Strange Itb Problem

[craig_007 1]

I appear to have a problem with my MI.

 

My car seems to be going through plugs for fun, I started it up on Saturday left it too idle up to temp with no probs at all, Went back to it today and it's running on 3 cylinders !! Changed the plug for another and back to 4 cylinders !!

 

Now when I try the dead plug in a plug lead with the engine running there is a really good spark at the plug !! I would have though there would be no spark if the plug was dead !!

 

Also with the engine running on 4 cylinders, ITB 1&2 closest too the flywheel appear to be doing the majority of the work, What I mean by this, If I disconnect a plug lead on say cylinder 1 the engine really dies but if I go to cylinder 4 and do the same it hardly makes any odds ??

 

I have balanced both banks of bodies to each other, Im at the stage where I'm at a loss as I don't know where to go next, My only unknown quantity is the injectors. I've cranked them over into milk bottles and the quantity of fuel was the same, I've checked resistance at the injectors and there all bang on.

Edited May 23, 2011 by craig_007

[Tom Fenton 1,542]

Do a compression test next job before anything else.

[craig_007 1]

nipping out just now to do compression test

 

OK compression test seems good.

 

210 psi across the 4 cylinders at operating temp.

Edited May 23, 2011 by craig_007

[STEVEBOXER 0]

Hi,when you remove plug lead and engine note/tickover changes doesnt that mean that the plug/lead is working.When you remove a plug/lead and nothing changes surely there is a fault with that one.(I think lol)

[brumster 135 1 Cars]

Which plug appeared knackered in the first part of your test?

 

Air leak? Blocked injector?

 

Are you running any sort of sequential injection or do all injectors fire at the same time anyway?

[craig_007 1]

Plug 3 was the one I replaced tonight, The injectors all fire at the same time.

 

Could it maybe running to rich ar idle and this is maybe what is fouling the plugs. On idle with the cold start off the best AFR I can achieve is 12.8/13.0-1 ?

 

If I reduce the fuelling any more at idle I cannot get the car to start as I pressume there is not enough fuel getting through, Also if I reduce the fuelling at say 1000rpm when I go to rev the car the AFR gauge goes off the scale lean and the car stutters to rev ?!

[allye 530 3 Cars]

What colour is the plug in question? Should be able to diagnose at least something from that! (unless it's the same as the others :/)

[Tom Fenton 1,542]

Could well be too rich and fouling. 13:1 is a bit rich at idle, it would be OK for cold start but once the engine is up to temp a bit rich.

 

Don't know what ECU you have, but I would suggest you need to increase the startup fuelling and decrease the running fuel. Also increase the acceleration enrichment to get rid of your lean stutter when you try to rev it.

[Anthony 1,003]

Are you sure that the bodies are properly balanced - as in, balanced using a synchrometer and all idling at the same values?

 

One pair of bodies doing more of the work than the other pair is exactly what you get if they're out of balance, and the effect if 3&4 were drawing in less air would be that they'd be running much richer on idle - quite possibly rich enough to foul the plug up. Make sure that you balance them using the throttles and not the bleed screws (assuming your bodies have them fitted) as otherwise you'll have all sorts of balance issues just off idle and on light throttle cruise.

 

Until the bodies are balanced 100% you're wasting your time trying to set up the idle and startup fuelling IMO.

 

I'd expect idle mixture to be somewhere around 14-14.5:1 when warm, so do this first and then add cold-start enrichment as required to get it to start and idle when cold.

[craig_007 1]

I will recheck the balancing of the bodies, Mines don't have the idle screws .

 

My ecu is Lumenition and I'm not overly familiar with the settings although the main fuel and ignition map is simple enough !!

 

My cold start AFR is low 11s !!

 

I assume cold crank would be my cold start fuelling ? If so it says 69.53 %

 

Ideally I need to know what the settings on the side of the Lumenition software do as what I'm being told makes sense regarding accelaration enrichment and start up fuelling makes perfect sense.

 

Any idea what one it's likely to be.

 

Accel. trip 255 dTPS

Accel. FACT 0 %

Accel Decay 99.61 %

 

These are the 3 I can see with relation to the throttle.

 

I take it the way to balance jenvey bodies is via the small allen key bolt in the middle of the 2 sets of bodies ?

Edited May 23, 2011 by craig_007

[petert 588]

Most engines idle a lot smoother at 0.9lambda (low 13's) than they do in the 14's. Factory settings are there for emission reasons. After you get the hot idle correct, add just a few percent for cold start. To get an accurate idle AFR you will need a wideband sensor in the downpipe.

[craig_007 1]

I've got a wideband in the down pipe just now, This is where I have been taking my readings from.

 

I'm going to get my synchrometer back later on and check the balance of the bodies before I go any further.

 

I've also sussed out the settings on the Lumenition ecu.

 

Here is some info I found regarding fuel enrichment.

 

Acceleration Factor

 

Name Range Value Resolution (Mines is showing 0% so is doing nothing)

ACCEL FACT. 0 - 100 % 1%

 

This scalar sets the magnitude of the Acceleration Enrichment value to be added to the Normal Map derived Injection Pulse Width. Once a Delta TPS value is measured which exceeds the threshold value then the Delta TPS value is multiplied by this scaling parameter to produce the additional fuel pulse width.

 

Normal usable values are in the range 5% to 25%. A very large value in this scalar can sometimes cause an engine to "stumble" due to over fueling.

 

Acceleration Enrichment Threshold

 

Name Range Value Resolution

ACCEL TRIP 0 - 255 dTPS 1 dTPS (Mines is set at 255 so again is doing nothing)

 

The ACCELERATION ENRICHMENT TRIP THRESHOLD is set by this scalar. It is calibrated in Delta TPS. This has the effect of setting the rate of change of throttle position required to trip the Acceleration Enrichment Mode.

 

A large value set here will mean that it is very difficult to trip the Accel Enrichment whereas a lower value means that it will trip very easily. The usable range is normally 4 to 20 Delta TPS counts.

 

To switch off the acceleration enrichment function set this scalar to 255.

 

The next one I'm overly sure of yet !

 

Acceleration Decay Rate

 

Name Range Value Resolution

ACCEL DECAY 0 - 100 % 1%

 

This parameter has the effect of controlling the rate of decay of the Acceleration Fuel part of the Final Injection Pulse Width.

 

In operation a small value will cause a quick decay of Accel Fueling whilst a large value will cause the additional fueling to be removed more slowly.

 

Normal values lie in the range 50% to 99%.

 

The Acceleration Enrichment Fueling can be removed by decaying the amount of additional fuel every injection pulse or conversely by having it decayed at exact time intervals (every software background loop, 8mS). The two modes are selected by use of the SETUP REGISTER.

 

Now regarding the cold crank

 

Cold Crank Injection Factor

 

Name Range Value Resolution

COLD CRANK 0 - 100 % 1 % (Mines is set at 69%, I assume I will increase this a little when I alter the running fuel map ?)

 

The COLD CRANKING FACTOR is used to define the level of fueling enrichment required during the cranking phase of cold engines.

 

The number which the user calibrates is a simple %age which has the effect of going from no enrichment to over 5 times the normal warm idle pulse width. In operation the effect is also proportional to the difference between the Engine coolant Temperature and the threshold set by TEMP THRESHOLD. Hence as the engine is restarted from hot the Cranking Enrichment Factor achieves a minimum of value of +100 %. this level of enrichment is still required to start even a hot engine.

 

Not overly sure on this one either !

 

Warm-up Factor

 

Name Range Value Resolution

WARMUP FACT 0 -100 % 1 %

 

The WARM UP FACTOR is a calibratable parameter for setting the level of warm up enrichment of fueling to be used between the Cold Cranking Phase and the Engine Coolant Temperature exceeding the value set in TEMP THRESHOLD. The system tends to work like an automatic choke.

 

In operation if the user tends to find that the cold engine tends to start very easily but dies soon after this is an indication of inadequate warm up fueling being present.

[petert 588]

Tuning the cold cranking and warm up maps can be very painful. You basically only get one chance each morning. So it can take a fortnight or more to get right!

[craig_007 1]

Yeah I can imagine that being a bit of a pain but on the bright side I have an idea now on how to get my idle fuelling set up so can hopefully achieve a better AFR at idle.

[Tom Fenton 1,542]

I would set all the acceleration fuelling settings to the mid point of the parameters they suggest and then try it.

[craig_007 1]

Will do Tom at least then I have a starting point.

 

If I get the idle set up to what I'm after and get the car reving free enough at idle am I correct in saying I should only then need to adjust the fuelling map for the under load set up ?