HellCreek Posted April 13, 2020 Share Posted April 13, 2020 I drove it today to go to the post office. It started fine, but when I pulled out into traffic, it started surging and running rough. I turned the engine off when I went inside the post office, and when I came out I couldn't start the engine. I turned the key, but no response from the starter. The fuel pump and the ABS pump were running. I thought the shift lever was not fully into Park, so I cycled the lever and still nothing. I did that about three more times, then tried to start it in Neutral. That time it started. The engine stuttered a little but then settled down and ran o.k. I also noticed that I could hear the fuel pump running as I was driving. I thought the fuel pump was supposed to quiet down after the engine started. So, long story short, what I have done so far has not fixed the problem. Link to comment Share on other sites More sharing options...
jdog Posted April 13, 2020 Share Posted April 13, 2020 Ok, have you checked the wires at the starter relay? You said you replaced the cables, did any of the other cables look suspect. Link to comment Share on other sites More sharing options...
Ωhm Posted April 13, 2020 Share Posted April 13, 2020 Make/break (a couple of times) connector at the ECU. Inspect pins/terminals on both the harness side and ECU side. Could help. Link to comment Share on other sites More sharing options...
HellCreek Posted April 13, 2020 Share Posted April 13, 2020 Those will be next. Thanks, guys. I changed the battery cables because the lead terminals were broken, and I wanted a good connection. Link to comment Share on other sites More sharing options...
jdog Posted April 13, 2020 Share Posted April 13, 2020 Make/break (a couple of times) connector at the ECU. Inspect pins/terminals on both the harness side and ECU side. Could help. Tcu as well Link to comment Share on other sites More sharing options...
jdog Posted April 13, 2020 Share Posted April 13, 2020 Those will be next. Thanks, guys. I changed the battery cables because the lead terminals were broken, and I wanted a good connection. That's good, most people just rig it to get by Link to comment Share on other sites More sharing options...
HellCreek Posted April 13, 2020 Share Posted April 13, 2020 24 minutes ago, jdog said: 1 hour ago, Ωhm said: Make/break (a couple of times) connector at the ECU. Inspect pins/terminals on both the harness side and ECU side. Could help. Tcu as well TCU? Link to comment Share on other sites More sharing options...
jdog Posted April 13, 2020 Share Posted April 13, 2020 Trans control unit Link to comment Share on other sites More sharing options...
HellCreek Posted April 13, 2020 Share Posted April 13, 2020 Got it. Link to comment Share on other sites More sharing options...
HellCreek Posted April 17, 2020 Share Posted April 17, 2020 i disconnected the TCU and checked the connectors, and they were clean with no recessed pins or sockets. I re-checked the other critical connectors, i.e., TPS , IAC, O2, CPS, water temp sensor, MAP sensor with a vacuum gauge per Don's earlier post, and Air temp sensor and did the ohm tests as outlined in the FSM, and all checked within parameters. I removed the IAC to see if it was dirty, and it was clean. I then cranked the engine and it started right up (with the TCU still disconnected. I did notice a strong fuel odor, which I had noticed before but forgot to mention it. Could that be an indicator of the surging and missing problem? I also crawled under the vehicle and checked the position of the neutral safety switch, since I had the problem with it not cranking at the post office. Oh, I also checked the ECU connector and it was clean with no recessed posts or sockets. Link to comment Share on other sites More sharing options...
HellCreek Posted April 17, 2020 Share Posted April 17, 2020 On 4/13/2020 at 1:15 PM, jdog said: Ok, have you checked the wires at the starter relay? You said you replaced the cables, did any of the other cables look suspect. I also checked the starter relay, which in this case is inside the power distribution center and not attached to the coil bracket as on my '89 MJ. I had to consult the wiring diagram in the FSM to find it. Link to comment Share on other sites More sharing options...
jdog Posted April 17, 2020 Share Posted April 17, 2020 Check the 02 sensor Also fuel pressure Link to comment Share on other sites More sharing options...
HellCreek Posted April 17, 2020 Share Posted April 17, 2020 I can only find a O2 sensor heating circuit test in the FSM. How do you or can you fully test he O2 Sensor? Link to comment Share on other sites More sharing options...
HellCreek Posted April 17, 2020 Share Posted April 17, 2020 Fuel pressure is 39 psi with the pressure regulator disconnected and 30 psi with the vacuum line connected. Spot on with the FSM. I recently replaced the fuel pump, rail and regulator. Link to comment Share on other sites More sharing options...
HellCreek Posted April 17, 2020 Share Posted April 17, 2020 I can get an NTK heated O2 sensor on Rock Auto for $24.00. Should I just go ahead and replace it? Link to comment Share on other sites More sharing options...
jdog Posted April 17, 2020 Share Posted April 17, 2020 thats up to you, only way I know how to check it is with a scanner. Link to comment Share on other sites More sharing options...
HellCreek Posted April 17, 2020 Share Posted April 17, 2020 I don't have a scanner. Is there anything else that would make it emit a strong fuel odor? It smells like exhaust fumes and burns my eyes, slightly. Link to comment Share on other sites More sharing options...
HellCreek Posted April 17, 2020 Share Posted April 17, 2020 Jason, I see you are an ASE certified Tech. Is the NTK O2 sensor a good brand, or should I look at something else? Link to comment Share on other sites More sharing options...
jdog Posted April 17, 2020 Share Posted April 17, 2020 Wish I had a answer for you, I have not used them so I cannot say Link to comment Share on other sites More sharing options...
cruiser54 Posted April 17, 2020 Share Posted April 17, 2020 NTK is fine. Link to comment Share on other sites More sharing options...
HellCreek Posted April 17, 2020 Share Posted April 17, 2020 Thanks, Cruiser. Link to comment Share on other sites More sharing options...
eaglescout526 Posted April 17, 2020 Share Posted April 17, 2020 3 hours ago, HellCreek said: Is the NTK O2 sensor a good brand NTK is OEM. I found that out when I ordered a NOS one from a dealer. Link to comment Share on other sites More sharing options...
HellCreek Posted April 24, 2020 Share Posted April 24, 2020 Well, I replaced the O2 sensor, hoping it would eliminate the "rich burning" exhaust odor. It didn't. I also removed and cleaned the neutral safety switch, since I was having the no-start problem at times. Removing and replacing that thing is a major pain in the rear. Fortunately, I have small hands, but I could use another joint about midway of my palm. Between the exhaust and the transmission oil cooler tubes, there is simply no room to maneuver. I did discover a good way of indexing the NSS when re-installing. Put the transmission in Neutral and connect an ohm meter (analog is best) to the black and black-with-white-tracer wires in the connector, and when it does a full sweep, tighten the bolt. I'm not sure whether the O2 sensor fixed the stumbling and surging problem, but I am not encouraged, seeing that it did not cure the odor issue. Any thoughts? Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted April 25, 2020 Share Posted April 25, 2020 Just catching up on the recent posts. Maybe the O2 sensor will fix it, they can cause all kinds of problems. The check light for a O2 failure on the 91-92(?) were a separate light from the check engine, that required a Chrysler/jeep tool to reset, many owners just pulled the bulb. I have two PCMs from when I was testing the pcm by swapping, on the original pcm the O2 light been reset by Jeep, the used PCM had the light come on. I think it was mostly a mileage thing or perhaps when it failed the light stayed on, i don’t remember correct the answer now. My random thought is if this Jeep still a random problem try swapping in a different PCM, they don’t often fail but when they do all kinds of crazy problems can intermittently appear. The odd problem we had I think was water from the windshield leaking got the brake switch and/or TCU and caused the situation where my in-laws thought they jeep didn’t have power on a hill, couldn’t accelerate, etc, I never saw it and most of that they describe about vehicles having trouble is normally wrong. On the fly I replaced the TPS and Brake switch, on the 91 up the brake switch surprising ties in to a number of systems like Cruise control and the torque converter locking up or not. Similarly TPS also ties in to a few systems. And tps could cause issues with power. I was never sure about what the problems was, I had to drive a ways to pick the Jeep up from the house where they left it parked, so I picked the parts up and took a chance on fixing it and driving back. Never gave me any trouble, been years and lot of miles and a few 3 hour trips on the highway since then. Of other odd problems those 91-up 4.0 Jeeps have is crank position and cam position sensors, crank position on the bell housing is famous for the woes it causes. Cam position is not as infamous but can cause all kinds of trouble, some times it’s actually the distributor physically wearing out wobbling around. On the 1991 4.0 the cam position sensor was a pain, I think it had to be removed by taking the distributor out and taking it apart, many years since I’ve messed with it so I might be wrong. But I do remember it was easier to replace it with a rebuilt, I pretty sure the later 94-95 distributors could be swapped in as the signal was the same and so were the plugs on the harness. The benefit being the cam position sensor was easier to replace. Sorry to ramble on randomly, maybe this helps somebody. Edit: I forgot about the MAP sensor, never actually had one fail on those jeeps. But if the vacuum line becomes disconnected it runs poorly. Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
Snowstorm87MJ Posted April 25, 2020 Share Posted April 25, 2020 i don’t think anyones mentioned injectors if they did i missed it, but maybe one of the injectors is intermittently firing and causing problems. 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