5 replies to this topic

[6speedmanual]

Hi all

New on here and hoping for some ideas around a poor running MPI.

Have had a search but not found anything to give me teh fix I'm looking for.

 

1998 MPI

 

Ign on, fuel pump primes.

Engine starts OK.

Seems a bit rough at idle but smooths a bit out as it warms up.

 

Problem is than when one blips the throttle, either medium or fast the engine gasps - feels like lack of fuel.  (bit like a weber with failed acceleration pump, if you know what I mean).  When throttle blipped quickly it feels as engine about to stall as the revs pick up so poorly.

When raising revs slowly, fuel supplier seems to keep up and it can reach rev limiter (6200rpm)

 

On the road when pulling away very gently it is ok but as soon as there is any fuel demand (opening the throttle) it gets very little performance and barely accelerates.  upshift into 2nd and same effect.

 

Have fitted new fuel pump, fuel pressure regulator and fuel filter.  These did not seem to make any difference to the issue.

 

All sensors plugged in.

Coolant temp sensor resistance changes with temperature

So does Inlet manifold temp sensor.

Idle Control valve is doing its job and controls idle revs accoding to various loads, eg headlamps being switched on.  Also manages revs so as to catch engine as it drops back to idle from raised rpm.

Throttle is correctly closed at idle (no residual tension in cable)

Tappet clearance set to 0.014" across all valves

New plugs correctly gapped

Compressions 175-180 psi on all cyls.

New coolant.  No boiling or ejection of coolant

5 litres of fresh fuel in tank

 

 

Had car at MoT test garage.

 

Basic idle test

CO 1.3%  (Not OK)

Lambda 1.2 - 1.4  (not OK)

HC 170 - 200  (OK)

 

Fast idle test 2500 rpm

similar

 

Any ideas appreciated!!!

Have I missed something obvious?

 

What other sensors can I check using volt or ohm meter?

 

Heeeeeeeeelp!   :)

 

Cheers

Peter

 

[FlyingScot]

On first impression I would have said check the throttle position sensor TPS for correct operation.
However given that the fuelling appears to be off from the emissions reading....

When did the problem develop? Can you give any clues about that? Has the car been sitting or been in use?

What condition is the exhaust and catalyst in it almost sounds like you could have some kind if blockage or restriction.

FS

[Ruckus]

Has it been on a Rover T4 diag?

 

I had a similar problem, But mine didn't lack power it just tried to stall if you blipped the throttle hard, in fact once in a while it would stall.

It would also die as you approached junctions and came off the throttle quickly.

 

I took it to a MG specialist and they found the ICV was not in the right position and was a bit lost in it stepper operation.  

No other diag kit had found this.

 

The problem has come back for me , but we think that was due to a compression and leak down test confusing it. once my engine is back it they are going to reset it again as they are pretty sure that's all it needs... or a new ICV.

[Ipod]

Hace you taken the CAT off to check for blockage or damaged.

Years ago mine had slightly broken up inside and kinda blocked the flow, resulting in lack of power and a kinda missfire

[MiniGrin]

Throttle position sensor, I had the same with mine and that's what it turned out to be. This helped however mine was still running rough, so I had it scanned with the T4 (by Vauxhall of all people) and it turned up some errors and a problem with another sensor somewhere in the engine (id never have thought to check) changed it out, now runs perfectly! May be worth checking it with a T4 and see what it brings up.

 

[FlyingScot]

OP we need some input from you to help......

FS

Edited by FlyingScot, 25 June 2014 - 05:18 PM.