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Car Forum / Jeep / June 2007Lost top end power in 88 Cherokee 4.0.
Ok, I am on a fishing expedition for likely things to check. Our 88 Cherokee with the 4.0 has lost power above half throttle. It goes fine up to that point, then just bogs, no matter what gear it is in. It has been neglected for 4 years as far as tuning goes due to me not being up to it. I first changed out the 'very' dirty distributor cap and rotor which made starting 'much' faster and smoother. I then changed the gas filter because it was once again rusted to the rot point after about 8 years. Air filter is new. I cleaned the connections on the TPS and IAC and verified the TPS doesn't have any 'dead' spots with my meter. I cleaned the CPS and coil connections also. No joy on any of that. I have been having some cold idle issues and have been thinking on cleaning the IAC, but don't know if that will have a top end effect or not. I am also thinking on unplugging the EGR just to make sure it isn't blown vacuum wise because it only bogs under throttle when things like the EGR are active. Any other ideas? Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > Any other ideas? Did you open up the old fuel filter, or blow it backwards into a can to inspect for dirt or sparkles that could indicate a pump dying? I would run a fuel pressure test, and then a cat pressure test.  SignatureStupendous Man, Defender of Freedom, Advocate of Liberty >> Any other ideas? > > Did you open up the old fuel filter, or blow it backwards into a can to > inspect for dirt or sparkles that could indicate a pump dying? > I would run a fuel pressure test, and then a cat pressure test. Yes I did blow out the filter and besides being a bit hard to blow through, it appeared ok. Rotted pretty bad though. I have no cat to check, well there has been nothing 'in' the cat since before I bought it and it still passed emissions great. I have no real way to check for fuel pressure I don't think unless one of my old compression testers could be converted?? The miss is pretty consistent. Thanks, Mike > I have no real way to check for fuel pressure I don't think unless one > of my old compression testers could be converted?? > > The miss is pretty consistent. I would use a guage capable of 100PSI, but your local parts store may rent them. A "miss" and "bogging down" are two different things. If it is a miss, I would change plug wires just to eliminate that possibility, then if not effective, follow the fuel pressure. Plug wires can do this, but they will usually give you some backfiring along with the bogging down. Earle > Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 33 lines] > Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) > Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 27 lines] > > Any other ideas? Look at simple things, it sounds like it might be starving for fuel? Test fuel pressure and flow, consider clogged catalytic converter, look for a stopped up fuel vent. You changed the fuel filter, is there possibly another one, maybe in the tank? SignatureXS11E, Killing all posts from Google Groups The Usenet Improvement Project: http://blinkynet.net/comp/uip5.html > Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 33 lines] > Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) What does exactly "then just bogs" mean? The Jeep does not go any faster, or it stalls and stops? What precise noises/knocks and symptoms, etc? On idle, what happens if you press accelerator until above half throttle? Is there a loss of power? If the fuel pressure is low, the engine can run fine upto a point, until the demand for fuel exceeds the supply due to low pressure. >> Ok, I am on a fishing expedition for likely things to check. >> [quoted text clipped - 37 lines] > faster, or it stalls and stops? What precise noises/knocks and > symptoms, etc? Stalls and stops and sputters until the gas pedal is let up on. No backfires. EGR now unplugged. > On idle, what happens if you press accelerator until above half > throttle? Is there a loss of power? If I go fast on the pedal, there is a dead spot. No load and smooth pedal seems to work. > If the fuel pressure is low, the engine can run fine upto a point, > until the demand for fuel exceeds the supply due to low pressure. I knew there was a reason that filter was the second thing I went after. ;-) I don't have a pressure gauge other than a compression gauge though. I also have verified the coil wire still has a connection with the ohm meter. It is a bit higher per foot in resistance than the plug wires, but only a bit, .7K vs .5K. Hmm the others I have around seem the same too.... I made sure the main power had good connections also. Mike >Stalls and stops and sputters until the gas pedal is let up on. > >No backfires. > >EGR now unplugged. Run it hard and make it bog and them pull over and remove a plug and see if it is white or sooty. I tend to think you are getting a fuel starvation here that surfaces at higher power settings. Hard to be sure without feeling it but the plugs would confirm a lean out. Might start by changing fuel filter like someone else suggested and maybe a fuel pressure check too. ----------------- TheSnoMan.com > Run it hard and make it bog and them pull over and remove a plug > and see if it is white or sooty. I tend to think you are getting a > fuel starvation here that surfaces at higher power settings. Hard > to be sure without feeling it but the plugs would confirm a lean > out. Might start by changing fuel filter like someone else > suggested and maybe a fuel pressure check too. Don't disagree with you at all but the OP says he already replaced the fuel filter, my question: Is there another filter somewhere? I had a Cherokee years back but I no longer have the service manuals so I don't know if there is another filter. What about the fuel vent? That's easy to check by driving with the gas cap removed. SignatureXS11E, Killing all posts from Google Groups The Usenet Improvement Project: http://blinkynet.net/comp/uip5.html >> Run it hard and make it bog and them pull over and remove a plug >> and see if it is white or sooty. I tend to think you are getting a [quoted text clipped - 11 lines] >What about the fuel vent? That's easy to check by driving with the gas >cap removed. Fuel vent is viable too but more so with a fuller tank when there is less air to expand as volume in tank increase. . If filter has been changed then fuel pressure shuold be checked too and if you had a gage with a long hose on it to could drive vehcile to failure mode and check pressure while doing it and if pressure stays good than fuel system can be ruled out but if it dropped then you have your culprit. Also I am not sure if the is a screen or sock filter in tank on fuel pickup on that model Jeep in regards to a second filter. ----------------- TheSnoMan.com >> Run it hard and make it bog and them pull over and remove a plug >> and see if it is white or sooty. I tend to think you are getting a [quoted text clipped - 11 lines] > What about the fuel vent? That's easy to check by driving with the gas > cap removed. There is a sock filter on the pump in the tank. What would I explode if I try blowing back through the line from the tank side of the inline filter. The tank is new since we bought the Jeep, but... I will go try some more up top electrical things first now. Mike > There is a sock filter on the pump in the tank. > > What would I explode if I try blowing back through the line from > the tank side of the inline filter. Give it a try, the worst that can happen is the tank and the gasoline in it will detonate with enough force to destroy the known universe.... Seriously, remove the gas cap and blow back VERY gently, you should hear bubbling in the tank, don't use a compressor, just blow into it, compressed air might possibly damage the filter and/or pump. > The tank is new since we bought the Jeep, but... > > I will go try some more up top electrical things first now. It sure sounds like fuel starvation but it may not be? SignatureXS11E, Killing all posts from Google Groups The Usenet Improvement Project: http://blinkynet.net/comp/uip5.html > > There is a sock filter on the pump in the tank. > > [quoted text clipped - 13 lines] > > It sure sounds like fuel starvation but it may not be? All such problems became nothing more than a bad memory when I moved from Seattle to Colorado. I feel your pain. Heh, heh. Cheers, Earle >> There is a sock filter on the pump in the tank. >> [quoted text clipped - 7 lines] >hear bubbling in the tank, don't use a compressor, just blow into it, >compressed air might possibly damage the filter and/or pump. You could be real slick about it and use regulated air to about 1 PSI or even blow on it (as you can mkae about 1 PSI or so that way) and it should blow easily. If not there is a restriction >> The tank is new since we bought the Jeep, but... >> >> I will go try some more up top electrical things first now. > >It sure sounds like fuel starvation but it may not be? There could be a vacum leak in feed line that cause air to be drawn into fuel line at higher flow rates which then causes pump to cavitate and loose pressure. ----------------- TheSnoMan.com Mike, it really sounds like a fuel delivery problem. Because you changed the fuel filter, I would suspect the fuel line is pinched or you have had a piece of rubber fuel line come loose and restrict the flow. It also could be a fuel pump on the way out. The other obvious thing would be a collapsed baffle in your muffler restricting exhaust flow. I've had that happen to me. Either the fuel is not getting in or the exhaust is not getting out. I wouldn't suspect ignition because it doesn't miss or backfire. Merrill > >> Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 66 lines] > > - Show quoted text - > Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 27 lines] > > Any other ideas? I've had this situation twice. First time was a dying fuel pump - and it progressed to dead pretty quickly. Second was a shorted cable to the CPS. Didn't tie it back properly and the exhaust got it. Same symptoms, except my max RPM was 1000-1200 RPM, period. Crept home at idle <g>. SignatureWill Honea Water in your float bowl. God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com http://www.billhughes.com/ > Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 33 lines] > Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) SignaturePosted via a free Usenet account from http://www.teranews.com Yes Bill I agree that it sounds like water in the float bowl, but I thought the Canadian 88 4.0 was FI. Don't hesitate to tell me I am wrong. Merrill On May 27, 9:38 pm, "L.W. \(Bill\) Hughes III" <billhug...@cox.net> wrote: > Water in your float bowl. > God Bless America, Bill O|||||||O [quoted text clipped - 43 lines] > > - Show quoted text - Hi Merrill, I would seem so as all Ford and GMs were electronically injected by '83. But Chrysler dances to a different tune, like this newer than a CJ, YJ: http://home.sprynet.com/~dale02/list.htm God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com http://www.billhughes.com/ > Yes Bill > > I agree that it sounds like water in the float bowl, but I thought the > Canadian 88 4.0 was FI. Don't hesitate to tell me I am wrong. > > Merrill SignaturePosted via a free Usenet account from http://www.teranews.com You're right, I was thinking of Mike's '86 CJ: http://billhughes.com/mikeRomain/ God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com http://www.billhughes.com/ > Yes Bill > > I agree that it sounds like water in the float bowl, but I thought the > Canadian 88 4.0 was FI. Don't hesitate to tell me I am wrong. > > Merrill SignaturePosted via a free Usenet account from http://www.teranews.com > You're right And you are wrong. Again. [insert blather here] There you go again, from the biggest loser of them all! The jealous, really jealous, I can't believe how jealous this little draft dodging coward schizophrenic psychopath liar hiding in Vancouver via S0106000ea6ba70e7.vn.shawcable.net 24.86.24.251 intrepidator@shaw.ca who's only way to get attention is to make a fool of it's self. With an obsession with perverts and goats, where it writes via remailers, and cross posts to other perverts to no one's surprise. With extreme jealous ranting over my documents, possessions, successes, manliness and super Southern California body. Committing forgery over many of them proving I'm a responsible American man. You remind me of a little rat dog, like a Mexican Chiwawa with it's senseless barking, me too, me too. You're even more senile than I first thought. And the poor thing, you're too girlie to take responsibility for yourself again, by signing your statement like a man. You're not worth any more time when a cut and paste this same paragraph it fits so well! God Bless America, Bill O|||||||O mailto:LWHughes3rd@aol.com http://www.billhughes.com/ > And you are wrong. > > Again. > > [insert blather here] SignaturePosted via a free Usenet account from http://www.teranews.com > Water in your float bowl. With a TPS and IAC? SignatureStupendous Man, Defender of Freedom, Advocate of Liberty > Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 33 lines] > Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) Since you are just fishing... check the ignition coil input/output coil voltages and the capacitor. Verify spark can jump a large gap when engine is not running. Check this article: http://mgaguru.com/mgtech/ignition/ig108.htm Do you sense that there are "misses"? I would still check the fuel pressure and the fuel presssure regulator. Still no joy. Have a fast idle (2000 rpm) issue when first started that mellows down. It seems to be an RPM limiter under load. If floored in neutral, the engine will die, it will not catch back as the rpm comes down unless the pedal is let up on. If coaxed up in neutral the engine will rev high. When in 1st, it picks up fast to about 2000 rpm, then hits a wall. Holding it to the floor causes 'misses' and sputtering with a decrease in power and speed until the pedal is let up on. I have no way to verify fuel pressure other than to say this power issue has been going on for several weeks with a 'stable' screw up. When pumps go, they usually go sooner than later totally, but.... Things done: Cap and rotor Gas filter Air filter new Ran with open gas cap Checked plugs, all 'very' even and evenly burned almost to the 'worn out' point with a perfectly 'normal' coloring. Gap was almost 50, put it back to 35. That would go with the plug wires also checking out ok on my meter with an ohm check. They are OEM 'lifetime' wires about 10 years old. Checked and cleaned CPS (about 5 years old) with attention to the wire's routing. Cleaned main battery terminals and cable ends. Cleaned TPS and checked it for smooth ohm reading all the way up. Cleaned IAC connection, but not the unit itself??? Can that affect top end? Cleaned coil connections and verified the meter readings. Seem ok. Got 1.5 ohm between the plus and minus pins, infinity between plus and case and 'less than infinate' my books says between coil negative and high tension post or 4.5 K ohm on the meter. Unplugged EGR. No change so put it back. Cleaned connections on the MAP sensor and verified the vacuum line. I have to wait until later to have a friend go under to blow out the fuel pump. Mike > Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 33 lines] > Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) >Still no joy. > [quoted text clipped - 51 lines] >I have to wait until later to have a friend go under to blow out the >fuel pump. The anti drain back check valve in the pump will make it difficult, if not impossible to blow back through the pump. However, if it's easy to blow back through it would indicate the the rubber hose from the pump to the sending unit outlet has come loose or failed. Very common and most likely cause of the problem you describe. You could also be describing an ignition coil failure. Even if your measurements look good, and it appears to create a strong spark, it could still be shorted internally, causing your problem under load. You'd need a scope to see it though. >Mike > [quoted text clipped - 35 lines] >> Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 >> (More Off Road album links at bottom of the view page) > The anti drain back check valve in the pump will make it difficult, if > not impossible to blow back through the pump. However, if it's easy to [quoted text clipped - 6 lines] > could still be shorted internally, causing your problem under load. > You'd need a scope to see it though. Nice try, thanks. The pump holds blow back pressure. It didn't have any pressure when the filter was unhooked though.... If the spark was messed, I would think I would see dirty plugs, not perfect wear ones.... Do you or does anyone know if there a return line pressure valve on this 88 4.0 or is it just a metered hole? I am thinking about pinching off the return line to see what happens.... Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) >> The anti drain back check valve in the pump will make it difficult, if >> not impossible to blow back through the pump. However, if it's easy to [quoted text clipped - 15 lines] >If the spark was messed, I would think I would see dirty plugs, not >perfect wear ones.... Not necessarily. >Do you or does anyone know if there a return line pressure valve on this >88 4.0 or is it just a metered hole? > >I am thinking about pinching off the return line to see what happens.... The fuel pressure regulator is on the fuel rail at the front. It's a spring loaded diaphragm with a vacuum hose attached to it. Spring pressure determines fuel pressure. Vacuum assists in overcoming spring pressure to open the bypass under low load (high vacuum) conditions. On high load (low vacuum) it takes more fuel pressure to open the bypass. The result is slightly higher fuel pressure under load. Be careful pinching off the return line. You could easily end up blowing off the hose I mentioned earlier. You really need a fuel pressure gauge to see what's going on. An old low side R12 gauge would work. Otherwise you're in for some guesswork. >Mike >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >88 Cherokee 235 BFG AT's >Canadian Off Road Trips Photos: Non members can still view! >Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 >(More Off Road album links at bottom of the view page) >> The anti drain back check valve in the pump will make it difficult, if >> not impossible to blow back through the pump. However, if it's easy to [quoted text clipped - 20 lines] > > I am thinking about pinching off the return line to see what happens.... Mike, a $15 fuel pressure guage set would have already saved you that much in irritation! A borrowed freebie would have been even better. I have the MPI manual for the Renix setup (87-90 or so) and it give a cookbook sequence that is pretty sure to identify about any fuel delivery problem. If it weren't for the bleed down check (how much it drops in 20 minutes) you could be done in 15 minutes. Be VERY careful pinching off that return line w/o a guage! Even with a failing pump it would hit over 90 PSI inside a few seconds and that will definitely blow hoses, especially as old as ours are. The second is that the return line comes off the front end of the fuel rail and it's a metal pipe until it gets way down into the works - hard to reach and control - plus it is very likely old and ready to crack as soon as you pinch it. If you do this, pinch the line, have someone turn the key on and be ready to quickly turn it off. You really do need to scrounge up a guage. Until I found what I wanted, I cobbled one out of a cheap 0-100 PSI water guage I had laying around. SignatureWill Honea > Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 33 lines] > Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) > Ok, I am on a fishing expedition for likely things to check. > [quoted text clipped - 33 lines] > Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) Mike, curious; what is the latest? >> Ok, I am on a fishing expedition for likely things to check. >> [quoted text clipped - 35 lines] > > Mike, curious; what is the latest? The vehicle hasn't been here, it is used by my wife to go to work. I might look more at it this weekend depending on rain. There is one ratty coil to ignition module connection I want to address and I want the fuel pump connection cleaned just in case. Mike We solved our power loss problem. RIP 88 Cherokee 316K km We had a nice ten years together. Don't even think there is enough metal left on it to make a new car door once it's melted down.... Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) Mike, Did you find out what it was ? Dave Milne, Scotland > We solved our power loss problem. > [quoted text clipped - 12 lines] > Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) Nope. Mike > Mike, Did you find out what it was ? > [quoted text clipped - 16 lines] >> Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 >> (More Off Road album links at bottom of the view page) You getting another ? Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ > Nope. > [quoted text clipped - 20 lines] > >> Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 > >> (More Off Road album links at bottom of the view page) I had another one with almost no rust to transplant the drivetrain over to but was unable to do so before the government showed up with a warrant to steal my second XJ for 'disuse'. I was not physically able to do the swap in time to prevent this theft so I had to sell it to a scrap yard. My wife found a mint one owner 90 Cutlass from a friend with about everything new including BFG tires for $100.00 so we bought that. It goes on the road today and the plates come off the poor old Cherokee. Mike > You getting another ? > [quoted text clipped - 26 lines] >>>> Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 >>>> (More Off Road album links at bottom of the view page) Hi Mike, Sorry to be thick, but how on earth can the government take your car for 'disuse' ? How long can you 'disuse' it before they decide that they have a right to meddle in your affairs ? Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ > I had another one with almost no rust to transplant the drivetrain over > to but was unable to do so before the government showed up with a [quoted text clipped - 38 lines] > >>>> Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 > >>>> (More Off Road album links at bottom of the view page) The second it has no valid plate and/or insurance on it, it is against the law to have it on your property here in Toronto Canada. They also can come and steal the contents of your garage legally if the door is open or broken open. It is then consider 'public access' or some such stupidity. Because we rent they do not legally have to give us any warning to do this before 6 apes show up in a truck. I literally had to stand there with a large pipe in my hands while the cops came to shut them down long enough for us to board up the door. They were going to steal all my camping gear, my canoes, my tools, our bicycles, etc. The cops were just a little sympathetic making the guy swear he wasn't coming back. I had tow truck driver friends hear the police radio call and show up for 'moral' support too. heh heh... I can't wait to get out of this hell hole, I'll tell ya. Mike > Hi Mike, > [quoted text clipped - 47 lines] >>>>>> Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 >>>>>> (More Off Road album links at bottom of the view page) > The second it has no valid plate and/or insurance on it, it is against > the law to have it on your property here in Toronto Canada. [quoted text clipped - 6 lines] > shut them down long enough for us to board up the door. They were going > to steal all my camping gear, my canoes, my tools, our bicycles, etc. Pshh. Canada. Get a big, slobbering Rottweiler ... or a gun. Craig C. >> The second it has no valid plate and/or insurance on it, it is against >> the law to have it on your property here in Toronto Canada. [quoted text clipped - 13 lines] > > Craig C. My Bouvier de Flanders/ Irish Setter cross that weighed in at 150 lb passed away a couple years back, but he only 'looked' the part. Have seen many a door to door salesman jump my porch railing when his head came out the screen door's window with a woof though. LOL! I am 6'4, 210 so standing there 'playing' with a 5' pipe in my hands, (as a pry bar for the door you know now...) well.... I save the gun for when it's really needed... Mike We have a law against "entering" which offense this falls into. We also have "citizen's arrest" which empowers you, somewhat. Of course, a shotgun helps immensely too. tw > The second it has no valid plate and/or insurance on it, it is against > the law to have it on your property here in Toronto Canada. [quoted text clipped - 16 lines] > > Mike If not too late...for fun..., try running it with the exhaust disconnected. (I think merrill suggested clogged exhaust in an earlier post) All the best, Andy > If not too late...for fun..., try running it with the exhaust > disconnected. (I think merrill suggested clogged exhaust in an earlier > post) > All the best, > Andy As I mentioned, there is no cat and the muffler is brand new and it ran with neither when the pipe into the cat rotted off a bit ago. No matter, it is parked now. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) |
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