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Ben. T
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87 325IS 5th cylinder not firing
Hi guys. I have a 1987 325IS that isn't firing its 5th cylinder. We know it is getting spark, cause we removed the spark plug while the car was running and there was no change, we know it has gas because the Injectors have been checked and the 5th cylinder is the only one having an issue. We also know that air isn't the issue because of its forced intake system. We tested the injector lines with a node light, and the light said it was fine. You guys have come through for me before, and I really appreciate it, but this is a puzzler...
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08-17-2011, 03:09 PM
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Registered
Join Date: Nov 2004
Location: Atlanta
Posts: 773
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Did you actually see the spark coming from the 5th cylinder plug?
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08-18-2011, 11:34 AM
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Ben. T
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Yep. Spark plug was new as well.
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08-19-2011, 02:45 PM
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Registered
Join Date: Nov 2004
Location: Atlanta
Posts: 773
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If you're getting the fuel and the spark, then perhaps you have low compression in the 5th cylinder.
Last edited by Yurick; 08-22-2011 at 04:43 AM.. |
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08-21-2011, 03:06 PM
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Ben. T
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We did a cylinder test when the issue first reared its head. It was a little low, but not enough to cause the issue. Sorry, probably should have mentioned that.
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08-23-2011, 08:14 AM
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In the shop at Pelican
Join Date: Aug 2002
Location: Los Angeles, CA
Posts: 10,459
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What is the actual compression number for cylinder no. 5?
Did you remove the fuel injector and verfiy that fuel is coming out of it? What kind of spark plugs are you using? You mentioned this is a forced intake motor, supercharged? turbo? |
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08-23-2011, 08:33 AM
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Registered
Join Date: Nov 2004
Location: Atlanta
Posts: 773
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Given the fuel, compression, and spark, it should fire! You must be missing one or several of those three.
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08-23-2011, 09:31 AM
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bostongrun
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I had the same problem. A misfire on cylinder number five on a later Model e36. Had 170lbs of compression. Replaced the coil pack, finally I put a new injector in and it quit misfiring. Sometimes those multimeter tests of those components dont work that well because they involve microscopic cracks in the internal windings in the coils and injectors. As they heat up open circuits manifest due to the expansion of the wires. When the components are stone cold there are no open circuits.
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08-23-2011, 07:36 PM
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In the shop at Pelican
Join Date: Aug 2002
Location: Los Angeles, CA
Posts: 10,459
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E30's dont have coil packs. Just a regular old coil. We need more info here.
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08-24-2011, 07:33 AM
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Registered User
Join Date: Sep 2010
Posts: 180
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Have you checked your pulse signal wire and the crank angle sensor? they normally either work or they don't but perhaps they are giving a weak signal somewhere?
Compression test may not show a valve problem? It could be worth removing the head and checking the whole set up? Earths, coil earths, engine earths etc? When its running on 5 cylinders, have to tried to listen witha mechanics stethascope to all the injectors and make sure they are ticking evenly etc? |
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08-30-2011, 04:10 AM
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In the shop at Pelican
Join Date: Aug 2002
Location: Los Angeles, CA
Posts: 10,459
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signal wires either work or they dont. That's not the problem. I'll bet he's got a clogged injector.
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08-30-2011, 01:35 PM
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Ben. T
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Hey guys. Thanks for all the info. Here is some of the answers thus far. Compression on #5 cylinder is 118 psi. The others were all between 125 and 138. My mistake the car is not forced injection. Totally stock motor. We had all the injectors cleaned and word from the performance shop was that they were all ~10% down. Now they are good. We have taken the manifold off and cleaned everything as well as changed some hoses etc.. Unfortunately nothing definitive was found to be out of sorts. We are putting the car back together today so we will soon find out. The injectors have been mixed up so it will be interesting to see if the problem is still there or has it moved to a different cylinder. We will let you all know. Again, thanks for the info. Great help!
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09-05-2011, 11:28 AM
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Ben. T
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Nothing has come of reassembly. We have also replaced coil in hopes that might be the issue. Unfortunately, it didn't solve the issue. We also ran the car in 4rth gear up to 65000 rpm and the engine compleatly cut, and then restarted again. Please, if you have ANY ideas, let me know. My dad and I are beginning to think a shop might be the only other option at this point...
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09-17-2011, 04:54 PM
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In the shop at Pelican
Join Date: Aug 2002
Location: Los Angeles, CA
Posts: 10,459
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You need to check continuity between the ECU and the injector. DO you have the Bentley manual? You need to go over all of the ECU checks in there.
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09-18-2011, 09:00 PM
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Registered User
Join Date: Sep 2010
Posts: 180
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Compression seems a bit low.......I'd be looking for about 150 -165 across all cylinders.......#5 is your lowest perhaps you have a problem in that cylinder or valve train.....
Totally agree with Jareds suggestion too, but perhps its time to remove the head and refresh the engine! Mark |
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09-19-2011, 05:23 AM
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