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Car Forum / Jeep / April 2007Still having high idle problem on 88 Jeep Comanche (4.0l)
So I'm getting good vacuum using the very imprecise "finger over the hose end" at the CCV hose, and the TPS sensor goes from about 1 to 5 volts. Is there some other things I should check? Today it behaved differently than usual, hitting close to 3000 rpm while "idling". Usually it starts at about 800rpm when I start it up, and stays constant at about 1500. Could having a bad CCV valve be causing my problem? I'm getting some oil in my air filter as well, and as per these websites, it seems that may be that cause of the oil: http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=257836 http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=257985 I did try sealing around the grommets with some RTV silicone, but it didn't seem to make a difference. I guess I KNOW that I need to fix the CCV hoses/valves, but can this be causing my problem with the high idle? If nothing else, I'm figuring that oil in the air filter probably isn't helping keep the throttle body really clean, since the oil can get into the air system from there. Clint Have you cleaned the throttle body? It's real easy and will eliminate that as a source of the problem. Oil in the CCV system doesn't help either, and cleaning the orifices is in principle also easy. Earle > So I'm getting good vacuum using the very imprecise "finger over the hose > end" at the CCV hose, and the TPS sensor goes from about 1 to 5 volts. Is [quoted text clipped - 19 lines] > > Clint Well, I got in there with a brush and solvent, and took off some stuff on the sides (beside the butterfly valve, for lack of the technical phrases). But it's opening and closing easily, and it's stopping when it hits the metal stop on the outside of the throttle. But is it perfectly clean? No. Should I scrub some more? Clint > Have you cleaned the throttle body? It's real easy and will eliminate > that [quoted text clipped - 34 lines] >> >> Clint Scrub till you'd eat from it. Carl > Well, I got in there with a brush and solvent, and took off some stuff on > the sides (beside the butterfly valve, for lack of the technical phrases). [quoted text clipped - 44 lines] >>> >>> Clint Agreed. The IAC too. (Idle Air Controller). This can get jammed with tiny amounts of deposits. I would probably use carburetor cleaner. Earle > Scrub till you'd eat from it. > [quoted text clipped - 48 lines] > >>> > >>> Clint I'm thinking it may not be too easy to haul the throttle body off, but I'd imagine that would make it much easier to clean properly? Clint > Agreed. The IAC too. (Idle Air Controller). This can get jammed with > tiny [quoted text clipped - 61 lines] >> >>> >> >>> Clint That's the thinking. The theory is that your IAC has carbon in it, which is making it function improperly, which is what is messing with your idle speed. Cleaning the contacts for the various sensors mentioned can help too. Earle > I'm thinking it may not be too easy to haul the throttle body off, but I'd > imagine that would make it much easier to clean properly? [quoted text clipped - 66 lines] > >> >>> > >> >>> Clint http://members.cox.net/wilsond/tb/tb.html God Bless America, Bill 0|||||||0 mailto:LWHughes3rd@aol.com http://www.billhughes.com/ > I'm thinking it may not be too easy to haul the throttle body off, but I'd > imagine that would make it much easier to clean properly? > > Clint  SignaturePosted via a free Usenet account from http://www.teranews.com It's only four bolts that hold the TB on, and the cables. Takes about 5 minutes to pull. Don't loose the cable clips, and be sure you make a note of what cables go where. Carl > I'm thinking it may not be too easy to haul the throttle body off, but I'd > imagine that would make it much easier to clean properly? [quoted text clipped - 70 lines] >>> >>> >>> >>> Clint This is probably a really dumb question, but how do you remove the linkages from the throttle body? Some of the posts I've seen indicate it may just be a simple ball/socket joint, which means I just didn't use a big enough hammer (figuratively speaking, of course) on it. Thought I'd check in here first, though. Clint > It's only four bolts that hold the TB on, and the cables. Takes about 5 > minutes to pull. Don't loose the cable clips, and be sure you make a note [quoted text clipped - 82 lines] >>>> >>> >>>> >>> Clint No clues for getting the linkages off? Should I just pry a bit with a screwdriver? Clint > This is probably a really dumb question, but how do you remove the > linkages from the throttle body? Some of the posts I've seen indicate it [quoted text clipped - 91 lines] >>>>> >>> >>>>> >>> Clint Well..... sort of..... You have to pull it off perfectly square with the backing plate on the TB or one side of the clip will usually snap off. Old spring steel and the slightest corrosion..... When you snap this clip, you can do a decent paper clip bracket to hold it back on or you need to buy new linkage... My 86 CJ7 has the paper clip fix thanks to Bill H. I will go look at the 88's to make sure it is the same. OK, nope, it is a plastic clip on our 88 with maybe a spring clip in the end of it. It 'looks' like it should pull off square, but I don't know for sure... 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) > No clues for getting the linkages off? Should I just pry a bit with a > screwdriver? [quoted text clipped - 97 lines] >>>>>> >>> >>>>>> >>> Clint Thanks, Mike. I appreciate you digging into it for me. Clint > Well..... sort of..... > [quoted text clipped - 118 lines] >>>>>>> >>> >>>>>>> >>> Clint When our 88 does that, I pull off the electrical plug to the TPS and give it a spray with contact cleaner then am usually good to go for a year or more before it needs it again. Electronic contact cleaner is the best, but WD40 will work. That works every time on ours. 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) > So I'm getting good vacuum using the very imprecise "finger over the > hose end" at the CCV hose, and the TPS sensor goes from about 1 to 5 [quoted text clipped - 19 lines] > > Clint I've tried cleaning the contacts on the ISS and TPS with electrical contact cleaner and a toothbrush, with no change. Forgot to mention that. Clint > When our 88 does that, I pull off the electrical plug to the TPS and give > it a spray with contact cleaner then am usually good to go for a year or [quoted text clipped - 33 lines] >> >> Clint BTW, this problem SEEMS to have started about the same time as I hauled the old radiator and water pump out and replaced it. Could very easily just be coincidence, though. I've tried checking all the vacuum hoses in particular around the area I was working in, but nothing popped up. I'm tempted to head out to a wrecker, and see about snagging an old throttle body (preferably with sensors), just for S&G. Give me something to swap out some parts to try seeing what's wrong. So it's not seeming that bad CCV valves/hoses should be causing the high idle, though? Clint > So I'm getting good vacuum using the very imprecise "finger over the hose > end" at the CCV hose, and the TPS sensor goes from about 1 to 5 volts. Is [quoted text clipped - 19 lines] > > Clint You are correct about looking for a vacuum line loose. The CCV, if pulled off at the manifold will cause a steady high idle, but normally it gets blocked which just pukes oil into the air filter. It would be worth inspecting the rubber grommet where it enters the manifold for cracks though. 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) > BTW, this problem SEEMS to have started about the same time as I hauled > the old radiator and water pump out and replaced it. Could very easily [quoted text clipped - 34 lines] >> >> Clint So I did my thorough cleaning of the throttle body, and it seems to run smoother and more consistent. Don't know about eating off it, but there's no more black gunk in there. But now immediately after firing it up, it goes up to about 2000 rpm, and sits there. I tried unplugging the two sensors (one at a time) and then starting it up. When I did that to the IAS, it started like I had my foot on the gas (rapid increase in engine speed). Shut it down, plug in the IAS, then unplug the TPS. Well, that made it run exactly as it did with it plugged in; start and run at 2000 rpm. So I'm thinking the TPS is shot, and I should replace it. Make sense? I had tried adjusting the TPS with no joy as well, even when I went to one extreme to the other. I haven't re-measured the output of the TPS; I'll probably do that later today. But it seems it should be doing something useful. Clint > So I'm getting good vacuum using the very imprecise "finger over the hose > end" at the CCV hose, and the TPS sensor goes from about 1 to 5 volts. Is [quoted text clipped - 19 lines] > > Clint So I stopped by the local parts place, and they wanted $280 for the sensor! The manual transmission one was twice as much as the automatic one, and of course, I've got the more expensive of the two. *sigh* I thought the automatic one had an extra electrical connector on it? So shouldn't it be the more expensive of the two? Ah, well, logic isn't required, I guess. I checked a "parts recycler", and they had the automatic transmission version in stock, but it was still $75, which seems pretty steep for a used part like that. I think I'll have to find a "pick-your-part" type place. I can yank it out in no time, at least. Clint > So I did my thorough cleaning of the throttle body, and it seems to run > smoother and more consistent. Don't know about eating off it, but there's [quoted text clipped - 38 lines] > > - Show quoted text - > So I stopped by the local parts place, and they wanted $280 for the > sensor! The manual transmission one was twice as much as the [quoted text clipped - 7 lines] > used part like that. I think I'll have to find a "pick-your-part" > type place. I can yank it out in no time, at least. I checked Advanced Auto Parts online and they get in the vicinity of $75 for a new one - several suppliers to chose from. Before you go throwing money at it, remove the old one and spray it well with WD40 or contact cleaner. You should be able to get some to filter inside. Get as close to the unit as possible and measure the resistance between all the pins. That !!@#$% thing is a simple rheostat so if you turn it as far as it goes in one direction, you should get several ohms (not sure of the exact value - sorry) between one of the pins and the other two. Leave one end of the ohm meter where it was and turn the thing about half way. Now you should see about half the resistance at one of the pins. Swap thing around to be sure you have contact between all 3 pins at some point. I have been able to clean the wiper arm in a couple of them by soaking the thing in WD40 for a days or so - the shaft is not sealed, so the solvent will seep in - and it sure beats $75! FYI, AA lists the same part for the 87-90 Comanche, Cherokee, and Wagoneer with the 4.0 engine. SignatureWill Honea whonea@yahoo.com I've got some contact cleaner, as well as some WD40. I'll maybe give that a whirl. As far as suppliers goes, that's the kind of price I was hoping/expecting. But apparently up here in Canada, they make them things out of gold. On the plus side, if I find an old Jeep, I'm pretty sure I can haul that piece off in about 2 minutes! :) I'm getting very intimate with my throttle area... Clint >> So I stopped by the local parts place, and they wanted $280 for the >> sensor! The manual transmission one was twice as much as the [quoted text clipped - 29 lines] > FYI, AA lists the same part for the 87-90 Comanche, Cherokee, and Wagoneer > with the 4.0 engine. If you have a multimeter, here are the pinouts for the TPS. With the key in run and the engine and AC off, you put the meter into the back side of the plug and take a voltage reading. With the throttle at rest, the volts should be 200 MV. At wide open, the volts should be 4.8V max. They should smoothly increase as the throttle opens. 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) > I've got some contact cleaner, as well as some WD40. I'll maybe give > that a whirl. [quoted text clipped - 42 lines] >> Wagoneer >> with the 4.0 engine. To go off on a (yet another) small tangent, is there a way to test the IAS to make sure it's working correctly? BTW, I took off the TPS, and tested the resistance as it rotated through it's range. But without having a known good one, all I can say is that it does go through a range of resistances smoothly. I also learned something today, and I'm going to post it in the interest of assisting others. Otherwise I'd just hide my red face behind the computer screen. When putting the TPS on, the default position seemed to have the lever arm on the wrong side of the throttle body arm. This would cause the TPS to be rendered pretty much useless, as far as I can see, as it won't move with the throttle body lever. Whoops. So just watch that if you need to replace/adjust that. Clint > If you have a multimeter, here are the pinouts for the TPS. > [quoted text clipped - 57 lines] >>> Wagoneer >>> with the 4.0 engine. Does your meter not have a volt setting? Mike > To go off on a (yet another) small tangent, is there a way to test the > IAS to make sure it's working correctly? [quoted text clipped - 77 lines] >>>> Wagoneer >>>> with the 4.0 engine. I measured before, and was getting < .5V. But whether it was exactly .2V or not, my meter didn't give me confidence enough to say yeah or nay. Clint > Does your meter not have a volt setting? > [quoted text clipped - 85 lines] >>>>> Wagoneer >>>>> with the 4.0 engine. There is a special tool my book calls an 'exerciser' to test the idle stepper. The book sort of implies a high moves the pintle out and a low in, but it doesn't say for sure. It, the ISS has a moving part that can stand to be cleaned. Mike > I measured before, and was getting < .5V. But whether it was exactly > .2V or not, my meter didn't give me confidence enough to say yeah or nay. [quoted text clipped - 96 lines] >>>>>> Wagoneer >>>>>> with the 4.0 engine. > There is a special tool my book calls an 'exerciser' to test the idle > stepper. The book sort of implies a high moves the pintle out and a > low in, but it doesn't say for sure. > > It, the ISS has a moving part that can stand to be cleaned. Be careful. Never start the engine with the IAS motor removed or the little pintle will shoot across the garage and the unit is toast. With the ignition on, motor not running. back-probe the connector and find the ground and +5v (should be the outside two wires) If there isn't 5v there then you might have a break in the harness or just not a good contact with the wire. Now measure the center wire against the ground. Throttle butterfly Voltage CLOSED >200 mV OPEN <4.8 V The transition between full open and closed should be smooth with no jumps or dropouts. SignatureDougW So I went out to a local wrecker, and they had about 6 Cherokee's, all of about the right vintage. 3 of them still had their IAC's, but all of them were automatic's, so I couldn't yank the TPS's. Kind of disappointed by the lack of selection on those. Anyway, the "new" IAC only cost $2 (the entire throttle body with add-ons was only $20), but it had exactly the same effect as the old one. *sigh* So I'm still looking for a TPS to plug in there. Anyone know if the automatic tranny version of the sensor has any hope of working? Or would I just be asking for even more pain? Clint > There is a special tool my book calls an 'exerciser' to test the idle > stepper. The book sort of implies a high moves the pintle out and a low [quoted text clipped - 104 lines] >>>>>>> Wagoneer >>>>>>> with the 4.0 engine. Now I am more thinking you are missing something... CCV unplugged or one of the lines to the air filter box. There is one way down low in the front by the rad that controls the heat pipe for the air filter. 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) > So I went out to a local wrecker, and they had about 6 Cherokee's, all > of about the right vintage. 3 of them still had their IAC's, but all of [quoted text clipped - 121 lines] >>>>>>>> and Wagoneer >>>>>>>> with the 4.0 engine. Left or right side? Can you give me more specific directions on what I'm looking for (besides a dangling hose)? Should I be looking up from underneath? All these problems (idling) seemed to start when I replaced the rad and water pump, so this very well could be the culprit. Clint > Now I am more thinking you are missing something... CCV unplugged or one > of the lines to the air filter box. There is one way down low in the [quoted text clipped - 133 lines] >>>>>>>>> Wagoneer >>>>>>>>> with the 4.0 engine. I will look tomorrow on mine for sure, but I think it is at the bottom front side of the air filter box. There should be an outlet there for a heat pipe that runs to the exhaust to suck hot air when the engine is cold. These heat pipe hoses usually rot away but there is a vacuum motor down there to turn it on. It would be a small vacuum line on a nipple. My Haynes implies there could be a vacuum line on the fender side of this motor. Mike > Left or right side? Can you give me more specific directions on what > I'm looking for (besides a dangling hose)? Should I be looking up from [quoted text clipped - 143 lines] >>>>>>>>>> and Wagoneer >>>>>>>>>> with the 4.0 engine. Well, I've definately got a rotted away hose, so I'm assuming that's the heat pipe hose. I'll go take a look. That rotted hose is right where the radiator hoses attached, so if there was any vacuum hoses around there, they'd be at risk of getting bumpted in the setup of the new rad. The FSM doesn't show anything funky in the vacuum diagram in that area, however. But I'd sure be happy to be proven wrong! Thanks again. Clint >I will look tomorrow on mine for sure, but I think it is at the bottom >front side of the air filter box. There should be an outlet there for a [quoted text clipped - 153 lines] >>>>>>>>>>> and Wagoneer >>>>>>>>>>> with the 4.0 engine. Never mind. I checked it out. There is a square box on the front of the air filter box that the rotted hose goes into. On the fender side, there is an airhose that runs into a nipple on the top of the square box. All that is still connected. Nice when the FSM vacuum diagram so closely matches reality. Or am I expecting too much? The funky toilet float in the bumper isn't shown either, and I've checked both those hoses as well. Clint >I will look tomorrow on mine for sure, but I think it is at the bottom >front side of the air filter box. There should be an outlet there for a [quoted text clipped - 153 lines] >>>>>>>>>>> and Wagoneer >>>>>>>>>>> with the 4.0 engine. |
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