poor running, misfire?
Discussion
following my thread 'won't rev past 2000rpm' i've had the wedge ('87 350i) into a TVR specialist who got the car running again by re-setting the fuel pressure, changing the plugs, replacing a broken coil, rebuilding the distributor (rusty trigger wheel) and replacing the ignition module. However the car now has a slight running problem, which i can't get to the bottom of!
When driving with the accelerator in a constant position the car seems to have a juddering or slight misfire, however it does rev quite freely and the 'hesitation' or 'juddering' doesnt seem to be there when accelerating?
The car has magnacor 8.5mm leads (not sure how old), i have swapped the airflow meter (Co etc set up)which made no difference, the dist cap and rotor have also been changed!
Any ideas out there?
When driving with the accelerator in a constant position the car seems to have a juddering or slight misfire, however it does rev quite freely and the 'hesitation' or 'juddering' doesnt seem to be there when accelerating?
The car has magnacor 8.5mm leads (not sure how old), i have swapped the airflow meter (Co etc set up)which made no difference, the dist cap and rotor have also been changed!
Any ideas out there?
Hi
i've spent nearly £600 and the car still doesn't run right ! I rang the Specialist again today and suggested the throttle pot, he said definitely not - i am going to try one all the same (might as well i've changed everything else)!
Are the throttle pots the same regardless of whether they have the white or black plug (mines white)?
i've spent nearly £600 and the car still doesn't run right ! I rang the Specialist again today and suggested the throttle pot, he said definitely not - i am going to try one all the same (might as well i've changed everything else)!
Are the throttle pots the same regardless of whether they have the white or black plug (mines white)?
Hi
i have tested the throttle pot again today and the control voltage was 4.41v, the green/red with ignition on was 0.8 (i am sure this was 0.3 prior to going in the garage) so i have adjusted this to give .35v, it only seems to rise to 3.99v though at full throttle? The butterfly gap is 0.002" as suggested.
I went around the block and it made no difference (even trickling along at a constant throttle in 1st gives a slight juddering feeling), further to this it makes no difference if i disconnect it all together? Why?
I have tested the amplifier as suggested in wedge pages (5b Module located on dist). With ecu plug off, voltmeter between -ve terminal on coil and lucar clip from amp - on cranking the engine this gives between 9 and 10v? according to the info it should be 6 - 9 volts, what could be wrong? The coil and amp were fitted by RTR last week.
Items replaced so far include fuel pump, fuel filter and pressure set. New plugs, rotor arm, lucas dist cap. New HT leads, new coil and amplifier. Distributor rebuilt/fitted by rtr.
i have tested the throttle pot again today and the control voltage was 4.41v, the green/red with ignition on was 0.8 (i am sure this was 0.3 prior to going in the garage) so i have adjusted this to give .35v, it only seems to rise to 3.99v though at full throttle? The butterfly gap is 0.002" as suggested.
I went around the block and it made no difference (even trickling along at a constant throttle in 1st gives a slight juddering feeling), further to this it makes no difference if i disconnect it all together? Why?
I have tested the amplifier as suggested in wedge pages (5b Module located on dist). With ecu plug off, voltmeter between -ve terminal on coil and lucar clip from amp - on cranking the engine this gives between 9 and 10v? according to the info it should be 6 - 9 volts, what could be wrong? The coil and amp were fitted by RTR last week.
Items replaced so far include fuel pump, fuel filter and pressure set. New plugs, rotor arm, lucas dist cap. New HT leads, new coil and amplifier. Distributor rebuilt/fitted by rtr.
Edited by johntom on Sunday 22 June 22:27
When testing the ignition amp (as per wedgepages efi test 5b) i am getting between 9 and 10 volts between the coil -ve and the lucar clip back to the ignition module (when cranking the engine, ecu plug removed), what would make it higher then the suggested 6 - 9 volts? should there be some sort of balast resistor (the coil/ ign. amp are new)?
Hi
thankyou for your response. In your previous post you mentioned the 'supression capacitor', i have noticed two small cylinders near the coil which were previously lucar clipped to the old coil - now the lucar clip is unconnected? is this the 'supression capacitor' and should this go to the +ve or -ve terminal?
many thanks for your help and patience.
prior to going into the garage the car ran very smoothly, it just wouldn't rev past 2000rpm. I think this new fault is possibly connected to the repair work on the previous fault, ie distributor rebuild, new ignition module, coil etc?
thankyou for your response. In your previous post you mentioned the 'supression capacitor', i have noticed two small cylinders near the coil which were previously lucar clipped to the old coil - now the lucar clip is unconnected? is this the 'supression capacitor' and should this go to the +ve or -ve terminal?
many thanks for your help and patience.
prior to going into the garage the car ran very smoothly, it just wouldn't rev past 2000rpm. I think this new fault is possibly connected to the repair work on the previous fault, ie distributor rebuild, new ignition module, coil etc?
Edited by johntom on Monday 23 June 22:50
Thanks for your replies, i have bought a temp sensor off fleabay just in case - awaiting delivery. The Tvr specialist replaced the coil, plugs and ignition module as they said the plugs weren't the right ones (although it ran fine on them before) and the module and coil brought back the rev range (original fault was not reving past 2000rpm). They rebuilt the dist. due to a rusty/worn gear on the top, they have set and rechecked the timing, co. etc. I surpose i am trying to replace suspect parts because its cheaper to buy them/fit myself (via ebay and if they don't improve the situation i have spares) than take it to a garage and pay £45+vat/h and top price for the parts ie new plugs, coil, ign. module, rebuild dist = £576.00!
Will fit the temp sensor asap and report back. Many thanks
Will fit the temp sensor asap and report back. Many thanks
Hi
this afternoon i have fitted a new engine temp. sensor and throttle pot, still no difference. Your can feel the engine is running rough even with the bonnet up. I have tried a second hand coil and another ignition module, again no difference.
New parts so far, HT leads. dist cap, rotor, plugs, coil, ignition module, throttle pot and engine temp sensor.
Interestingly i had the bonnet up and the coil -ve lead off, with the intention of testing the coil. I unlocked the passenger door and as i opened it the alarm (sigma S30) started to beep and the engine cranked over - moving it forward on the starter ! I went round to the drivers side and pressed the blipper to make it stop! What is happening - could there be a circuit from the immobilsor effecting the car's running?
Sometimes you can try and start the car without knocking off the alarm and it will turn over and make the alarm sound today it happened and it carried on after i removed the key!
this afternoon i have fitted a new engine temp. sensor and throttle pot, still no difference. Your can feel the engine is running rough even with the bonnet up. I have tried a second hand coil and another ignition module, again no difference.
New parts so far, HT leads. dist cap, rotor, plugs, coil, ignition module, throttle pot and engine temp sensor.
Interestingly i had the bonnet up and the coil -ve lead off, with the intention of testing the coil. I unlocked the passenger door and as i opened it the alarm (sigma S30) started to beep and the engine cranked over - moving it forward on the starter ! I went round to the drivers side and pressed the blipper to make it stop! What is happening - could there be a circuit from the immobilsor effecting the car's running?
Sometimes you can try and start the car without knocking off the alarm and it will turn over and make the alarm sound today it happened and it carried on after i removed the key!
Hi
the fuel pressure was set to 36psi? by RTR. I tried to test it prior to taking it into them and it was 30 psi with the old pump and 32psi with the new one (which i've left on). Yes the fuel is new and i have tried injector cleaner. I will look at the regulator.
Would you assume the pressure is too high or too low and which way would you turn the allen screw?
the fuel pressure was set to 36psi? by RTR. I tried to test it prior to taking it into them and it was 30 psi with the old pump and 32psi with the new one (which i've left on). Yes the fuel is new and i have tried injector cleaner. I will look at the regulator.
Would you assume the pressure is too high or too low and which way would you turn the allen screw?
Edited by johntom on Thursday 3rd July 19:50
Hi
i decided to check the plugs (fitted by the specialist). The NGK website recommends BPR5E, the car had B7ECS (which are a shorter reach plug) and according to NGK are for the 4.0, 4.5 and 5.0 engines?
I have fitted some BPR5ES tonight and the car drives much better, certainly more responsive. Still a slight hint of 'judder' but definitely much better.
www.ngk.co.uk
i decided to check the plugs (fitted by the specialist). The NGK website recommends BPR5E, the car had B7ECS (which are a shorter reach plug) and according to NGK are for the 4.0, 4.5 and 5.0 engines?
I have fitted some BPR5ES tonight and the car drives much better, certainly more responsive. Still a slight hint of 'judder' but definitely much better.
www.ngk.co.uk
Edited by johntom on Saturday 5th July 12:59
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