4bangerjp.com
General Forums => The Mess Hall => Topic started by: 87comanche on August 20, 2006, 07:54:46 PM
-
Hey guys-
I just intalled a Clifford header to my 87 2.5, and a new EGR valve
to boot, and when I start her up (she DOES start), she races like
mad. With 180K, I don't want to blow the motor, so I need some
enlightenment.
(deleted a long post)
If anyone could help me figure what goes where, I'd be most grateful. There are two vacuum ports on the throttle body itself, two on the air cleaner (though only one is functional), and an "L" fitting off the intake manifold that supplies vacuum.
The Chilton's vac. diagram isn't specific about where the vacuum lines go, or maybe I'm just an idiot.
Does screwing up the vacuum lines commonly cause an engine to race like crazy? I'm not ruling out the possibility that I f-ed something else up, either. What I do know is I didn't touch anything on the left side of the motor.
Thanks!
87C
-
could be a gasket but ya a vacume line is possoble what exactly did you change
-
Sounds definatly like a vacuum leak. It will cause the engine to race over 1000rpm at idle.
Air could be leaking in front a vacuum lint but since the intake was removed to fit the header, it's probably leaking from there. Very common.
-
Make sure your egr is holding a vacuum, put short piece of vacuum line on it and suck, then hold your tongue on it for a minute. The rubber diaphram could be bad inside it.
-
Put a new EGR on it. I don't think it's leaking at the manifold -- I put a new gasket on. I'm a dunce - the EGR tube doesn't fit up to the new header flange, so I had removed it, causing a giant vacuum leak from the manifold.
-
well thats probly the problum right there let me know how it goes
-
don't forget to check for the alignment of the manifold itself. you can cock them slightly sideways and then tins if air will enter the manifold and the engine will go to redline when you start it but it sounds like you have the problem solved just thought I'd throw some knowledge out there for ya.
-
superman, yj mechanic,
Thanks. The manifold shouldn't be cocked because I left the alignment plugs in. I have to bend and fab the egr tube to mate up to the flange on the header. Flippin Clifford..... :oops:
-
best of luck on that let me know how it turns out
-
Ok, I figured that part out. Anyone know what vacuum lines hook up to the back of the air cleaner? One's functional (top) and one's a dud. Also, the L vacuum port on the back of the manifold - gives vacuum to the HVAC and where else? Almost got this thing back together!
:x
-
DAMMIt. :x
Got the EGR tube all hooked up and it STILL races!! I know the intake and exhaust manifolds are on properly, I'm 95% sure the vacuum lines are now routed right, could the lean running from the open header make the engine race? I'm completely baffled.
87c
-
what you need to do is really simple ive been doin it for years to check for manafold leaks you pore walter around the manafold and when the engin starts to die out you know where the leek is simple but be carful not to pore to much walter you dont whant to hydry lock the engin good luck and let me know what you do
-
you mean to see if it's leaking where the intake bolts to the head? I think that would be next to impossible, since I have a new gasket on there, and the manifolds are cranked down to the head. I mean, I put the same intake on there that I took off, so I don't know how it would be leaking now.
-
Has the computer been reset by removing the power?
-
rember anything is possoble any thing can happin and it does all the time $hit hapins. well it was just advice you dont have to take it but its never let me down! good luck
-
Has the computer been reset by removing the power?
Does an 87 need to be reset that way? I thought only OBD computers work that way.
-
Anything which incorporates integrated microchips can get hung in the wrong state even without Microsoft running on it. clearing it is an easy task and should have been disconnected when doing the work.
-
Anything which incorporates integrated microchips can get hung in the wrong state even without Microsoft running on it. clearing it is an easy task and should have been disconnected when doing the work.
LOL :lol:
Ok, I'll disconnect the negative cable for a couple hours tonight, try it again in the morning. Also going to re-check the vac lines, the bolts, and the throttle plate. I'll report back tomorrow.
Superman: I appreciate your input!
T
-
Disconnect the negative for a couple minutes should be plenty, the thottle plate should just be cracked open about a 1/8 inch, make sure you dont have a sticking thottle linkage. If a vacuum line is connected to the wrong location you may create the condition discribed. Also I am wondering if the throttle body is stuck, check your connections because if it is getting constant voltage it would cause it to stay wide open or if it got any dirt or water it could get stuck wide open. My Dad had this happen once and we pulled the thottle body injector out of the air horn connected the wires and started the car, it simple shot a constant stream of fuel instead of a normal spray pattern, it looked like a skirt gun. this was due to water causing the injector to stick open. If you do this just make sure you aim it away from the engine area so you dont cause a fire.
-
Troubleshooting, I thought of some things to possibly check plus sharing my own troubleshooting technique may help you. I am thinking the EGR could be mounted backwards, if I remember right this is possible on some engines, or maybe the unit sold to you has the valve setup for the opposite air flow direction or incorrect spring tension. I would remove it again and do a close inspection to compare old to new units making sure the valve configuration inside them match and mounting direction match, installing the old unit is even a good test. As I mentioned before, put a small piece of vacuum hose on the top of each unit and suck a small vacuum then hold your tougue over the hose end for a minute. If the rubber bellows inside does not leak they are good. Many times I just clean the carbon off an EGR and do this vacuum check then reinstall if they function. A bad EGR usually makes the engine idle really rough due to the valve not opening at all caused by a blown rubber diaphram, an EGR should open to allow some exhaust gas to recirculate (loop) back to the intake during warmup only and failure would not cause the engine to race now that I think about it. So, let's backtrace all the items you had to disconnect when you did the job and re-mate all the electrical connectors, recheck all the electrical and vacuum lines for correct location too. I am also wondering what the thottle body state would be if it were not getting a proper signal, could it be stuck wide open? Sometimes they get stuck wide open from dirt or water getting in them. Anyway now for the vacuum line issue, you have ported vacuum ports on your intake & thottle body and you have non-ported connectors, this means some of the vac connectors have a pin hole or orafice in them (ported) to cut down or restrict the amount of vac to certain items while other items use full open ports. this is why a vac line on the wrong connector can cause racing. Example, I created this condition once when I hooked the vac line from the distributor advance unit to a non-ported connection on a carburator which caused the distributor to peg full advance as soon as the engine started because it recieved full vacuum, once I moved it to a ported connection it only recieved a very small (restricted) amount of vac during initial acceleration as needed. So you can see how a wrong connection can make all the difference, some vac connectors are restricted and some are wide open but they look just the same externally! (ported & non-ported) Testing, you can also do testing with a vacuum cap/plug assortment kit by disconnecting and capping off one line at a time to see if one of the vacuum connections is responsible for the racing condition. each time you remove a line cap it's port on the intake or throttle body and plug the hose end, start the engine, if the racing continues reconnect the line and goto the next line performing the same test, when you finally get to the line causing the problem you will know because your idle will drop way down near normal. The next step will be to figure out why the line you identified as causing the engine to race, why it creates the problem, so see what it goes to, it maybe some kind of sensor, isolate down to the line, then zero in on the related component(s). When your done let me know your results.
-
Hey thanks for all the thought on it. I'm going to test what I can tonight when I get home. Just for the record, and I don't know how different your 89 YJ2.5L is from my 87 MJ2.5L, but I have the lines as follows:
bottom port on TB ---> MAP sensor
top port on TB .........> valve cover (these first two I know to be correct)
vacuum port on back of manifold (L port)--> to EGR solenoid and to narrowed port on back of air cleaner (also tried dummy port on back of air cleaner, and no change in idle speed).
EGR solenoid............> EGR valve
Can anyone with a 86-88 TBI 4banger MJ/XJ verify this??
-
well, went over everything with a fine-toothed comb. Checked all the electrical connections, vacuum connections seem right (see post above). Checked the throttle plate; unplugged the negative cable for about 30 minutes while I checked over everything. I took a couple of photos, I don't know how helpful they'll be. Found a couple of vacuum lines disconnected on the passenger side of the engine, where I WASN'T working. Wonder if the vacuum system was fubar to begin with and now by connecting it correctly, I'm screwing it up. It's still racing.
First picture shows one of the loose connectors in my hand. The other is circled in red at the bottom. It's also loose on my 88 4.0, so I'm not too concerned about it.
Second picture shows the EGR solenoid. Tube on the left supplies vacuum from the manifold, and right vacuum tube goes directly to the EGR.
(http://xs206.xs.to/xs206/06365/egrsolenoid.JPG.xs.jpg) (http://xs.to/xs.php?h=xs206&d=06365&f=egrsolenoid.JPG)
(http://xs206.xs.to/xs206/06365/P1010147.JPG.xs.jpg) (http://xs.to/xs.php?h=xs206&d=06365&f=P1010147.JPG)
-
Have you had a chance to do the vacuum line testing yet?
"Testing, you can also do testing with a vacuum cap/plug assortment kit by disconnecting and capping off one line at a time to see if one of the vacuum connections is responsible for the racing condition. each time you remove a line cap it's port on the intake or throttle body and plug the hose end, start the engine, if the racing continues reconnect the line and goto the next line performing the same test, when you finally get to the line causing the problem you will know because your idle will drop way down near normal. The next step will be to figure out why the line you identified as causing the engine to race, why it creates the problem, so see what it goes to, it may goto some kind of sensor, isolate down to the line, then zero in on the related component(s). When your done let me know your results."
-
No -- it got dark! :shock:
I'll give it a go this weekend.