ComancheKid45 Posted July 7, 2012 Share Posted July 7, 2012 Alright, well its late but I figured id see if i could gather up any other thoughts from you guys. The issue lies within "Oscar" an 88 AW4 4.0L. Ever since purchasing it, ive have a "missing" condition at idle and while driving it likes to buck intermittently from around 1200-1750 RPM under light load, kinda while lugging the engine through the shifts... I checked the TPS and even replaced it and the entire throttle body from a parts Jeep. New (less than 1k miles) Plugs/Wires/Cap/Rotor Same for the o2 sensor Ive cleaned up and check over the Ign. coil but have a newer 1 on another truck I'm gonna swap and try out. All Engine and Chassis grounds are clean, refreshed and tight Cleaned and resealed the C101 connector MAP, IAT, and Knock sensors check out ok New Fuel pump installed less than 1k ago I'm beginning to think something with the EGR system might be the culprit here. The truck drives great and has plenty of power under load and minus these two small issues. I just know theres something not quite right... Thanks for any ideas fellas. I have a few other things i can toy with but it never hurts to gather some other opinions ;) Link to comment Share on other sites More sharing options...
Minuit Posted July 7, 2012 Share Posted July 7, 2012 A problem with the EGR valve seems plausible to me. Pretty much the same problem my father's Buick had til the EGR was replaced. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 7, 2012 Share Posted July 7, 2012 How is it at light throttle cruise under no load? Link to comment Share on other sites More sharing options...
ComancheKid45 Posted July 7, 2012 Author Share Posted July 7, 2012 Ha Ha. Basically the condition only shows itself under light throttle. If i hammer on it and get it up to speed you don't even notice the issue, but your really gotta lay into it. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 7, 2012 Share Posted July 7, 2012 Remove the EGR and see if it's leaking internally or not seating well. Another easier thing to do is reach in to the diaphragm of the eGR with your fingertips and pull it toward you and see what happens to the idle. Link to comment Share on other sites More sharing options...
KYMJ Posted July 7, 2012 Share Posted July 7, 2012 You might try adjusting tyour TPS as well. I had similar conditions that were cleared up by adjusting it. Link to comment Share on other sites More sharing options...
ComancheKid45 Posted July 7, 2012 Author Share Posted July 7, 2012 Another easier thing to do is reach in to the diaphragm of the eGR with your fingertips and pull it toward you and see what happens to the idle. When the EGR rod is pulled towards me, the truck gets worse and worse and then stalls out alltogether. (stupid question) Is that how its suppossed to work or have I found my issue? Thanks! Link to comment Share on other sites More sharing options...
cruiser54 Posted July 7, 2012 Share Posted July 7, 2012 That's what is supposed to happen. That's not saying the EGR is seating fully and sealing though. Did this engine behavior just begin recently? Link to comment Share on other sites More sharing options...
cruiser54 Posted July 7, 2012 Share Posted July 7, 2012 Did you ever do this? Cruiser’s Renix Sensor Ground Test This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate. Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too. You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well. Revised 06/12/2012 Link to comment Share on other sites More sharing options...
ComancheKid45 Posted July 8, 2012 Author Share Posted July 8, 2012 This symptom has been around since the purchase of the truck, unknown how long prior... Ill swap the EGR valve with 1 from the parts Jeep and recheck the TPS and grounds tomorrow or early this week. Thanks guys! Link to comment Share on other sites More sharing options...
ComancheKid45 Posted July 8, 2012 Author Share Posted July 8, 2012 Recleaned the C101 connector as well as removed and throughly cleaned the EGR valve and ports. The problem seems to have been deminished a bit but at idle its still missing. Ill put some more miles on it and also check the TPS again this week. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 8, 2012 Share Posted July 8, 2012 Recleaned the C101 connector as well as removed and throughly cleaned the EGR valve and ports. The problem seems to have been deminished a bit but at idle its still missing. Ill put some more miles on it and also check the TPS again this week. Glad to hear of the improvement. I'm getting more and more inclined to advise people to eliminate the C101 and solder the wires directly together. Link to comment Share on other sites More sharing options...
mpace6a Posted July 9, 2012 Share Posted July 9, 2012 My old chevy had the same problem, which turned into backfiring and not downshifting. Replaced the egr valve, that more or less solved it. Then timed it which solved the shifting problem. then seafoam for good measure :thumbsup: Link to comment Share on other sites More sharing options...
ComancheKid45 Posted July 9, 2012 Author Share Posted July 9, 2012 Well after a few miles of driving, the problem is still very visable. Next steps include checking the TPS, swapping ECUs and even swapping Distributors... The joy of having a parts Jeep is the ability to swap parts, ha ha, i know its not the right way to go about diagnostics, but I'm sure to find the culprit of this issue :rotfl2: Link to comment Share on other sites More sharing options...
cruiser54 Posted July 9, 2012 Share Posted July 9, 2012 Did you do the sensor ground test yet? Link to comment Share on other sites More sharing options...
ComancheKid45 Posted July 9, 2012 Author Share Posted July 9, 2012 Performed the Sensor gound test (All grounds are clean and tight) Reset the TPS Swapped ECUs (then swapped back) Checked Cap/rotor/wires and plug gaps Swapped to coil (then swapped back) No dice, it acts like more of an ignition problem than fuel related. My Temp gauge reads normal but it sure feels like its awful hot in the engine bay.....excessive heat messing with something? No much left i havent messed with...Coolant temp sensor on the block? Fuel injectors? Never changed the fuel filter... (truck has plenty of power though) Pretty lost here anymore. O Well I'm done for the night, who knows it just might be 1 of those things that fixes itself... Link to comment Share on other sites More sharing options...
cruiser54 Posted July 10, 2012 Share Posted July 10, 2012 Try this: Remove the distributor cap and cut a "window" into the side of the distributor cap at the #1 spark plug wire post . The "window" should be large enough to allow easy visual inspection of the position of the distributor rotor at the #1 spark plug wire post. Reinstall the distributor cap. Install a ¾” wrench or socket onto the vibration damper retaining bolt. Rotate the engine in a clockwise direction until the #1 cylinder is at top dead center. Align the timing mark on the vibration damper with the "0" degree mark on the front cover timing scale. The tip of the distributor rotor should be near the #1 spark plug wire post. Disconnect the distributor electrical connection. Remove the distributor holddown clamp, holddown bolt and distributor. Remove the distributor cap and rotor. Place the distributor housing upside down in a soft jaw vise. Scribe a line 1/2 inch from the end of the distributor locating tab. Cut the distributor locating tab at the scribed line with a saw. Remove any burrs and metal filings from the distributor. Reinstall rotor. If necessary, using a flat blade screwdriver, turn the oil pump gear drive shaft until the slot is slightly past the 11 o'clock position. The oil pump gear drive shaft is accessible through the distributor mounting bore in the engine block. Visually align the modified locating tab area of the distributor housing with the holddown clamp bolt hole. Turn the rotor to the 4 o'clock position. Lower the distributor into the engine block until it seats. The rotor should now be very close to the 5 o'clock position. Reinstall the distributor cap with the cutout "window". Rotate the distributor housing until the trailing edge of the distributor rotor tip is just departing from the #1 spark plug wire post terminal . Reinstall the distributor holddown clamp and bolt.. Reinspect the position of the rotor to the #1 spark plug wire post to insure that it has not moved. Install the new distributor cap, reconnect the distributor electrical connections. Revised 07/03/2012 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now