Drives perfectly fine but I'm curious what isn't right

[roboman]

Bear with me here... this is much easier to understand when it's demonstrated in-person and not typed.

My 1999 4.0 SOHC for as long as I've driven it and can remember doesn't climb in RPMs when mashing - it basically sticks at a certain range until it upshifts. What I mean is that I can floor it, and the RPMs are dependent on my foot. There's no seducing increase in acceleration up to redline - the max RPMs I can reach while in drive (neutral is as high as desired) is a hair over 3000. Example: if I'm going slow and light enough on the throttle and it's warmed up, it will engage into 4th gear (auto 5) at 30 mph and the RPMs will increase with speed from 1600 or so up to 2100 before it goes into 5th at 45 mph. But if I were to mash it, the RPMs will go no higher than 3000, and it will go almost straight there instead of climbing up and up and eventually redlining.

Gas mileage is within EPA ranges for appropriate driving, tranny shifts are smooth, nothing else seems problematic, and all in all, there is nothing that is undriveable about

Does this make sense? I can provide more technical details if needed, and I realize how confusing this all might sound so if something needs clarified, please ask. I'm thinking of grabbing the video camera and putting it on YouTube to better show what I mean.

I've tried asking on other forums and people have suggested checking the TPS, catalytic converter, or fuel pump.

Here's what I WISH mine did (in terms of the climbing RPMs) as most of you probably experience. And it might be worth noting that I probably can't go over 30 in first gear if it's in drive whereas this video is in first up to 50: http://www.youtube.com/watch?v=VnQklLd42MI

Once again, if you need to know more or want me to make a video, I will! Just let me know. Thanks in advance!

 

[Rick]

Have you used a code scanner to see if the computer has stored any faults?

 

[YountExplr]

maybe check how much slack is in your gas pedal? I know mine had some slack in it and I tightened it up and it made a big difference. Here is a video thread about it.
http://www.explorerforum.com/forums/showthread.php?t=242299

 

[roboman]

I've done absolutely nothing myself to try and diagnose it. There's nothing undriveable about what's going on now, but there's something that just isn't right. Do you think it would be worth it to take it in to be scanned just for this?

YountExplr - that's an interesting video and kind of neat. I don't have time to watch the whole thing at the moment but I will check that out later.

 

[Willard]

All I can say is for some reason it sounds like it's not kicking down into lower gears like it should. When you mash it at 30mph it would likely jump down to 2nd gears and should shift at redline through the rest.

The suggestion about the gas pedal could be it. Search for the "Ziptie throttle cable mod" on here and do that and see what happens.

 

[roboman]

Well, i don't really think it has to do with shifting down. That was just an example of when I'm babying it. It's more of a throttle issue than the transmission not responding.

 

[YountExplr]

have you tried the throttle cable mod yet? My bet is that is your problem.

 

[roboman]

@YountExplr - I put one zip tie on and I probably gained 250 rpms which gives me 3350 or so total. Then I put another one on a day later and I'm not sure If I can fit another on the cable before it effects the idle. But I've been away since the day I put the second tie on, so I haven't driven it yet to see how much of a gain I got.

I never actually removed the intake hose assembly and whatever else to get to the throttle body to see how far it was actually opening, but it was obvious when I looked under the dash and played with the cable that there was a significant amount of slack.

This fix has worked to up my RPMs though so I'm happy about that. The increase, though, is still based on my foot position, but I'm happy about what I have so far with what the zip ties did.

Thanks for that procedure!