AnotherOldJeepGuy Posted January 25 Share Posted January 25 Interesting. I used up all my brake cleaner spray recently but will pick up a new can and give that a try. Link to comment Share on other sites More sharing options...
pizzaman09 Posted January 26 Share Posted January 26 3 hours ago, AnotherOldJeepGuy said: Interesting. I used up all my brake cleaner spray recently but will pick up a new can and give that a try. Spray some near the header while at it, particularly near the back of the engine. Link to comment Share on other sites More sharing options...
gogmorgo Posted January 26 Share Posted January 26 You can also just use water while the engine is running to find a small vacuum leak. The rpm will dip while the water is being pulled in (temporarily stopping the leak) and going through the engine, sometimes it makes noises. No harm in doing it either, it’s no worse than driving in the rain. Smoke testing works by pushing pressurized smoke into the system and seeing where it leaks from. Potentially you could do similar with soapy water, but I’ve never attempted it. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted January 27 Share Posted January 27 Well since I do already have water I'll try that first. I don't know that I have any setup to allow introducing pressurized smoke, that's an interesting suggestion but I'll just hope for water working.. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted January 29 Share Posted January 29 On 1/26/2025 at 3:59 PM, gogmorgo said: You can also just use water while the engine is running to find a small vacuum leak. The rpm will dip while the water is being pulled in (temporarily stopping the leak) and going through the engine, sometimes it makes noises. No harm in doing it either, it’s no worse than driving in the rain. Got out my handy spray bottle full of water and proceeded to soak down every hose I could see, no change in engine rpm or sound. I also sprayed what I could from the top of the intake and header mating points with same results. I didn't climb under and try from that side yet. I used my spray bottle because I had good control of what I was spraying. I may try the hose next which will be a lot more water and not very well focused, so more of a shotgun than a rifle, but if I do get a response maybe I'll learn something new at that point. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted January 31 Share Posted January 31 On 1/29/2025 at 7:45 AM, AnotherOldJeepGuy said: You can also just use water while the engine is running to find a small vacuum leak On 1/29/2025 at 7:45 AM, AnotherOldJeepGuy said: Got out my handy spray bottle full of water and proceeded to soak down every hose I could see, no change in engine rpm or sound. The shotgun approach was much more successful diagnostics. My spray bottle just was not shooting out enough water. With the hose, and the hose was not really on that strong more of a strong mist, the reaction was there almost immediately. Spray on the plug side didn't seem to have any effect, but spray on the injector side caused the rpms to drop quickly. I only sprayed from the top. There was some drop with spray near the back but in this case the biggest reaction was near the front. I sprayed primarily in a line from front to back just where the intake connects as best I could aim there anyway. Significant rpm drop, which did quickly cure itself when I took the spray away. So it would seem there is some leakage there. In fact I believe that if I held the mist at a particular front point for a bit longer I would probably have caused a stall. It does make some logical sense that the front is worse, and overall that this symptom appeared after a couple attempts to clean out years of old oil sludge. It seems possible that I just got lucky and "cleaned" enough of to expose small leaks that was previously clogged with said sludge. In any case, it seems that the bolt tightening suggested by @pizzaman09 could be the answer. Or it could be that 35 year old gaskets have run their course. I am not convinced my ESM degree (Enhanced Shad-tree Mechanic degree) is sufficient to replace both intake and head gaskets. Although I think I saw somewhere it is really 1 common gasket, I don't know that makes it any more likely my degree is enough! At least not until I get my car back from the shop so that I don't end up with zero transportation if I delve into this repair. Alternately, holding the rpms up enough to not stall is pretty easy. So I get why the water, if it got in to the air/fuel mix in the intake would bring down the rpms. Water doesn't explode at all the same as gas. But other than Jethro Bodine , I don't think anyone really believes you can use water for fuel. So the reason the leak is causing the stall is not water which was a diagnostic tool, it's air. Is it just that the extra air is throwing off the mix, or is there more to it than that? If the leak was a hose instead, would that have been doing the same thing or something different? Link to comment Share on other sites More sharing options...
gogmorgo Posted February 1 Share Posted February 1 The logic I was told is that the water getting pulled through the leak is thicker than air so it momentarily is blocking the leak. There’s undoubtedly some effect on combustion running water through the engine, but mostly you’re noticing the change in airflow into the engine. It’s going to set the idle air control to basically closed with all the extra leaking air flowing in, and when that extra air stops it has to respond by opening the idle control back up to compensate. The intake and exhaust manifolds use a combined gasket. The head gasket is its own thing so no need to worry about it right now. If the manifold bolts have been loose any leaking exhaust will burn holes through the gasket, potentially also on the intake side, so while you might get lucky just snugging up the bolts it’s likely it’ll mean a manifold gasket is in your truck’s future. But the good news is it’s not difficult to change the manifold gasket. All you really need to do is unbolt the manifolds from the head (intake may also be bolted to power steering pump) and push the manifolds over out of the way, get the old gasket out of there, and scrape any remaining gasket off sealing surfaces on the manifolds and head, then put it all back together. Unplugging the injector harness might give you some extra room to work. Link to comment Share on other sites More sharing options...
pizzaman09 Posted February 1 Share Posted February 1 It's easy enough to try to tighten each bolt and you'll see if it helps. When I did mine, I found that the back bottom stud had backed out of the block and was missing, all of the nuts were loose. I have yet to change the gasket and I think it does leak some but doesn't effect the way it seems to run. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 1 Share Posted February 1 These two were very loose. The top one I could wiggle the washer by hand. The washers didn't wiggle by hand for the others I could reach from the top without disassembling things. I was afraid that turning either was going to be a problem since they have been there for so long, but I let penetrating oil soak in for only about 5 min and they turned easily. After tightening just these two I tried the water again and there was no rpm loss in this area, which was the worse area I had seen earlier. Water towards the back effected rpm slightly but not as much as here. I will be pulling the injectors in the near future because I have one leaking, at that time I'll see if the others along the top will tighten also. In the mean time I'll see if the stalling has improved, seems like that is likely to be a yes, but will see how the next couple days go. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 4 Share Posted February 4 Although the water test did show a change after tightening the two up front that were loose, the stalling did not improve. Hoping to get to the injector leak today, so maybe a few others can be snugged. Link to comment Share on other sites More sharing options...
Eagle_SX4 Posted February 4 Share Posted February 4 7 hours ago, AnotherOldJeepGuy said: maybe a few others can be snugged. All of the top manifold bolts can be reached with a box end wrench. All of the lower bolts can be tightened from the top. You will need a socket and some extensions to clear the intake manifold. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 4 Share Posted February 4 Got the injectors out and the leaky one replaced. While I had the fuel rail out I was able to get to the bolts circled in blue. So in total this round and the last I have checked 7 and 5 of them were loose enough that I could tighten them. The ones in red I could not reach from the top. The 2 circles with "?" are ones I am guessing might be there. Don't know yet if I fixed my leaky injector issue or not, it didn't leak on initial start up, but it was not leaking 100% of the time. As for stalling, it still did. Question: I replaced some hoses previously, and after doing so the engine ran a little rough. The fix was to reset the computer by leaving the battery disconnected overnight. It is running a little rough after this work. I'll assume for the moment it isn't the new injector cause if that wasn't working I think it would be more rough that I am seeing. So the question here is, did tightening these bolts put me in the condition where I need to reset the computer again? Note that for the 3 hours or so while I did this work the battery was already disconnected. Still, I am not sure what I might have don't here that would make the idle rough other than the computer needs reset "more". Oh might as well share my "protect the injectors while being maneuvered for install" method. Fingers cut out of used gloves fit pretty well over them... Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 4 Share Posted February 4 4 minutes ago, Eagle_SX4 said: All of the top manifold bolts can be reached with a box end wrench. All of the lower bolts can be tightened from the top. You will need a socket and some extensions to clear the intake manifold. I was generating my new post while you were answering.... I did not see those but I'll look again. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 5 Share Posted February 5 A computer reset doesn't seem to have made any difference this time, not a big surprise since it was really already reset. Short test drive, very rough. The only thing I KNOW is different is 1 new injector and a few manifold bolts being tighter. I am going to disconnect the electric connection to the new injector and see if anything changes, maybe I got a bad new injector. If that doesn't prove useful, I guess I'll disconnect each of the others 1 at a time to see if I learn anything that way. Link to comment Share on other sites More sharing options...
Ωhm Posted February 5 Share Posted February 5 3 hours ago, AnotherOldJeepGuy said: Note that for the 3 hours or so while I did this work the battery was already disconnected. Still, I am not sure what I might have don't here that would make the idle rough other than the computer needs reset "more". 1 hour ago, AnotherOldJeepGuy said: A computer reset doesn't seem to have made any difference this time, not a big surprise since it was really already reset It's not really a 'computer reset', but a 'Relearn Procedure' that the ECU will perform when battery is disconnected. This may take some driving cycles and possibly up to 40 engine starts. Not saying this will cure your problems, just saying it's a relearn procedures. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 5 Share Posted February 5 1 hour ago, AnotherOldJeepGuy said: I am going to disconnect the electric connection to the new injector and see if anything changes Well my shade tree mechanic degree is not cutting it. Seems like any time I touch anything, I go backwards! The new injector is, call it position 1-6 from front to back, is at position 4. So I disconnected it. I really could not tell a noticeable sound difference when I started up. So my first though, that injector isn't working. But, then I ALSO unplugged position 3 and started. I still cannot really hear a difference. I'm not taking it around the block, but I would surely have expected to hear a change of some kind with 2 of 6 injectors unplugged. Should I expect to notice a difference with 2 of 6 injectors not providing fuel? Link to comment Share on other sites More sharing options...
Ωhm Posted February 5 Share Posted February 5 3 minutes ago, AnotherOldJeepGuy said: Should I expect to notice a difference with 2 of 6 injectors not providing fuel? Tough call here. With 2 injectors disconnected the ECU will see a lean condition and add fuel using the other 4 injectors. Injectors are not like pulling a spark plug wire off. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 5 Share Posted February 5 21 minutes ago, Ωhm said: Tough call here. With 2 injectors disconnected the ECU will see a lean condition and add fuel using the other 4 injectors. Injectors are not like pulling a spark plug wire off. Ah I was assuming 1 injector per cylinder and expecting if two were not working I would hear something. But I think you are saying the ECU will use what it has available to get the RPM it wants, and I might not be able to hear a lot of difference. Quite frustrating! Link to comment Share on other sites More sharing options...
llhat Posted February 5 Share Posted February 5 think i'd take Ohm's hint and get some spark plug boot pliers and pull some spark plug wires.... Normally with disabling two adjacent cylinders via plugs and no change could indicated a head gasket issue... but think premature here... but a compression test would not hurt, just take time. Ohm, during the relearn process... drive it like you stole it or what? Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 5 Share Posted February 5 I'll hold off on the plug test yet. The rough running only started with I pulled the injectors to replace a leaky one, and when that was out also tighten intake bolts that might be loose. I don't disagree that a compression test and a spark plug test might be worthwhile, but nothing I did was on that side of the engine, so for the moment (and particularly since I don't have anything to test the compression with anyway) I want to spend a bit more time on the driver side of the engine for the moment, but I'll put that on the list! Link to comment Share on other sites More sharing options...
pizzaman09 Posted February 5 Share Posted February 5 The manifold leaks probably were not helping you. I happened to tighten my manifold the same time I swapped a crap new Bosch O2 sensor in. So even though my truck stopped stalling, it intermittently ran rough at idle due to it being lean. The O2 sensor was super slow to react. When I got my REM, I realized this and bought a good NTK, which instantly fixed the problem and allowed the engine to run super smooth at idle as it was not going very lean for extended periods of time. My point is, what is the condition of your O2 sensor? Could it be damaged? Vibration from a hammer or some other unfortunate hit can ruin an O2 sensor, they are fragile. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 5 Share Posted February 5 I had a new Throttle Pos Sensor, so I put it in just in case. No change here (so I'll just probably put the old one back in, or I'll just keep it for a spare). I also repeated the water test from last Saturday, which indicated a leak in the front and back of the intake mating surface at the top side. On that day I tightened only 2 bolts up front and that eliminated the rpm loss when water was applied up there. I waited until today to tighten others when I had the fuel rail out. With what I tightened today I repeated the water test and there was no rpm change anywhere I applied water. I added on spraying up from underneath and no rpm change there either. So it would appear that the leaks are either closed, or at least now so small that the water test can't find it. That seems to be a step in the right direction at least. Link to comment Share on other sites More sharing options...
AnotherOldJeepGuy Posted February 5 Share Posted February 5 1 minute ago, pizzaman09 said: The manifold leaks probably were not helping you. I happened to tighten my manifold the same time I swapped a crap new Bosch O2 sensor in. So even though my truck stopped stalling, it intermittently ran rough at idle due to it being lean. The O2 sensor was super slow to react. When I got my REM, I realized this and bought a good NTK, which instantly fixed the problem and allowed the engine to run super smooth at idle as it was not going very lean for extended periods of time. Well that is something I have not yet replaced, so might as well do it next! Link to comment Share on other sites More sharing options...
Ωhm Posted February 5 Share Posted February 5 Your symptom does sound like a faulty O2 sensor. @pizzaman09 good suggestion. Link to comment Share on other sites More sharing options...
Ωhm Posted February 5 Share Posted February 5 7 hours ago, llhat said: Ohm, during the relearn process... drive it like you stole it or what? 88 FSM Computer Relearn Procedures.pdf Link to comment Share on other sites More sharing options...
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