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happypatrol

Engine splutter on hard acceleration. Some tec Questions

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happypatrol

Having just finished the worlds slowest engine rebuild I am at the end of my tether with this car now.

 

Engine starts and runs perfect.  Idles great. Revs up freely when the car is not moving.  No smoke etc.  Would appear to be running perfectly.

 

When I accelerate hard from 2000 up to 4000 odd RPM I have this weird engine splutter where it struggles to build up revs.  The harder you accelerate the worse it is.  If you come off the throttle a little it subsides.  And as I say if you drive like a granny it is fine.

 

So far I have changed the following.

 

Air flow meter

Ignition amp

Coil

Distributor with 2 different units one which is brand new.

 

I've spent countless hours on this and it is still the same.

 

My plugs are burning clean, no black carbon or white build up either.  It also passed its emissions on MOT no problem.

 

 

One thing I did try was to unplug the coolant temp sensor when the engine was running but this caused the engine to cut out.  This sensor is also brand new.

Can anyone advise on this or recommend a garage in Glasgow area that could assist.

 

Is this something which could be diagnosed on a rolling road...?

Does any one know if there is a way to figure out if it is a fuelling issue or an ignition issue.?

Should there be a air/valve on the ignition advance?  I have a little one way valve but don't see these mentioned anywhere.?  Have tried it on/off/round both ways. makes no difference.

Can you mix up the injector multi-plugs.  Are they specific to each injector 1234...?

 

Any help would be great.

 

Cheers

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Tom Fenton

How old is the petrol in the tank, I've once had a similar issue with a car that had been stored for a long time, a fresh tank of fuel and it was back to normal.

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jackherer
49 minutes ago, happypatrol said:

Can you mix up the injector multi-plugs.  Are they specific to each injector 1234...?

No, they batch fire and are all wired together.

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happypatrol

Cheers for that Info. I thought as much and I had marked them at the time anyway. 

 

@tom.  The car had ran out of fuel just after the rebuild. I have since been to the petrol station and refilled. I will however keep driving it and use what is left up and refill. It is just so annoying as u can’t accelerate or it just bugs down

and does t really  go any faster. 

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happypatrol

Could the fuel filter be partially blocked?

 

Im not sure how the fuelling works.  Does it require more fuel pressure when under acceleration or if it idles ok would this rule out fuel pressure issue?

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Tom Fenton

Certainly for the minor cost I’d change the fuel filter to rule it out.

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jackherer

I would take the fuel injectors and fuel rail off then turn the engine over with them aimed into a bucket or something so you can see if they are all working well and equally. I would also take the fuel pump cradle out of the tank to inspect the short hose from the pump itself to the top of the cradle, I've seen these almost dissolved due to the ethanol content in fuel these days.

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happypatrol

Fuel fliter is ordered.

 

Will check the tank too.

 

and the injectors.  I can look at the spray pattern too.  It was running fine before I stripped it.  I thought electrical but im sure if it was a broken wire it would more than likely not run at all.

 

Is it normal that it would cut out when I disconnect the coolant temp sensor though?

 

Cheers guys

 

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jackherer

Yes, when you disconnect the ECU coolant temp sensor it injects the fuel that would be required at -20c or something which is way too much at normal temperatures therefore it cuts out.

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happypatrol

That makes sense.  Well that is also working properly then. hahah.

 

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jackherer

It's working to some degree! There is still a chance it could have a minor fault. I would expect it to be lumpy at idle too if it was faulty but you never know...

 

To thoroughly test it you need to measure the resistance of the sensor with a multimeter with the coolant at a known temperature. Then you need to measure the resistance at the relevant ECU pins too in case there is a wiring problem in between.

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PhilNW

Check the fuel pump pressure/regulator, it may be getting short of fuel at higher revs

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Gaz205

I chased my tail with exactly the same issue. Had the injectors cleaned, New fuel filter, amp paste, New plugs and leads, swapped dizzy.....

The fault was a seal in the fuel pump dropping pressure. When that was repaired it turned out the pressure regulator had been bodged to allow the lower pressure so fitted a replacement and the car runs perfectly making 112bhp (with a pinch of salt)

I wish I'd had the fuel pressure checked before shelling out.

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jackherer

What seal in the fuel pump? There aren't any that I'm aware of.

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DamirGTI

There's two seals in the pump inside (if you strip the cylinder housing and pull the pump assembly out) , and if bad these can also be the source of pressure drop .. but me thinks he meant the "mushroom" shaped rubber grommet which connects the fuel pump outlet to the pump housing .

 

 

D

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jackherer
1 hour ago, DamirGTI said:

but me thinks he meant the "mushroom" shaped rubber grommet which connects the fuel pump outlet to the pump housing .

Yes, me too! That's also what I meant when I talked about the hose from the pump to the top of the cradle in my earlier post. I was thinking of phase 2s where it is a S shaped hose, I forgot it was a weird shape in earlier cars. Mushroom is about right LOL

 

I've never taken a pump apart before so I didn't know they had internal seals, do you know if they have them on phase 2s as well?

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Gaz205

Unfortunately the seal fault was found by the mechanic. It was one that he repaired with a fresh o ring though. Phase 1 car.

If needed i can call and ask him, it was however the solution to low pressure, but not allowing any fuel to leak.

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happypatrol

UPDATE 

 

Finally fixed. 

 

Ordered a fuel filter mainly to rule it out. As I went to remove it I notice the bottom hose at a slight angle. When I removed the pipes then realised it was totally bent. Obviously letting enough fuel through on idle etc but it was to be proved. 

 

Fitted the new filter. Took it for a spin. In first gear when the car lit up the front tyres for the first time in a long time I knew it was sorted. Took it a blast and couldn’t stop laughing. Bit had a proper drive in this car for four years. 

 

Thanks for all your help guys. Will tryn post pics of the car soon. 

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jackherer

Thanks for the update. That's an unusual one!

 

It's a fuel pressure issue but you wouldn't have seen it with a fuel pressure gauge unless you had it rigged up so you could see it while driving which is not an easy thing to do safely.

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Gaz205
On 8/12/2019 at 11:02 PM, jackherer said:

Thanks for the update. That's an unusual one!

 

It's a fuel pressure issue but you wouldn't have seen it with a fuel pressure gauge unless you had it rigged up so you could see it while driving which is not an easy thing to do safely.

He had the benefit of a rolling road so maybe that was how he did it ?

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Gaz205

For info to the OP I changed my fuel filter and it cured it for about 40mins. It seemed each time the fuel system was depressurised it cured it as it was happy when I had the injectors off too. 

Fingers crossed this is a final cure for yours though!

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jackherer
5 minutes ago, Gaz205 said:

He had the benefit of a rolling road so maybe that was how he did it ?

I was replying to the OP's post about a kinked pipe.

 

You're right though, a rolling road would indeed let you watch a loosely rigged up fuel pressure gauge while 'driving' safely. It's a lot harder on the road though.

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Gaz205
5 hours ago, jackherer said:

I was replying to the OP's post about a kinked pipe.

 

You're right though, a rolling road would indeed let you watch a loosely rigged up fuel pressure gauge while 'driving' safely. It's a lot harder on the road though.

Ah ok sorry!

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DamirGTI
On 8/8/2019 at 12:25 AM, jackherer said:

I've never taken a pump apart before so I didn't know they had internal seals, do you know if they have them on phase 2s as well?

 

Yes , both the "roller-cell" (ph1) and the "turbine" (ph2) pumps have O-ring seals in between the core and the outer cylinder sleeve . 

 

I remember two of my spare ph1 pumps needed longer cranking time from cold to build up the pressure to start the engine , if it wasn't the bleed valve i guess it could be the said O-rings going bad i.e. leaking pressure via the top or the bottom of the cylinder sleeve .

 

D

Edited by DamirGTI
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