Scorpio engine help needed, please...

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caleyfan
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Scorpio engine help needed, please...

Post by caleyfan » Sat Aug 10, 2013 6:28 pm

I have a Scorpio with an engine problem that I'm struggling to solve.

Here's a description of what's happening;
The engine will start after several attempts but only if you feather the throttle. Once the engine starts you can only keep it running if you constantly feather the throttle. If you try to hold the revs at any speed the engine will just fade and die unless you start feathering the throttle again. The maximum RPM achievable is between 2000 and 2500. If you try to run it above around 2500 the engine chokes and starts to die.
I have been able to keep the engine running by feathering the throttle until the engine reaches normal temperature and then it is possible to get it to idle on it's own for 10-15 seconds before it dies again. When it starts to die you can keep it going by feathering the throttle again.
When it is running it sounds OK - no popping or roughness.

Here's what I've done so far;
New distributor cap
New plug leads
Cleaned and set gaps on plugs
Spark present on all plugs
Primary coil and secondary coil resistances are in spec
Connected OBD1 reader and no fault codes displayed.
Have not been able to check timing because I cant get to the engine bay in time to keep it running to use my strobe, however, I have made fine adjustments to the distributor to see if timing makes any difference but it seems to run best where it is set.

I have just about run out of ideas. I have not checked the injectors yet but looking at the plugs the combustion in all cylinders seems to be OK, maybe a bit rich, so I think the injectors are OK?

One thing I have noticed is that I'm not seeing any condensation coming from the exhaust, which seems a bit odd.

If anyone has any suggestions I would be really grateful as I'm not sure where to go next.
Thanks.

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Re: Scorpio engine help needed, please...

Post by Bob Weir » Sat Aug 10, 2013 11:14 pm

Move crank to 10 deg remove dizzy cap & move dizzy so rotor is at #1 cyl to set base timing. Buy water temp sensor (under throttle body). This sensor known to fail & cause no start. Because EEC doesn't have correct eng temp to regulate mixtures.

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Re: Scorpio engine help needed, please...

Post by scorpioaddict » Sat Aug 10, 2013 11:19 pm

Bring a wire from the starter solenoid up top, reachable from the front of the car. Then you can just jump it to the battery and start the engine, w/o having to crawl inside, etc.

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Re: Scorpio engine help needed, please...

Post by Ed Lijewski » Sun Aug 11, 2013 8:19 am

Interesting. No codes found suggests the coolant temp sensor is OK (but I'd run the check again to be sure). No condensation suggests the catalytic converter isn't hot enough (because the engine won't stay running). Symptoms may suggest fuel or/and air starvation. Replacing air and fuel filter can't hurt and might help. Checking fuel pressure would also be good to do. The symptoms don't point to a vacuum leak but I'd check for that as well.

YMMV ;-)

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Re: Scorpio engine help needed, please...

Post by caleyfan » Sun Aug 11, 2013 9:58 am

Thanks everyone for your help so far.
Here's an update on additional tests etc;

The ACT sensor appears to be ok (at least at room temp) - I measured 29.7K ohm at ambient temp (75 deg F) which would appear to be in spec.

I ran the OBD1 test several times again and got a pass each time.

I have removed and cleaned the air filter and box. It was fairly clean but it's now very clean.

I was able to keep the engine running long enough (by constant feathering of throttle) to get it up to normal operating temp. Temp gauge registered ok so water sensor appears to be ok.

At normal operating temp the engine was willing to idle a bit without stalling. When it's cold it will stall immediately if you are not feathering the throttle. At normal operating temp it would idle for 10-15 seconds before stalling. During this time it does hunt around if left to it's own control ie sits at around 900 rpm but will hunt up to 1100/1200 and drop to 400/500. It manages to keep adjusting for a while but eventually the revs will drop so low it can't recover. When it's cold it will not run at all on its own.

When at normal operating temp the max possible rpm is still around 2500 - you cannot get it to go higher.

I'll post more info as I discover more.

My next steps are to test injectors, fuel pump pressure, fuel filter and remove / check air inlet manifold. Any other suggestions would be gratefully received.

Thanks.

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Re: Scorpio engine help needed, please...

Post by Ed Lijewski » Sun Aug 11, 2013 10:21 am

Just to confirm the air filter isn't restricted remove it during one of your next tests. FYI, the engine temp sensor is not the critical sensor referred to above-that one is separate and is the engine coolant temp sensor which the ECU relies on to adjust fuel mixture. Both those sensors are located next to each other underneath the throttle body. If you do remove the TB to clean it, that's the time to install a new one just because ... The ACT sensor shouldn't be involved with your issues. Along with cleaning the TB also thoroughly/thoroughly clean the idle air control valve.

How many miles on the car? Is the gas in the tank fresh?

YMMV ;-)
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Re: Scorpio engine help needed, please...

Post by caleyfan » Sun Aug 11, 2013 11:03 am

Thanks for the clarification on the sensor Ed.
I will go ahead and remove the TB and replace the temp sensor. I'll also make sure I clean the idle air control valve.

In the mean time I'll try running without the air filter. I agree it does behave like an air / fuel starvation issue but there's probably several issues at play.

I really don't know about the fuel. I thought about that too. I believe it has been sat for some time and there are only a couple of gallons in the tank so I will try to siphon this out and add a couple of gallons of fresh fuel. As for miles I believe it's done around 70k? The installed speedo shows 13K but the original speedo is in the trunk and shows 57K. Looking at the wear on the seats I'd say 70K would be close to the mark.

Thanks again.

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Re: Scorpio engine help needed, please...

Post by In XS 7 » Sun Aug 11, 2013 5:55 pm

Yup, if I were you I will replace the gas in the tank with some gallons of fresh gas first and give it a try, seems like that can be your issue, or the car is starving. My money is in a gas issue. :cheers
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Re: Scorpio engine help needed, please...

Post by Father Adam » Mon Aug 12, 2013 5:19 am

I'd agree with that, old stale petrol will cause all sorts of running problems :roll:
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Re: Scorpio engine help needed, please...

Post by DAReese » Mon Aug 12, 2013 9:17 am

Father Adam wrote:I'd agree with that, old stale petrol will cause all sorts of running problems :roll:
If you believe it is a fossil fuel, it is all old.
David Reese

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In XS 7
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Re: Scorpio engine help needed, please...

Post by In XS 7 » Mon Aug 12, 2013 1:17 pm

DAReese wrote:
Father Adam wrote:I'd agree with that, old stale petrol will cause all sorts of running problems :roll:
If you believe it is a fossil fuel, it is all old.
Yes, but you can't make a car run with it in it's original/raw state, and after the process to turn the raw oil into gasoline/petrol it will loose it qualities to be used in a car after some time and evaporation plus contamination don't help either, even a little bit of water in that fuel will ruin it. :cheers
Miguel.
89 XR4Ti Monique; Waking up a real "Night/Mare-Coor".
T5, NPR IC, PIMP ECU, Walbro 255, Dual piston BOV, Manual BC, 3" exhaust, One piece Aluminum drive-shaft, mc2 LSD, Boport 1.5 cam, Ported and polish head, big valves, 80# injectors, Bob's log, (soon HY35).

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Re: Scorpio engine help needed, please...

Post by caleyfan » Mon Aug 12, 2013 10:47 pm

Thanks everyone. I really appreciate all your advice.
Before I start stripping the fuel system and intake manifold I will remove the fuel in the tank and replace it with some ethanol free gas (I have a station that sells this just a mile from my home).
I'll let everyone know what happens when I get this done.

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Re: Scorpio engine help needed, please...

Post by Ed Lijewski » Tue Aug 13, 2013 7:37 am

Change the fuel filter before any "stripping".

YMMV ;-)
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Re: Scorpio engine help needed, please...

Post by ford.scorpio » Tue Aug 13, 2013 11:23 pm

How's your TPS? I have seen some whacky issues over the years caused by these little sobs.....

Funny thing; sometimes they show up on your reader; sometimes they don't.

Personally, I always travel with spare TFI and TPS in my glove-box.....
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Re: Scorpio engine help needed, please...

Post by caleyfan » Sat Aug 24, 2013 5:45 pm

Sorry I have not posted an update for a while but my wife has been ill and I've not had time to do anything on the car until today.

Here are the latest tasks I have completed;
Drained fuel tank. Replaced fuel filter (found the old one was not blocked) and added new fuel - no real change. The engine seemed to run a little better when I could get it to run but that was probably down to the new fuel?
I checked the fuel delivery pressure at the fuel rail and found it only reads about 7psi and as soon as the pump is deactivated the pressure drops to zero almost immediately, so it's looking like a fuel pump issue.
I have drained the tank again and will begin removing it as soon as I can to get to the pump to see what's going on.

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