SoCalManche Posted January 1, 2022 Share Posted January 1, 2022 Need expert eyes on this one; I think the head is done but I may be overthinking since I saw that being the cause of a similar issue for someone else. The ol' girl has started running a little louder than normal, seems there's some extra chatter coming from the head/valve cover. Left it alone since her smog this year was actually even more pristine than her smog from last year (no idea how). Well, she chewed up and spit out another alternator, which is a completely different story, but once I replaced it, and the sparkplugs as well, she now will not go into closed loop, and will run rich the entire time. Prior to changing the spark plugs, REM showed O2 sensor running properly (flipping back and forth between rich/lean), and went into closed loop accordingly. I was forced to drive the MJ to work a couple days later and its the only time the REM started showing the flip of rich/lean and closed loop until I came to stoplight; once she went back to idle as I stopped, went directly to rich and open loop condition; drove it once or twice more, and it didn't happen again. - I have three O2 sensors that all test within proper ohms (~5-7ohms?) - Nothing else was touched when replacing my blown alternator besides the spark plugs - When back-probing the engine-side harness to O2 sensor, I can get battery voltage to show, but can't get the other voltage number to read, 5V I think? (sorry, it's been a couple weeks since I've scoured all the other forums on this topic) - She starts up just fine, just won't pop into closed loop or pop out of rich condition. Thoughts? Link to comment Share on other sites More sharing options...
jdog Posted January 1, 2022 Share Posted January 1, 2022 How's the cts read? Compression numbers? How do the plugs look that came out and what was installed? Link to comment Share on other sites More sharing options...
SoCalManche Posted January 1, 2022 Author Share Posted January 1, 2022 3 minutes ago, jdog said: How's the cts read? Compression numbers? How do the plugs look that came out and what was installed? CTS is fairly new, I'll have to check tomorrow. Same with compression, I will have to try to check it tomorrow. As for the plugs that came out, they were fouled pretty good, but I chalked that up to the seafoam treatment I threw into the throttle bottle (stalling it on purpose and whatnot). Link to comment Share on other sites More sharing options...
eaglescout526 Posted January 1, 2022 Share Posted January 1, 2022 Ever put ATF in the oil to help keep things clean? Link to comment Share on other sites More sharing options...
SoCalManche Posted January 1, 2022 Author Share Posted January 1, 2022 1 minute ago, eaglescout526 said: Ever put ATF in the oil to help keep things clean? Can't say that I have. How much ATF should be thrown in? Side note - you don't think that seafoam treatment broke up a bunch of carbon and now that's wreaking havoc in the head? Link to comment Share on other sites More sharing options...
eaglescout526 Posted January 1, 2022 Share Posted January 1, 2022 I usually run a quarter of a quart, not too much. It is entirely possible but it shouldve at least blown it all out. Hopefully it didnt mess with the seals on the valves. But since you can't get it to go into closed loop, some where is a sensor not reporting correctly and keeping it in OL. I almost wonder if its a cooling sensor or a vac sensor. As for 5V at the O2 plug, you need to have the key in, ignition on but engine not running to see if its got 5V. Link to comment Share on other sites More sharing options...
jdog Posted January 1, 2022 Share Posted January 1, 2022 What plugs did you install? Link to comment Share on other sites More sharing options...
SoCalManche Posted January 1, 2022 Author Share Posted January 1, 2022 13 minutes ago, jdog said: What plugs did you install? My bad. Champion Copper Plus. Link to comment Share on other sites More sharing options...
jdog Posted January 1, 2022 Share Posted January 1, 2022 No worries just trying to get the basics out of the way Link to comment Share on other sites More sharing options...
SoCalManche Posted January 1, 2022 Author Share Posted January 1, 2022 6 minutes ago, jdog said: No worries just trying to get the basics out of the way I'm just trying to figure out why it decided to start running normal under load for about a mile until it went back into idle and then back to rich/open loop. I've been scratching my head for a couple weeks. Link to comment Share on other sites More sharing options...
jdog Posted January 1, 2022 Share Posted January 1, 2022 I'm still leaning towards a bad sensor Link to comment Share on other sites More sharing options...
SoCalManche Posted January 1, 2022 Author Share Posted January 1, 2022 6 minutes ago, jdog said: I'm still leaning towards a bad sensor The odds of a sensor going bad right when I swap the plugs? Damn, I need to play the lottery! Link to comment Share on other sites More sharing options...
JustEmptyEveryPocket Posted January 1, 2022 Share Posted January 1, 2022 41 minutes ago, SoCalManche said: sensor going bad right when I swap the plugs Main ground is right near there. Have you thoroughly checked and cleaned all those terminals? Link to comment Share on other sites More sharing options...
cruiser54 Posted January 1, 2022 Share Posted January 1, 2022 8 hours ago, JustEmptyEveryPocket said: Main ground is right near there. Have you thoroughly checked and cleaned all those terminals? Have you completed Tips 1 through 5 at www.cruiser54.com? Also check this: Link to comment Share on other sites More sharing options...
boxyjeep Posted January 1, 2022 Share Posted January 1, 2022 What voltage is coming from the O2 sensor? If it's not varying, it's a bad O2 sensor. Link to comment Share on other sites More sharing options...
SoCalManche Posted January 1, 2022 Author Share Posted January 1, 2022 16 hours ago, JustEmptyEveryPocket said: Main ground is right near there. Have you thoroughly checked and cleaned all those terminals? Yes, all grounds are squeaky clean. 8 hours ago, cruiser54 said: Have you completed Tips 1 through 5 at www.cruiser54.com? Also check this: Yessir, I've done those as well as most of the other tips as well (if they are applicable to '86 2.5L) Link to comment Share on other sites More sharing options...
SoCalManche Posted January 1, 2022 Author Share Posted January 1, 2022 Dry Compression Test: 1 - 145 / 2 - 145 / 3 - 147/8 / 4 - 140 Wet Compression Test: 1 - 152 / 2 - 162/3 / 3 - 160 / 4 - 151/2 Cylinder 1 is a PITA to properly test dry, let alone wet, so that number could be off a bit for the wet test. Tested cylinder 4 twice with somewhat same result (first test was at 149/150). Link to comment Share on other sites More sharing options...
cruiser54 Posted January 1, 2022 Share Posted January 1, 2022 That's all good. Link to comment Share on other sites More sharing options...
SoCalManche Posted January 1, 2022 Author Share Posted January 1, 2022 Just now, cruiser54 said: That's all good. Forgot to add this photo. Is there a reason why 2 and 3 are fouled even though they have best compression? These are the new plugs put in after alternator swap by the way. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 1, 2022 Share Posted January 1, 2022 Intake manifold leak? Link to comment Share on other sites More sharing options...
jdog Posted January 1, 2022 Share Posted January 1, 2022 Either that or how are the plug wires? Cap? Link to comment Share on other sites More sharing options...
SoCalManche Posted January 1, 2022 Author Share Posted January 1, 2022 21 minutes ago, jdog said: Either that or how are the plug wires? Cap? Wires are new, I'll have to check the cap but I think I threw a new one on a while back. Shouldn't have a leak at the intake since it hasn't been touched, but maybe a crack randomly developed. Link to comment Share on other sites More sharing options...
cruiser54 Posted January 1, 2022 Share Posted January 1, 2022 Just now, SoCalManche said: Wires are new, I'll have to check the cap but I think I threw a new one on a while back. Shouldn't have a leak at the intake since it hasn't been touched, but maybe a crack randomly developed. You MUST check that the intake and exhaust manifold fasteners have not loosened up. Also, the hoses pictured below. Link to comment Share on other sites More sharing options...
SoCalManche Posted January 3, 2022 Author Share Posted January 3, 2022 Update: Finally put everything back together after compression test, started her up, and IAT finally bit the dust. Wires are fraying and causing REM not to read properly. A while back, this issue would happen, but even with the misread, she would still run closed loop and O2 still did its job. At at stand still until I can find another IAT. On same note, when I pulled the IAT, she was somewhat pretty wet with fuel; is that due to lean condition on cold start? As for the potential intake leak, all good; all bolts seated properly and the TB vacuum points you showed that are notorious for leaks, yes, I've always had a very minor hiss right at that point; it's never hindered running condition however. I will get O2 voltage reading once "new" IAT is installed. Link to comment Share on other sites More sharing options...
eaglescout526 Posted January 3, 2022 Share Posted January 3, 2022 I might have some IATs from a bunch of 2.5L manifolds I have. Link to comment Share on other sites More sharing options...
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