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1986 S3 turbo backfire problem no acceleration - Engine/Ancilliaries - The Lotus Forums Jump to content
olivernardone

1986 S3 turbo backfire problem no acceleration

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Hey guys, im new here and decided to join the forum since I recently purchased a s3 turbo csi injected, 

the car was bought not starting with a history of engine rebuild so i thought it would be a fun project car... i'm pulling my hair out!!!!!!!!

1 checked why it wouldn't start... bad reluctor and timing off by one tooth on the exhaust side.

 

2 took engine out changed timing belt etc etc all according to workshop manual.

 

3 replaced everything in the car started it and ran it for half an hour  everything felt good, till i tried to give gas....  i must have made enemies with the whole neighborhood, and scared everyone.

it backfires so loud and does not let me accelerate seems as if it is off timing  but having double checked everything is ok

 

would anyone have experianced this?

 

thank you in advance   

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Welcome to TLF Oliver. :welcome:

 

You should duck over to the Introductions section and say hi in there as well.

 

As to what is going on with the car, not sure. If you have set up the timing to the manual and it all checks ok, you would not expect that. anymore.

Someone will be along who may have a much better idea soon.

 

Pictures are also a bonus for all of us lot as well. :)

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I dont know anything about your fuel injection but you should start at the begining and check from the start. I dont mean take everything apart and rebuild again!

 

One thing thats easy to do is to get the timing out by 180 deg?

 

Backfiring sometimes is caused by an air leak?

 

Im not sure but maybe someone else will stop by with some good ideas,

 

Buddsy 

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Run for half an our. Was it just idling?

Is it backfiring through the exhaust?

Can be running too rich, or croos firing due to a cracked distributor cap.

Lars

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Worth checking the centrifugal advance/retard on the distributor. And the valve timing, too...easy to fool yourself with that. Loud bangs from the exhaust must mean that ignition is happening with the exhaust valve still open...or a very rich mixture leaving unburnt fuel in the exhaust to go BANG! when ignited by the flame from the exhaust valves. Have no experience of the fuel injection system, so can't offer any useful suggestions there.

Going to be a fun diagnosis.....(!)

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Thank you guys so much for your time!!!!!!!!

 

Unfortunately this car was adapted to meet emissions in north america i think, i have a vacuum advance system

the cap rotor and reluctor are new 

checked for any vacuum leaks  

nothing!!!!!!!

I let the car idle for a total of half an hour before i started revving up the engine. new to lotus so I wanted to take it slow

Then she started backfiring loud through the exhaust. heard some in the intake but nothing to compare 

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Worth checking the engine compressions to see if you have any leaks through the valves. Ought to be around 130psi for a low comp turbo...Check compressions with throttle wide open, all the plugs out and give it 10 rotations or thereabouts to get anb accurate reading for each cylinder. Turn the fuel pump off and unplug the ignition first, too...fuel pump can be turned off by pulling out the red knobbything on the cutout on the wheel arch and the ignition can be isolated by unplugging the connector to the distributor. 

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Just a thought but you need to line up the cam timing before checking the ignition timing with a lamp. It is very easy to think the timing is properly set only to discover the cams are out of alignment.  

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hey guys 

checked all timing. everything is good  

noticed that when i start the car cold it does not misfire until it reaches normal running temperature 

then when i reach 2500rpm it misfires specially on the cylinder number 1

:( finally got beautiful weather to try out the car.... its stuck in the garage

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Is the this backfire through the exhaust?

If, you propably have an issue with cyl 1 ignition. Being plug, cable...

Why not swapping it with a another cyl. to see if you switch the problem?

 

Lars

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backfires through exhaust, tried new parts with no success .

the only thing i saw is that this only happens when the car warms up

otherwise at cold start up it runs beautiful and accelerates fine no backfires at all

 

I even changed the module the ignition coil and the wires 

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Have you checked the valve clearence?

Sounds like your exhaust valve at cyl. is too tight.

 

Lars

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With a spark tester I see the spark disappear as soon as i reach +- 2500rpm

Trying to figure out how the vacuum advance works. I wonder if the mechanism advances so much that it loose contact to send spark to the cylinder number one

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Its known that the leads to the pick-up in the dizzy can break down internally on models with vac advance.  maybe worth a look?  you could also temporarily unplug/block the dizzy vacuum to see if the problem goes away?  

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The vacuum advance would not come into play at higher revs and no load.

 

When you checked the ignition timing did you check it throughout the rev range with the vac advance disconnected? If you set the timing at idle with the vac advance connected thats your problem because it will be miles out at higher revs and probably spark when the rotor arm is not in contact with the cap contact.

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I thought timing was checked at idle with advance connected. Never heard of checking timing with engine revving away.

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The vacuum advance will be operating at full 

 

I thought timing was checked at idle with advance connected. Never heard of checking timing with engine revving away.

 

Checked the manual: The timing should be set at 3500-4000 RPM. There are various engine specs with differing values which vary from 24-28 degrees.

 

The vacuum advance should always be disconnected as it introduces a variable which you cant control, as it varies with engine load. You cant simulate load in the garage unless you happen to have a dyno!

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This long weekend I got to put so time on the car.

After 2x 3x 4x checking what i did and reading the shop manual

I took out the dizzy again and called the previous owner and his mechanic.

They told me they had trouble after they had played with the dizzy  and just gave up. They then parked the car. fast forward ten years I realized the pick up coil (magnetic) spacer is installed backwards

can anyone explain why that would affect my timing???????

Thank you all for your help

is this the initiation process with lotus????  

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Could it be a fueling problem - took my old banger out for a spin today and it was backfiring and juddering constantly. Put some petrol in and the problem went away instantly. The fuel quage must be miles out as it was indication a quarter tank.

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Result - well done you.......must be happy bunny now

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Enjoy!

 

I think you will learn to appreciate the injection, no fuel smell and no sputtering or flat spots. Make sure you start fresh with a clean fuel filter, these system need to run clean!

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