Intermittent misfire on 4Y EFI

[Ryperd]

Ryperd has developed an intermittent misfire, which I am struggling to diagnose. It seems to happen with a warm engine, not necessarily under load. I can't tell if it is only one or multiple cylinders (could I get any useful diagnostic info from the Dicktator?). Most of the time it's a very light hesitation, but occasionally it is heavy, with a sudden drop of around 500rpm.

I have replaced the spark plugs, leads, and distributor cap, as well as the two fuel filters. My imagination tells me that it improved after that, but it is still misfiring. Misfire could be caused by weak spark, fuel mix, or compression problems.

Spark
I've already replaced the plugs, leads and distributor cap, so unless I'm unlucky and one of them is a dud, I should be able to rule those out as the culprit. Other possible causes could be the rotor or the coil. Am I missing anything else? The rotor looks good to me, so I'm not suspecting that at this stage. When I pull the leads and check for spark using a screwdriver against the engine block, the spark seems weak to me. Could that indicate a problem with the coil? How do I test the coil?

Fuel mix
I've already replaced the fuel filters, so it's unlikely to be a blockage. Other possible problems could be fuel injector, fuel pump, or an air leak somewhere. The injectors and pump are less than a year old, so they shouldn't be giving problems, but could it be that I had a bad tank of petrol and one of the injectors is blocked? Any straightforward ways to test? The air filter looked good, but I guess I should replace that just to be on the safe side. Any other fuel mix issues I should check?

Compression
It's a new engine (less than 2 years), so I don't expect there to be any compression issues. There are no other symptoms that would point to the problem being here (temperature is regular, not losing water, not using oil). I could do a compression test, but I'm thinking the problem is most likely spark or fuel?

Is there any good way to figure out whether the problem is confined to one cylinder, or if it's a general issue?

[LouisZ]

Spark plugs bpr5es or bpr6es? If its a only a bp5/6es it will give a bad spark on the system. Needs the internal resistor.

Then could be a blocked injector too. One have to pull the injector rail with the fuel supply still connected. Prime it normally and look if all 4 injectors inject with an even cone. If one give a even cone its blocked and needs cleaning.

The pressure valve can be cause too. Check pressure while idling at 2.6 to 2.8 bar. Rev up a bit and if it falls below 2.6 bar its the pressure valve.

[Family_Dog]

]Had the same a while ago. Turned out to be a loose pin of the plug connecting the distributor wires. Corrected that, problem solved.

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-F_D

[Ryperd]

Spark plugs bpr5es or bpr6es? If its a only a bp5/6es it will give a bad spark on the system. Needs the internal resistor.

Turns out this was the problem. Replaced the bp6es with bpr6es and no more hesitation. One of the plugs also felt a little loose, which could have contributed to the intermittent issue.

[LouisZ]

Nice.

[Dadz Toy]

Spark plugs bpr5es or bpr6es? If its a only a bp5/6es it will give a bad spark on the system. Needs the internal resistor.

Turns out this was the problem. Replaced the bp6es with bpr6es and no more hesitation. One of the plugs also felt a little loose, which could have contributed to the intermittent issue.

What??????????????????

I was told SPECIFICALLY NOT to use Resistor plugs as they are for Wasted Spark systems only

Down here in the Cape we use BP7es's only with 1.5mm gaps.

My Efi has been operating flawlessly since my conversion nearly 9 yrs ago!

Other thing that can play up on a Diktator installation is the Ignitor (TP100), keep it clean and dry ne.



Rich

[LouisZ]

Nope.

The Dictator needs the Resistance. About 2 years ago I had an installation that gave lots of misfiring. Changed injectors, cleaned the second set, changed igniters, changed the mag adaptor 4 times, opened wiring and did fuel pressure tests without anything helping. Changed the fuel regulators out. Loaded a bunch of maps on.

Absolutely nothing helped. My time was running out for the dyna, I phoned up Johan from the dyna centre and asked what next I can do. He do lots of installations with Dicktator and he simply asked me what sparks were in.
He told me sraight forward you use the R type sparks. The Dictator do not have resistance inline with pulse wire.
It must have resistance. Well I tried it and after the change of sparks to R no misfire, no hesitation.

1st thing to do on an Efi. The rest follows.

[Dadz Toy]

Jeepers, that's news to me!

Every day's a school day hey!


Rich

[Ryperd]

So the new spark plugs resulted in no stutter for a couple of thousand kilometers. But driving back from Nelspruit to Pretoria a couple of weeks back, the misfire was back with exactly the same symptoms.

Reading over some previous posts, the symptoms described here sounded exactly the same as what I have:

I'm convinced its something electrical or a vacuum hose.
I have a constant engine temperature and pressure.

And its never the same, sometimes it will idle very smooth and the next time fluctuate from 2000 to 500 to 2000 to 500.

The problem there turned out to be an interrupted spark in the dizzy, so I checked again, and noticed what looked like carbon buildup on the contact between the coil and distributor cap:



After cleaning that up with some sandpaper I haven't had any more stutters. It might be too soon to say it's fixed, but hopefully we don't have any more misfires!

[LouisZ]

Your becoming an Expert!!

[Ryperd]

Your becoming an Expert!!

If I was an expert I would have checked that first! But learning a lot from you and others on the forum.

[Mud Dog]

Hopefully that was the only problem and it's now sorted.

[Stef]

MMM....interesting wrt to the plugs....running BP6ES currently on the 2.4 AFAIK and although I have no issues it feels somewhat lazy these days...as if there is no bottom end grunt .

Definitely going to check the plugs....injectors next

[Kaspaas]

Glad my problem-solving assisted you in some way Rudi!
Hope its sorted now.

[Stef]

Changed to BPR6ES and 95 Octane fuel....a bit better on the bottom end now, felt a minor difference on plugs alone....weird

[Borntofish]

Ek wonder watse plugs het ek in myne....Sal moet gaan kyk.

[The Legend]

Ek wonder watse plugs het ek in myne....Sal moet gaan kyk.

Werner dit is nog steeds diesefde plugs wat jy laas ingesit het.

[The Legend]

My workshop manual says the correct sparkplug for the 4Y EFI is NGK BPR 5EP11 but they are not available at spareshops .At the moment I use the ones recommended by Louis- no problems with them.

[Borntofish]

Werner dit is nog steeds diesefde plugs wat jy laas ingesit het.

Ek weet, maar ek het net gevra vir plugs vir n 4Y....Nie geweet die goed is verskillend nie.

[The Legend]

Werner ek het sommer net jou been getrek.