Buck531 Posted January 18, 2008 Report Share Posted January 18, 2008 I know Dave is going to swing by on Sunday to take a peek at it but I just figured somone here might be able to give me a few ideas. Basically you start it and it runs rough. Like I vac leak.. a bad one. you give it gas above 2k and it seems better. If you drive it it'll move. Just when you let off the gas it feels like it's going to stall out. And it will if you let it. The brakes are VERY soft. If you don't constantly pump them really quick it never builds up pedal. The brake light IS on. I did find something on some jeep forum that if you have no pedal and the brake light is on that the booster needs replaced. They said this would cause a rough idle too. Is it safe to say that if the brake booster is bad and is leaking, would cause a REALLY bad vac leak thus causing the car to run like ass at idle. Correct? If that's the case, anyone have a 4.0L Jeep brake booster for cheap? I've also read about taking some TB cleanerto the TB and such. Then I also read about the CPS going bad. I just don't want ot buy $200 in parts and it doesn't do shit. I know I have to eliminate things. We've already checked the timing, rotor, cap, plugs. I've changed the fuel injectors. We emptied the oil pan and it had a good 2 gallons of oil in the pan (yes.. most of it was oil/gas though maybe due to the old injectors being shit. Alos, right before it shuts off at idle if I let it, the check engine light comes on and doens't come on when you turn it back on. TIA. Quote Link to comment Share on other sites More sharing options...
TurboRust Posted January 18, 2008 Report Share Posted January 18, 2008 you paid 200 bux.. this is a beater, drive it until it blows and quit bitching.. Quote Link to comment Share on other sites More sharing options...
Buck531 Posted January 18, 2008 Author Report Share Posted January 18, 2008 you paid 200 bux.. this is a beater, drive it until it blows and quit bitching.. Can't drive it if A: it has very or NO brakes. B: it won't idle. at all. If you let off the gas.. in 10 seconds it dies. Quote Link to comment Share on other sites More sharing options...
twistedfocus1647545489 Posted January 18, 2008 Report Share Posted January 18, 2008 I think the CPS usually causes a no-start condition (although Cherokees are notorious for them going out). It sounds more like your low idle is related to a bad or improperly set TPS. Think old school post-style radio knobs... the hiss they get in the area you use them the most after years of use. TPSs are very similar and can pick up the same sort of noise in the signal. You can tell if you hook up an analog voltmeter and do a slow sweep b/c the needle on the voltmeter will spike or dip instead of rising steadily. Mine needs replaced, and in the interim I just manually set the idle a bit high (about 900 when it should be 750) and when it warms up it falls down to about 500 and runs rough but will keep running. If you do that, I would definitely recommend that you reset the TPS voltage because using the stop on the throttle body to manually raise the idle without doing so will cause it to think it's at part-throttle. The good news is that it's free to check the adjustment of the TPS and cheap to replace it. I found a good writeup on setting the TPS on Renix jeeps (which I assume yours is, what year is it?). You can find write ups on both engine series' online. From there I would look at the IAC. You can easily take it off to clean it while you're messing with the TPS. Sometimes that's enough to "un-stick" it for a while, but in the end if it seems related to your bad idle, I'd replace it. Also, have you checked to see if there's fluid in the reservoir. If it's empty I'd pop the drums loose to check for a busted wheel cylinder first, then suspect the booster. Quote Link to comment Share on other sites More sharing options...
twistedfocus1647545489 Posted January 18, 2008 Report Share Posted January 18, 2008 I just learned to read and realized you said it's a 1994 model. I think the TPS on yours is a bit different than mine, but the concept is the same. Just the wiring and voltage to set it at differs. Quote Link to comment Share on other sites More sharing options...
Buck531 Posted January 18, 2008 Author Report Share Posted January 18, 2008 I think the CPS usually causes a no-start condition (although Cherokees are notorious for them going out). It sounds more like your low idle is related to a bad or improperly set TPS. Think old school post-style radio knobs... the hiss they get in the area you use them the most after years of use. TPSs are very similar and can pick up the same sort of noise in the signal. You can tell if you hook up an analog voltmeter and do a slow sweep b/c the needle on the voltmeter will spike or dip instead of rising steadily. Mine needs replaced, and in the interim I just manually set the idle a bit high (about 900 when it should be 750) and when it warms up it falls down to about 500 and runs rough but will keep running. If you do that, I would definitely recommend that you reset the TPS voltage because using the stop on the throttle body to manually raise the idle without doing so will cause it to think it's at part-throttle. The good news is that it's free to check the adjustment of the TPS and cheap to replace it. I found a good writeup on setting the TPS on Renix jeeps (which I assume yours is, what year is it?). You can find write ups on both engine series' online. From there I would look at the IAC. You can easily take it off to clean it while you're messing with the TPS. Sometimes that's enough to "un-stick" it for a while, but in the end if it seems related to your bad idle, I'd replace it. Also, have you checked to see if there's fluid in the reservoir. If it's empty I'd pop the drums loose to check for a busted wheel cylinder first, then suspect the booster. There's pleanty of fluid in the resevoir. It just feels like I'm using manual brakes. It doesn't get tight until I hit the floor. I'm going to pop off the brake booster hose and plug it just to see if the idle changes. That could be my massive vac leak. The jeep will be towed here in about an hour if anyone wants to come over and dork with it (too bad it's too f'n cold and my Lumina is in the garage and doesn't move). Quote Link to comment Share on other sites More sharing options...
twistedfocus1647545489 Posted January 18, 2008 Report Share Posted January 18, 2008 I'd say we could check it out in my garage if you still want to come over and pick up those bling-bling gold wheels, but right now my tools mainly consist of a hammer, screwdrivers and tape. Quote Link to comment Share on other sites More sharing options...
Buck531 Posted January 18, 2008 Author Report Share Posted January 18, 2008 I'd say we could check it out in my garage if you still want to come over and pick up those bling-bling gold wheels, but right now my tools mainly consist of a hammer, screwdrivers and tape. Its not really driveable. Virtually no brakes and I have to give it gas if I let off the pedal or it'll die. (not fun driving). It's getting towed here today and I'm going to check a few things on it. I probably won't be over today to get the wheels. Probably tomorrow sometime after 3 ish if I can get this jeep running (can't fit the wheels in any of my other cars.. lol). Quote Link to comment Share on other sites More sharing options...
badasskylark Posted January 18, 2008 Report Share Posted January 18, 2008 Jeepforum.com they have an awsome Cherokee section. Quote Link to comment Share on other sites More sharing options...
Buck531 Posted January 18, 2008 Author Report Share Posted January 18, 2008 COmpression test: 1 - 120 2 - 115ish 3 - ZERO 4 - 90 5 - didn't check 6 - didn't check Head gasket kit from advance is like $60 bucks. Days worth. Not bad. Now I Just need to get the damn motor in my lumina so I can drive it and put the jeep in there and work on it. woot. Quote Link to comment Share on other sites More sharing options...
TurboRust Posted January 19, 2008 Report Share Posted January 19, 2008 sorry man I was just being a dick, gotta put a motor in my beater taurus i bought. we should have a party. Quote Link to comment Share on other sites More sharing options...
Dave1647545494 Posted January 19, 2008 Report Share Posted January 19, 2008 no green fords in bucky's garage again................... ever don't forget to get the head pressure tested and maybe a quick valve job Quote Link to comment Share on other sites More sharing options...
Buck531 Posted January 19, 2008 Author Report Share Posted January 19, 2008 no green fords in bucky's garage again................... ever don't forget to get the head pressure tested and maybe a quick valve job True.. no fords ever in my garage.. especially green with the WRONG motor in it.. lolz. I don't have the money for the head work Dave. its' a beater truck and don't feel like spending more money than what I bought it for. A quick $50 gasket set from Advance (comes with lim, head and valve cover gasket) should do the trick. I got about 4 holes in the exhaust too so that'll need some attention eventually. I was looking at the gasket for the 4.0. holy shit those cylnders are close to each other! the picture looks freakin' paper thin between them. Quote Link to comment Share on other sites More sharing options...
Buckeye1647545503 Posted January 19, 2008 Report Share Posted January 19, 2008 did you put a bit of oil in the zero cycl. to make sure it is losing it from above the block? Quote Link to comment Share on other sites More sharing options...
Buck531 Posted January 19, 2008 Author Report Share Posted January 19, 2008 No. dave said for me to do it. It didnt' have any wierd sounding noises coming from the bottom end. I'm not worried about it. Spend a few hours ripping the top half off. If the motor is shot.. I'll just replace it. On a side note, i can't find head bolts for this thing for the LIFE of me. napa nor advance has anything for head bolts. Just the gasket set. Hell even ebay doesn't have any. wtf? Quote Link to comment Share on other sites More sharing options...
Buckeye1647545503 Posted January 19, 2008 Report Share Posted January 19, 2008 If you do the oil it can save you time and money, I have had jeeps run fine with a bad hole. What happens if you unplug the vac hos on the booster and plug it? Most straight 6's will run enough to ignore the bad hole. The vac leak may be your biggest problem as far a drivability are they torque to yeld ? Quote Link to comment Share on other sites More sharing options...
Buck531 Posted January 19, 2008 Author Report Share Posted January 19, 2008 If you do the oil it can save you time and money, I have had jeeps run fine with a bad hole. What happens if you unplug the vac hos on the booster and plug it? Most straight 6's will run enough to ignore the bad hole. The vac leak may be your biggest problem as far a drivability are they torque to yeld ? Yeah, i thought the brake booster if it were leaking would cause the really bad idle. I plugged it earlier today and it did nothing. I got zero compression on cylnder 3 man. nothing. nada. no idea if they're TTY or not. Can't find anything. Quote Link to comment Share on other sites More sharing options...
Buckeye1647545503 Posted January 19, 2008 Report Share Posted January 19, 2008 look at the torque spec if it is a number only they are not if it is a number plus a number of degrees then it is Quote Link to comment Share on other sites More sharing options...
TA In Progress Posted January 19, 2008 Report Share Posted January 19, 2008 Usually if the head bolts are TTY, then they're readily available. I would assume with as many of these on the road as there are, Fel Pro would make them if they were TTY, but who knows? Quote Link to comment Share on other sites More sharing options...
Dave1647545494 Posted January 19, 2008 Report Share Posted January 19, 2008 4.0 head bolts are reuseable Quote Link to comment Share on other sites More sharing options...
Buck531 Posted January 20, 2008 Author Report Share Posted January 20, 2008 Also thought about it today. With the zero compression in 3, and the amount of fuel that was in with the oil, I think possibly either the valve got burnt or it's bent. Since I don't hear anything rattling around I think it's a burnt valve with a nice sized hole in it. what causes burnt valves anyways? Quote Link to comment Share on other sites More sharing options...
Dave1647545494 Posted January 20, 2008 Report Share Posted January 20, 2008 get it pressure tested its worth the extra money Quote Link to comment Share on other sites More sharing options...
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