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Mars478
Joined: 02 Nov 2013
Posts: 222
Location: NY
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 Posted: Tue Jul 08, 2014 3:30 am Post subject: After an hour of driving, a cylinder (or two) cuts out. |
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I've been dealing with a strange issue that has cropped up as I drive the car more often. It will run great for the first hour, but about after an hour of driving the car will start to cut out on one or two of the cylinders. When it is running on less than 4 cylinders you can get it to fire properly in a certain RPM range, but if you give it full gas it will just cut out and fire on whatever amount of cylinders it wants. It sounds like a subaru when it's misfiring.
Am I right to think that the issue is injector related? The spark plugs are new, the wires look good, the rotor and cap look good. I think the injectors have to be re-sealed/o-ringed because I hear a hissing noise near all of the injectors which goes away if I mess around with them.
Any ideas?
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924, 82, 5 speed, dark red, 500 dollar special.
Daily: 99 ML320, 210k and still trucking. |
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Fasteddie313
Joined: 29 Sep 2013
Posts: 2595
Location: MI
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| Posted: Tue Jul 08, 2014 4:07 am Post subject: |
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if you adjusted your AFR on a coldish engine before the WUR came completely back to hot engine operation mode then you may be relying on the WUR's cold engine enrichment dropping the control pressure to run well and may be leaning out too much after you get everything completely up to temp and the WUR restores standard higher control pressure..
in other words try dialing the miss out of the hot engine with the air fuel ratio screw when it occurs..
come to think of it, something wrong with the WUR's electric heating element may extend its warm up time like your experiencing..
just a symptom theory... actually I have no idea... so don't go replacing your wur just on my hunch unless the other more experienced surgeons around here concur..
symptoms seem opposite of ignition to me though... I would expect bad plugs to work better after there hot and cause problems more so on a cold start..
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80 Turbo - Slightly Modified |
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Fasteddie313
Joined: 29 Sep 2013
Posts: 2595
Location: MI
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| Posted: Tue Jul 08, 2014 4:21 am Post subject: |
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pull the plugs once you get this symptom to occur...
look at them for lean/rich condition and the general how is this engine running right now inspection...
it would be the cat's ass if you had a wideband or other afr reading device/sniffer to tell you whats happening while the symptom presents its self...
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80 Turbo - Slightly Modified |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Tue Jul 08, 2014 4:35 am Post subject: |
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smoke test the intake to check for air leaks. . .
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Mars478
Joined: 02 Nov 2013
Posts: 222
Location: NY
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| Posted: Tue Jul 08, 2014 4:52 am Post subject: |
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| Fasteddie313 wrote: | pull the plugs once you get this symptom to occur...
look at them for lean/rich condition and the general how is this engine running right now inspection...
it would be the cat's ass if you had a wideband or other afr reading device/sniffer to tell you whats happening while the symptom presents its self... |
The car has an Air/Fuel ratio gauge installed by the PO but I'm pretty sure it doesn't actually work because it sits at 15.0 always.
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924, 82, 5 speed, dark red, 500 dollar special.
Daily: 99 ML320, 210k and still trucking. |
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Mars478
Joined: 02 Nov 2013
Posts: 222
Location: NY
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| Posted: Tue Jul 08, 2014 4:53 am Post subject: |
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| Fasteddie313 wrote: | if you adjusted your AFR on a coldish engine before the WUR came completely back to hot engine operation mode then you may be relying on the WUR's cold engine enrichment dropping the control pressure to run well and may be leaning out too much after you get everything completely up to temp and the WUR restores standard higher control pressure..
in other words try dialing the miss out of the hot engine with the air fuel ratio screw when it occurs..
come to think of it, something wrong with the WUR's electric heating element may extend its warm up time like your experiencing..
just a symptom theory... actually I have no idea... so don't go replacing your wur just on my hunch unless the other more experienced surgeons around here concur..
symptoms seem opposite of ignition to me though... I would expect bad plugs to work better after there hot and cause problems more so on a cold start.. |
I haven't adjusted anything in regards to this. If it helps describe the problem, the car takes a few minutes to rev freely, upon startup it doesn't like to rev up easily.
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924, 82, 5 speed, dark red, 500 dollar special.
Daily: 99 ML320, 210k and still trucking. |
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pmcaya2
Joined: 24 Nov 2005
Posts: 191
Location: Scio, NY USA
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| Posted: Tue Jul 08, 2014 1:21 pm Post subject: |
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| Quote: | | I hear a hissing noise near all of the injectors which goes away if I mess around with them. |
I don't like the hissing sound that goes away when you mess with it. Pull injectors and re-install with a lite coating of lithium grease. Also check vacuum connections in the vicinity of the hiss. As Rasta said, check for vacuum leaks in the intake handling housing. The system needs good consistent vacuum to lift the plate in the fuel distributor. Any leak will bog down the injector mixture.
Hope that this helps. Keep us posted. - Peter |
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Mars478
Joined: 02 Nov 2013
Posts: 222
Location: NY
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| Posted: Wed Jul 09, 2014 2:56 am Post subject: |
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| pmcaya2 wrote: | | Quote: | | I hear a hissing noise near all of the injectors which goes away if I mess around with them. |
I don't like the hissing sound that goes away when you mess with it. Pull injectors and re-install with a lite coating of lithium grease. Also check vacuum connections in the vicinity of the hiss. As Rasta said, check for vacuum leaks in the intake handling housing. The system needs good consistent vacuum to lift the plate in the fuel distributor. Any leak will bog down the injector mixture.
Hope that this helps. Keep us posted. - Peter |
With the injectors is there a risk of them breaking off? What do you recommend for pulling them apart from the special tool that I don't have? I want to soak and clean all of the injectors overnight/replace the o-rings.
I checked the whole intake area for leaks by wiggling everything and checking all of the lines and I didn't find anything except for some vacuum lines that should be replaced.
Thank you everyone for your suggestions, this forum is a wealth of knowledge. I am happy I am finally able to enjoy my car 
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924, 82, 5 speed, dark red, 500 dollar special.
Daily: 99 ML320, 210k and still trucking. |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Wed Jul 09, 2014 3:09 am Post subject: |
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| Mars478 wrote: | | I checked the whole intake area for leaks by wiggling everything and checking all of the lines |
Not to be argumentative, but it is really difficult (impossible) to get a reliable diagnosis of your air system with a visual inspection. You really need a smoke test, which a friendly shop shouldn't charge more than .5 to one hour for. . .highly recommended on a toofah, which will never run right with an air leak.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Mars478
Joined: 02 Nov 2013
Posts: 222
Location: NY
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| Posted: Wed Jul 09, 2014 3:14 am Post subject: |
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| Rasta Monsta wrote: | | Mars478 wrote: | | I checked the whole intake area for leaks by wiggling everything and checking all of the lines |
Not to be argumentative, but it is really difficult (impossible) to get a reliable diagnosis of your air system with a visual inspection. You really need a smoke test, which a friendly shop shouldn't charge more than .5 to one hour for. . .highly recommended on a toofah, which will never run right with an air leak. |
Totally understand. Apart from taking it to a shop is there a way to do it yourself? I have noticed that there is some electrical tape on the part of the black intake tube that connects to the throttle body... I am not sure exactly where and I have to take a picture of it but I will post it here when I do.
I assume replacing all the vacuum lines will also improve how the car runs correct?
This issue with the car is just weird to me because it happens almost exactly after an hour of driving and I wonder what it is that causes it because I am certain that the car fully warms up within the 1 hour period so it can't be that.
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924, 82, 5 speed, dark red, 500 dollar special.
Daily: 99 ML320, 210k and still trucking. |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Wed Jul 09, 2014 4:28 am Post subject: |
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If there is a way to build a tester I would be interested in hearing about it. The machines are quite expensive.
Oh, and if there is tape on the intake boot. . .bet it's torn. Buy a new one, they are dirt cheap.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Mars478
Joined: 02 Nov 2013
Posts: 222
Location: NY
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| Posted: Fri Jul 18, 2014 2:58 am Post subject: |
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Here's an update on this. I pulled all 4 injectors (man... what a pain that was, a health dose of WD-40 helped a lot). The O-rings were basically rock solid, no "rubber-y" aspect left to them at all. The injectors easily spun in the plastic holders. Ordered a set of Viton O-rings that should be here soon. I also pulled the Cold Start valve and cleaned it up a little bit.
The injectors have been soaking in sea foam for the past few days, and even an hour in I saw all the little pieces of crud just starting to come out of the injectors. I made a small video of the injectors working and the atomization wasn't as good as I'd like it to be, but in a test in which I put all 4 of the injectors into equally sized water bottles they all put out the same amount of fuel (or at least for me to not notice a difference)
Onto the intake boot, it was indeed ripped, so I will have to order another one. In the meantime I have re-wrapped (as the PO had done originally) the rip in electrical tape many times over. Here is a picture of the rip with the e-tape peeled off.
Would it be correct to theorize that after an hour or so of driving the e-tape would loosen enough was letting in unmetered air in and causing my issues? Along with the extremely hardened injector O-rings? Fuel delivery does not appear to be an issue here...
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924, 82, 5 speed, dark red, 500 dollar special.
Daily: 99 ML320, 210k and still trucking. |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Fri Jul 18, 2014 3:21 am Post subject: |
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Probably not. I say that because its not a one time thing, if you've encountered the same scenario more than once. You would have to theorize that the tape loosens and reseals itself when it cools only to loosen again.
You definitely need to clean your fuel system and fix your air leaks first. If the problem persists you will need to have everything ready to do your tests when the problem is present or setup the testers so they can be monitored during the drive. I would start first by checking fuel pressure during the episode. A weak pump, the voltage supply & grounds (which decreases when wiring gets hot) to the pump and other parts of the circuit are possibilities for fuel pressure decreases when hot. |
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Mars478
Joined: 02 Nov 2013
Posts: 222
Location: NY
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| Posted: Fri Jul 18, 2014 3:27 am Post subject: |
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| jason c wrote: | Probably not. I say that because its not a one time thing, if you've encountered the same scenario more than once. You would have to theorize that the tape loosens and reseals itself when it cools only to loosen again.
You definitely need to clean your fuel system and fix your air leaks first. If the problem persists you will need to have everything ready to do your tests when the problem is present or setup the testers so they can be monitored during the drive. I would start first by checking fuel pressure during the episode. A weak pump, the voltage supply & grounds (which decreases when wiring gets hot) to the pump and other parts of the circuit are possibilities for fuel pressure decreases when hot. |
Regarding the bolded bit, I may have goofed up what I meant, but yeah that's what I meant regarding my theory....
Unfortunately I need to buy a tester.
The fuel pump is literally brand new from a package and is a CIS one. Battery is brand new as well. Grounds are a good point.
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924, 82, 5 speed, dark red, 500 dollar special.
Daily: 99 ML320, 210k and still trucking. |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Fri Jul 18, 2014 3:50 am Post subject: |
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The battery shouldn't play a role in it. The power output from the alternator on its own is enough to run all the systems of the car. As wire gets hot, it looses conductivity. This is true for power & grounds, switches, relays, etc. I mention this only because of the time frame in which the problem starts, its just an example of a possibility. If you are having a fuel delivery issue, fuel pressure is the first place to start. The reason for the pressure loss, if one exists, is the next step. A new pump doesn't guarantee a good pump, especially if there is gunk in the tank. Never assume anything, sooner or later you'll waste time chasing a problem because you assumed something was good that turned out to be bad. I'm not saying you have a bad pump, just keep your mind open to all possibilities.
I'm sure you know by now that a pressure tester is a necessity for working on cis.
At this point, cleaning of the fuel system and your air leaks should be your first priority even if it turns out they are not the source of your problem. |
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