97' Sport mild bucking, hesitation

My 97 Explorer Sport has been starting a little rough in the mornings. Its smoothed out in a couple seconds as the idle gets a little higher, but the past 2 days, its hesitated / had a mild bucking.

I drove it around my neighborhood and the hesitation went away pretty quickly. This morning it was fine for about a mile, then a little hesitation / bucking again, and it went away and my 15 mile drive to work had no issues.

Its going to my trusted mechanic in a couple days, but im nervous. Anyone want to enlighten me? I have no "check engine" light on and there are no leaks, well maintained, no noises.

Thanks!:1zhelp:

You'll want to check the coolant level to make sure it is full. An air pocket in the cooling system could cause a waaay off reading from the coolant temperature sensor which will throw off the air fuel ratio.

Also, when is the last time the Explorer had a tune up, plugs, wires, filters, and preferrably fuel injector cleaner added to the tank? If it's been quite some time, check those items.

You will also want to check the EGR system for a stuck valve, dirty valve, or faulty DPFE sensor. Does the Explorer idle smooth, even when it's bucking/hesitating? Is the bucking only at idle?

-Rod

Thanks for the reply! I got the wires, plugs and tune-up done about a year ago, and i do use the STP fuel injector cleaner now and then, but mostly i toss in a bottle of dry gas with every other fill up.

I did have an issue last year with my check-engine light coming on saying i had a exhaust problem, and brought it to the dealer and it turned out just to be in need of a software upgrade.

The hesitation / bucking is NOT when its just sitting at an idle. I'll start it up in the morning, and it starts up a little rough...instead of the loud "VROOM" sound, its more of a "BUB-BUB-BUB" like a harley or something.

Just went out and it was WORSE! it wouldnt stop! So i stopped at the local oil change place i go to,..they looked under it and it wasnt leaking anything, but i noticed water dripping...opened the hood,..it was condensation on the AC unit...but the damn AC has been off! im in Massachusetts and its 60 deg. here!

Anyways, the guy says it could be :

bad gas (i do go to BJ's wholesale and gas up)
bad fuel filter
EMF valve (?)
transmission

But it has been starting rough, but then smoothing into an idle ok,...sometimes....and i drove home after leaving the oil change place, and it was fine, no bucking,..no nuthin. ODD!! HELP!!! PLEASEEEEE!

Have you been using the defroster, or do you have the Electronic Automatic Temperature Control and have it set to "Auto?" If so, both of those settings will enable the A/C compressor.

I suspect the shop said or meant EGR rather than EMF valve. If they definitely said EMF, then find another shop :) .

Gas drier is usually just isopropyl alcohol and won't really do much to clean fuel injectors.

Does the rough start and hesitation seem to only occur after the vehicle has been sitting a short time, or overnight, or seem completely random? What does the exhaust look and smell like when it's starts rough (ie: black and smells like raw fuel)?

Your '97 would have the OBD-II diagnostics which will include emissions monitors. Find someone with a scan tool that can access your PIDs or Component Parameters and see if there are any misfire counts. The misfire counts will be stored, even if they are not over the threshhold to set a diagnostic code.

-Rod

Hey Sho,..thanks for replying again.

No, mine doesnt have the Auto option....but i did have the blower on in the cool-range, so who knows...that could be it.

As for the exhaust, its fine....no black, thick smoke or anything resembling an oil leak. It starts rough when its been sitting a while...hours. Minutes, then its no prob. Just bizarre that the drive home from the oil change guy was fine,..not 1 buck or anything.

What would be a tell-tale sign of a tranny problem?

From the symptoms I've read so far, I wouldn't suspect a transmission problem. However, if you want more of a warm fuzzy, then check the transmission fluid level. While you have the dipstick out, not the condition of the transmission fluid. If the fluid has a strong odor or dark color, then you should have the transmission serviced with a new filter and fresh transmission fluid. When the pan is down for the filter change, have the magnet inspected for abnormal debris.

Since the problem seems to occur after the trucks been sitting for quite some time and the exhaust is not black, it sounds like you may have a fuel pressure issue. Possibly a weak fuel pump, restricted fuel filter, faulty fuel pressure regulator.

I would suggest for your next step that you put a fuel pressure guage on the fuel rail and check for pressure when the key is turned to run, then again after you start the vehicle and it is running. Then replace the fuel filter and measure the pressure again. If the pressure increases, then give it a couple of days to see if that helped the problem. If the pressure is low and does not change after the filter change, then suspect a weak fuel pump.

One other thing to check is the battery voltage. If the battery is weak, but the charging system is strong, the battery may be losing just enough voltage that the PCM goes dumb momentarily after the vehicle starts. After a few seconds, the alternator provides enough current and voltage the get the PCM into the normal voltage range and the roughness smoothes out. When you are at the store to pick up a fuel pressure guage and fuel filter, have them load test the battery and check the condition of the charging system.

-Rod

Wow!! Thanks for the wealth of knowledge! I'll give that a whirl today and let my mechanic check it out tomorrow as well.

I checked the tranny fluid and its pretty clean, but is scheduled for its yearly change/filter in december. However, should it be suspected, i'll have it done immediately.

The battery is getting a bit old, so that might need changing. Yet another thing i'll have taken care of. Interstate batteries ok? Diehard's are usually my 1st choice.

At any rate, i thank you for your help and especially your sharing of yer extensive expertise.

I'll post again when i find out what the deal is.

Thanks again!

-Xthird

I've been pleased with my experiences with Interstate batteries. I don't have much experience with DieHard. Some people swear by them, some people swear at them. I imagine the same could be said for Interstate. When AstroLite batteries were around, we started having problems with their batteries. We explained the situation and that we were switching to Interstate. Their rep told us a story that there are only three battery houses in the US that make the batteries for all the different brands. I don't remember who the battery manufacturers were (I think Exide was one) and supposedly AstroLites came off the same line as Interstate or something. However, we had far fewer come backs on Interstate batteries.

-Rod

Interesting, definatly. My mechanic installs only Interstate, and i trust this guy with my rides.

Im just hoping that it isnt anything serious. Ive babied this vehicle and have had it serviced even when i merely have a feeling that something might be wrong....i prefer to do maintenence BEFORE something goes wrong. I hate these little surprises.

Thanks again for all the good info! If anything else comes to mind, dont hesitate to throw it out there.

I havent started it today, but here's a question: With the "bub-bub-bub"-harley type rough starts that quickly go away in a matter of a few seconds, could this be a timing belt issue? I had it replaced at 60k and now its 124k.

I would not expect a timing belt to cause this type of issue and dissipate after a few seconds. However, don't delay changing that belt too long, if it breaks it will leave you sitting. They usually break when you're in the middle of no where during a nasty storm. This would be a good item to apply your maintenance habit towards. :)

-Rod

UGH!!! Im a wreck here.

Just got off phone with mechanic...says it might be the start of a head gasket problem. I swear, if thats it then i'll be extremely upset.

He says he needs more time to diagnose the problem, says it is definately weird what its doin...but needs more time to diagnose it.

I would be very surprised if a head gasket problem went away after only a few seconds with no other symptoms such as white exhaust or overheating. I don't think you should let his phone diagnosis concern you yet.

-Rod

Yeah, Rod, im hoping the same....

No overheating, clean fluids, NEVER abused, well-maintained, no white smoke, no missing coolant...God help me.

Thanks Rod

Well that's a new one.......the start of a head gasket problem?? Ya that happens when you start the car for the 1st time............sooner or later it will probably go.!! I would check the fuel rail/pulsator/ or the fuel pump. Maybe you have a small leak or some dirt in there. bogging will occur when there is fuel starvation or power loss. if the engine runs (idles) fine than it is a fuel problem. Tho BJ"s gas is cheap there are filters on their pumps too. If you suspect it is their gas then use an octane booster for 1 tank .

Thanks 97.

I actually have to take it to the dealer tomorrow cuz my mechanic couldnt find the issue.

He said he checked all plugs and they showed no problems, corrosion or signs of wear due to coolant in the cyliders. So he said its most likely not a head gasket problem.

He also drove it to the next town over with a scanner hooked up in order to see if there were any codes, any misfires, any sensor issues and all numers were fine and operating properly. He said i should go do a dealer who most likely has a better scanning system than his and can be more thorough.

The dealer is literally across the street from him, so they can cross the road and get the ride no problem,...and they dont charge until they have diagnosed the problem.

Hope it isnt anything serious like a bad fuel injector or something.

Ok,...im getting mad here.

Just called the Dealer service boss,...it did buck a lil for them too, but then was ok. Scanner showed no codes at all. They are gonna let it cool and see if it does it again (DUH! of course its gonna do it again!)

:banghead:

Well,...dealer thinks it is a cracked head. Is keeping it overnight to check. Plugs were replaced back in Spring time so theres no way to see if there is definatly coolant in a cylinder.

Pray for me!

Well, if the cylinder is burning coolant, the plug from the bad cylinder should be exceptionally clean, more so than the other 5 plugs. Also, the crack would allow compression into the cooling system which would show up as bubbles in the cooling system. I would also expect a crack to exhibit itself worse as the engine warmed up and the head/crack expands.

Has the truck been using coolant?

-Rod

Not to my knowledge. The overflow resevoir was dry a ways back, but there were no problems back then. Whenever the oil was changed, they topped off any fluids, but it was never LOW.

Well, i'll know tomorrow AM if im a goner.

Does the entire engine need to be replaced? or just the head?

Well, I'd be quite surprised if even a head needs to be replaced, but I don't have the vehicle in front of me. Unless the dealer can provide hard evidence that the head is the problem, you may want to consider getting a third opinion. Maybe you can get at least two centers to agree.

-Rod

Yeah, i'll def. look into that.

However, a engine replacement would be $5K+!!!

Can the head be replaced only and save some $$ ? This is a little out of my league.

Well,...dealer sez coolant in cyl #3. Either head or head gasket. My trusted mechanic is getting back to me with prices.

I really was hoping someone else would chime in. I don't understand how a cracked head would get better as the engine warms up and not have other symptoms like overheating, etc.

You should be able to replace the head without replacing the engine, but you'd want to weigh the cost against the mileage on your engine. If you plan to keep the vehicle a long time, replacing the engine may be worth the extra.

I still struggle to understand how your symptoms line up with a cracked head/head gasket leak.

-Rod

Talked with a co-worker to make sure I'm not crazy. He agrees that the symptoms you've described here do not match an issue with the head or a head gasket. He suggested paying the $20 or so to have the dealer run a combustion products test on the cooling system. He said these testers are quite common and should not be hard to find one nearby.

-Rod

Tech said that there is some, but very little in the cyl when they turn it over. And that it will only get worse.

Look, im getting a newer ride. This one ive had for 4 years and it has been good to me.

New question is this: Do i fix and trade it in? Or do i just get it to the dealer for my new ride and let them deal with it?

Chances are pretty good that the difference in trade in value between the way it is now and if you were to fix it will not be enough to offset the cost of fixing it.

It seems like if there is so little coolant in the cylinder, it would not cause the bucking or hesitation. If there is enough coolant in the cylinder to cause the bucking/hesitation, it should also be enough to cause a white puff of exhaust upon startup, or when it is bucking/hesitating.

-Rod

Well, my trusted mechanic is going to start taking apart the head on Friday and he'll determine if it needs a new head or a head gasket. Hes already found a supplier of heads at about $300 each, and this guy wouldnt stiff me. I plan on selling it after, but i need something to trade in. So i'll fix it for a grand or a lil more, then flip it for $4-5k.

I just hope i dont get a "doesnt look like it needs either a gasket or head" and then im back at square 1.

I had the fuel line tested if there was a clog or vacuum problem and all tests came clear. The amount of coolant leaking into the cyl is so small (because i caught it early) that its not going to make it smoke or smell like cotton candy. We'll see how things go.

Ok,...closure time:

It was the head,...had a crack in it. There was corrosion on the valves of cyl #3, and my mechanic says that he can order new ones at $300 a piece, vs. Ford which would be $900 a piece.

So yeah, new heads, new head gaskets, the rest of the car "could last forever the way ive taken care of it", so i'll sell it after.

So if anyone around MA. wants a really well-maintained Explorer Sport 1997, let me know! lol

Thanks for all your help, people!