maestro turbo misfire

[henocsr]

I have just rebuilt the carb on my maestro turbo. It was running fine before hand, i need to replace the throttle spindle as the end was broken.

I have fitted new seals to the float chamber and dashpot, and i have replaced and adjusted the float. the needle valve and needle are still the same. I did how ever remove the stepper motor to check the o rings, which were ok, but as i had a brand new stepper motor i fitted that.

on refitting the carb the car started but would not go onto choke and ran with a large misfire. I then swapped back the oriangal stepper motor and the car wouldnt even start unless i gave it some throttle and when running it was misfiring.

The workshop manual says that you should never remove the stepper motor as it is pre set at the factory, but i guess others in the club have done so and not had any problems

anyone have any ideas?

[G Force]

Hi henoscr.

There should be no problems from removing and fitting the stepper motor, you just need to take care not to damage the O rings when refitting the motor.

As for the problem you need to double check all the pipes etc. are all correctly orientated and you have no air leaks from anywhere. Think back over what you have done to see if you can be totally sure you fitted and set everything up correctly.

Did you by any chance have to renew the plenumn chamber to carb gaskets, because although they look and fit ok, the turbo ones are different to the N/A ones??

Regards, G Force:)

[henocsr]

i havent renewed the gaskets as i did that only about 3000 miles ago when i built the engine, and i used a genuine turbo headset.
I will strip the carb again tomorrow and make sure the needle jet is sitting correctly. i removedthe float chamber vent pipe and with the starter solenoid wire removed i turned the key to postion 3 and the chamber didnt over fill out of the vent so i know that the new float is ok

[henocsr]

well i have got it running today needle valve was set to high:banghead:

Out of interest would a fuel ecu from an other electric carb model work on my car. I am suspecting the ecu a bit as the auto choke is still messing about.

Before christmas i had problems with it coming off choke to quick and cutting out. i replaced the coolant temperture sensor with a new genuie part and still the saem. Replaced the air temperture sensor and it is mcuh better, but driving home at night on christmas day when taking my foot off the throttle for roundabouts the cars idle dipped and the stepper didnt seem to want to do any thing about it. I have fitted a brand new stepper motor as i had one spare and after staring the car today it was still not right.

Starting the car from cold and leaving it running on the drive with out driving brings the choke on and it sits and starts to warm up but then you will notice the idle get less and less to the point the car cuts out. Restarting it it starts on choke and continues like this till the engine is warm, when it idles at 900rpm

Disconnecting the coolant sensor moves the stepper but not half as far as it should

[G Force]

well i have got it running today needle valve was set to high:banghead:

Out of interest would a fuel ecu from an other electric carb model work on my car. I am suspecting the ecu a bit as the auto choke is still messing about.

I don't see why not? A fuel ECU from a 2.0l carb variant should work ok enough to check whether or not you have a problem with the turbo fuel ECU.


Starting the car from cold and leaving it running on the drive with out driving brings the choke on and it sits and starts to warm up but then you will notice the idle get less and less to the point the car cuts out. Restarting it it starts on choke and continues like this till the engine is warm, when it idles at 900rpm

Disconnecting the coolant sensor moves the stepper but not half as far as it should

If you disconnect the coolant sensor when hot and the engine speeds up but not enough, you can adjust the fast idle speed on the fast idle adjuster to achieve a speed of 1100 +/- 50 rpm.

When you converted the EFI to turbo did you wire in the ambient air temp sensor, the little black oblong one with two brass lucar connectors, that sits in the loom on the N/S inner wing? If so check that its resistance is in tolerance with the temperature.

Did you also fit a throttle pedal switch to the throttle pedal assembly, because the EFI does not have one fitted? If so check that it is operating correctly.

The idle speed control needs both these inputs to control the idle speed and warm up, any problems with either and you will have idling issues, particularly noticeable in the extreme weather we are having.

When you built the engine etc. did you notice the small plastic "top hat" restrictor in the breather hose that connects to the inlet manifold. It sits on top of the one-way valve that screws into the inlet manifold, then the rubber breather pipe pushes over the top of it.

Without the restrictor you cannot get the car to idle properly and it also affects the co setting. You end up having to screw the mixture screw in too far to compensate for the extra air at idle, then you can't always get the idle speed setting slow enough. The restrictor can sometimes get stuck up inside the breather hose sideways, causing a similar problem.


Regards, G Force:)

[henocsr]

well i have been messing about with it today. It now refuses to come on to choke. The stepper motor works (goes fully in when coolant sensor wires joined and goes fully out when coolant sensor open circuit)

I guess one of the choke holes is blocked, it runs fine when it is warm, its just the choke.

When i converted to turbo i used a complete vehicle loom from a maestro turbo fuse box, engine harness etc. The car is just like a factory turbo (apart from the body kit)

the toohat breathr restricor was missing on the donor car show i used a modified washer pipe joiner, it has been fine though i have ordered a geniue part (hopfully it is still avaiable system says it is though you never know 100% till it goes to the warehouse

It was running fine till christmas night when it started messing its idle when slowing down, and it always started on choke perfectly (till the stepper would wind it back before the car had warmed)

[G Force]

Hi henoscr

I have come across slithers of rubber in the choke passage and in the main jet on a few occasions especially when the carb or stepper motor have been removed, so that like you say is a possibility.

The bleed hole for the restrictor is only about 1.5mm, if that helps?

Worth checking if the stepper motor comes onto full choke when the ign is first turned on when cold, because when the coolant sensor plug is removed (open circiut) that only moves the stepper motor to fast idle not full choke.

Regards G Force:)

[henocsr]

Right

I found a broken wire coming out of the coolant sensor causing it when warm not to come off fast idle. Repaired the wire and removed the dash pot and reset the needle valve. Turned the key and it started first time, no misfiring etc, ran till warm came of choke and was perfect..........................but the car yesterday morning was not cold due to the sun.

Retryed this morning and although it started and will run it misfires, the misfire improves as it warms up and disappares in the end

[G Force]

Retryed this morning and although it started and will run it misfires, the misfire improves as it warms up and disappares in the end

Hi henoscr, could the misfire be related to something else, like say the HT leads?

[henocsr]

well it could be i guess, damp could have got into them over the 2 weeks it has sat.

I will try a set of leads tomorrow first thing in the morning and see if it misses. I will be annoyed if it is the leads as they are not even a year old

[henocsr]

well i have sorted it:)

i found the carb vent valve was sometimes opening and closing causing the problems. i fitted a manula choke to confirm if the auto choke was the problem and i found that the car still behaved in the same way.

I have removed the valve and blocked the pipe for now and refitted the auto choke. I also fitted a new amibant temp senor behind the indicator as theold one was going open circiut when below 3 degrees were the new one doesnt.

Just fitted my rust free tailgate as well only need to drill the millon holes for the spoliers now:D oh and tax it and get it back on the road ready to move house