tdtony Posted February 9 Share Posted February 9 I fixed my stalling at idle issue by deleting the EGR, but now my truck stalls when decelerating. I checked the CPS based off cruisers tip and I got ~.25 AC Volts. This is below the .5V cruiser says I should get, but I haven't had any issues starting the truck up. Is it worth replacing the CPS or should I be looking somewhere else. Cruiser mentioned that some new CPS' will make .2V out of the box, does anyone have a recommended brand if I do decide to replace it? Link to comment Share on other sites More sharing options...
89 MJ Posted February 9 Share Posted February 9 I’ve had good luck with Standard parts and NTKs. I’d recommend getting the CPS for a high altitude emissions truck. This will advance the timing and give you some more power. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 9 Share Posted February 9 I can't see a CPS causing stalling on deceleration but the Jeep starts well. My website outlines the procedure for increasing the CPS output and advancing it should you decide to do that at some point. Have you ever cleaned your throttle body and IAC? That IAC is gonna likely be moving in a different range than it used to when the EGR was letting gobs of air into the system. It's a maintenance thing anyway. I'd try that first. Also, make sure your intake manifold bolts haven't loosened up. common issue. Link to comment Share on other sites More sharing options...
tdtony Posted February 9 Author Share Posted February 9 Yeah, I've cleaned the throttle body, replaced the IAC and tightened the manifold bolts. I should probably mention I smoke tested the engine, and after deleting the EGR the only leak was around the throttle body shaft. So I ordered a bored throttle body from stroked jeep that's supposed to be delivered next week. I'm not sure if that's enough of a leak to cause this issue Link to comment Share on other sites More sharing options...
Ωhm Posted February 10 Share Posted February 10 Let's see what the ECU thinks. Using your REM, what are your STFT and LTFT values? Link to comment Share on other sites More sharing options...
tdtony Posted February 10 Author Share Posted February 10 When it goes into closed loop the STFT drops to single digits and then settles bouncing between ~30-60. On deceleration it sometimes drops to 0 and goes into open loop. LTFT stayed at 128, but I only drove it for a few minutes. I don't know how long it takes to update Link to comment Share on other sites More sharing options...
Ωhm Posted February 10 Share Posted February 10 STFT is trying to take away fuel (sees RICH). Don’t know why LTFT stays at 128. Not sure if driving vehicle is necessary, let’s see how Fuel Trim’s act at IDLE. Watch the Fuel Trim's. Also, At IDLE does O2S signal switch rapidly between RICH/LEAN during Closed Loop (CL)? What is your INJ PW time (mS)? Did you mention before VAC (not MAP reading) was ≈16”Hg, or was that the MAP reading. If so, what is VAC (“Hg) @ IDLE? Just as a quick check look for fuel at the vacuum hose between the Fuel Pressure Regulator (FPR) and intake manifold. Leaky FPR. Link to comment Share on other sites More sharing options...
tdtony Posted February 11 Author Share Posted February 11 The A/F ratio swings right along with the STFT. I've attached a video The injector pulse width fluctuate between ~4.9-5.6 MAP is ~14.5-15.3 VAC is ~15.0-15.8 I let the truck idle for about 15 minutes in total and the LTFT was still at 128 The vacuum house coming off the FPR smelled faintly of gas, but didn't see any gas actually in it. Thanks for the help ohm! PXL_20240211_180403511_TS.mp4 Link to comment Share on other sites More sharing options...
Ωhm Posted February 11 Share Posted February 11 I've seen VAC=15"Hg before and @NickInTimeFilms mentions "greater than 15"Hg is good. But I've always like 18"Hg of vacuum for Intake Manifold vacuum, so OFF TOPIC here, what is a good reading for Intake Manifold vacuum ("Hg)? I don't think this is your problem. What I did notice is your O2S is sluggish. It does switch enough to keep ECU in CL, but should switch between RICH/LEAN closer to the speed of light (very fast). Suspect O2S. Thanks for the video. Link to comment Share on other sites More sharing options...
tdtony Posted February 11 Author Share Posted February 11 I bought the O2 sensor a few months ago, before I bite the bullet and buy another one, is there any way to test it? I think I saw a few post saying to check the resistance of the O2 sensor, but another from cruiser saying it wasn't worth it. I check the wiring going to the O2 sensor 11.8 volts on the orange wire, 5 volts on one of the black wires, and .8 ohms to the battery negative terminal on the other black wire. According to cruiser the orange wire should be getting between 12-14 volts. Could that be the issue? And what would cause lower voltage to the orange heater wire? Link to comment Share on other sites More sharing options...
Ωhm Posted February 11 Share Posted February 11 Disconnect O2S. On the O2S connector (component side) look for ≈6 ohms between C229_A and C229_B (heater). Engine Control Harness side shown below: Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted February 11 Share Posted February 11 Have you checked to make sure the torque converter isn’t remaining locked up when decelerating ? That will stall an engine. Link to comment Share on other sites More sharing options...
tdtony Posted February 12 Author Share Posted February 12 O2 sensor measures 5.2 ohms, so I'll order a new one tonight. My throttle body has a little vacuum leak from the shaft, but my new ones getting delivered tomorrow, so maybe that'll raise the manifold vacuum. Hey stroker, I haven't checked the torque converter, I'll try that tomorrow. Is there a write up on here for how to test it? If not I'm sure I'll find a video on YouTube or something Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted February 12 Share Posted February 12 1 hour ago, tdtony said: Hey stroker, I haven't checked the torque converter, I'll try that tomorrow. Is there a write up on here for how to test it? If not I'm sure I'll find a video on YouTube or something First of all you want to find a good place that you can get above 43 mile an hour that doesn’t have a whole bunch of traffic or anybody behind you. When you get above 43 miles an hour you are going to keep your right foot on the gas to maintain slightly above 43mph and use your left foot and lightly apply the brakes , you should notice the engine speed change to a higher RPM if I recall correctly. Somebody else may be able to explain it better than I can, but I had a Cherokee that would stalk when slowing down and that was the issue. I ended up replacing the transmission I never had a problem since. Seems to be more common in the 2wd for some reason Link to comment Share on other sites More sharing options...
tdtony Posted February 15 Author Share Posted February 15 I got a new NTK O2 sensor from rock auto, it tested about the same as the sensor on the truck ~5.3 ohms. I can't see any difference in how STFT or A/F ratio 1911932160_PXL_20240214_233039879_TS2.mp4 Link to comment Share on other sites More sharing options...
tdtony Posted February 15 Author Share Posted February 15 I uploaded a longer video of the REM. I couldn't get it to stall in the driveway, but even when driving the stalling is intermittent. When I'm decelerating while driving STFT will drop to 0 like in the video, but it will stay in Open loop for 15- 30 seconds before going back to closed loop or it will stall. I can try to get a video of it stalling while I'm driving it, but its kinda hard to record while driving. Watching the video back it seems like the truck switches in closed loop and the STFT drops until the O2 sensor starts updating the A/F ratio. Does that seem right? any idea what would cause the O2 sensor to lag like that? Link to comment Share on other sites More sharing options...
Ωhm Posted February 15 Share Posted February 15 Most O2S heaters fail OPEN circuit. Your ohms reading was good. Sorry if I miss led you on this being good or bad. Does the switch rate with the new O2S (REM set; EX=RICH/LEAN) change at a faster rate than the old O2S did? Does vehicle still stall on deceleration? I see you just posted a video, let me check it out. Link to comment Share on other sites More sharing options...
Ωhm Posted February 15 Share Posted February 15 17 minutes ago, tdtony said: Watching the video back it seems like the truck switches in closed loop and the STFT drops until the O2 sensor starts updating the A/F ratio. Does that seem right? Yes Use EX=RICH/LEAN instead of A/F. See if LTFT changes? 19 minutes ago, tdtony said: any idea what would cause the O2 sensor to lag like that? Note from REM readouts: Note: This is an REM only reading and is very approximate since narrow band o2 sensors are not absolutely accurate or consistent. This is only used to put a “Real” number to the otherwise meaningless o2 voltage, and should not be used for real tuning needs. Link to comment Share on other sites More sharing options...
tdtony Posted February 16 Author Share Posted February 16 No problem ohm. I'll test it again this weekend using the EX reading. I just had a realization this morning. I disconnect the battery cause I have a slight parasitic drain that I haven't chased down yet. this is probably causing the ECU to reset right? Which would affect the ability for it to store and change the LTFT? Link to comment Share on other sites More sharing options...
Ωhm Posted February 16 Share Posted February 16 1 hour ago, tdtony said: this is probably causing the ECU to reset right? Which would affect the ability for it to store and change the LTFT? Yes and Yes. Resets LTFT back to 128 with each battery disconnect. 88 FSM Computer Relearn Procedures.pdf Basically, it says just keep driving the vehicle after each START UP. Link to comment Share on other sites More sharing options...
tdtony Posted March 4 Author Share Posted March 4 I haven't had a chance to drive my truck much, or work on it in the last few weeks, so I'll keep the battery connected and drive it a bit and see if the ECU fixes everything for me. While googling around I found a post where a few people mentioned stalling during deceleration and that a new distributor solved their problems. Is there any way to check if my distributor is good, or should I just go ahead and do cruisers tip 13 about distributer indexing? https://www.cherokeeforum.com/f2/engine-stalls-when-i-stop-rapid-deceleration-107531/index2/ Link to comment Share on other sites More sharing options...
cruiser54 Posted March 4 Share Posted March 4 Do my Tip. Link to comment Share on other sites More sharing options...
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