Faulty Fuel Injector causing mis at startup?

[eightynine4x4]

Hey all,
89 2.9 auto
So like 50% of the startups, I get a mis and the truck dances until I throttle it up a couple / few times. Then the mis goes away once it’s forced past whatever issue it’s having.

I’ve replaced pretty much all the ignition electricals, done the timing, replaced the fuel regulators and filter, done an in line fuel injector clean out with a reputable system for this. This is of course over a span of time and the issue has not disappeared.

The mis never happens after the truck is running on all cylinders.

Something is stubborn somewhere. I’m guessing it’s fuel related, since gassing it gets it past the issue. Or at least fuel component related.

For what it’s worth, sometimes this misfire happens again when starting up warm. Go to the store with a perfect drive, start it up 5 minutes later and it’s fully misfiring.

I just got word that injectors can also be burned out or faulty, at the “coils”?.. not just dirty or clogged with fuel gunk. Is that true? If so, I’m considering replacing all the injectors. Isn’t the cheapest idea but maybe it’s worth the risk?

 

[rubydist]

imho, that is a reasonable guess. The sticky injector may not be firing until you rev up the engine enough that it gets enough pulse-width to fire the injector, and once its moving it may work fine until it sits and sticks again.

Rather than starting with replacing the injectors, I would run some good injector cleaner through a couple of tanks of gas and see if that makes any difference. I also have learned the hard way that buying the brand name gas is worth it, because they do put more additives in that help the injectors work better longer, so my recommendation is to skip the budget gas pump and buy Shell/Exxon/Mobil/Phillips66/Chevron branded gas.

 

[rusty ol ranger]

Dump some lucas injector treatment down it. You might get lucky

 

[eightynine4x4]

Thanks fellas,
I did an inline treatment with a good OTC system. Can't recall the chemical i used but it was something quality.
It helped performance overall, but I don't recall it solving the mis during startup. That was over a year ago though, so maybe problems have crept back.
I'm not opposed to giving this in line treatment another shot, but I've decided I'm curious enough to learn the injectors better so ordered a set of replacement mesh basket filters and gaskets for them. Only 10 bucks for the set so why not.
I do know that this truck has done a whole lot of sitting in its life, years of non operation. So i'm hoping that when i open up the injectors i will find them gunky enough to place some blame here. In any case, i think putting new filters and gaskets in the injectors is a good thing to do regardless since it's cheap.
I debated buying new injectors but decided staying OEM was better. Hoping none of them are truly faulty.

 

[rusty ol ranger]

Thanks fellas,
I did an inline treatment with a good OTC system. Can't recall the chemical i used but it was something quality.
It helped performance overall, but I don't recall it solving the mis during startup. That was over a year ago though, so maybe problems have crept back.
I'm not opposed to giving this in line treatment another shot, but I've decided I'm curious enough to learn the injectors better so ordered a set of replacement mesh basket filters and gaskets for them. Only 10 bucks for the set so why not.
I do know that this truck has done a whole lot of sitting in its life, years of non operation. So i'm hoping that when i open up the injectors i will find them gunky enough to place some blame here. In any case, i think putting new filters and gaskets in the injectors is a good thing to do regardless since it's cheap.
I debated buying new injectors but decided staying OEM was better. Hoping none of them are truly faulty.

I bought ebay cheapos for my 2.9. Got all 6 for like 50 bucks i think. Ive had no issue with them

 

[SenorNoob]

I have a similar condition on warm restarts if it only sits a few minutes. I suspect a cracked head leaking into cylinder when engine is warm and no compression or injectors leaking slightly when warm. After it burns the cylinder out it's good.

 

[eightynine4x4]

I have a similar condition on warm restarts if it only sits a few minutes. I suspect a cracked head leaking into cylinder when engine is warm and no compression or injectors leaking slightly when warm. After it burns the cylinder out it's good.

Would i be able to spot the injectors leaking when warm, if they were? I guess the fuel would just evaporate immediately.
I've got an injector rebuild kit arriving in a few days. Planning to take them out and do that, and it would be nice to discover that the baskets were gunked a little bit due the truck having lots of years sitting in the past.

 

[SenorNoob]

Most likely leaking into the cylinder. So unless you wanna pull the spark plugs on a hot engine...

Edit: I wasn't aware there was an at home way to rebuild injectors. All I've ever seen are replacement "hats" (the plastic piece on the lower end) and o-rings.

 

[eightynine4x4]

Most likely leaking into the cylinder. So unless you wanna pull the spark plugs on a hot engine...

Edit: I wasn't aware there was an at home way to rebuild injectors. All I've ever seen are replacement "hats" (the plastic piece on the lower end) and o-rings.

You mean coolant leaking into cylinder through cracked head? I've got no other signs of cracked heads. Also mine is an 89, so hoping it's less likely the heads are cracked. Knock on wood. I haven't done a compression check yet, but i have the tester for it.

 

[SenorNoob]

Coolant or fuel into intake/cylinder through open valve. Either way it runs rough till it clears out, but only when restarting from warm.

 

[eightynine4x4]

Coolant or fuel into intake/cylinder through open valve. Either way it runs rough till it clears out, but only when restarting from warm.

Gotcha! Well, my mis happens just as much, or more, when the engine is cold. Maybe 50-75% when cold, 25-50% when warm. I get plenty of clean startups when warm. So if it's the cracked head expanding when hot and leaking fuel or coolant into cylinder, it's not the same cause of misfire when cold I suppose. Fingers crossed it helps to refurb the injectors. I'm also replacing the IAC valve this weekend, not that i expect that to be related but it might help with warmup idle which is sometimes pretty up and down. Hot idle is basically perfect.

 

[Lefty]

I had a similar problem but used injector cleaner a second time on a second fill up. Sure enough it worked.

 

[rubydist]

A leaking fuel injector causes 2 issues at warm restart: first, one cylinder is flooded and will not fire reliably until that excess fuel is burned or blown out. second, the fuel rail pressure is low which results in a lean condition on all the other cylinders for a short time until the pump can get the rail pressure back up to where it should be. If you cycle the key a couple times before starting, that will bring the fuel pressure up and resolve the 2nd issue, but you still have the 1st one.

imho, a coolant leak will show up other places too, like the coolant reservoir going low, white smoke (at least sometimes) etc. so you can usually tell that its a leaky injector if you have none of those other symptoms of a head gasket leak.

 

[eightynine4x4]

A leaking fuel injector causes 2 issues at warm restart: first, one cylinder is flooded and will not fire reliably until that excess fuel is burned or blown out. second, the fuel rail pressure is low which results in a lean condition on all the other cylinders for a short time until the pump can get the rail pressure back up to where it should be. If you cycle the key a couple times before starting, that will bring the fuel pressure up and resolve the 2nd issue, but you still have the 1st one.

imho, a coolant leak will show up other places too, like the coolant reservoir going low, white smoke (at least sometimes) etc. so you can usually tell that its a leaky injector if you have none of those other symptoms of a head gasket leak.

That makes me think it’s a leaky fuel injector. I actually hadn’t had that on my radar, just been thinking dirty/clogged fuel injectors. It would also make sense that even doing a fuel injector clean out, no matter if it’s inline or lots of bottles in the tank, would not solve the problem of bad startups although would help injector performance in general.
And I do use that approach of holding the key a couple times and usually it helps. Didn’t really put two and two together as to why that worked. And I’ve replaced the fuel pump (since it was groaning like a dying animal), replaced the regulator since I still go weird readings, confirmed pressure post pump pre regulator which was like 90-100 psi, but do recall inconsistent readings post regulator even after reg replacement I so knew there was still some issue… I soon after developed a substantial visible leak at the shrader valve which I then replaced, and which I then blamed the inconsistent readings on and noticed an improvement so just called it a day. At that point I thought I was good to go with fuel pressure, but eas disappointed that my startups STILL benefited from holding the key a couple times. Oh and I replaced the fuel filter of course, and checked a replaced some lines from tank.

So a COLD leaky injector would be slowly dripping fuel into the cylinder, and a HOT leaky injector could be doing the same thing just at a higher rate due to injector gaskets swelling/deforming this way or that due to temp change? In other words is this problem usually remedied by an injector rebuild with new gaskets and screens and what not? Are the gaskets the cause? Or is it an injector itself that has to be totally replaced? Like a slight deformation of the hardware?

I was planning on doing an injector rebuild this coming week, but maybe I need to just buy a new set of injectors to be sure I’m solving the problem.

As for heads/gasket leak… I get typical moisture burnout when starting and warming up the engine, but never once have I ever seen smoke of any sort coming out the tailpipe once the engine is warmed up.

 

[rusty ol ranger]

Pull the plug. If its clean its coolant. Coolant steam cleans the end of it.

Speaking of plugs...whens the last time it had a set?