350 FHC running like a dog
Discussion
Seems my car really doesn't want me to go the BBWF. It is sputtering, and backfiring and generally not happy.
I replaced the headgaskets a few weeks back, new rotor arm, dizzy cap, HT leads and plugs and it ran sweet as a nut. Then the rear exhaust section fell off, and it started to get very unhappy when warm. I noticed that I now have a bit of burned carpet where the exhaust would be blown onto the bodywork, just below the fuel tank. The exhaust is now fixed, with s/s headers, centre and rear sections, but she became very unhappy.
From cold overnight she would drive fine upto about 60c coolant temp, and then bog down, stalling at junctions etc. However if left for an hour over lunch, she ran fine with a hot engine on the way back to work. I used to get 250miles from a tank of fuel that is now down to 150 !
So I've checked the following by substitution: AFM & ECU - still the same. Checked the coolant sensor and air sensor as per the EFI tests 8,9,10,11A all fine. Tested the Throttle pot - seems ok. Tested the fuel pressure - 2.75Bar no vacuum, down to 2.2 Bar with Vacuum (a little high). I then checked the timing marks on the pulley, with a dial guage in number one cylinder, it was 2 degrees out, corrected the timing from 10 BTDC to 4, and she is now much, much worse. Plug #1 is black as sin, and a bit oily, and I get lots of unburned fuel comming out. I've got NGK BPR6E plugs in with 0.85mm gap - surely these plugs are hot enough to burn the crud off? I have been driving to/from work 10 miles ish each way - but all was fine till the exhaust fell orft.
Any suggestions, before I go totally berzerk ? (Yes, I do have fire insurance, but probably not a good idea).
-Stressed Jim
I replaced the headgaskets a few weeks back, new rotor arm, dizzy cap, HT leads and plugs and it ran sweet as a nut. Then the rear exhaust section fell off, and it started to get very unhappy when warm. I noticed that I now have a bit of burned carpet where the exhaust would be blown onto the bodywork, just below the fuel tank. The exhaust is now fixed, with s/s headers, centre and rear sections, but she became very unhappy.
From cold overnight she would drive fine upto about 60c coolant temp, and then bog down, stalling at junctions etc. However if left for an hour over lunch, she ran fine with a hot engine on the way back to work. I used to get 250miles from a tank of fuel that is now down to 150 !
So I've checked the following by substitution: AFM & ECU - still the same. Checked the coolant sensor and air sensor as per the EFI tests 8,9,10,11A all fine. Tested the Throttle pot - seems ok. Tested the fuel pressure - 2.75Bar no vacuum, down to 2.2 Bar with Vacuum (a little high). I then checked the timing marks on the pulley, with a dial guage in number one cylinder, it was 2 degrees out, corrected the timing from 10 BTDC to 4, and she is now much, much worse. Plug #1 is black as sin, and a bit oily, and I get lots of unburned fuel comming out. I've got NGK BPR6E plugs in with 0.85mm gap - surely these plugs are hot enough to burn the crud off? I have been driving to/from work 10 miles ish each way - but all was fine till the exhaust fell orft.
Any suggestions, before I go totally berzerk ? (Yes, I do have fire insurance, but probably not a good idea).
-Stressed Jim
Forgot to mention, I have replaced the Air filter and fuel filter too.
Yes, Coolant sensor fine at ECU plug, and makes no difference if substituted for a fixed resistor when engine hot.
Will be replacing the plugs with heat range 5, which is a bit hotter, and listed for the Land rover 3.5 V8, and doing a Compression test today...
She was running a bit rough before the head gasket replacement, and also afterwards until I changed the plugs - number one plug was misfiring only. After a few tank fulls of fuel, a more aggressive rough running set in, as if all 8 plugs are fouled. I think the previous plugs were heat range 5 too, so maybe the previous Owner was trying to correct for wet fouling.
-Jim
Yes, Coolant sensor fine at ECU plug, and makes no difference if substituted for a fixed resistor when engine hot.
Will be replacing the plugs with heat range 5, which is a bit hotter, and listed for the Land rover 3.5 V8, and doing a Compression test today...
She was running a bit rough before the head gasket replacement, and also afterwards until I changed the plugs - number one plug was misfiring only. After a few tank fulls of fuel, a more aggressive rough running set in, as if all 8 plugs are fouled. I think the previous plugs were heat range 5 too, so maybe the previous Owner was trying to correct for wet fouling.
-Jim
jchase said:
Forgot to mention, I have replaced the Air filter and fuel filter too.
Yes, Coolant sensor fine at ECU plug, and makes no difference if substituted for a fixed resistor when engine hot.
Will be replacing the plugs with heat range 5, which is a bit hotter, and listed for the Land rover 3.5 V8, and doing a Compression test today...
She was running a bit rough before the head gasket replacement, and also afterwards until I changed the plugs - number one plug was misfiring only. After a few tank fulls of fuel, a more aggressive rough running set in, as if all 8 plugs are fouled. I think the previous plugs were heat range 5 too, so maybe the previous Owner was trying to correct for wet fouling.
-Jim
Yes, Coolant sensor fine at ECU plug, and makes no difference if substituted for a fixed resistor when engine hot.
Will be replacing the plugs with heat range 5, which is a bit hotter, and listed for the Land rover 3.5 V8, and doing a Compression test today...
She was running a bit rough before the head gasket replacement, and also afterwards until I changed the plugs - number one plug was misfiring only. After a few tank fulls of fuel, a more aggressive rough running set in, as if all 8 plugs are fouled. I think the previous plugs were heat range 5 too, so maybe the previous Owner was trying to correct for wet fouling.
-Jim
If it's any use - I run B7 ECS NGK's..
Jim - before you thought it was running lean. But now the plugs are all carbonised - that points to too rich (that and the milage per tank!).
In which case could it be the connection to the temp sensor sender - or the wiring? If it goes o/c then it will run too rich.
I would check the resistance of the sender, then again from the ECU multiplug, to see if the wiring is dodgy. Also clean the contacts on the sender plug on the loom.
In which case could it be the connection to the temp sensor sender - or the wiring? If it goes o/c then it will run too rich.
I would check the resistance of the sender, then again from the ECU multiplug, to see if the wiring is dodgy. Also clean the contacts on the sender plug on the loom.
wedg1e said:
Just get it there Jim, we'll fettle it 
I'll Stick a few bits of test equipment in the boot(such as it is!). Vaccum pump/tester
compression tester
EFI fuel pressure guage (adapted to fit in place of the cold start injector)
and the trusty DVM.
Edited by leorest on Saturday 15th July 08:21
Cheers leorest, But I already have all those toys, and still she is unhappy.
New coolant sensor in - no change, new set of plugs - no change. New plugs are very sooty, which implies rich running. I tried all day to find a 2.5 Bar regulator (presuming the 2.75 bar reading I get is the cause), but the nearest place was Boston, a two hour drive, and of course the car won;t drive! They seem like nice blokes - they map webber Alpa injection systems.
As a last ditch attempt I have thrown some injector cleaner into the tank, and run the car for 20 minutes - fan kicked in, and the engine stayed at an indicated 95 constantly. Now I seem to remember the fan would kick in and out intermittently when I was in a traffic jam in Germany last summer where the outside temperature was comparable to today. So she be running hot, and yet rich, maybe I'll have to christen her Paris...
-Jim
New coolant sensor in - no change, new set of plugs - no change. New plugs are very sooty, which implies rich running. I tried all day to find a 2.5 Bar regulator (presuming the 2.75 bar reading I get is the cause), but the nearest place was Boston, a two hour drive, and of course the car won;t drive! They seem like nice blokes - they map webber Alpa injection systems.
As a last ditch attempt I have thrown some injector cleaner into the tank, and run the car for 20 minutes - fan kicked in, and the engine stayed at an indicated 95 constantly. Now I seem to remember the fan would kick in and out intermittently when I was in a traffic jam in Germany last summer where the outside temperature was comparable to today. So she be running hot, and yet rich, maybe I'll have to christen her Paris...
-Jim
Fixed (I think) Turned out to be the damned Vacuum Delay Module. The car now cruises at 82 Celcius instead of 90, and after a brisk run, the temp rises to a mere 92, not >100 !
She now is capapable of pulling away from the lights in 4th gear, and is happy to be driven as low as 400rpm. So far, no misfires (finger crossed)
My Fuel pressure gauge turned out to be inaccurate, as I replaced the fuel regulator with a 250kPa unit and got a reading of 2.80 bar as opposed to 2.75 Bar.
So, what this vacuum delay thingy does, and what its time constant should be is a mystery to me. But it is acting like a one-way valve at the moment.
-Jim
She now is capapable of pulling away from the lights in 4th gear, and is happy to be driven as low as 400rpm. So far, no misfires (finger crossed)
My Fuel pressure gauge turned out to be inaccurate, as I replaced the fuel regulator with a 250kPa unit and got a reading of 2.80 bar as opposed to 2.75 Bar.
So, what this vacuum delay thingy does, and what its time constant should be is a mystery to me. But it is acting like a one-way valve at the moment.
-Jim
It's supposed to be a leaky one-way valve. But sometimes it stops being leaky, or stops being a one-way valve, or just gets connected back to front by mistake. Basically a nightmare waiting to happen, and I suggest you get rid and replace it with a plain pipe at the first hint of a suspicion of a potential problem.
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