joints on the ecu, checked for air leaks, disconnected the cold start injector, adjusted the overrun air valve, replaced the engine temp sensor, fuel filter, spark plugs, leads, coil dizzy cap, rotor arm, distributor with ignition amp (it died one day) and the coolent thermostat.
It is better but is still rough for up to a minute from cold start, the idling sometimes hunts a little (+/- 100 rpm maybe) and it can stall. What I have noticed is that if you blip the throttle on the 2nd to 1st down change just before stopping the car has a tendancy to stall on idle. If you slow in 2nd and down change to 1st without throttle it generally dropps to a steady idle. My theory is that excess fuel hangs around in the plenum/trumpets and causes an over rich stall if the throttle is touched. I think the next step is a rolling road tune with a possible ecu upgrade at Austec.
Does it stall if you blip the throttle from idle?
I've noticed that when it's about to stall if I catch it before it does and rev the car up to about 2000 rpm for a few seconds, it will settle back down to idle again for a while before trying to stall but does hunt when idling.
From searching various other posts it does seem to indicate a faulty potentiometer.
From searching various other posts it does seem to indicate a faulty potentiometer.
Probably not the fix but had similar symptoms and it was down to poor connections on the air flow meter. The plug on the cable connectors (female) were a tad slack. I could feel no physical resistance when pushing it on. Very carefully I tightened them up, they looked like they might snap, and hey presto.
If you have multimeter you can do a basic check on the pot.
Apologies if this is egg sucking...
The pot has three connections, two of them on either end of a resistance track the other is connected to the wiper that travels along the track.
With the ignition off.
Disconnect the pot connector.
If you check the resistance across pairs of wires on the pot you should find that the reading on one pair does not vary when you open the throttle - these are the two wires on either side of the track.
Leave one of these connected and connect the other multimeter probe to the other wire. Open and close the throttle, you should see the resitance vary smoothly through the range - this is easier with an analogue multimeter, unfortunately not common now. You are particularly interested in the reading around the throttle closed position so look carefully for any sudden jumps in resistance that may indicate a fault in the track.
If you are happy to re-adjust the pot position then you can try loosening the adjustment screws and turn the pot anti-clockwise as this will let you see the track past the current closed throttle position. If that makes sense? You will need to set up the pot by following the instructions in the pdf if you move it.
Running through the tests in the pdf is easier with some help as you need to make connections at the ecu and under the bonnet at the same time. I am going on holiday on Saturday or I would offer to help, if I have time I will check the pot on our car and post the readings I get.
Apologies if this is egg sucking...
The pot has three connections, two of them on either end of a resistance track the other is connected to the wiper that travels along the track.
With the ignition off.
Disconnect the pot connector.
If you check the resistance across pairs of wires on the pot you should find that the reading on one pair does not vary when you open the throttle - these are the two wires on either side of the track.
Leave one of these connected and connect the other multimeter probe to the other wire. Open and close the throttle, you should see the resitance vary smoothly through the range - this is easier with an analogue multimeter, unfortunately not common now. You are particularly interested in the reading around the throttle closed position so look carefully for any sudden jumps in resistance that may indicate a fault in the track.
If you are happy to re-adjust the pot position then you can try loosening the adjustment screws and turn the pot anti-clockwise as this will let you see the track past the current closed throttle position. If that makes sense? You will need to set up the pot by following the instructions in the pdf if you move it.
Running through the tests in the pdf is easier with some help as you need to make connections at the ecu and under the bonnet at the same time. I am going on holiday on Saturday or I would offer to help, if I have time I will check the pot on our car and post the readings I get.
Edited by toltec on Wednesday 28th June 10:15
toltec said:
Running through the tests in the pdf is easier with some help as you need to make connections at the ecu and under the bonnet at the same time. I am going on holiday on Saturday or I would offer to help, if I have time I will check the pot on our car and post the readings I get.
Be aware that the PDF is basically for Rover SD1. It states that there should be no gap top or bottom of the throttle plate, but in fact it needs to be set to 0.005" then set throttle pot to around 325 mVolts
dickymint said:
toltec said:
Running through the tests in the pdf is easier with some help as you need to make connections at the ecu and under the bonnet at the same time. I am going on holiday on Saturday or I would offer to help, if I have time I will check the pot on our car and post the readings I get.
Be aware that the PDF is basically for Rover SD1. It states that there should be no gap top or bottom of the throttle plate, but in fact it needs to be set to 0.005" then set throttle pot to around 325 mVolts
Didn't notice that, I used a combination of the bible, epistles, efi pdf and posts on this site when I worked out a test schedule. Does the throttle plate go out of adjustment? Ours was ok when I checked.
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