Hey everyone I am new at this thread stuff so I hope I get it right. I have a 02 TJ 4.0 approx 186000mi never had to do anything but normal maintenance to it. Adout a month ago I got a check engine light so I went and bought a small scanner to see what’s up. The scan tool said I had a random misfire on #1 cylinder. So I cleared the code and it came right back. I pulled the spark plugs to get a reading on cylinders. All looked about the same light brown color no fouling. I then ran a compression the cylinders are as follows #1 125 #2 125 #3 100 #4 135 #5 135 #6 135 this was a dry check. So I replaced the plugs with autolite plugs I ohmed the injectors they were all close to the same I don’t know where to get the specs I need but it was running so I figured this would work for a base. I went a head and changed the injectors out from single hole to 4 hole, replaced the coil pack with a new one. O yea I forgot to mention that after I replaced a part I would run it again and I still had the same problem. So I checked the wiring to the injectors to see if Mickey had a party under my hood found no problem there so I took my volt meter and checked voltage to each Injector they all had the same voltage give or take.1 . While it is idling I removed each injector wire one at a time to cause a misfire #1 was the only one that did not change the idle. So I started checking for vacuum leaks non found. Can anyone give me a suggestion please I can’t check for spark off the coil pack any idea will help. Thanks.
Misfire after replacing spark plugs
- Thread starter Sonny
- Start date
Rubicon88
TJ Addict
Rubicon88
TJ Addict
He stated a new one...
But he didn't state the brand.
Moreover for $25 I'd highly suggest putting in the OEM recommended plug..NGK ZFR5N..all 6 for $25-30
Get to ground zero as much as possible..ground zero being oem base
Swap injector #1 with #3 and see if the misfire chases it.
This will confirm injector or not.
(New parts can be bad out of the box unfortunately) and in the OP's case nothing should be taken for granted at this point.
I had a new set of NGK plugs in had 100mi on them and reading trough threads that said some TJ don’t like them so I replaced them with autolite. The coil pack is an AA brand. After more wiring research I found a very small nik I my injector harness made by Mickey in the back almost to the firewall. I repaired that reassemble every thing that I took apart. Fired it up and it ran great just like it’s old self. Thanks to everyone for listening to my problem and your suggestions. Now drove it about 200mi ran great. I was pulling into my driveway today and got a check engine light. Grabbed the scan tool it said rich fuel on bank #2. It’s a inline 6 how do figure this out. I got 2 converters 2 O2 sensors in each one. Any ideas! Thanks
Rubicon88
TJ Addict
Since you purchased a Scan Tool to read DTCs; what was the code (As R88 responded above) ?
IF the code referred to O2 sensor voltages the do a Live Scan of the O2 sensor voltages. Once the engine is warmed up; the voltages should be modulating from 0.3V to 0.7V; where the full range is 0.1-0.9V. The closer you get to 0.9V the richer the engine is running.
IF the voltage is not modulating or stays closer to 0.9V; you have found the affected O2 sensor.
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Okay new old problem, I am getting a p0175 code I have replaced all the o2 sensors with NTK brand. This is intermittent problem I can drive to work about 80mi round trip sum times the code will show up when I get to work and then it might take 2 or 3 trips no cracked manifold or vacuum leaks. Any ideas thanks