Hesitation/Stumble during acceleration

[amw027]

Lemme start with a bit of info, I purchased a salvaged(due to an electrical issue that has already been fixed) 94 ford explorer 4.0 4x4 4door v6 eddie bauer edition from a private seller with 151,000 on it about three years ago. Currently it has about 178,000. I love my truck! For a few months it was home so getting rid of it is out of the question. Up until about a year ago everything was fine, I do all the work on my car myself. (with the help of my chilton and my dad on the phone) the bigest project was the intake manifold gasket(which my dad had to do) but all was well. Recently I have noticed a leak in the tranny, but cant identify where its coming from, once it shifts into 1st gear the car will "jerk" around while shifting to 2nd gear. It does this no matter the temp of the engine. I have tried everything I can think of and nothing is working. WORK DONE: New fuel filter, new spark plugs(with a plan to change plug wires and coil pack), new fuel pump relay, tbi mounting gasket was replaced while the engine was torn apart to change the intake manifold gasket, along with a list of other things from radiatior hoses to thermostat gasket and housing.

I've always been the type to do things on my own but since I'm not a mechanic and I've done everything i can possibly think of, I'm in need of a lil push in the right direction. I welcome any suggestions.

 

[Wolfie_85]

Does it do that going into any other gear? Going up a hill or incline, does the engine stumble under the load? I'm only asking to determine whether or not your issue is with the transmission or the engine. Check your tranny fluid, too.

 

[amw027]

yea it does stumle going up a hill but only if i was stopped at the bottom. Although depending on the length of the hill or the incline it will stumble the whole way up. The tranny has been on mind a lil lately. I've had a leak for about a year now and in an attempt to protect the tranny I've been changing out the fluid and filter every 6 months but when I change the fluid its never all that dark nor does it smell horribly burnt. I've been doing a lot of research on rebuilding the tranny myself. personally i feel like everything that i have read is making a bigger deal out of it than it is. From what I've read as long as u can keep everything organized, cleaned and lubed putting it back together will be easier. Am I misreading everything? Is this something an amature diy-er can do?

Forgot to say, occasionally if I'm on the freeway, and speed up it will sometimes stumble.

Some previous suggestions were to clean the throttle body(or make sure its as clean as it can be without removing anything), make sure the throttle position sensor does not have any debris in it, replace the vacuum modulator valve on the transmission(sounds kind if complicated but with enough research i think i should be able to do it). Do these suggestions sound like they will fix the hesitation or stumble or is this a waste of money and not going to do anything?

 

[Wolfie_85]

It sounds like you either have something causing the engine to misfire (or a fuel pressure issue), or your transmission isn't shifting properly.

You said you did plugs, wires, etc...so that rules out lots of things (unless you have a cracked spark plug wire or something). You could do a fuel pressure test. Check the gap on your plugs (should be .54). Make sure the wires are properly seated. Not that you wouldn't notice it at idle, but never hurts to check and be optimistic.

Rebuilding a transmission is not something I personally would do. There's a reason transmission shops have a great deal of scrutiny to overcome. But, if you want to try, go for it. Just make sure you have some instructions handy, and maybe a buddy who knows about transmissions in case you hit a rough patch.

In summary, I would pull codes first, check everything under the hood over real well. But without driving it myself, it sounds like it could be either transmission or engine. If you don't know what you're feeling (not a dis, just saying you might be learning, and there's nothing wrong with that), it's hard to say. Any sounds? Notice it at or between shifts?

 

[amw027]

I did the spark plugs almost 2 yrs ago but I'm going to do them again soon(just trying to save the money) and when i do, I'm going to, at that time change plug wirees and coil pack, so its has not been do yet but is on the list.

How do I check fuel pressure?

 

[2stroke]

sounds like an engine problem to me. If its tranny, it sounds like torque converter to me. That is a rare problem though. As for shift points, it shouldn't matter. I can be in 5th gear with mine, and it will pull smooth from 500 rpm to redline.

 

[Wolfie_85]

There is a valve for the fuel pressure on the passenger side of the engine, if you're looking at your intake manifolf from that side, you'll see it. You can rent a fuel pressure gauge from an auto parts store to test it. Advance Auto charges the price of the tool, you get it back when you return it. So, free! The exact specs are here on the forum for the pressure. If it's been a couple years for plugs and wires, definitely check em out. If you can't replace them this minute, you'll at least know whether or not it's the problem.

 

[mr cribb]

I don't know what plugs you are running, but I try to run factory plugs. Example being Ford gets Motorcraft, Chevy get AC Delco... you get the point.

I have been around several motors that pissed a fit about the type of plugs used. To alleviate this issue I run factory type plugs.

Spark plugs and wires are simply preference based. There's been much discussion over this, all in all it comes down to what you like.

I have a misfire on a hot restart, and it does even itself out. I have replaced my plugs wires and a different coil pack. My plugs and wires have almost 30k miles on them. I may have a fuel pressure issue, but I don't drive it often enough to warrant an investigation of the fuel system.

 

[amw027]

[MENTION=128768]Mr.C[/MENTION]ribb - Current plugs are autolite platinums almost 2 yrs old, current wires and coil pack I have no idea only had the truck 3 yrs never replaced them, but when i do change the plugs I am also going to change the wires and coil pack to make sure there are no issues there.

[MENTION=123810]wolfe85[/MENTION] - Thank you for all your suggestions, I will post again when i change out the new plugs and acessories and test the pressure of the fuel system.

[MENTION=235549]2stroke[/MENTION] - shift points on my truck go as follows 1st- 2000, 2nd- 2200 to 2400, 3rd around 3000, and 4th- around 4500, havent paid much attention to 5th gear. Idk if those are normal. Had a vacuum issue a while ago but that kinda fixed itself i guess idle in park used to be around 1000, now its back to about 600-700 in drive its about 1100. I noticed that the stupid elbows at the back of the manifold(? i think) kept poping off so i got some hose clamps and put them back.

Thank you all, Happy Exploring!!!!!!!!!

 

[vq5speed]

Most likely an engine issue. Tranny issues would normally be slipping out of gear. Hold first gear to long before it shifts. Engine revs without going into gear. Those are types of Tranny issues you'll have. Stumbling misfiring are engine issues. But one's interpretation of stumbling may be mis-firing to someone else. So there is a big difference between stumbling and misfiring 2 different issues. I would not rule out bad wire and plugs just because you replaced them once. I had a misfire issue and had put new OEM replacement wires and plugs maybe 3-4 months old. I redid it all again with higher quality wires and new plugs and the misfire went away.

 

[malohnes]

I think you've a vacuum leak at least causing some of your issues. I'd scrutinize your vacuum lines. They are prone to getting brittle with age and heat and can cause all sorts of issues like you describe.

 

[amw027]

[MENTION=85020]vq5speed[/MENTION]- Wouldn't a misfire put the check enigine lite on tho? Check engine light has only come on once since I've had the truck, for mas airflow sensor(i just didnt plug it in all the way after a repair). Hasn't been on since and I'm fairly certain it works cuz light comes on real quick and then goes off right away when i start the car( as due all the lights). The abs light has been on for a while, not sure why.

[MENTION=117556]malohnes[/MENTION]- But all my idles are normal from what I've been told and idk know where I'd start looking for holes or cracks.

 

[vq5speed]

No you won't get a check engine light from just a misfire. The engine may seem to run ok at lower speed but misfires at freeway speeds or when you accelerate hard.

 

[2stroke]

I have a hunch you simply have a bad sparkplug or wire. At minimum, ohm all the wires, visually check the wires and plugs, then check gap on the plugs. Sounds like the plug gap opened up to me. If you have put about 30,000 miles on these plugs, its about the time you might see problems with standard plugs.

 

[amw027]

[MENTION=85020]vq5speed[/MENTION]- Good to know, Thank you.

[MENTION=235549]2stroke[/MENTION]- While wires and coil pack are unknown, the spark plugs(again autolite platinums) have maybe 15,000 miles, its ony been about 18 months. They were also my first thought and the next repair i was planning.

 

[amw027]

ok so I went to a friends tranny shop and found out my vacuum modulator valve is bad. That was already on ly list of culprits. Any suggestions or easy instructions to replace it.I have the part already.

 

[amw027]

new vacuum modulator valve installed today, not too much of a change really shifting is weird, i do still think i definetly have a misfire. My truck shifts into first perfectly, never been better, but everything after that is a mess. I was told I was being sold a pre-adjusted valve but I'm not sure they are correct. Would any one be able to tell me the right specs for this valve for my truck. Also, is it bad to drive it if the valve is not properly adjusted?


I also just remebered when i took the old valve off, there was no rod/pin and my new valve did not come with one either. Now to me that rod/pin sounded pretty important, so it sounds bad.What do I do?????

Is it bad to drive it without the pin???