Kyleinreallife Posted February 13, 2018 Share Posted February 13, 2018 2 parter: this question stemmed from me trying to diagnose my idle. What effect does a cat have on engine performance? PO told me it would pass smog, it didn’t. I cut the cat off and it was empty. I put on a new cat, felt less power, passed smog and put the old empty cat back on. Curious as to what’s going on. 2nd part: It’s had a low hunting idle since I bought it, bounces between 4 and 7 hundred, smells rich and feels slightly underpowered when accelerating. Have not done: smoke test. Have done: Tightened manifold and valve cover bolts Tightened manifold to down tube bolts New plugs/wires New cap/rotor New tps(adjusted properly) New egr Cleaned throttle body Cleaned iac( wasn’t much build up/don’t know if operational, idk what effect it would have if not working) New vacuum lines I tested the o2 sensor with my multimeter and was it okay from my understanding...I believe per cruiser54 you need an analog voltmeter to test properly? PO installed Ford Mustang 4 port injectors, unsure of new or not. Had a temporary issue of power loss on number 4 cylinder. On my way to my pop’s to pull the fuel rail, I filled up and dumped some injector cleaner in the tank, power came back after about a mile and haven’t had an issue since, other than the idle and acceleration that’s been there the whole time. Thoughts? Suggestions? Also, exhaust set up: manifold-pre cat O2- cat-straight pipe turn down. That’s what I got it with, an open cat and no muffler, now I can weld and build an exhaust system if someone could inform me what components are/are not necessary and what effect having/not having them would have. I would like it to be a bit quieter, but I don’t want to lose anymore power. Solving the idle and underpowered acceleration are my primary concern. 87' XJ Wagoneer I-6 AW4 NP242 Link to comment Share on other sites More sharing options...
Eagle Posted February 13, 2018 Share Posted February 13, 2018 This is a tough issue to address, because we don't know what you think the acceleration should be. What vehicles are you comparing it to, and how do you typically drive? Have you ever driven a truck with an in-line 6-cylinder engine before? The '87 was the first year of the 4.0L, it was rated for less horsepower than the '88 and following years -- and then in 1991 came the HO (for "High Output) and even more power. The 87 is not a high RPM engine. If you're accustomed to rice rockets, you probably keep your foot on the floor and let it shift at 4,000 RPM (or higher. That's not how the 4.0L engine (especially the early ones) want to be driven. The torque peak for that engine is at a little over 2,000 RPM -- revving it far beyond that before shifting is a waste of gas and an exercise in frustration. What you have is a torque engine, made for lower RPM pulling power -- it's not a Z28 that starts producing power at 6,000 RPM. Link to comment Share on other sites More sharing options...
Jeep Driver Posted February 13, 2018 Share Posted February 13, 2018 Low idle, burns rich. I'll just give you my experience- MAP or vacuum tube to MAP -or- O2 -or- temp sensor. Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 13, 2018 Share Posted February 13, 2018 " PO installed Ford Mustang 4 port injectors, unsure of new or not." Ford Mustang 4-holers came in many flavors and sizes. What's the p/n stamped on them? Get the p/n and look up the injector's specs. It's a good possibility they are way oversized for your engine and are the reason why you're running rich and underpowered. Link to comment Share on other sites More sharing options...
Kyleinreallife Posted February 13, 2018 Author Share Posted February 13, 2018 " PO installed Ford Mustang 4 port injectors, unsure of new or not." Ford Mustang 4-holers came in many flavors and sizes. What's the p/n stamped on them? Get the p/n and look up the injector's specs. It's a good possibility they are way oversized for your engine and are the reason why you're running rich and underpowered. Will do and get back to ya, thanks!87' XJ Wagoneer I-6 AW4 NP242 Link to comment Share on other sites More sharing options...
Kyleinreallife Posted February 13, 2018 Author Share Posted February 13, 2018 Low idle, burns rich. I'll just give you my experience- MAP or vacuum tube to MAP -or- O2 -or- temp sensor. MAT or water temp?87' XJ Wagoneer I-6 AW4 NP242 Link to comment Share on other sites More sharing options...
Kyleinreallife Posted February 13, 2018 Author Share Posted February 13, 2018 This is a tough issue to address, because we don't know what you think the acceleration should be. What vehicles are you comparing it to, and how do you typically drive? Have you ever driven a truck with an in-line 6-cylinder engine before? The '87 was the first year of the 4.0L, it was rated for less horsepower than the '88 and following years -- and then in 1991 came the HO (for "High Output) and even more power. The 87 is not a high RPM engine. If you're accustomed to rice rockets, you probably keep your foot on the floor and let it shift at 4,000 RPM (or higher. That's not how the 4.0L engine (especially the early ones) want to be driven. The torque peak for that engine is at a little over 2,000 RPM -- revving it far beyond that before shifting is a waste of gas and an exercise in frustration. What you have is a torque engine, made for lower RPM pulling power -- it's not a Z28 that starts producing power at 6,000 RPM. Previous vehicles: 95xj I-6, 85 Toyota sr2 4banger, 87 comanche I-4 ...it’s not a butt dyno issue, something’s up with the air/fuel mixture 87' XJ Wagoneer I-6 AW4 NP242 Link to comment Share on other sites More sharing options...
Kyleinreallife Posted February 13, 2018 Author Share Posted February 13, 2018 " PO installed Ford Mustang 4 port injectors, unsure of new or not." Ford Mustang 4-holers came in many flavors and sizes. What's the p/n stamped on them? Get the p/n and look up the injector's specs. It's a good possibility they are way oversized for your engine and are the reason why you're running rich and underpowered. 0280150556https://www.fiveomotorsport.com/bosch-yellow-top-19lb-fuel-injectorThese are what’s installed, I’m not sure what it means for performance...87' XJ Wagoneer I-6 AW4 NP242 Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 13, 2018 Share Posted February 13, 2018 39 minutes ago, Kyleinreallife said: 0280150556https://www.fiveomotorsport.com/bosch-yellow-top-19lb-fuel-injector These are what’s installed, I’m not sure what it means for performance... These are oversized for your 87 engine, ~22lbs @ 39psi. Plus they have a higher coil resistance, so they could be flowing even more. The Ford "yellow top" injectors have been used in a Renix with reported good results, but not this p/n that I've ever seen. Throw a set of pressure gauges on them and see what pressures you are actually running at w. and w/o vacuum. Link to comment Share on other sites More sharing options...
Kyleinreallife Posted February 13, 2018 Author Share Posted February 13, 2018 These are oversized for your 87 engine, ~22lbs @ 39psi. Plus they have a higher coil resistance, so they could be flowing even more. The Ford "yellow top" injectors have been used in a Renix with reported good results, but not this p/n that I've ever seen. Throw a set of pressure gauges on them and see what pressures you are actually running at w. and w/o vacuum. This is my first time troubleshooting an injector issue, could you give a little more detail? I’m not sure what 22lbs @ 39psi means, what is that referencing? And am I testing the injectors specifically with some sort of gauge? Or putting a gauge on the Schrader valve on the fuel rail?87' XJ Wagoneer I-6 AW4 NP242 Link to comment Share on other sites More sharing options...
Kyleinreallife Posted February 13, 2018 Author Share Posted February 13, 2018 How would I check w and w/o vacuum? Which line would I plug?87' XJ Wagoneer I-6 AW4 NP242 Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 13, 2018 Share Posted February 13, 2018 Link to comment Share on other sites More sharing options...
Eagle Posted February 13, 2018 Share Posted February 13, 2018 10 hours ago, Kyleinreallife said: Previous vehicles: 95xj I-6, 85 Toyota sr2 4banger, 87 comanche I-4 ...it’s not a butt dyno issue, something’s up with the air/fuel mixture There is no comparison between the '87 and '95. The '95 is an HO -- the torque peak is at 4,000 RPM, compared to 2,000 RPM for the '87. The '87 was rated at 173 horsepower, the '91 - '95 were rated at 190 horsepower (and felt like more of a difference than that due to the change in the torque curve). The HO still produces acceleration well into the RPM range -- the Renix engines basically fall on their face above 3,000 RPM. They'll rev higher, but doing so is useless. In my '88 XJ and MJ, I use 2,250 RPM as my shift point, for pretty much all driving conditions (both are 5-speeds, so I obviously have control over the shift point). Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 13, 2018 Share Posted February 13, 2018 51 minutes ago, Eagle said: There is no comparison between the '87 and '95. The '95 is an HO -- the torque peak is at 4,000 RPM, compared to 2,000 RPM for the '87. The '87 was rated at 173 horsepower, the '91 - '95 were rated at 190 horsepower (and felt like more of a difference than that due to the change in the torque curve). The HO still produces acceleration well into the RPM range -- the Renix engines basically fall on their face above 3,000 RPM. They'll rev higher, but doing so is useless. In my '88 XJ and MJ, I use 2,250 RMP as my shift point, for pretty much all driving conditions (both are 5-speeds, so I obviously have control over the shift point). ^^^ All true of course, but by stating these incontrovertible facts, we'll have to endure yet another "HO myth" post from Cruiser. Link to comment Share on other sites More sharing options...
Marine1Texas Posted February 13, 2018 Share Posted February 13, 2018 I agree the 87 4.0 renix runs out of steam above 3000 rpms. When I am out of 2wd low on the highway in 2wd high the renix has good low end Torque. Even in 5th gear, it is good from 45mph @1400 rpms all the way up to 80 mph @ 2800. When I am in 2wd low working in the back the truck just craws all over everything with no problem or revving much above 1500 rpms. It is a little 4.0 work horse of a engine that does not need to rev much to reach peak power. I like to shift right around 1900 to 2000 rpms when I have to get up and go. If I am putting around I will shift about 1600 rpms. I use the 31's with 4.10 on d44. Link to comment Share on other sites More sharing options...
SatiricalHen Posted February 14, 2018 Share Posted February 14, 2018 This won’t fix your issues, but will improve power. You can get an ecu out of an 89-90 xj or mj and it’ll add a few ponies. Just figured I’d mention it since this is a thread about power, I’m also having running issues, but I haven’t solved anything much yet. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
johnj92131 Posted February 14, 2018 Share Posted February 14, 2018 I hate the idea of trying to fix an engine that has been bastardized by an unknown number of "mechanics". Return the engine to stock condition!! Get back to basics. Maybe not what you want to hear, but you have a bunch of old issues to fix first. Link to comment Share on other sites More sharing options...
MuchRespect Posted May 10, 2018 Share Posted May 10, 2018 Figured I'd toss a cat/exhaust question out here rather than start a whole new thread: Had my clogged cat cut off a few weeks ago and replaced with a down-pipe. Catless, I'm running well with good power, but it is very fumey, so much so that my gal says she won't come camping until I clean up the smell. Can anyone recommend a quality high-performance cat that won't reduce my power too greatly? Link to comment Share on other sites More sharing options...
johnj92131 Posted May 10, 2018 Share Posted May 10, 2018 Where are you located? Link to comment Share on other sites More sharing options...
MuchRespect Posted May 11, 2018 Share Posted May 11, 2018 4 hours ago, johnj92131 said: Where are you located? Los Angeles Link to comment Share on other sites More sharing options...
Ωhm Posted May 11, 2018 Share Posted May 11, 2018 6 hours ago, MuchRespect said: Catless, I'm running well with good power, but it is very fumey, Running rich kind of fumy? Link to comment Share on other sites More sharing options...
MuchRespect Posted May 11, 2018 Share Posted May 11, 2018 4 hours ago, Ωhm said: Running rich kind of fumy? Sorry, I'm new to the lexicon. I've got pretty good throttle, much better than with the clogged converter, though I guess that's to be expected. I don't have much of a baseline because as this is the only MJ Renix I've driven. I need to give it a lot of throttle in 1st to get it moving and when I do there's a lot of exhaust. Basically, looking for a converter rec that you guys know and trust before I just buy the first thing that fits my truck. I also don't know how much I should expect the performance to change once I do. Thanks in advance for any advice Link to comment Share on other sites More sharing options...
Ωhm Posted May 11, 2018 Share Posted May 11, 2018 Running Rich: Unburnt fuel in exhaust. Soot on inside tailpipe. Burning sensation in the eyes. Vehicles driving behind you slow down or attempt to pass you quickly. A new catalytic converters will not solve this problem. Link to comment Share on other sites More sharing options...
MuchRespect Posted May 11, 2018 Share Posted May 11, 2018 2 hours ago, Ωhm said: Running Rich: Unburnt fuel in exhaust. Soot on inside tailpipe. Burning sensation in the eyes. Vehicles driving behind you slow down or attempt to pass you quickly. A new catalytic converters will not solve this problem. Thanks for the explanation. I have a suspicion that might be what's going on. Any advice on how to diagnose and fix? Link to comment Share on other sites More sharing options...
Ωhm Posted May 11, 2018 Share Posted May 11, 2018 The possibility for running rich are many. What do the spark plugs look like? Are all vacuum lines secure and not leaking? etc etc. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now