Bogging at 4000 rpm

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Bogging at 4000 rpm

Post by toolmanchris » Tue Nov 21, 2017 10:32 am

I suppose if its not working properly it could also be messing about with the fuel/air ratio at higher speeds as well?


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Bogging at 4000 rpm

Post by scimjim » Tue Nov 21, 2017 10:44 am

High idle speed is probably because the throttle plates aren’t fully closed.


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Bogging at 4000 rpm

Post by DARK STAR » Tue Nov 21, 2017 12:31 pm

The idle speed control has always been like that, it doesn't bother me (and it has never bothered the engine - it was quicker than a 300+ bhp Corvette to 240 km/h)
I just thought I'd mention it.
I presume it is always in cold start mode :roll:

So, do we think it is a good idea to change the TPS?
Or try the new ECU before I send it back to Andy?


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Bogging at 4000 rpm

Post by tony.idle » Tue Nov 21, 2017 3:32 pm

I've just read this posting end-to-end and haven't seen a single mention of beating it with a large hammer so ..... well done everyone for having the patience. I've had a possibly irrelevant thought though: I noticed that the plug leads appear to be very close to, or even mixed with, wiring to the ECU. Is it possible to move the HT leads away from other wiring a little? It is possible that the engine shifting due to the failed gearbox mount has moved the relationship of HT leads to loom wiring. And have you changed the plugs recently? If you have did you use resistor plugs?


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Bogging at 4000 rpm

Post by DARK STAR » Wed Nov 22, 2017 5:32 pm

Thanks Tony, plugs are new and listed for 2,9, no idea if they are resistor plugs.
I'll have a look at the wiring runs.

Today I had an opportunity to take the car out and found yet another strange happening.
After a few days off, when plugged back in the idle speed control seems to work (for the first time ever :shock: )
This means that when cold the engine idles at 1300 rpm dropping to the usual 1100 rpm when hot.
If this continues I will have to look at adjusting those much-discussed throttle plates ...

It still doesn't like accelerating.


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Bogging at 4000 rpm

Post by tony.idle » Wed Nov 22, 2017 8:51 pm

Chris

There are still too many variables: remove and thoroughly clean the ISC. Do the same with the throttle bodies / MAF metering and while you're at it check butterfly operation and static setting - reset it as the manual suggests. Check when it's reconnected that you are getting WOT with the pedal to the floor. You need to ensure that basic adjustments are correct and that everything that can be visually checked has been before continuing to hunt down the fault. It doesn't matter whether any part mentioned above is causing the fault. At this age all engine controls need to be checked / serviced anyway. Doing that will eliminate a lot of unknowns and the fault might just be spotted when doing so.


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Bogging at 4000 rpm

Post by DARK STAR » Sun Nov 26, 2017 5:20 pm

Meanwhile, back at the asylum, I ordered a TPS, medium price, for '92 Scorpio.
It doesn't fit ...
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Bogging at 4000 rpm

Post by DARK STAR » Sun Dec 03, 2017 4:26 pm

After that brief excursion into fantasy land (they are refunding me even my return postage :-) )
I tried to adjust the throttle plates, but either I don't understand the instructions, which is quite likely, or they are already at ground zero.
The operating lever wasn't even touching the throttle stop, still isn't, just in case it decides to adjust itself as the idle speed control did :roll:

So I changed my ECU with Superchip for Andy's without - and eliminated two possible causes at the same time.
The difference was noticeable without the Superchip, slightly lower idle speed and much smoother take up at low revs.
But it still wouldn't rev ...

I may try getting under the beast and checking the fuel pump and filter, they are recent but the symptoms are classic fuel starvation.
I have a spare pump but it's Ford so of course the inlet/outlet are not standard :bh
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Bogging at 4000 rpm

Post by Coupe Racing » Sun Dec 03, 2017 5:36 pm

Has the fuel pressure been checked and the vacuum at the fuel rail regulator ( if fitted )


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Bogging at 4000 rpm

Post by DARK STAR » Sun Dec 03, 2017 5:51 pm

I can't remember, it's been going on so long (and I get confused with my two other cars which have not been working properly :roll: )
I've nothing to measure the pressure but I seem to think I checked petrol was passing and commented that it didn't seem a very strong flow.
There is a pressure regulator fitted - and I can never work out which is the entry and which is the exit :mrgreen:
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Bogging at 4000 rpm

Post by Coupe Racing » Sun Dec 03, 2017 10:19 pm

The flow should be quite dramatic as EFI requires pressure
I would check the fuel pressure


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Bogging at 4000 rpm

Post by DARK STAR » Sun Dec 03, 2017 10:23 pm

Back to the hot-wiring !
It's just a bit irritating to take the boot interior to bits each time :roll:


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Bogging at 4000 rpm

Post by DARK STAR » Fri Dec 15, 2017 4:56 pm

Been a bit busy but finally got back to the job in hand.

With the boot strewn around the garage and odd wires all over the place I took the (wrong) hose off the pressure regulator and squirted petrol all over the engine.
Put it back and took off the correct hose, fuel flow looked feeble and this was confirmed at less than a litre per minute (600cl in fact) !
Even to a bear with very little brain it is obvious that this is not enough for an engine of over 200 bhp.

So I took some more of the boot to bits and disconnected the fuel pump to see how much it was pumping.
This was somewhat different, at 4 litres per minute, and would probably fill the inspection pit in about half an hour.
That meant that the filter was prime suspect so I checked that in turn, getting only just over a litre per minute out of it (1,3 litres).

First things first, I opened up the filter and found it clogged with black deposit :shock:
I only ever use branded 98 octane without ethanol so what is all this crap in the filter?
I cleaned it all out and will put it back tomorrow, it is the hour of the 'apéro' and my beer won't wait.

Two questions, is it normal to have such a drop in flow rate between the back and the front, most of the pipe run is original black nylon tube with good quality braided flexibles each end ?
And if it is, would the 2-ish litres per minute which arrive at the engine be sufficient ?
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Bogging at 4000 rpm

Post by Coupe Racing » Fri Dec 15, 2017 5:23 pm

If the fuel flow at the entrance to the fuel pressure regulator is high , and low after the regulator , then the regulator is doing its job by creating high pressure in the fuel rail to feed the injectors . The pressure is required to aid fuel atomisation


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Bogging at 4000 rpm

Post by DARK STAR » Fri Dec 15, 2017 5:30 pm

It was the feed pipe to the regulator Steve.
The pressure put out by the pump is 4 litres per minute, the (clean) filter shouldn't reduce that but the pipe run seems to.
I'll check the actual flow at the regulator tomorrow.
But the question is how much petrol should be feeding the regulator so that it can create the necessary pressure ?
If I had the slightest idea how to convert flow rate into pressure it might help 8)


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