Restoring the power of a 1986 110bhp XU92C engine

[amilo123]

A couple of days ago I went on the motorway to find out what this engine can do after all these years... I found that the acceleration is quite slow, 0-100kph in 15s and top speed of 155. I couldn't pass that speed, the car just couldn't go any faster. From what I know the top speed of my car should be 210 if I am not mistaking, and the acceleration around 10s.

The car didn't shake or anything it was quite stable, only the engine produced a lot of noise at 4500rpm, but nothing scary

Any ideas on what could I do to restore its power?

[amilo123]

A little more details about the state of this engine....

The timing belt is new, just got it changed. The oil also new. Spark plugs under 5000km from last summer. It leaked some oil but that is fixed now. It leaks some exhaust fumes, but I don't think that can be the problem.

Oil temperature isn't quite ok, on the motorway it went up to 110 degrees. Oil pressure seemed ok then, but sometimes it can drop suddenly, not enough to light the warning light but still I can feel the car hesitating sometimes when accelerating, even if the engine is warmed up. This is a very old problem.

The air filter is from last summer, it is k&n sport filter. The gas filter as well is new.

Another thing I noticed is that the idle speed when warm is 1000rpm and after driving for a longer period it can get to 1200rpm. Not ok right?

[alargeau]

I don't know about acceleration since I drive quite slowly (price of gas...) but I'm quite sure I can get 15s too with my 1.3 engine!
Did you check the carburettor?

[amilo123]

I don't know about acceleration since I drive quite slowly (price of gas...) but I'm quite sure I can get 15s too with my 1.3 engine!
Did you check the carburettor?

it was checked last summer, and it's gaskets were replaced...

[missa91]

What fuel to you use? In my experience it has a lot to do with the quality of the fuel, also, some residue in the exhaust manifold could reduce the power of the engine. Also, have you checked your compression ratio?

[alargeau]

Also, have you checked your compression ratio?

+1!

[missa91]

if there is a big difference in the ratio there is your problem, also if the engine is ok and the ratio not that bad, consider opening it and changing the piston rings, valve stems and all affected seals. Not as big a investment but worth wile.

[SRDTURBO]

Valves... maybe the camshaft is worn or too far from the valves.

[amilo123]

What fuel to you use? In my experience it has a lot to do with the quality of the fuel, also, some residue in the exhaust manifold could reduce the power of the engine. Also, have you checked your compression ratio?

I use premium 95 fuel, from lukoil. There is a problem with the exhaust manifold, it is cracked, nothing big, but some fumes escape....It's about 100euros to replace but I am hesitant because when the mechanic would take it off, I thought there would be a problem with the screws because there are very old, and I am afraid that something might break. So I thought that the risk isn't worth it, although the mechanic said that this could affect my mileage...

Also how to I check the compression ratio? Would the guy who knows carburetors be able to do this?

[missa91]

Go to your mechanic. The engine needs to be totally cold for the test. You need a compression gauge and you remove all spark plugs for the engine to turn lighter. You put the gauge on the spark plug holder and turn the key. The compression is red then of the gauge. these gauges can be bought for 10eur, so you could do it yourself

And about the screws, I'm sure it's nothing a little WD40 couldn't fix. Besides, I was thought how to get these broken screws out. You weld a electrode to the end and then carefully bend it, so you can use it as a key.

[alargeau]

Yes, good piece of adive!! You can totally do it yourself, you just need to buy a compression meter and they're quite cheap.

[beni]

anyway, it's better to be two to test compression because you have to turn the key and hold the tester in the same time !

[amilo123]

ok, I will do it friday.

and when I turn the ignition key, do I have to keep the acceleration pressed all the way?

also do I have to disconnect the fuel pump so not to flood the engine?

[beni]

yes, you have to keep pressed the accelarator all the way

[thefunkyboy]

That's strange because I tried with/without pushing the accelarator. No change

And you Beni? you have seen a lot of difference?

P.S: that was on a GTi