Topic: Need help with Prob!

[roksld13]

Hi guys i have an issue (or what i think to be an issue) Ive got a 97 2.5l 116000 miles on it, 4.88 gears, banks header, 4.0l tb on 33 bfg's.  OK hears the prob, going down the high way through 3rd gears is very slow but not really my prob.  When i get to 4th at 3000 rps that's it no more, so i shift and the same thing in 5th.  3000 rps and I'm done it will not go any more and I'm running about 70 mph by then. 
The only reason i think this is a bit odd is because when i had my 35's on I don't remember that being a issue. 
You think I'm reading into something a little to much or does this sound like something i need to inspect a bit farther?
Also it shakes very bad when and If i do get past 70mph i.e. going down a hill or a good tail wind.
Thanks for the info!

[sharpxmen]

Hi guys i have an issue (or what i think to be an issue) Ive got a 97 2.5l 116000 miles on it, 4.88 gears, banks header, 4.0l tb on 33 bfg's.  OK hears the prob, going down the high way through 3rd gears is very slow but not really my prob.  When i get to 4th at 3000 rps that's it no more, so i shift and the same thing in 5th.  3000 rps and I'm done it will not go any more and I'm running about 70 mph by then. 
The only reason i think this is a bit odd is because when i had my 35's on I don't remember that being a issue. 
You think I'm reading into something a little to much or does this sound like something i need to inspect a bit farther?
Also it shakes very bad when and If i do get past 70mph i.e. going down a hill or a good tail wind.
Thanks for the info!

i don't think 70mph in 5th is a bad achievement (at 3000rpm). does it go over 3000rpm in 4th or 3rd? - just trying to understand what problem you describe, is it that the engine does not rev over 3000 rpm in any gear or that you can't go more than 70mph in 5th.

[aw12345]

He has a problem in 3th and 4 th also pretty much will not go over 3000 rpm

[sharpxmen]

He has a problem in 3th and 4 th also pretty much will not go over 3000 rpm

maybe lack of fuel in that case (considering that it can rev it fine over 3000 rpm in 1st and 2nd)

[FourbangerYJ]

If your have floor mats or carpet check to make sure that the pedal is not getting caught on anything and won't go any further and stopping the RPM's.

[sharpxmen]

If your have floor mats or carpet check to make sure that the pedal is not getting caught on anything and won't go any further and stopping the RPM's.

yeah, never thought of that - on the same lines maybe have someone floor the pedal (with the engine off) and try to open the throttle by hand in the engine bay to see if there's any more travel - could be the cable jacket or plastic holder(s) of the jacket as well.

[Jeffy]

That's strange since you had 35's and went down to 33's.  Did you change your speedometer gear so it's not thinking you're going much faster?

[aka-justin]

I can't get mine to register over 70 mph any more without prataclly blowing up the motor, but it's really 15% faster than the reading (80.5 mph) since the speedometer gear is still at stock teeth count.  Not having the speedo calibrated also throws the computer out of it's parameters making the air/fuel ratio off as well. (just learned that from Jeffy)

[YoungJeeper]

Seems to me the drivetrain is slipping.. Do you have an auto? Maybe a slipping clutch?
Or maybe wranglers on 33s shouldn't go 80? You've probably hit the jeep wall I've heard so much about but never even attmpted to reach... I shake at 75 lol

[aw12345]

Well the big question for starters is will it rev to close to 5 grand in first second and third? if no, start with part 1 if it's a manual get er rollin in first gear then whem it barely rolls stick it in third and floor it, if it does not back fire then the plugs and wires should be ok then it's on to fuel or an exhaust restriction. Thias is the none scientific method, but it gets you pointed in the right direction fairly quick. a fuel supply problem will show mostly in 5 th gear or near the top in 4th it will hold basck at full throttle, but will pick up speed when you ease up on the throttle a little.

[sharpxmen]

just occurred to me - could be the catalytic converter too

Seems to me the drivetrain is slipping.. Do you have an auto? Maybe a slipping clutch?
Or maybe wranglers on 33s shouldn't go 80? You've probably hit the jeep wall I've heard so much about but never even attmpted to reach... I shake at 75 lol

if the clutch would be slipping then he would see the rpms going up and the speed not increasing, not the case by what he describes.

[roksld13]

Well I do have a high flow cat and new cat back on the way, so exhuast retrictions will be fixed if that's it, as for fuel, from what y'all described that may be a good place to start. Should I get a fuel pressure gauge and check it that way?
Jeffy, no I have not changed the speedo gear from factory. I have had a buddy ride next to me and tell me my speed from that but I assume as I go faster the gap from what I see on my speedometer and how fast I am accually going increases. Mabye, it's science!! Lol

bye the way thanks for all the info everyone. 

[jfrabat]

Well I do have a high flow cat and new cat back on the way, so exhuast retrictions will be fixed if that's it, as for fuel, from what y'all described that may be a good place to start. Should I get a fuel pressure gauge and check it that way?
Jeffy, no I have not changed the speedo gear from factory. I have had a buddy ride next to me and tell me my speed from that but I assume as I go faster the gap from what I see on my speedometer and how fast I am accually going increases. Mabye, it's science!! Lol

bye the way thanks for all the info everyone. 

A fuel gauge would be the ticket to test fuel pressure...  As for the speed, change the speedo gear; the ECU uses this input for its calculations, so even if this is not the cause of your problem, you should change it.  And the best way to accuratly measure your speed, IMHO, is a GPS; ty borrowing one from a buddy if you dont have one.

Well the big question for starters is will it rev to close to 5 grand in first second and third? if no, start with part 1 if it's a manual get er rollin in first gear then whem it barely rolls stick it in third and floor it, if it does not back fire then the plugs and wires should be ok then it's on to fuel or an exhaust restriction. Thias is the none scientific method, but it gets you pointed in the right direction fairly quick. a fuel supply problem will show mostly in 5 th gear or near the top in 4th it will hold basck at full throttle, but will pick up speed when you ease up on the throttle a little.

I would start here if I were in your position; make sure ignition is not your problem, and if it is not, then move to fuel pressure (wich would be my first guess, but since it is more expensive to test if you dont have a gauge, I would make sure it is not ignition first).

[Jeffy]

Well I do have a high flow cat and new cat back on the way, so exhuast retrictions will be fixed if that's it, as for fuel, from what y'all described that may be a good place to start. Should I get a fuel pressure gauge and check it that way?
Jeffy, no I have not changed the speedo gear from factory. I have had a buddy ride next to me and tell me my speed from that but I assume as I go faster the gap from what I see on my speedometer and how fast I am accually going increases. Mabye, it's science!! Lol

bye the way thanks for all the info everyone. 

I would spend the $20 to recalibrate it.  Your PCM is cutting back on your air/fuel maps as it thinks you're going faster then what you're actually doing compared to your RPM's.  Might not fix the problem completely but it might be contributing a bit.

At minimum you should be using a GPS.  Depending on how accurate the other guy's speedo is and how accurate he can read it and any fluctuation you're not getting an accurate reading.

[roksld13]

Het jeffy, where do I take it to recalibrate it? Like a dealer? Would I still need the speedo gear? And if I fluctuate between 35s and 33s what tooth count would y'all recamenened?