robbie95 Posted May 19, 2018 Share Posted May 19, 2018 Basically, long story short. I'm having issues going up hill, acceleration is kind of sluggish and it has a hard time going above 55mph. I don't have a tachometer so I don't know what my rpm's are, but when I get it up to 50-55 mph, the rpms sound high. Any thoughts? Link to comment Share on other sites More sharing options...
Smokeyyank Posted May 19, 2018 Share Posted May 19, 2018 Its a 4 banger...so yeah not going to be a torque monster. Did the issue just start? What about time size or anything else that might be an issue. Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 19, 2018 Share Posted May 19, 2018 1 hour ago, robbie95 said: Basically, long story short. I'm having issues going up hill, acceleration is kind of sluggish and it has a hard time going above 55mph. I don't have a tachometer so I don't know what my rpm's are, but when I get it up to 50-55 mph, the rpms sound high. Any thoughts? What size tires and what axle ratio do you have? Link to comment Share on other sites More sharing options...
amsuco Posted May 19, 2018 Share Posted May 19, 2018 We just went through these same symptoms on a non-jeep vehicle. It turned out to be the cat. You might want to check it out. We were afraid we might be looking at tranny work. It's nice to get a pleasant surprise every now and then! Link to comment Share on other sites More sharing options...
Pete M Posted May 19, 2018 Share Posted May 19, 2018 did this problem come on suddenly or slowly? Link to comment Share on other sites More sharing options...
Dzimm Posted May 19, 2018 Share Posted May 19, 2018 If this problem just started to happen, my first thought is a clogged cat as amsuco mentioned. Same symptoms happened on my XJ a few years ago and it was due to a clogged cat, which was replaced with a cheap eBay universal cat that's still going strong. More info is definitely needed though, such as tire size and gears for any further thoughts. Link to comment Share on other sites More sharing options...
robbie95 Posted May 20, 2018 Author Share Posted May 20, 2018 So, I don't really know much about gear ratio's etc, still a noob, but I have 235/75 r15's on there right now. I'm assuming its the stock axle ratio. I think it came on slowly, because I've been driving it for a while and just started to notice it having more and more trouble going uphill and going above 55. Yes, I know it's a 4banger lol, I don't really want to go fast, but struggling to make it to 55? That can't be normal. Right? Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 20, 2018 Share Posted May 20, 2018 Look for a tag on the diff cover and the gear ratio will be stamped on it. If it's never been opened up, there's a good chance the original tag is still there. This one is a 4.10. Other options could be 3.07, 3.55, & 3.73. The numerically higher the ratio, the better, especially for a 4-banger. Link to comment Share on other sites More sharing options...
dvitha Posted May 20, 2018 Share Posted May 20, 2018 have you had a tune up lately ? Most of the 2.5L with ax5 I have seen came with the 4.10. In 5th gear your at 2225 rpms in 4th your at 2612 rpms with those 235/75515s tire. On a flat road you should have no problems keeping up at 55 mph even with over sized tires. They do cost you mpg on the 2.5L It should be able to handle going up a hill at 55 mph with out to much trouble. I would check plugs, wires, cap, rotor, fuel pressure, air filter as a start. Robbie95 below was oem specs with your setup. As you know 2.5L needs to rev to make more HP, and your torque is pretty steady up to about 3k where it drops off quick. That jeep mj 2.5L came with 4 tire sizes these are rpms at 55 mph in 5th then 4th gear 26.5 inch 195/75r15 - 5th 2430 rpms - 4th 2860 rpms - Best for cruising speed and power slight less mpg 27.4 inch 225/70r15 - 5th 2350 rpms - 4th 2765 rpms Best mpg 27.7 inch 215/75r15 - 5th 2325 rpms - 4th 2740 rpms Best mpg 28.3 inch 225/75r15 - 5th 2276 rpms - 4th 2680 rpms - mpg is hit with any hills at 55 mph or above Link to comment Share on other sites More sharing options...
robbie95 Posted May 20, 2018 Author Share Posted May 20, 2018 I just recently replaced spark plugs, spark plug wires, distributor, distributor cap, and the air filter a few weeks back when I did a tune up. Haven't check my fuel pressure though, I'll have to check that and see whats up. I have some blow by so my air filter usually always has a little bit of oil on it, but not much I can do about that atm. Link to comment Share on other sites More sharing options...
robbie95 Posted May 20, 2018 Author Share Posted May 20, 2018 1 hour ago, HOrnbrod said: Look for a tag on the diff cover and the gear ratio will be stamped on it. If it's never been opened up, there's a good chance the original tag is still there. This one is a 4.10. Other options could be 3.07, 3.55, & 3.73. The numerically higher the ratio, the better, especially for a 4-banger. Doesn't have a tag on mine unfortunately :/ Link to comment Share on other sites More sharing options...
robbie95 Posted May 20, 2018 Author Share Posted May 20, 2018 On a side note, my valve cover gasket did start leaking, and I'm replacing it as we speak, but while taking the bolts out, one of my bolts broke, so I have to find the right size bolt for it. Might check my spark plugs to see if they have oil on them, might be a long shot but worth a shot. Any ideas what size bolt goes into the 2.5 valve cover? I'm reading its a 1/4 - 20 but not too sure. Link to comment Share on other sites More sharing options...
Jeep Driver Posted May 20, 2018 Share Posted May 20, 2018 Yes, 1/4 20. Link to comment Share on other sites More sharing options...
dvitha Posted May 20, 2018 Share Posted May 20, 2018 Do the mod to valve cover so you don't get so much oil in to you air filter. I like to do a pcv and then no more oil on air filter. Link to comment Share on other sites More sharing options...
robbie95 Posted May 20, 2018 Author Share Posted May 20, 2018 10 hours ago, dvitha said: Do the mod to valve cover so you don't get so much oil in to you air filter. I like to do a pcv and then no more oil on air filter. Is there a write up somewhere about this? Link to comment Share on other sites More sharing options...
Dzimm Posted May 20, 2018 Share Posted May 20, 2018 15 hours ago, robbie95 said: So, I don't really know much about gear ratio's etc, still a noob, but I have 235/75 r15's on there right now. I'm assuming its the stock axle ratio. I think it came on slowly, because I've been driving it for a while and just started to notice it having more and more trouble going uphill and going above 55. Yes, I know it's a 4banger lol, I don't really want to go fast, but struggling to make it to 55? That can't be normal. Right? It doesn't accelerate well at all and sounds like it's struggling to breath right? The more you describe it, the more it sounds like the cat. With the truck off, climb under and bang around your cat and listen for anything rattling around in there. I'm almost positive that's what it is. Link to comment Share on other sites More sharing options...
robbie95 Posted May 20, 2018 Author Share Posted May 20, 2018 34 minutes ago, Dzimm said: It doesn't accelerate well at all and sounds like it's struggling to breath right? The more you describe it, the more it sounds like the cat. With the truck off, climb under and bang around your cat and listen for anything rattling around in there. I'm almost positive that's what it is. I agree, fired up the truck this morning and was listening to it.. (Most of the time I just get in and drive) When it's idling it has this like "rattling" sound that comes from either the muffler or cat, I'm not really sure, but when I tap the cat with a hammer or something when its off, it doesn't sound like a rattle, or if it does, it's not very distinct. If I take off the cat, do I have to weld the new one back on there? Or can I use the exhaust clamps to reinstall it? I figure while I'm doing that I might as well replace the muffler too. Link to comment Share on other sites More sharing options...
dvitha Posted May 20, 2018 Share Posted May 20, 2018 Ditto! ^ I did not think about that, since these old truck are exempt here, and we just hollow them out after 100k and put back on for view inspection. Link to comment Share on other sites More sharing options...
Dzimm Posted May 20, 2018 Share Posted May 20, 2018 6 hours ago, robbie95 said: I agree, fired up the truck this morning and was listening to it.. (Most of the time I just get in and drive) When it's idling it has this like "rattling" sound that comes from either the muffler or cat, I'm not really sure, but when I tap the cat with a hammer or something when its off, it doesn't sound like a rattle, or if it does, it's not very distinct. If I take off the cat, do I have to weld the new one back on there? Or can I use the exhaust clamps to reinstall it? I figure while I'm doing that I might as well replace the muffler too. Exhaust clamps will work just fine. I've always done exhaust work myself and just used exhaust clamps. Link to comment Share on other sites More sharing options...
robbie95 Posted May 20, 2018 Author Share Posted May 20, 2018 what do you guys think about running straight pipe? is it really obnoxious? edit : just went ahead and ordered what I need, cat, clamps and a new o2 sensor, anything else you think I'll need? will a cutting wheel on a grinder suffice or should i borrow a sawzall? Link to comment Share on other sites More sharing options...
Eagle Posted May 21, 2018 Share Posted May 21, 2018 Does the '91 still have a flange at the front end of the catalytic converter, or is a male-female slip connection? If it's a flange, you'll need a new flange gasket, probably new bolts -- and I hope you ordered a direct-fit converter, not a universal fit. Link to comment Share on other sites More sharing options...
Pete M Posted May 21, 2018 Share Posted May 21, 2018 yup, obnoxious is the word I would use. I broke the pipe upstream of the muffler on a wheeling outing and had to drive 2 hours home. anything over 900 rpms attracted a lot of unwanted attention. Link to comment Share on other sites More sharing options...
Eagle Posted May 21, 2018 Share Posted May 21, 2018 Looks like the '91 still uses the flange and gasket: Link to comment Share on other sites More sharing options...
robbie95 Posted May 21, 2018 Author Share Posted May 21, 2018 45 minutes ago, Eagle said: Does the '91 still have a flange at the front end of the catalytic converter, or is a male-female slip connection? If it's a flange, you'll need a new flange gasket, probably new bolts -- and I hope you ordered a direct-fit converter, not a universal fit. https://www.rockauto.com/en/moreinfo.php?pk=129238&cc=1181764&jsn=376 that is what I ordered right there, gonna order a gasket really quick, what size bolts are they? edit: so will the cat fit right on the tail pipe? or am i going to need to find one of those little adapters and some pipe? going to be using clamps too btw, don't know how to weld. Link to comment Share on other sites More sharing options...
Eagle Posted May 21, 2018 Share Posted May 21, 2018 The cat doesn't mate to the tailpipe, it goes into the muffler. Don't remember for certain, but I think the bolts I used are 5/16x1.5 or 5/16x2. Link to comment Share on other sites More sharing options...
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