Poor performance, hesitating

[markovic.mr]

Hello fellas,

Thing I didn't tell you of my car yet is that I'm running it on LPG most of the time, not petrol fuel. It is cheaper and I don't warm up the planet

BUT, from time to time I like to run it on petrol, just to keep the injectors and overall fuel system healthy.

I have a problem with it, though. A car has very poor acceleration, hesitating and kinda choking. At the exhaust from time to time white smoke appears (when it's in its "choking" phase). NONE of this happens when I'm driving the car on LPG - it runs just fine, no white smoke or any choking or hesitating.

IAT checked - works fine
ECT checked - works fine
TPS adjusted long time ago, checked and it's fine

I have no cat(alyst) in my car.

Does anyone have any suggestions what can be causing my problem?

I think it's not due to stuck injectors - that's just the last thing I'll check.
Actually, I'm kinda convinced that the car is running very rich, cause fuel consumption is high (my fuel level meter works like a "second" needle on an analogue clock - unfortunately it's goin' in the opposite direction)

I think I'll try to mess a bit with MAP sensor and I have a question: have anyone played with CO adjustment resistor? How can I check is it in the right position without measuring the CO level at the exhaust? I checked its position, and the pot is turned to the extreme left. So it's pretty suspicious to me - I guess it can be causing these problems?

Also, what's the little screw for - that's positioned at the top of the intake manifold? It affects the idle speed, but what it exactly does?

Thanx for the replies, I really appreciate any help.

 

[Chris H]

the screw on the TB is discussed in one of the guides I wrote. Its the throttle plate bypass screw. It should be screwed right in the idle c0ontrol valve looks after the air bypassing the throttle plate.

The CO adjuster if its turned all the way to the left has been set wrongly. Someone has probably turned it up to try and get a bit more power.

But get it set up on a CO meter to see whats happening.

The injectors could very well be at fault as well. Also the fuel pressure regulator, I assume its the early style one with the reg above the rail? They can leak internally which can cause a lot of issues

 

[markovic.mr]

the screw on the TB is discussed in one of the guides I wrote. Its the throttle plate bypass screw. It should be screwed right in the idle c0ontrol valve looks after the air bypassing the throttle plate.

I'll try to find the guide you wrote, a link would be useful

Also the fuel pressure regulator, I assume its the early style one with the reg above the rail? They can leak internally which can cause a lot of issues

Did not think of that. But it seems that it's pretty tough thing to check when I don't have proper tools, I looked at the manual in Autodata.. I'll see.

 

[The T.I.B.]

http://www.retro-renault.com/forums/engine/

 

[markovic.mr]

OK, I've found the thread.

I forgot to tell you that I've cleaned both the TB and ISCV couple of months ago.

Let me ask you something, just to check if I got it right: to adjust the bypass screw at its right position - engine idling, I screw it all the way down, BLOCK the pipe from ISCV and adjust the idle speed at 950 +-50rpm? Is that correct?

 

[Chris H]

just screw the screw all the way down, the idle should then sit at 950 +-50rpm. Blocking the icv pipe the revs will fall further anywhere between 750 and 900 rpm depending on how much crankcase blow by etc you have.

 

[Chris H]

i also changed the guide to make a bit more sense.

 

[markovic.mr]

Today I've set the plate bypass screw, and turned the CO adjustment resistor from its extreme position to middle. Nothing significant happened, when the car is standing, throttle seems just fine, but on the road, under load it is still hesitating and has lousy and lumpy acceleration.

 

[Chris H]

check the map pipe for blockages and also the fuel pump might be dying

 

[markovic.mr]

Map pipe checked, looks just like new.

Though I'm driving it on LPG most of the time, I'm trying to have at least 5-10l of petrol in the fuel tank...but it's not always the case. I guess that low level of fuel in the tank is bad for the pump...might be that it's blocked or needs cleaning or something.
I'll try the next simple thing - I'll just pour about 15l of petrol and see if any changes.

That's about all I can do in small amount of time which I don't have - planning to go on summer vacation this weekend, there is a lot of other work to finish till then, so I doubt that I can manage to check all those things in a proper way (measure fuel pressure & fuel delivery rate etc.)...

Thank you anyway for all suggestions, I really appreciate it. If anyone has an idea what else could I check that is simple - not much time consuming - say it!

Thanx again.

 

[Chris H]

the pump has a filter sock on its inlet and if the tanks rarely kept full they rust inside and then the flakes block the filter socks inlet. So might even be just that.

The fuel tanks are bad for rusting through on the 19's