meangreene

I bought this truck with a bad head changed head put new timeing gears plugs ,wires,cap,button,fuel filter,tps sensor new gaskets ohmed out all injectors sensors checked all vaccum lines truck is driveable but it has just a little miss to it at cold idle cant tell it when it warms up it doesnt do it ever time but when driveing it lags until you hit about 3200 rpm then its like hiting nos it kicks in runs like a bandit until it drops back down i thought maybe a stopped up injector i have run several bottels of lucas through it !!!!!!!!!!!! ideas hints facts anybody have a clue thanks

abecedarian

Punctuation?

Takenover

Run a bottle of rxp through your fuel. Pull the vacuum line off the brake booster while its running, and let it suck in a bottle of seam foam. It will smoke like nobodies business for a few seconds, but it will burn off alot of the carbon build up.
Cold start injector working? Timing is on? tps adjusted right? rechecked valve clearance?
egr valve stuck? pcv valve stuck? Could be a number of things to cause a miss.

abecedarian

At least be more specific-
cold start injector is working while cranking the engine to start and turns off after you release the key
timing and idle speed have been set properly- after the engine has fully warmed up and with the jumper in the diagnostic connector during adjustments
TPS is reading IDL to the ECU with the throttle fully closed
what are the valve clearances supposed to be?

and having read, re-read, and re-re-re-re-re-read the OP's post, it has a miss at idle when cold that goes away, mostly, with the engine warmed up
so we need to verify that the warm idle speed is set properly and that the cold idle speed is at least the same, and should probably be higher than the warm idle speed at least until the coolant temp is around 100F at which time the cold and warm idle speeds should be the same, i.e. no change in idle speed as the engine warms up.

Personally, I would've liked a post that made sense to read so I didn't have to delve into every possible thing that could cause a misfire with a cold engine.

And if I really wanted to, I would've asked what the spark plug gaps were set at.

meangreene

Well first of all Abecedarian I am a gearhead not a english major are we talking trucks or proper grammer you dont like my post dont read it. To everone else thanks for your reply . I was meaning it runs smooth cold idle speed drops down when it warms up

abecedarian

Well, you're welcome: for both my grammar critique and my other reply which you either have ignored or didn't see.

As for "runs smooth cold and idle speed drops [when warmed up]"- that's the way it's supposed to work. However, you also said in your original post:So does it run smooth cold or does it have a little miss?

What about my question regarding spark plug gaps? What are they set to?







For the record:

• I am also a bit of a gearhead having previously received certifications on Caterpillar, Detroit and Cummins diesel engines as well as Allison and other various transmissions used on OTR trucks and several tractors as well as casually delving into Perkins engines as well as hydraulic controls.
• I have installed two lift kits on two vehicles during down-time at work, while sitting in the parking lot at the Motel 6, including getting the alignments on both set to within .1 degree on all angles and within 1/8" on toe.
• I have rebuilt a few engines including a Type IV VW, repaired the turbo on my 79 Mustang, and besides that- I've done all mechanical work, on every vehicle I've owned over the last 20+ years; including the 88 4Runner, 91 Pickup, 72 Firebird, 89 Celica and 82 CX500TC motorcyle whenever possible. The exceptions to that being when I do not have the tools or facilities to perform the repairs, don't have the time or the warranty provided by letting someone else does the work is worth it to me.
• My major in high-school (if you can call it a major) was computer science. I did not go to a college proper so do not have a real "major".
• Anyone who speaks English as their primary language should at least know what commas and periods are and should know what a sentence is and how to form one. In this case, I could care less about paragraphs, but when it takes 3-4 times longer to interpret what someone writes than it does to formulate a response....

meangreene

It runs smooth when cold. I know idle slows down when it warms up. I am saying thats when it starts missing when it gets warm. Set plugs by spec in repair manual don`t remember the number off top of my head. Are you a school teacher perhaps?

tim a.

Hey Abe,can you include a pic of your johnsen along with your resume?I mean while ya got it out.....!Mr Mean,your post was baffling,and lack of punctuation and or grammar makes it tough to follow.Now I aint bee's as smart as everybdy else,but I would surmise you have a vacuum leak,the low idle speed being the big clue.As the engine warm up,your ported vacuum switch opens,applying vacuum to the rest of the circuit.Take a can of brake clean and spray the top of the engine while running and listen for rpm changes,You should be able to find it easily.Make sure all hoses are going to the right component.Please report your findings.

meangreene

Tried it no luck checked ever thing I know. Checked spark,vacuum, fuel,etc don`t know where else to look. Like i was saying what puzzels me is when your driving and the engine reaches 3200 rpm. Its like another cylinder kicks it doesnt miss it runns out good until it drops back below 3200. I was just giveing Abe a hard time.

abecedarian

Nope, not a school teacher. Go figure, eh? I gravitated away from being a paid mechanic and instead spend my time building and upgrading cell sites.

Sorry tim a., this is 'mostly' a family friendly site, so no johnson pics. However, I have used these "Johnson & Johnson" products.


Now back to the main issue at hand- you're more than welcome to give me a difficult time.

Seriously though....

Assuming when the head gasket was repaired, the head itself, including the valves and seats, were checked and is fine...
Assuming when the head was installed, new chain, guides and tensioner were installed...
Assuming you've checked and set all the valves appropriately...
Assuming you've checked and set all the spark plugs correctly and have new, or at least known good wires, cap, rotor, and the coil is in good condition...
Assuming you've set the idle speed (~750 RPM) and timing to spec (5 BTDC), with the engine fully warmed up and using the jumper in the diagnostic connector...
Assuming that the cold engine idle speed is higher than the idle speed when warmed up...

It sounds like you may have a fuel delivery problem, possibly an injector with a bad spray pattern, maybe a loose injector plug or issue with the injector wiring splices in the harness. Possibly a leaking / dribbling cold start injector.

A cold engine will be a bit more tolerant of injector problems as long as it's getting the rich mixture it needs. As the engine warms up, idle speed lowers to normal, and the mixture is leaned out by the ECU, poor injector spray patterns will have a more pronounced affect on engine operation. At sufficiently high RPM's, turbulence in the intake tract can sometime atomize fuel droplets that weren't otherwise sufficiently atomized.

However, what we have here is a consistant problem that intermittently goes away. Injectors do wear out, though theoretically they shouldn't. Overheating an engine (blown headgasket, right?) exposes the injectors to abnormal operating conditions that can cause injectors to similarly malfunction. Injectors are basically glorified electric solenoids cooled by the fuel that flows through them. But when an engine overheats, that heat can be conducted up through the intake manifold and conducted into the injectors causing the injector to warp, the pintle to deform, etc. The injector will still "ohm out" properly, but may not flow fuel properly, thus won't create a proper, atomized fuel spray.

Heck, that can even happen to an injector that's never overheated but has been exposed to dirty fuel.

Have you checked the fuel filter?

meangreene

All your assumtions are true head was from Oriely Auto Parts. All new gaskets,head bolts gears,chian,so on so forth.I am in process of going over timeing, valves agian! I thought it might be a bad injector but they ohmed out ok.But what your saying makes sense I thought about replaceing them but i was not sure they were the problem. Is there another way to check them with out pulling them and takeing them to a shop. Or can you narrow down wich injector is causing the problem if in case this is the problem. thanks Abe glad to know you got a sense of humor.

tim a.

How did you get from a warm miss to another cylinder kicking in?I would venture you have some type of timing issue.Seems to me an injector would be a consistant miss,but thats not always the case.Try adding propane to the intake{carefully} while its missing.If the miss goes away,you know its leaned out and a fuel problem.You can also use a non contact thermometer to inpect exhaust manifold for temp differences.A cooler cylinder is a giveaway to a dying injector.Man your spelling is painfull,bro.

meangreene

I was trying to discribe that in my first post. But ever body flipped out ya my typing ain't much better and ain't is not a word I know.Would the heat not transfer across the manifold to give the same reading over all? Ill give it a try see what i come up with thanks for the tips guys!

meangreene

The timeing is not advanceing by the book its supposed to be 5 deg cold. When warm between 10-14 deg pick up ohms out ok. But know all of a sudden its gives me a 31 code mas air flow but it ohms ok too. Anybody????????????

meangreene

O I forgot it smells ritch and black smoke.

tim a.

Did you short the connector to set the timing?I doubt the afm would give a miss,but if it was bad it would certainly give you a rich run condition.Just because it ohms out doesnt mean its good.

meangreene

Yea i put the jumper in! Is there another way to test the afm? If it is malfunctioning will it keep the timeing from advancing.