Engine misfire, 350i.
Discussion
Someone that has had the same problem or know how to trouble shoot? Any detailed literature available somewhere? I would be most grateful for any advise, please.
I Have a 350i from –87 with the Lucas “flap meter” fuel injection. It has started to misfire and quite badly, car can be driven but just about, if one really nurses the accelerator. As soon as anything but a throttle position for the lightest of loads is used it will start to spit and misfire. One can get it up quite high up in the revs, but again, only with a very light load.
It started while I was about an hour and a half away from home. As it didn’t and doesn’t have any tickover, idle, it died in a crossing and had to be pushed over to the nearest bus stop. I put the + wire to the battery off and took a closer look around the engine for any obvious faults but all appeared normal. Put the wire on again and tried a restart. On second attempt, then using half throttle, it started although roughly. One could hold it running cleanly at 2000 rpm and off we went to a nearby friend. There the procedure was repeated but nothing changed. I had to get it home so I took off and drove very carefully keeping the load as light as possible.
It worked out well and we came home allright. But the strange thing was that I felt that it running better and better. Near home I first noticed that the normal bop, bop, bop bludder was back when lifting off the throttle. Then I found it to idle normally and I could apply full throttle again without any bogging. Problem solved automatically???
Following day I tried to start again. It started but with a very pumping idle. Like 400 – 1000 rpm. When I applied some throttle to get it out of the garage it misfired quite badly and I could not get it to idle again so it died and didn’t want to restart. I had the spark plugs out and they were wet. Had the distributor off, nothing visually abnormal. I tried a restart again but was only successful after disconnecting the extra “choke” injector and “injecting” a light spray of ether. I drove the car for 20 minutes but it was as bad as before.
I brought out Steve Heaths Wedge maintenance book but in terms of fuel injection trouble shooting it is not detailed enough. At least not for me. For instance it gives some values for some sensor resistances, but not all sensors I can find on the engine, and without exactly describing where they are located. I tried to go for the first one listed, coolant temperature, assuming it is one of the two in front of the engine, between the distributor and the plenum chamber. One of them gave 50 ohms at +20C and 220 just over +60C. The other one gave no value at all. Steve lists 2500 ohms at +20C and 600 at +60. It feels like I’m trying to trouble shoot blindfolded.
Help!
I Have a 350i from –87 with the Lucas “flap meter” fuel injection. It has started to misfire and quite badly, car can be driven but just about, if one really nurses the accelerator. As soon as anything but a throttle position for the lightest of loads is used it will start to spit and misfire. One can get it up quite high up in the revs, but again, only with a very light load.
It started while I was about an hour and a half away from home. As it didn’t and doesn’t have any tickover, idle, it died in a crossing and had to be pushed over to the nearest bus stop. I put the + wire to the battery off and took a closer look around the engine for any obvious faults but all appeared normal. Put the wire on again and tried a restart. On second attempt, then using half throttle, it started although roughly. One could hold it running cleanly at 2000 rpm and off we went to a nearby friend. There the procedure was repeated but nothing changed. I had to get it home so I took off and drove very carefully keeping the load as light as possible.
It worked out well and we came home allright. But the strange thing was that I felt that it running better and better. Near home I first noticed that the normal bop, bop, bop bludder was back when lifting off the throttle. Then I found it to idle normally and I could apply full throttle again without any bogging. Problem solved automatically???
Following day I tried to start again. It started but with a very pumping idle. Like 400 – 1000 rpm. When I applied some throttle to get it out of the garage it misfired quite badly and I could not get it to idle again so it died and didn’t want to restart. I had the spark plugs out and they were wet. Had the distributor off, nothing visually abnormal. I tried a restart again but was only successful after disconnecting the extra “choke” injector and “injecting” a light spray of ether. I drove the car for 20 minutes but it was as bad as before.
I brought out Steve Heaths Wedge maintenance book but in terms of fuel injection trouble shooting it is not detailed enough. At least not for me. For instance it gives some values for some sensor resistances, but not all sensors I can find on the engine, and without exactly describing where they are located. I tried to go for the first one listed, coolant temperature, assuming it is one of the two in front of the engine, between the distributor and the plenum chamber. One of them gave 50 ohms at +20C and 220 just over +60C. The other one gave no value at all. Steve lists 2500 ohms at +20C and 600 at +60. It feels like I’m trying to trouble shoot blindfolded.
Help!
Sounds exactly like the problem i have with my 1988 350i. Went out for a drive was about an hour from home. Started and it was misfiring and did not really respond to the trottle. After trying to drive it looked as if the ecu had reset and drove pretty normal but it idled at 2000rpm for a few secondes and then just dropped and stopped running. Started alright and drove it back, trying to avoid stopping. When i got to my brothers house it wouldn't start again. After two hours waiting it finally did and kept misfiring the whole way home. Got the spark plugs out and were wet. Tried resetting the ecu several times but can't figure out what the problem is. If i get any further i'll let you know. Please let me know when you make any progress! Hope to sort it soon!!
>> Edited by bhardy on Sunday 3rd August 09:47
>> Edited by bhardy on Sunday 3rd August 09:47
Just simply dissconnecting the cold start injector doesn't sound like the solution for me, although it can get an engine running if one needs to limp home. It is there for a reason and something controls it because of certain sensed conditions. Better advise anyone or have I misunderstood something?
/ Hans
/ Hans
I tried the removing the cold starter injector but as you already said it only helps to start the car. I discovered that the hose between the plenum and the airflow meter had a larg tear in it and replaced it with a new one, but there's no improvement. Someone told me this could be caused by a backfire, which could demage the airflow meter......hope thats not the case here.
An intermittent throttle pot usually gives the symptom that the car won't cruise on a light throttle; idle can be erratic, but the car responds normally under acceleration and will attain usual full speed.
A faulty coolant temperature sensor (NOT the brown one!) can cause all sorts of problems: a quick way to test it is (if you can get the car to idle) unplug it. If the engine dies then the ECU is reading the sensor. No change may mean the sensor is defective, or you have a broken wire. Chances are, if a multimeter across the sensor terminals gives ANY reading, it's probably OK (it would normally fail completely open-circuit, though this isn't 100%).
A new sensor is only about 12 GBP from your local Land Rover dealer, so it's worth getting one just as a spare.
A common problem is bad solder joints in the ECU: one way to test for this might be to extract the ECU from under the dashboard, lay it on the passenger seat and go for a drive. Try tapping the ECU with a screwdriver handle: if you have an intermittent in the ECU this MAY show it up by the fault clearing, random improvement/ disimprovement of the fault - but may not, so could still be an ECU fault.
I have been spending a lot of time and money on learning the Lucas/ Bosch system: I am currently trying to identify the symptoms of a faulty air temperature sensor (in the airflow meter). This may be another fault you guys could have.
From recent troubles I've worked on, I'd say the quickest way to identify the area of fault is to get someone else with a V8 to swap parts between systems. I know some folk will threaten doom and gloom if you try this, and as an electronics engineer I wouldn't normally advise it, but you can certainly check out the airflow meter, ECU, injector resistor pack* and coolant temperature sensor in minutes. Just be aware that tuning differences exist between ECUs so you may find (as we did) that one ECU may cause one car to run smoothly and another to hunt a little at idle.
The thermotime switch (the brown sensor at the top front of the engine) and the cold start injector can be disconnected without any problem: during the summer I'd be surprised if the V8 really needs any cold start enrichment anyway.
* If you have a multimeter and want to test the resistor pack: unplug the 10-way connector. There are two rows of pins. Taking the top row as an example, the right-hand pin is common. The other four pins are the other ends of the four resistors in that bank. From common to any of the other 4 should measure about 6 ohms. The bottom row is the same except that the lefthand pin is the common.
Ian
A faulty coolant temperature sensor (NOT the brown one!) can cause all sorts of problems: a quick way to test it is (if you can get the car to idle) unplug it. If the engine dies then the ECU is reading the sensor. No change may mean the sensor is defective, or you have a broken wire. Chances are, if a multimeter across the sensor terminals gives ANY reading, it's probably OK (it would normally fail completely open-circuit, though this isn't 100%).
A new sensor is only about 12 GBP from your local Land Rover dealer, so it's worth getting one just as a spare.
A common problem is bad solder joints in the ECU: one way to test for this might be to extract the ECU from under the dashboard, lay it on the passenger seat and go for a drive. Try tapping the ECU with a screwdriver handle: if you have an intermittent in the ECU this MAY show it up by the fault clearing, random improvement/ disimprovement of the fault - but may not, so could still be an ECU fault.
I have been spending a lot of time and money on learning the Lucas/ Bosch system: I am currently trying to identify the symptoms of a faulty air temperature sensor (in the airflow meter). This may be another fault you guys could have.
From recent troubles I've worked on, I'd say the quickest way to identify the area of fault is to get someone else with a V8 to swap parts between systems. I know some folk will threaten doom and gloom if you try this, and as an electronics engineer I wouldn't normally advise it, but you can certainly check out the airflow meter, ECU, injector resistor pack* and coolant temperature sensor in minutes. Just be aware that tuning differences exist between ECUs so you may find (as we did) that one ECU may cause one car to run smoothly and another to hunt a little at idle.
The thermotime switch (the brown sensor at the top front of the engine) and the cold start injector can be disconnected without any problem: during the summer I'd be surprised if the V8 really needs any cold start enrichment anyway.
* If you have a multimeter and want to test the resistor pack: unplug the 10-way connector. There are two rows of pins. Taking the top row as an example, the right-hand pin is common. The other four pins are the other ends of the four resistors in that bank. From common to any of the other 4 should measure about 6 ohms. The bottom row is the same except that the lefthand pin is the common.
Ian
dickymint said:
Exactly what i was trying to say 
Hope you realise Ian that im keeping all your advice in a seperate file as my reference manual!
Hmmmm..... maybe I should write a book... before someone else does! How does that expression go... "I taught him everything he knows. But I didn't teach him everything I know..."
Ian
This looks like its worth a try:
www.carelect.demon.co.uk/rrind.html
Have someone any experiance?
/ Hans
www.carelect.demon.co.uk/rrind.html
Have someone any experiance?
/ Hans
After some searching around I got a new coolant temp sensor from a Volvo dealer... Fordlogic is it? (Sweden)
Plugged it in yesterday. It runs!! What a relief!
Thanks for the support everyone, it would have been ten times harder without you and I have began to understand the EFI a bit better now. Thanks again.
/ Hans
Plugged it in yesterday. It runs!! What a relief!
Thanks for the support everyone, it would have been ten times harder without you and I have began to understand the EFI a bit better now. Thanks again.
/ Hans
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