Hi folks thought I would share the symptoms and fix for a fault on my 2003 1.8 Nevada in case it helps anyone. It initially confused us as it occurred immediately after we serviced it but turns out that was completely unrelated.
Symptoms
Car started and ran fine, but when hot developed a engine warning light, rough running and would not rev up. Allowing the car to cool overnight and it would again start fine and rev up and the engine warning light disappeared, until it was hot then it occurred again.
Diagnosis
Codes read and showed P0335 and P1345, Crankshaft position sensor and Crankshaft position-camshaft position correlation.
Fix
Got hold of a good crankshaft sensor, (thanks rhino666).
Simple fitting job (if you are flexible), with one bolt and adjusting the gap between the sensor and pulley to 0.8mm.
Now been done a couple of weeks including a track day and all is good.
Coincidentally, having fitted a new cam belt last week I found my car initially ran better than before (I think the inlet cam was times slightly out last time the belt was refitted).
Having got it really warmed up, it began to intermittently misfire. I first suspected the coil pack. However, I went back over everything I’d disturbed and discovered that the crank sensor was sitting very slightly too far away from the sensor plate. A quick tweak on the 10mm fixing bolt and repositioning it cured the problem.
I reckon this would make a good engine immobiliser! Very difficult for a potential car thief to spot and very easy to reverse.
Hmmm…my NB has suffered a very similar fault again this afternoon. I thought I’d cured it, as above.
After fetching my wife back from babysitting our grand daughter in Stockport I got stuck in very heavy, stop/start traffic leaving Manchester and it began to misfire, then to cut out repeatedly. It did restart fairly easily. I suspect the coil pack, but it might just as easily be the crank sensor, seeing as both have been disturbed when changing the cam belt (TBH I’m getting a bit sick of having reason to write about that pesky job). We waited at Mottram Esso Garage for an hour with the bonnet up and had a sandwich and a drink. Once the engine had cooled and the traffic jam cleared it was fine - Woodhead Pass and M1 et al. I’ll put the test light on it when I get chance.
In the mean time - any clues on where to buy a new NB coil pack at a reasonable price?
P.S. Who on earth decided that the coil pack should be bolted directly to the hottest part of the engine?
Having now checked for fault codes the car is actually showing a 0120 fault (TPS = Throttle Position Sensor).
Not what I expected hopefully a far less expensive fault to fix than a new coil pack. I’ve just removed the TPS from the car and tested its rate of change in resistance whilst operating it. There does appear to be a bad spot. The resistance increases steadily as expected when rotated to the “open throttle” position but then at about one third “open” it appears to have a very sudden resistance drop. They are a sealed unit so a new one has been ordered from Mx5 Parts.
Hopefully the new TPS will sort it Paul - certainly the error code is very specific.
Have to say I would usually recommend replacement of the entire throttle body with all sensors for a known working used item. These are the same for all MK2/MK2.5 cars and available very cheap as do not generally give issue.
You have the error code and what appears to be proof that the unit is faulty so much easier just to replace the TPS - hope it works, let us know.
The car has done less than 42,000 miles and the throttle body itself is in excellent condition - very clean internally and has no play on the spindle or on the butterfly itself.
As I’ve often found on an old, low mileage but well maintained car, it seems to be electrics/electronics that give most problems. The manufacturers do seem to have the basic metal mechanical reliability sorted, but not so good with longevity of electronic parts and the wiring.
The new TPS arrived this morning; as usual, MX5 Parts got the part to me in excellent time - only about 36 hours had passed since I ordered it.
It’s now on the car (a ten minute job to fit it to the throttle body and put the complete assembly back onto the intake plenum.
I disconnected the battery negative lead before I did the work, then reconnected it after the TPS had been replaced and plugged in. I fully exercised the throttle a few times with the ignition on. This cleared the 0120 fault code.
I gave the car a good run, again fully exercising the throttle (!) and got it very fully warmed up. There was no sign of a misfire or cutting out. I checked for fault codes afterwards and there are none.