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Showing results for tags '2.5l tbi'.
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Hi, Just joined but have been using these forums for a while for information. SO I have an 88 YJ with the TBI. My issue all started when I went to get it smogged last year. Short story it failed 3 times for high NOX @ 35mph. By the third failure I had replaced every sensor I could replace, including the EGR. The cataliytic converter only has about 1000 miles. I do have the snap-on diagnostic tester, just looking for some direction to narrow my troubleshooting. Currently the jeep wont idle on its own and I can smell that it is running very rich and it seems to run a bit rough. Thanks! -
Hello all, I am having some issues that have become more perplexing than my knowledge has the answers for so hopefully someone can steer me in the right direction. I started off by trying to improve the rough idle my Jeep has had for years. I rebuilt the TBI, new O2 sensor, new ISA, TPS, coolant temp sensor, MAP sensor, spark plugs, distributor, plug wires, battery, fuel and air filter and installed new vacuum lines wherever I could (minus the hard lines which are difficult to find replacements for). After this, the Jeep was running great for a week or so, idling smooth and better throttle response. However, few days ago it started stalling and dying after I would put it into gear and apply any gas to it. I started digging through old forums here on this site and working through the EGR system and cleaning up grounds. Now it actually won’t fire up at all, or will for a second and then die. Before this it would idle fine for a while then choke out and die. I have an inkling that the progressive nature of this may help figure out what’s going on... I’m thinking fuel pump, EGR, something electrical; but I honestly am lost at this point. My mechanical knowledge is pretty novice and I just work on my Jeep in my garage as a hobby so I have no electrical testing tools. Any help or thoughts would be much appreciated! Thanks in advance! -
Bought my son a nice 86 cherokee. It has an idle problem that is driving me crazy though. I've checked for vacuum leaks and found none. I've checked all the sensors according to what I've found on this site and they check good, except the tps, I havent checked it... I ran out of time the last time I got to work on it due to rain... So it is suspect. The problem is, when you start it, hot or cold, it will surge and sometimes die for about 45 secs to a min. I can see the IAC motor slowing decreasing the idle but then right before it dies, it will snap the throttle open. Somtime's it does die before it can open fast enough, but the IAC motor seems to be working. After that first min of surging, it runs great, won't die or surge again, until you shut it off for a few mins and restart. It will start right up everytime but go through its surge for a min and then run fine. You can keep it running by feathering it. Engine hot or cold it will do this. Could this be the tps? Its the 2.5l with the manual trans. -
Greetings, Have a 1989 YJ with the 2.5l TBI. Have had a sporadic idle, stall problem. Verified fuel delivery and injector performance, tested and/or replaced all sensors and IAC motor. Cleaned throttle body, checked for vacuum leaks. Kept looking over at the coil/icm assembly, but thought "no, just replaced those not too long ago." Long story short, tested the coil - badly out of spec. Changed out both coil and icm and finally (slow learner here) checked voltage entering coil. Constant 14 =/- volts at startup and run. Checked with my daughter who drives the vehicle and she confirmed after pondering that yes, seems to only happen after driving for quite a while - giving the icm/coil plenty of time to get nice and toasty. So, I'm guessing that means ecm troubles, as I know this problem has popped up from time to time but am wondering if it is possibly an ignition switch issue? So, I'm checking with the experts before I choose which pain in the butt part to remove first. Thank you. -
Hi, I've been hunting and chasing my tail to get some kind of throttle response from my wrangler above 45 MPH. I know these are not very powerful to start but I feel like what I'm experiencing is abnormal. Anywhere above about 45MPH when throttle is given There is little or no response from the engine. I have gone through the tuning and troubleshooting, replaced numerous things and adjusted what is able to be adjusted to the best of my understanding. Most recently I put a new cylinder head on due to a cracked web between valves on cylinder 4. I was so sure this was going to solve my issue considering the cylinder was down to 70psi compression. Though the engine runs smoother and quieter now it still is lagging at higher speed. 5th gear is pretty much useless unless going down hill. I have access to a modis scan tool so I can see ecu data. What is bothering me at this time is the engine rpm's are reading about 400 rpm's lower than my tach. Idling around 575 rpm's according to the scan tool data but reading around 1000 on the tach. In my opinion it feels like it is closer to the 1000 rpm range but I don't have a way to check it at this moment. My question is where does the ECU get the engine speed? is it from the ICM or the CPS? If its the cps can the cps fail in a way that it still reads but reads low? I may be barking up the wrong tree and I likely am. but right now I'm trying anything i can think of. Any other suspected areas to check? Any scan tool data that would be more important than others? Any suggestion is welcome. Thanks Dan -
I've been working on my 1987 YJ Wrangler 2.5L TBI for sometime now. I put in a new gas pump, gas tank, fuel filter plugs and a distributor cap. Before that I put in a new radiator due to an overheating issue. When I get out and drive for about 20 minutes it just dies and will not start back up. I let it sit for about 10 minutes and I can get another 20 minute run out of it. Please help me to get cruising again. -
On the passenger side engine compartment on my 89 yj 2.5 liter there is some diagnostic plug in connectors. which one is the connector for the isa motor control? Which one is D-1 and D-2? How are each individual holes in connectors numbered ( 1-2-3-4-5-6 etc>)? -
I recently bought a 1990 Jeep YJ with 4 cyl 2.5 TBI engine. The jeep runs great except during warm-up. It starts fine and runs and idles well initially. As soon as the temperature gauge begins to climb off the 100 degree mark, the engine begins hunting and surging and usually stalls. If I push down on the accelerator and run it to 1000+ rpm, I can get the engine to heat up to operating temperature. At that point (~160-170F) the idle becomes stable again. So far I haven't done a lot of troubleshooting but have checked the EGR valve, changed rotor/cap, air filter, and fuel filter with no success. I'm wondering if it might be a bad O2 sensor that's slow to heat up which will be the next thing I check/replace. Any ideas or help is much appreciated! -
I have replaced the gasket around the dist shaft, not much more that a week later it is leaking again. I used a feel-pro gasket, I have always had good luck with them. This area of the engine isn't pressurized is it? Both surfaces were very clean when I put it together. Possible that the crankcase isn't venting? -
So I replaced the head assembly, rods, lifters, cam, timing chain, etc. Everything except the pistons basically. I took it to a mechanic at first but after taking it apart e decided he didn't want to work on it. I've put it back together without any left over parts. I know the cam timing is ok, I lined up the dots on the sprockets (see photo). When I dropped in the distributor I had the oil pump notch just past the 3 o'clock position, and when it dropped in the rotor was at the 6 o'clock position just like the manual says. But to make things even better, when the engine is turning over, every once in awhile a puff of fuel will shoot out of the injector. I replaced the injector, same thing. The only thing I am not sure of being the same as before the work started is 1 orange wire (see photo). It goes to the connector (see photo) but I haven't followed it back any further. Anyone know what it is supposed to be connected to? Is there a wire that is supposed to be screwed to the distributor case? I replaced the distributor because the casing was cracked on the old one. -
I have purchased an 87 yj tbi 2.5. With help from this site I have been tinkering with this thing trying to get it to run as its suppose to especially in this cold weather. I was looking at my egr valve while I was replacing the vacuum lines and noticed it was unhooked and the line feeding it is plugged. I did notice that the vacuum port on the egr was facing the front of the jeep, that seems to be the wrong direction to me.
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I'm at my wits end troubleshooting my lil 2.5L engine. I googled and found your page from about a year ago. 1990 jeep wrangle 25l engine timing. Today I thought about timing. It misses, like running on only 2 cylinders when at low speed and and only pulling slightly. As I move into mid and upper rpm range it stops missing. I still do not have much acceleration but at least it stops missing. I've check and/or changed every sensor it has. TPS is only rough since I have not gotten my laser tach to work yet. In checking fuel I have only 10 psi so I know that's a problem. This started about a month after the SMOG guy changed the O2 sensor to pass smog. I've check the voltage when hot and it's within spec. I also had massive exhaust gasket leak so I cleaned the surfaces and replace the gasket. I'm a machine mechanic from way back in the Navy so I'm not just a new mechanic. I just can't quite figure this one out. I'll check timing tomorrow. Lowell -
Hello all! Running into an issues on my 1990 2.5l tbi std shift wrangler and need some help. First a little background. I was in the middle of a full rebuild when I had to relocate, so my brother back in Ohio is completing the rebuild. He put the fully rebuilt and assembled (by machine shop) motor in. I bought every sensor on the motor to replace, as well as new injector. Everything on the motor is new except the fuel pressure regulator and intake. A year ago I put a new fuel tank and pump/sending unit and filter in also. Now the problem.....My brother has everything together. It fires right up and idles great. When he is easy on the pedal it runs fine, but when he really gets on the Gas hard it falls on it's face. He has checked the timing per the manual a few times and it's good. When he puts the timing lite on it while running he is at 11 degrees before tdc, which if I remember correctly was what it was at prior to the teardown. He is stumped.....hes a Ford guy so this is his first jeep motor....and I am fairly ignorant (most would agree strongly). He does not have a fuel pressure gauge to check it (he was going to check AutoZone borrow a tool deal this week to see if ones avail). Any suggestions would be greatly appreciated! -
I hate to bring this up again, but I need help. I have a 1990 2.5 TBI wrangler that is killing me! I say I've been throwing parts at it, but given it's age everything I've done was either bad or well on its way. Now that almost everything has been replaced including the IAC I need help adjusting it. I assumed the IAC was in the correct position when I replaced it, but I'm suspect the PO had adjusted it when some of these parts I replaced went bad or possibly when they plated off the EGR (I replaced the egr and cleaned the egr tube) and now I find myself trying to adjust the IAC. I've adjusted it twice. The first time I was very close, but was not perfect so I adjusted it a turn more and it's acting up again. I've ready your very helpful advice, but call me slow I could use a bit more help or even pictures on how to do it the way you describe. The adjustments I made were before I found this page and I was told to just unplug it adjust it to 3500 rpm turn it off, plug it in, start it up for a minute then reset the ECU and I'd be good to go. Which is "close" to what I read here but miles away too. It did make it much better, but one more turn and it's back stalling out again. Can anyone give me pictures or better yet a video? I've hardly been able to drive the jeep since I purchased it. -
Here is 1987-90 Jeep YJ Wrangler and Jeep XJ Cherokee/MJ Comanche 2.5L TBI diagnostics information in PDF form. The first document includes all sensor and switch tests plus adjustments that affect engine tune, idle and reliability. Wiring schematics and ECU pin locations, test plugs and diagnostics included. Jeep 2.5L TBI Complete Diagnostics-Sensors-Switches.pdf Jeep 2.5L TBI ECU Inputs and Outputs.pdf Jeep 2.5L TBI MAP Sensor Test.pdf Jeep 2.5L Timing Chain and Tensioner.pdf Jeep 2.5L Valve Timing Check.pdf Jeep YJ 2.5L TBI Sensors and Pinout.pdf YJ Wrangler 2.5L TBI Wiring of WOT to ECU.pdf Jeep YJ 2.5L ISA Wiring Diagram.pdf 1987-90 2.5L TBI Intake Manifold and Sensors.pdf 1987-90 YJ Wrangler 2.5L TBI Emissions System Parts.pdf YJ Wrangler Fuel Filter and Guard.pdf 2.5L TBI ISA Motor Adjustment.pdf Used in conjunction with the many forum exchanges (search under "All Content" and "2.5L TBI" in the search box), plus the Jeep 2.5L TBI troubleshooting article at the magazine website, this information will help solve your Jeep YJ Wrangler or XJ Cherokee 2.5L TBI troubles. In references, the Model 81 is the Jeep YJ Wrangler. The Model 60/70 is the XJ Cherokee and MJ Comanche Pickup. Moses -
T-shooting an intermittent starting problem. About 80% of start-ups are perfect. When failing to start, it will turn over and over, but won't fire up. Sometimes starter fluid will cause it to fire up and then it runs fine, but that's only 50% effective. The rest of the time, only push-starting will work, but push-starting does work every time. Most obvious assumption is fuel problem, but fuel system checks out fine (replaced almost everything over time anyway). Ignition/electrical is fine. Also, the problem seems to be completely independent of outside and engine temperature. I started reading about ECU inputs, and discovered that during startup, an engaged WOT switch causes ECU to cut off fuel because ECU thinks it will flood the engine. The WOT switch is worn, but shouldn't prevent starting if disconnected. Would any other ECU inputs prevent fuel flow during start-up if their signals are outside normal limits? Service manual says during "Ignition On", CTS, MAT and MAP sensors begin providing input to ECU, but doesn't list MAT or MAP sensors during actual start-up. See attached page. So which sensors matter to ECU for start-up fuel supply calculations or decisions? Also, during push-starts, the ignition (key switch) is in the Run position, and not the Start position, which changes the ECU inputs, too. My shop has a DRB II diagnostics reader, but unless they hook it up when it happens to be misbehaving, shouldn't everything check out ok? Unfortunately, I've never been able to get it to fail at the shop. I also tried replacing the fuel relay. I also noticed that it is no longer cycling the ISA motor when it fails to start. It used to, but I can't figure out why it did that anyway. What are my next moves? Might be trying to oversimplify this, but what kind of intermittent problem would occasionally prevent a normal startup, but NEVER prevent a push-start from succeeding? -
I put a new 2.5l into the jeep and it only has 400 miles. It was running great till suddenly the issues popped up again. I hooked the scanner up and saw that the short term trim was ridiculously high. Its reference point at idle is 128 and its running at 180. The long term trim is at 109. the injector pulse is 2.0. The o2 sensor was reading no higher than 500mv. -
Hi, I have a 1988 Jeep Yj 2.5 with the renix computer. My last stop before I drive this thing off a cliff is here. I should have come here first. I hope one of you can help me. I love my Jeep but am so frustrated with it right now. Problem: Jeep is running super rich. I do not think it is ever coming out of closed loop. Points to know: - O2 sensor is recognizing that the jeep is rich. Volts sit between .94V and .99V JEEP RUNS AWESOME. No loss of power. No hesitation. Idles between 900 and 750 - Fuel smell coming from the tailpipe Emissions high on HC and CO Things I have tried: -Replaced o2 sensor -replaced fuel pressure regulator -replaced CTS replaced ISA replaced ECU replaced MAP Replaced MAT checked return fuel line for blockage. Had Head rebuilt. Vacuum was fluctuating and needed new valve guides. Was hoping this was impacting the MAP sensor. Nope I have gone through entire FSM diagnostic tree. The only thing that failed was the MAT sensor resistance never got down to 150ohms. Always stayed above 300. I even paid a mechanic $600 to try and uncover the problem. He confirmed it was not coming out of closed loop. Recommended changing the ECU. Which I did. I hope someone can help. Thank you all in advance. Carlos -
Hello im new to this i am from hawaii i have a 1989 jeep wrangler and have a brand new motor installed it had an idle problem so i changed the tps set it in between 4.6 and 4.7 on the multimeter which is what the dealer said to set it as and it runs for ten minutes and as soon as i tal the gad it sputter then dies any ideas ? -
Thanks for the engine information. Ok .... update for today. I'm really not finding a vacuum leak and before I build a smoke machine there's been this gnawing in the back of my mind to check the valve timing. I found this pdf manual http://oljeep.com/JeepEngines.pdf and on page 63 it tell how to check valve timing. So I removed all the plug, it was easier to rotate by removing all the rocker bridges, set up a dial indicator on the #1 intake push rod and checked .... Hmmm the dial moved .010 but I don't see the index mark anywhere (????) ... oh, there it is 3 inches to the left, or 3 inches BTDC ... really???? Guess I'll pull the timing cover and check it out.
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In the second pic I know the line at arrow #1 goes to the air cleaner. Can anyone tell me where #2 and #3 should go? first pic is just a close up of the connections in question. Thanks -
My 88 Comanche 2.5 liter doesn't have a wot sensor did some of them not come with them or maybe some one took it off when I wasn't looking
