Discussion
You'd struggle to get rich running at WOT; with that much air going through, the engine just loves all the fuel it can get its hands on. The worst case of overfuelling I ever experienced was when my ECU went on the fritz a few years back; it ran like a sack of hammers and used half a tank in 89 miles. The only time it would run at all properly was foot hard down, to get enough air in to dilute all the fuel. I 'fixed' it temporarily by unplugging half the injectors.
To get over-fuelling at full bore you'd probably need a blown PA transistor in the ECU, in which case you'd be lucky if the car would start, it'd be that rich (four injectors flowing 100%).
I'd be more inclined to look for UNDER-fuelling due to low fuel pressure or an ignition problem. The throttle pot is, to my mind, less suspect.
To get over-fuelling at full bore you'd probably need a blown PA transistor in the ECU, in which case you'd be lucky if the car would start, it'd be that rich (four injectors flowing 100%).
I'd be more inclined to look for UNDER-fuelling due to low fuel pressure or an ignition problem. The throttle pot is, to my mind, less suspect.
tony350i said:
Hi,
Could hesitation at wot be a mixture problem, would running rich possible be the calls.
Tony
Can you provide a better description of the problem, IE it happens on/off load or both. When you say hesitation, is the running becoming rough or is there just no power at top end etc etc.Could hesitation at wot be a mixture problem, would running rich possible be the calls.
Tony
Speculatively you could be right. Go for it!
But objectively, impossible to say without, at the very least, some decent clues, like plug colour, strange mpg, smell, smoke, straight lack or power, juddering, etc.
Or just as likely perhaps it is a symptom of general malaisse, in which case, a cost free tune up might be called for. That would check and fix everything.
Assuming the engine is in good mechanical condition with correct cam and lifter performance and timing, good compression within acceptable limits on all eight cylinders, good exhaust system with no leaks and fresh lubrication plus clean filters, then there are 15 easy steps to attend to with the Rover SD1 Efi V8 system to improve health/performance from its current condition.
1 Clean all ignition components externally and internally, spray with moisture inhibitor such as WD40 and wipe dry. Ensure the distributor vacuum and mechanical advance mechanisms are lightly lubricated, working correctly and the springs/bob weights are free of any corrosion.
2 Check security and eliminate any corrosion on all ignition Low Tension connections right back to the ignition switch, including all local earth connections.
Get some ideas here:
3 Clean and re-gap the spark plugs - replace if necessary.
4 Check for damaged or out of specification (measured suppression resistance) High Tension leads, Pay particular attention to the rubber boots. Clean and replace if necessary.
5 Set ignition timing to just eliminate pinking with normally available fuel.
See here for a neat process
(Note: Items 1-5 are to guarantee and maximise the best possible spark at exactly the right time. Check workshop manual for recommended component and timing specifications.)
6 Ensure the plenum idle air gallery is clear and not contaminated with goo.
7 Thoroughly clean the plenum breather gallery, flame trap and LH rocker cover breather filter
8 Ensure the throttle disc(s) is correctly seated at idle (or set to the recommended disc to tunnel gap where specified) to prevent "idle speed hang-up" and that the whole throttle mechanism is free of unwanted friction right through from accelerator pedal to throttle pot. (Note - items 6-8 are best performed by taking the Plenum Chamber to the workbench).
Go here for Plenum Solutions:
9 Set the AFM CO content to the recommended range erring just on the weak side of the mid-point. If a CO meter is not immediately available set the adjuster screw to 2.5 turns out, from fully home.
See here for AFM stuff:
Reset idle speed to the recommended level. The settings are interactive so recheck both.
10 Set the Throttle Position Sensor residual voltage to 325mv (some spec's call for 350mv). Ensure the sensor is not electrically noisy, causing random overfuelling.
See here for full detail:
11 Verify the fuel pressure operates in the range 26 to 36 psi. not more, not less.
Details here:
12 Test the integrity of the plenum and all its air/vacuum hoses for rogue air-leaks.
How To here:
13 Check all Efi loom wiring/connections for faults/corrosion including the Efi engine earth AND the engine earth strap.
Unusual Efi Earthing Issues here:...
14 Check and replace air and fuel filters if necessary. Ensure fuel tank is not generating crud.
15 Because the Plenum must be removed for proper cleaning and adjustment, lift and service the injectors, replacing filter baskets, pintle caps, fuel pipes and injector to manifold seals.
See here:
None of the above can yield anything over and above the system performance that existed when it was new but, be amazed at the horses the above program will release from a tired and maladjusted Rover SD1 Efi V8 system.
And the beauty of it is, apart from time, most of these actions are low cost, or cost free.
But objectively, impossible to say without, at the very least, some decent clues, like plug colour, strange mpg, smell, smoke, straight lack or power, juddering, etc.
Or just as likely perhaps it is a symptom of general malaisse, in which case, a cost free tune up might be called for. That would check and fix everything.
Assuming the engine is in good mechanical condition with correct cam and lifter performance and timing, good compression within acceptable limits on all eight cylinders, good exhaust system with no leaks and fresh lubrication plus clean filters, then there are 15 easy steps to attend to with the Rover SD1 Efi V8 system to improve health/performance from its current condition.
1 Clean all ignition components externally and internally, spray with moisture inhibitor such as WD40 and wipe dry. Ensure the distributor vacuum and mechanical advance mechanisms are lightly lubricated, working correctly and the springs/bob weights are free of any corrosion.
2 Check security and eliminate any corrosion on all ignition Low Tension connections right back to the ignition switch, including all local earth connections.
Get some ideas here:
3 Clean and re-gap the spark plugs - replace if necessary.
4 Check for damaged or out of specification (measured suppression resistance) High Tension leads, Pay particular attention to the rubber boots. Clean and replace if necessary.
5 Set ignition timing to just eliminate pinking with normally available fuel.
See here for a neat process
(Note: Items 1-5 are to guarantee and maximise the best possible spark at exactly the right time. Check workshop manual for recommended component and timing specifications.)
6 Ensure the plenum idle air gallery is clear and not contaminated with goo.
7 Thoroughly clean the plenum breather gallery, flame trap and LH rocker cover breather filter
8 Ensure the throttle disc(s) is correctly seated at idle (or set to the recommended disc to tunnel gap where specified) to prevent "idle speed hang-up" and that the whole throttle mechanism is free of unwanted friction right through from accelerator pedal to throttle pot. (Note - items 6-8 are best performed by taking the Plenum Chamber to the workbench).
Go here for Plenum Solutions:
9 Set the AFM CO content to the recommended range erring just on the weak side of the mid-point. If a CO meter is not immediately available set the adjuster screw to 2.5 turns out, from fully home.
See here for AFM stuff:
Reset idle speed to the recommended level. The settings are interactive so recheck both.
10 Set the Throttle Position Sensor residual voltage to 325mv (some spec's call for 350mv). Ensure the sensor is not electrically noisy, causing random overfuelling.
See here for full detail:
11 Verify the fuel pressure operates in the range 26 to 36 psi. not more, not less.
Details here:
12 Test the integrity of the plenum and all its air/vacuum hoses for rogue air-leaks.
How To here:
13 Check all Efi loom wiring/connections for faults/corrosion including the Efi engine earth AND the engine earth strap.
Unusual Efi Earthing Issues here:...
14 Check and replace air and fuel filters if necessary. Ensure fuel tank is not generating crud.
15 Because the Plenum must be removed for proper cleaning and adjustment, lift and service the injectors, replacing filter baskets, pintle caps, fuel pipes and injector to manifold seals.
See here:
None of the above can yield anything over and above the system performance that existed when it was new but, be amazed at the horses the above program will release from a tired and maladjusted Rover SD1 Efi V8 system.
And the beauty of it is, apart from time, most of these actions are low cost, or cost free.
Hi,
I think I found the problem, the magnetic pick up on the dizzy has two pin connections and one of these wasn’t very tight , gave it a little squeeze and drove the car to the Kent & Essex meet at power speed today it drove well, saw my first wedge 400 (red) and the rain stand away, and to top it all I watched my mate spin his striker as I was following him coming of a roundabout and he ended up face the wrong way, all ended ok no damage just hurt pride and he will have to get use to his new nick name (spinner) Lol
Thanks For all the ideas but Luckily it was a simple fix
Regards
Tony
I think I found the problem, the magnetic pick up on the dizzy has two pin connections and one of these wasn’t very tight , gave it a little squeeze and drove the car to the Kent & Essex meet at power speed today it drove well, saw my first wedge 400 (red) and the rain stand away, and to top it all I watched my mate spin his striker as I was following him coming of a roundabout and he ended up face the wrong way, all ended ok no damage just hurt pride and he will have to get use to his new nick name (spinner) Lol
Thanks For all the ideas but Luckily it was a simple fix
Regards
Tony
tony350i said:
the magnetic pick up on the dizzy has two pin connections and one of these wasn’t very tight , gave it a little squeeze and drove the car ........ at power speed today it drove well ...... Luckily it was a simple fix
Good news - but am I the only one struggling to see a connexion between a hesitation fault at WOT and a loose magnetic pick-up wire?There does not seem to be an engine energy/power related relationship.
Unless it was related to engine speed as opposed the throttle position where the pulsing output was simply dying at higher pulse rate?
But then it would also manifest itself in low gear - high rpm!
On the other hand, its working again, so no worries there then - (as Sparky's magic piano commented) - For Now!
Can anyone explain?
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