‘93 Renault 5 1400cc fuel injection. Runs perfectly well when cold, once warmed up it runs very unevenly on a light throttle. I’m only getting 20mpg and the plugs are sooty, suggesting over-rich fuel mix. It hesitates and stutters to the point of being almost undriveable when going slow or in traffic. Even cruising at speed, if you're off the throttle to slow down and then back on it lightly, it misses like mad. On half or full throttle it is ok, and the acceleration is fine. I've done the obvious things - new plugs, leads, diz cap, air cleaner, the warm air / cold air flap in the air intake is working ok, and checked for air leaks on the injection system. I’ve checked all the injection-related stuff, all the sensors give true readings, injector resistance is 1.4 ohms and no insulation leakage to earth so that seems ok. I’ve used STP injector cleaner (getting really desperate now) but that did nothing. I put it into the local garage for diagnostic testing and they came up with a faulty stepper. Stepper faults usually relate to tickover problems and mine ticks over like a Swiss clock, but I stripped and cleaned it and checked it on the car- motor opens and closes ok and contacts read (0v-5v as throttle opens & closes) so it seems to be doing what it should. Someone with exactly the same fault remedied it by replacing the EGR valve but my model doesn’t have one. Could it be the ECU? I understand to get this checked will cost £80/hour so I want to be sure I’ve exhausted all avenues before I do this. Any thoughts or ideas will be greatly appreciated.
Does this model use a map sensor?? If so, your symptoms are that of the ecu being supplied with a map signal of low vacuum- i.e. throttle wide open, when its not. So check map sensor hose for leaks, and the sensor itself for giving a sensible output according to vacuum applied.
Right. Firstly then you need to remove the map sensor, and look at it orifice. Bet it will be full of crud and oil from the PCV system. I would clean it in anycase, you havent anything to loose. Use some brake cleaner, as opposed to carb cleaner- its less aggressive and do NOT squirt directly into it. Squirt across the appature, shake it around, and drain out. Repeat until the cleaner runs clear. Likewise do not blow into it with an air line- you will burst it.
Not sure of the specs on what type of map is on the R5. Could be a varying resistance, or digital sawtooth signal. If you can tell us what make of map sensor it is, it will help.
dirty. I thought there was a small piece of carbon in there but it turned out to be black plastic- the cage around the sensor is made from this so I think it is damaged anyway. I was expecting to see some kind of a diaphragm but it seems to be a round semi-conductor with two pins which seems like it may hinge as the vacuum alters. I couldnt get any readings off it for resistance changing when I manually pushed it but maybe that's not how it works anyway. There was no maker's name or branding on it, just the number; 2382 323005 322. I replaced it and run the engine. When I put the voltmeter across it the engine faltered but there was no discernible reading. Since cleaning it the misfire is present all the time and worsens when it warms up so it would appear this is the cause. I would like to be 100% sure it is this as a replacement costs a fortune and once you order from Renault thats a life commitment. Any further info will be gratefully appreciated.
quite dirty. I thought there was a small piece of carbon in there but it turned
The R5 Spi engine is quite a rare beast, and I have not worked on or seen one in the flesh, but the component you mention should be capsule like with a small hole in it, where manifold vacuum can act through, and the small disphragm (1p piece size) is inside out of sight. It should be a 3 wire component anyway. Doesnt sound to me as if you are cleaning the map sensor!
Thanks for that, I dont think this has one. What I took to be a MAp is probably an inlet air temp sensor as it’s resistance falls from 2.8k ohms to 850 ohms as the car warms up. It’s one of two sensors in the manifold and sits in the air-flow, which is why I wrongly assumed it to be a MAP. The other is similar to the coolant sensors, i.e. a brass bolt-type, flat at the end, which goes into a blind hole on the manifold casting. This reads 3.4 ohms cold and falls to 350 ohms as the engine warms up. The Haynes says this model has a MAP. I‘ve followed all the hoses off the manifold and there’s definitely no MAP but I did find, ahem (embarrassed cough) an EGR. Sorry about that, but it looks nothing like the pics in the Haynes and its not in the place shown. This opens and closes when I suck on the pipe and there is voltage at the solenoid when the engine is running. I’m stumped. It’s obviously a heat-related thing as the misfire gets worse as it warms up but if those sensors are working correctly I cant think of anything other than the ECU.
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