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Renix Guys...Long Post

19864cyl

NAXJA Forum User
Location
Alabama
1986, 2.5L, 4 speed, 19X,XXX miles

A little backstory:

Bought it from a friend after he pulled the motor to put new rings(it was smoking) in. He bought another project and never really messed with it once the motor was pulled. Pulled it home with a bucket of bolts and everything from the engine compartment riding in the cargo area. I finished tearing it down, had it bored, and bought a rebuild kit and put it back together. It was alot of work having no idea where everything went and figuring out which bolts went where. I literally took apart every single peice of the engine, intake, throttle body (took the tps off cleaned it because it was dirty and put it back on, which i think could have miss adjusted/calibrated it) every bolt. Once we dropped it back in and used our best guesses as to where everything we (vacuum hoses, ground wire, etc) couldnt get it to start. The problem was that we has the dist. 180 degrees out. Once we fixed the it ran. It had a high idle, but it ran smooth and idled pretty good. We didnt drive it though because we had clutch issues. Sometime while we we fixng the clutch i went back over the vacuum line and found that we had some wrong. I was going by the manual and not the diagram on the firewall. Im positive that all the vacuum line are right now. That brings us to the problems I have now.

Problems:
1. The idle is low (I dont have a tach)
2. It smells like it is running rich
3. It has a ROUGH idle, but sometimes it will idle good for a few seconds then back to the rough idle.
4. When you first crank it up it will drive decently, feels like it is not running as good as it should though.
5. If i turn it off for a few mins (like when im getting gas) and then crank it up, it will run terrible. It bogs, misses, skips, acts like it is starved for fuel, or like the coil stops working. Then a couple of mins later it will run decently. The longer it sits the less of a chance it will do that.
6. Sometimes it will have the problems from 5 even if I havent turned it off. It happens at totally random timeswith no predictability, and it might not even happen at all.
7. Its likes to miss, skip, bog, under really light throttle when im just cruising.

Bonus Problems:
1. Gas gauge reads way above full all the time.
2. Sometimes the low fuel light will come on even when it has alot of gas. Sometimes it stays off for days.
3. Temp gauge never moves, except for when Im turning the key to crank it. I read somewhere that if i were to pull the cap off and ground it and it goes all the way to the right, then it is the sender. It does do that.

It has:
new filters
new plugs
new wires
new rotor and cap

What ive done to fix it:

1. I made new grounds using 4 gauge wire. I even made a ground going from the battery to the frame.
2. Made positive all the vaccume line are exact according to the firewall diagram.
3. Checked and replaced any vacuum line that looked suspect.
4. Checked the timing at idle, it was around 15 advanced. If i reved it it would advance to past measurable. I know youre not supposed to even check it because the computer controls it.
5.Tested the Coolant Temp Sensor- It tested out exactly like lunghd.com said it should.
6. MAP sensor tested out right too.
7. I tried to test the TPS but i the instructions from lunghd.com didnt match my TPS. Maybe because its a 2.5L. Any ideas?
8. Used a stethoscope to check for vacuum leaks at the intake manifold. And everywhere else i could.
9. Tested the oxygen sensor and it was good.
10. I havent checked the egr solenoid, the IAC, or the TPS. Well I kinda checked the TPS. The terminals that lunghd said to check were different than mine. I did have a 5 volt signal in one of the though, just not the one that site said it should be.

What I think?
1. When I was building it i took the TPS off and didnt pay much attention to it. I have recently learned that even a new one has to adjusted. Is it possible I got it out of adjustment?
2. I dont think this would cause problems, but I have a pretty good exhaust leak where the exhaust manifold connects to the exhaust pipe. I dont have a donut gasket on there. Is it supposed to have one?
3. I was thinking about removing the grounds that ground to the dipstick tube. Extending the wires and grounding them directly to the battery in hopes that it would help. Good idea? Bad idea? I know that one of them is for the computer so I was hoping it might help out.
4. I dont think my symptoms (mine starts pretty easy) match the CPS so I didnt even check that.

Im at the end of my rope. I am open to any suggestion or idea that yall might have. Please ask me anything you can possibly think of no matter how obvious it may seem. Maybe I overlooked it. Shoot me any idea and I will give it a shot. Thank you in advance, and sorry that the post was so long. And congrats if you actually read the whole thing Haha.
 
Did you connect the ground wires to the engine? The ECU relies on ground circuits to give proper ignition and fuel signals to the engine. Bad grounds = bad running engine and weird electrical problems......................There is one from the drivers firewall to the back of the head.On the 2.5, I'm not sure if it has grounds at the dipstick tube like the 4.0, but worth investigating.
 
Did you connect the ground wires to the engine? The ECU relies on ground circuits to give proper ignition and fuel signals to the engine. Bad grounds = bad running engine and weird electrical problems......................There is one from the drivers firewall to the back of the head.On the 2.5, I'm not sure if it has grounds at the dipstick tube like the 4.0, but worth investigating.

I have the wires from the ecu grounded to the dipstick tube, just like the 4.0. I had one running from the firewall, by the map sensor, running to the right rear head bolt. I was able to look at another 86 2.5 and it had the ground running to the intake so i moved it. Im sure that is where it was supposed to be. Would it be a bad idea to move the ecu ground directly to the neg battery terminal, or should it be grounded to the block?
 
Just about the first thing I'd check for an intermittent bad idle is the EGR valve, to see if it is hanging open or failing to seat owing to carbon or wear. It might be worthwhile, especially if you can get it running right for a while first, just to crimp off or plug the vacuum line to the egr valve, and see if this helps anything. Most EGR valves have an open base, so you can reach a finger in and pull the diaphragm open. I've run across a problem on an 88 Renix 4.0 in which the valve wore and intermittently hung open, killing the idle. Reaching in and allowing it to snap shut solved the problem temporarily (once shut, I just unplugged the vacuum).

I believe that the EGR/canister purge solenoid will open the EGR if it fails, so to disable the EGR you cannot just unplug the solenoid.

Also, you should probably try adjusting the TPS. According to my Chilton Fuel Injection manual, you should back probe the connector with a good voltmeter. In other words, do not disconnect the terminals, but stick the voltmeter probes in where the wires enter. At wide open throttle, ignition on, engine off, you should see 5.0 volts at terminals B (-) and C (+). Now disconnect the positive from C and connect it to A. You should then see 4.6 to 4.7 volts at wide open throttle. There may be a better procedure in the proper Jeep manuals. I know that for the Renix 4.0, the updated procedure is based on percentage of voltage, rather than actual voltage, and I wouldn't be surprised if this has also been updated for the 2.5 at some point. But at least that's a start, and if you get a reading under 5.0 for the first point, you can probably just go ahead and shoot for ~94 percent on the second.
 
Pretty inconsequential but your gas gauge issue is probably an open or shorted wire to the sender.

Good luck on the rest of the project!
 
Just about the first thing I'd check for an intermittent bad idle is the EGR valve, to see if it is hanging open or failing to seat owing to carbon or wear. It might be worthwhile, especially if you can get it running right for a while first, just to crimp off or plug the vacuum line to the egr valve, and see if this helps anything. Most EGR valves have an open base, so you can reach a finger in and pull the diaphragm open. I've run across a problem on an 88 Renix 4.0 in which the valve wore and intermittently hung open, killing the idle. Reaching in and allowing it to snap shut solved the problem temporarily (once shut, I just unplugged the vacuum).

I believe that the EGR/canister purge solenoid will open the EGR if it fails, so to disable the EGR you cannot just unplug the solenoid.

Also, you should probably try adjusting the TPS. According to my Chilton Fuel Injection manual, you should back probe the connector with a good voltmeter. In other words, do not disconnect the terminals, but stick the voltmeter probes in where the wires enter. At wide open throttle, ignition on, engine off, you should see 5.0 volts at terminals B (-) and C (+). Now disconnect the positive from C and connect it to A. You should then see 4.6 to 4.7 volts at wide open throttle. There may be a better procedure in the proper Jeep manuals. I know that for the Renix 4.0, the updated procedure is based on percentage of voltage, rather than actual voltage, and I wouldn't be surprised if this has also been updated for the 2.5 at some point. But at least that's a start, and if you get a reading under 5.0 for the first point, you can probably just go ahead and shoot for ~94 percent on the second.

Thanks for the help. I willl have to try that method tomorrow. Do you the egr could cause all my problems? Is there a way to remove the egr system totally?
 
Put this under for what it's worth... a bad EGR normally presents itself under light throttle. It causes a hesitation or miss ( the one on my '89 XJ did). A simple way to check for intake leaks is to cover the throttle body with your hand with the engine running. If it does not die right off, then you still have an intake leak. The IAC could still be a problem. Remove it, clean it AND the passages (you may have to remove the TB to completely clean it). Your MAP tested, but did you check the vacuum line? The O2 sensor is the computer's last line of defense. It will change your air/fuel mixture if it senses a rich condition. Lastly, check ALL your grounds. It is extremely important. High resistance can affect the sensors and the computer.:us:
 
I wouldn't recommend defeating the EGR. If you haven't watched the news lately, the EPA has decided to wage war on CO2, and they will ram their program down the states' throats by threatening to withhold federal money--that is why we have so many screwed up federal laws being shoved down our throats by our own state legislatures and governors--the almighty federal purse string. For those of us still living in the "Free States" the end is coming. Full blown vehicle and emissions testing, and most likely "Pass or Crush" laws. Our fearless Socialist leaders are going to force us ignorant barbarians to be good little environmentalists one way or another.

Here is the EGR test procedure--ignore the parts about the vacuum transducer, it is only for 89 & 90:

Warm the engine to normal operating temperature.

Operate engine at idle speed.

Check vacuum at solenoid vacuum source.

Disconnect the hose and attach a vacuum gauge to it.

Vacuum should be at 15 inches.

If vacuum is low, check the line for kinks, twists, or a loose connection at vacuum connector on intake manifold.

If vacuum is ok, remove gauge, reconnect the line and proceed to next step.

Check vacuum at solenoid output port.

Disconnect the line and attach a vacuum gauge to output port. Vacuum reading should be 0 at this side of solenoid.

If vacuum reading is 0, leave the gauge connected and proceed to the next step. However, if vacuum is present check solenoid/ECU operation with the DRB-ii tester.

Disconnect electrical connector at solenoid and note vacuum at output port. Vacuum should now be present at output port.

If vacuum is present, proceed to EGR valve test. However, if vacuum is not present, replace the solenoid. Test the EGR valve as follows:

Leave solenoid electrical connector disconnected. Note the engines idle speed.

The engine should idle roughly or stall. If this occurs the valve is ok. If the idle does not change, proceed to next step.

Disconnect hose from the EGR valve and connect a hand vacuum pump to EGR nipple.

Apply a minimum of 12" of vacuum to the valve and note engine idle. If engine now idles rough inspect the vacuum line between the EGR valve and the solenoid.

If the idle did not change, remove the EGR valve and inspect the valve and the exhaust passage in the manifold for blockage, repair as necessary. If no blockage is present replace the EGR valve.

Vacuum Transducer Testing as follows:

Disconnect the transducer vacuum lines and back pressure line. Remove transducer.

Plug transducer output port. Apply 1-2 PSI air pressure to transducer back pressure port. Air pressure can be supplied with a hand operated air pump or compressed air (regulated to correct pressure). Apply a minimum of 12” of vacuum to the input port.

Replace transducer if it will not hold vacuum.
 
Put this under for what it's worth... a bad EGR normally presents itself under light throttle. It causes a hesitation or miss ( the one on my '89 XJ did). A simple way to check for intake leaks is to cover the throttle body with your hand with the engine running. If it does not die right off, then you still have an intake leak. The IAC could still be a problem. Remove it, clean it AND the passages (you may have to remove the TB to completely clean it). Your MAP tested, but did you check the vacuum line? The O2 sensor is the computer's last line of defense. It will change your air/fuel mixture if it senses a rich condition. Lastly, check ALL your grounds. It is extremely important. High resistance can affect the sensors and the computer.:us:

Im pretty sure that the intake is not leaking, I checked it with a stethoscope and didnt hear any air. I will try holding my hand over the throttle body method though just to be sure. Do you have a link that might show me how to clean the IAC? The vacuum line for the MAP is good. I sure that that the engine to firewall ground is good. The one i kinda wonder about is the one that connects to dipstick tube. Do you think it would be ok to lenghen the lines and ground them to the neg teminal on the battery? Or do they have to be grounded to the engine?

I wouldn't recommend defeating the EGR. If you haven't watched the news lately, the EPA has decided to wage war on CO2, and they will ram their program down the states' throats by threatening to withhold federal money--that is why we have so many screwed up federal laws being shoved down our throats by our own state legislatures and governors--the almighty federal purse string. For those of us still living in the "Free States" the end is coming. Full blown vehicle and emissions testing, and most likely "Pass or Crush" laws. Our fearless Socialist leaders are going to force us ignorant barbarians to be good little environmentalists one way or another.

Here is the EGR test procedure--ignore the parts about the vacuum transducer, it is only for 89 & 90:

Warm the engine to normal operating temperature.

Operate engine at idle speed.

Check vacuum at solenoid vacuum source.

Disconnect the hose and attach a vacuum gauge to it.

Vacuum should be at 15 inches.

If vacuum is low, check the line for kinks, twists, or a loose connection at vacuum connector on intake manifold.

If vacuum is ok, remove gauge, reconnect the line and proceed to next step.

Check vacuum at solenoid output port.

Disconnect the line and attach a vacuum gauge to output port. Vacuum reading should be 0 at this side of solenoid.

If vacuum reading is 0, leave the gauge connected and proceed to the next step. However, if vacuum is present check solenoid/ECU operation with the DRB-ii tester.

Disconnect electrical connector at solenoid and note vacuum at output port. Vacuum should now be present at output port.

If vacuum is present, proceed to EGR valve test. However, if vacuum is not present, replace the solenoid. Test the EGR valve as follows:

Leave solenoid electrical connector disconnected. Note the engines idle speed.

The engine should idle roughly or stall. If this occurs the valve is ok. If the idle does not change, proceed to next step.

Disconnect hose from the EGR valve and connect a hand vacuum pump to EGR nipple.

Apply a minimum of 12" of vacuum to the valve and note engine idle. If engine now idles rough inspect the vacuum line between the EGR valve and the solenoid.

If the idle did not change, remove the EGR valve and inspect the valve and the exhaust passage in the manifold for blockage, repair as necessary. If no blockage is present replace the EGR valve.

Vacuum Transducer Testing as follows:

Disconnect the transducer vacuum lines and back pressure line. Remove transducer.

Plug transducer output port. Apply 1-2 PSI air pressure to transducer back pressure port. Air pressure can be supplied with a hand operated air pump or compressed air (regulated to correct pressure). Apply a minimum of 12” of vacuum to the input port.

Replace transducer if it will not hold vacuum.

Thanks man I will use that. But it said to check the vacuum at idle, my car dosent exactly idle and the idle it does have seems too low to give a proper reading. Any ideas?

I have also noticed latley that the valve cover has been getting a thin coat of oil on the top of it. There is no oil around the the base its just on the top. Also the two egr valves seem like they are kinda loose in the hole. Could that be a problem. And I just now thought about it but the inside of the cover for the throttle body has a thin coat of oil in it too. Does that mean anything?

As far as the government, I agree with you 100%
 
Any ideas on why it runs worse if turn it off then turn it back on?
One possible explanation would be that the EGR shuts properly when you start up, but then messes up intermittently while running.

The question of defeating the EGR altogether I leave to others, but I think that temporarily defeating it by crimping off the vacuum line, and making sure that it has snapped all the way shut, would be of diagnostic value.
 
One possible explanation would be that the EGR shuts properly when you start up, but then messes up intermittently while running.

The question of defeating the EGR altogether I leave to others, but I think that temporarily defeating it by crimping off the vacuum line, and making sure that it has snapped all the way shut, would be of diagnostic value.

I agree, when testing do what you have to do to isolate the problem(s).
 
here a few pics of what i mean


This is the new direct to the frame ground, and the new ground to the starter.
groundwireresize.JPG


This is the dipstick ground location. I sanded the paint off the bracket but not on the back of the bracket where it connects to the block. Should I scrape it off? And can I just lengthen the wires and ground them directly to the battery????? At least that way I would know its not them. Or do they need to be grounded to the block?
ecudipstickgroundsresize.JPG


Might be hard to see, but there is a thin oil film inside here? Is that because of the EGR?
filminbreather.JPG


This is the wire that I used to replace the factory ground strap. I had the factory strap connected to the head but looking at another jeep showed me it was supposed to connected to the intake.
groundstrapresize.JPG


There is another thin layer of oil on just the top of the valve cover. Its hard to see but its only present in the center.
residueresize.JPG



Do yall see anything that looks out of place? See a better way to do something? Open to any suggestions.
 
PCV system could get struff oiley if it's not working. EGR just feeds exhaust gas back into the intake. Put a vice grips or something on the EGR valve hose to see it fixes your idle. I've pulled them out and tapped them around until they started working again.
 
I don't know about out of place, but that's got to be about the cleanest engine compartment I've seen in a long time.

Haha thanks man. I should have rebuilt an old car or something instead of buying this jeep. Its pretty dirty now, but it has come a long way. I just wish I could get it running good enough to get it muddy.

resize11.JPG


resize33.JPG


resize44.JPG


resize22.JPG


PCV system could get struff oiley if it's not working. EGR just feeds exhaust gas back into the intake. Put a vice grips or something on the EGR valve hose to see it fixes your idle. I've pulled them out and tapped them around until they started working again.

Yeah I havnt had much sleep in the past few days do i got them condused haha.
 
Sorry that I havnt had time to check everything out today. Any more ideas for the questions Ive asked........The ECU ground wire?????
 
Sorry that I havnt had time to check everything out today. Any more ideas for the questions Ive asked........The ECU ground wire?????

same wire as in your second pic from the first post with pics, yes?

I don't know that it'll help your idle, but I've see a ton of long term problems from painted ground connections. It looks as though you should pull the wire and bracket and wire wheel the surfaces back to bare metal. An additional cable back to battery ground will ensure a good connection, but isn't necessarily a "must do" if everything is clean and tight.
 
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