Rover Injection Diagnostic Help
Discussion
I've just finished installation of a 3.5L Rover V8 in an '87 280i. It's equipped with "hot wire" fuel injection system from an '89 Land Rover utilizing the 14CUX ECU.
It starts right up and (after running at 2500 RPM for a few seconds) settles down to a reasonably stable idle and seems to run fine. However, after reaching operating temperature, it starts surging drastically and erratically when you attempt to hold it at a cruise RPM (2000 to 2500). The RPM surges rapidly (at least once per second) by anywhere from 100 to 500 RPM. When driving, this surging becomes a severe bucking sensation that makes it impossible to actually drive, but it will "limp" home.
I've used my volt/ohm meter to check the integrity of everything I can (throttle position sensor, coolant temperature sensor, fuel temperature sensor, air bypass valve and oxygen sensors) and all check OK except for low voltage on the oxygen sensors. The documentation I've read says they should read anywher from 0.5 to 1.0 volts, but these are coming in at 0.12 and 2.0 volts. They were provided and installed by the shop that fabricated the exhaust system and are both NTK (NGK) units, but they don't seem to match and I'm unable to correlate the numbers stamped on them with any part numbers from the manufacturer.
Without access to a code reader, I can't be certain of the cause and was hoping someone might have some advice. I really suspect that the oxygen sensors are at fault. I've found some documentation on the proper wiring of standard 3-wire "Tritania" oxygen sensors, but can't be certain that I've got them wired properly. This is how I've got them setup:
O2 Sensor Black Wire <--> Rover Signal Wire (blue)
O2 Sensor Red Wire <--> Rover 12V+ Wire (white/orange)
O2 Sensor White Wire <--> Rover Ground Wire (black)
A code reader would certainly help, but thus far I haven't been able to locate one. Any sources would be helpful.
Also, apparently a different sending unit is required for the coolant temperature gauge. The one that came with the engine is giving false readings. Does anyone know a part number or a sender that will work with the VDO gauge in the TVR?
I really appreciate any help that anyone can provide. I've got a huge lump on my head from banging my head against the wall.
It starts right up and (after running at 2500 RPM for a few seconds) settles down to a reasonably stable idle and seems to run fine. However, after reaching operating temperature, it starts surging drastically and erratically when you attempt to hold it at a cruise RPM (2000 to 2500). The RPM surges rapidly (at least once per second) by anywhere from 100 to 500 RPM. When driving, this surging becomes a severe bucking sensation that makes it impossible to actually drive, but it will "limp" home.
I've used my volt/ohm meter to check the integrity of everything I can (throttle position sensor, coolant temperature sensor, fuel temperature sensor, air bypass valve and oxygen sensors) and all check OK except for low voltage on the oxygen sensors. The documentation I've read says they should read anywher from 0.5 to 1.0 volts, but these are coming in at 0.12 and 2.0 volts. They were provided and installed by the shop that fabricated the exhaust system and are both NTK (NGK) units, but they don't seem to match and I'm unable to correlate the numbers stamped on them with any part numbers from the manufacturer.
Without access to a code reader, I can't be certain of the cause and was hoping someone might have some advice. I really suspect that the oxygen sensors are at fault. I've found some documentation on the proper wiring of standard 3-wire "Tritania" oxygen sensors, but can't be certain that I've got them wired properly. This is how I've got them setup:
O2 Sensor Black Wire <--> Rover Signal Wire (blue)
O2 Sensor Red Wire <--> Rover 12V+ Wire (white/orange)
O2 Sensor White Wire <--> Rover Ground Wire (black)
A code reader would certainly help, but thus far I haven't been able to locate one. Any sources would be helpful.
Also, apparently a different sending unit is required for the coolant temperature gauge. The one that came with the engine is giving false readings. Does anyone know a part number or a sender that will work with the VDO gauge in the TVR?
I really appreciate any help that anyone can provide. I've got a huge lump on my head from banging my head against the wall.
Check the coolant temp sender first.
Also check whether the problem goes away at higher revs (say 3500 - 4000). If it only happens at mid/low revs under cruise conditions that may indicate that it's caused by a problem in closed loop operation. Assuming you *are* running with lambda sensors, check that they aren't crossed over as this will cause both sides to go to full correction. While it is in closed loop mode you should see both sensors cycling above/below 0.5V every second or so, this is the characteristic behaviour of a healthy system. Also check that you are getting the right reading from the tune resister.
Also check whether the problem goes away at higher revs (say 3500 - 4000). If it only happens at mid/low revs under cruise conditions that may indicate that it's caused by a problem in closed loop operation. Assuming you *are* running with lambda sensors, check that they aren't crossed over as this will cause both sides to go to full correction. While it is in closed loop mode you should see both sensors cycling above/below 0.5V every second or so, this is the characteristic behaviour of a healthy system. Also check that you are getting the right reading from the tune resister.
Yep, the problem does go away at higher revs and only seems to occur in the 2000 to 3000 RPM range. While I do have a 280i of my own and am sure I'll be envious of this one once it's sorted out, this particular car belongs to a friend and customer. He's extremely anxious to get it back on the road (it's been a year since the V6 self-destructed), so today I went ahead and ordered both O2 sensors (Bosch) and a new coolant temp sensor. My portion of this project has been to integrate the Rover electrics for the EFI and all the plumbing, and when working on the wiring I did my best (using multiple wiring diagrams, wire tracing and other docs) to verify that I had the injector harnesses matched with the proper lambda sensors. So, I'm pretty sure it's not a crossover issue, but I will make a point of rechecking. I did pull the NTK sensors and there are numbers stamped on the bases, but the guys at the NGK tech support line were unable to recognize them. So, the owner of the car decided to bite the bullet and go for new sensors. I'll post the results once they arrive and I get them installed. Thanks for all the feedback. -Bob
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