Finally built up the courage and did a compression test. I believe the compression tester is a little high with its 200PSI readings!! However it gives me a rough indication where things are at; Passenger side DRY Front - 203 psi Middle - 211 PSI (cylinder which isn't firing. relief, guessing wiring now) Rear (Firewall) - 160PSI (scarrrrrry! cylinder does fire fine though) Drivers side DRY Front - 217psi Middle - 204psi Rear (Firewall) - 205psi All were tested with no other spark plugs in other cylinders, full reliant battery and foot stuck right into the floor. would love to do wet test - how much oil or ATF fluid would I pour into cylinders prior to attaching compression tester?
My understanding is that cylinder 6 usually drops before the others in an otherwise healthy engine. (if one is to have an issue that is).
Thanks for that. I know right, cylinder 6 doesn't look like it's on this planet! Back in 2011 I was told that cylinder 6 had compression issues. Might be going for a how long is a piece of string question here, but a car with low compression on one cylinder, will it just continue running like that or will the whole engine die one day? The car when I bought it had a cracked radiator. I'm guessing the lack of maintenance from the previous owner has come back to strike me as cylinder 6 is also more further than any other cylinder from the cooling system. I'm at a relief though with the cylinder 4. Compression seems to be okay.
It will be ok for a while, but the other 5 are dragging it along for the ride. That will increase, but as to when? Sorry, my crystal ball is a little cloudy today and I can't answer you right now. When you have an appreciable drop in power, time to replace at least the rings, but at most the whole engine. At that time decide if it's a rebuild or a replace.
Hey feel sorry you have had a bit of a run around with this! Just to expand more / add to what others have already said in the hope it helps more. Its unlikely the motor will die from the cylinder six issue, instead it will just drag the other cylinders down over time as stated until you lose compression. Cylinder six is on the end of everything including fuel rail, so it tends to go before the others as stated as it tends to run lean from the way the plenum flows as well. At the moment the pressure will really be on those other cylinders given the n04 cylinder is not firing so, avoid any work with the motor until its fixed. Dont put any more than a couple of drops in the cylinders (three is max - you only need two) any more and the oil will detonate and the cylinder will run away by itself - lol not t mention oil means dropping carbon around the valves and this may not be helpful if you have valves that are not sealing properly (which can be a loss of compression and could even be a cause of why cylinder six is low - low compression doesnt always mean bad rings hence why wet a wet test is helpful) There is obviously a power loss from the cylinder not firing even if you think it doesnt feel like it - evident by the lumpy idle itself Injector strobe test lights are very cheap (you only need the one) and can be handy in the toolbox for this sort of checking, it will tell you in a simple form of yes or no as to whether the circuit is complete or not. Its possible it could be the ECU as mentioned, this has happend to quite a few over the years. You test at the ECU pin for this. You test the circuit by using the injector test light or by checking ohms using the multimeter from both ends - you will need to run a thick wire to do this as the test probe leads arent that long (the thicker the wire the better, since the ohms measurement will include this section of the wire. The multimeter manual will show you what settings and how to do it - o just type in google how to test ohms multimeter Have you done a vacuum leak test? I had a similiar run around once before, checked everything and it all came up good but was clearly not running on cylinder four properly, turn it off on conzult and no change, so it indicated that the cylinder was not firing - yet the injector and lead was working, spark was there and fuel was there with good compression, drove me nuts at the time only to find out later that it was all from a vacuum leak near the cylinder. It appears that although everything was running fine the vacuum leak was enough to effect the cylinder from working correctly even at idle! Made me pull my hair out after the big run around I went through. There are a few vacuum ports near cylinder four, so check that they are not loose and that there is no leak at the other ends as well. Goodluck with it - really hope you get a fix soon! Jamie
The loss of compression issue means next to nothing and the engine will run on quite happily. The offending cylinder will not bring the rest of the motor down with it at all. The remaining good cylinders wont know the difference. Usually bad valve/seat is the issue. Rarely will rings alone result in gross compression loss. Unless the thing has had a piston grab (seizure) at some time in its life. Certainly not without accompanying oil blowby/usage/and smoke so if its not using undue oil and blowing smoke then id discount rings as a problem Compression leaking is rarely an issue above low engine speeds where the leak actually has enough time to drop the compression pressure. The result is a loss of power on that cylinder. As revs rise, the leak loss is less and the throbbing in the exhaust note reduces. Bottom line is the engine will over time, slowly drop more and more compression and the effects will be notices higher in the rev range until whatever is causing the comp loss results in enough loss of comp pressure to causes major missfiring or severe oiling up of the sparkplugs in the remote chances of buggered rings. Burnt valve/s are the usual results of extended running with gross compression loss. You can determine what is the cause of the leakdown in lieu of a pressure/leakdown test just by removing all the other plugs and winding the engine over compression on the offending cylinder by hand and listening to where the leak is going. Listen for hissing down the oil filler hole for rings leaking, into the Throttle body on the offending side for inlet valve leaks. If you hear almost nothing yet the pressure drops off then its safe to say its an exhaust valve leak. Remember, your ALWAYS going to hear slight hissing leaks into the crankcase no matter how good the engine due to ring end gaps letting gas past (unless you have gapless top rings) but if you compare what you hear against better cylinders then youll get a good idea of whats happening. Ghetto leakdown test but good enough to point to the offending parts. For me, Id be ignoring anything to do with compression loss and sort your wiring/ECU gremlins causing the dead cylinder. E
And that is the exact approach I will be taking. I have ordered a new wiring specialties wiring loom. The old loom is a birds nest and a half..
Installed new wiring specialties wiring and alternator loom and #4 still doesn't fire. Tried changing coil packs, PTU and spark plugs but still #4 has no signs of life. I'm now leaning towards the fact that maybe my and the jspec ECU I tried are both at fault. This issue is killing me!
could also be a blocked injector if youve confirmed spark and compression, all thats left is fuel if you can hear it clicking, then its unlikely the ecu can pull them and have em cleaned and flow tested pull the CAS off and have the ignition on and CAS plugged in, rotate the cas slowly by hand you should be able to hear each injector fire(click) without the rest of the engine noise getting in the way
Injectors just got ultra sonically cleaned, flow tested and rail cleaned around a month ago. Cylinder 4s click doesn't sound as loud as other injectors when connected in car. When I got the injector flow tested, all 6 injectors clicked fine when 12v were wired to them. Resistance is also perfectly within spec across all injectors.
Why do you say the cylinder is not firing? I have been following this thread for a while now and it just does not addup so I went back to your initial diagnosis and ask the question "how did you know that cthe cylinder was not firing? MichaelZ.
Bumpy idle with engine and car vibrate like crazy. At idle, pulling each coil pack connector I get a drop in RPM except for when I do it to #4. Same goes for when I turn the cylinders off via data scan. Its not too bad when I am cruising along as I think the ECU adjusts the other two cylinders to contribute more to make up for that dead cylinder. Worst issue since I have had the car in my possession. Tried everything I can think of to battle this issue. No love Goal is to get it firing before the GOR cruise.
One more test that might help. This quote got my attention this morning. There should be a constant 12volts on the positive side of the injector. It seems that there is a high resistance in either the of the wires going to the injector. Since you have changed the engine harness then it eliminates the wiring to the ECU which only leaves the positive wire to the injector. I would suggest the following test. With the ignition on and all the injectors connected up measure the voltage between the W/B wire on No 4 injector and ground. Then measure the same W/B wire on the other injectors. This voltage should be the same as the battery voltage. If, as i suspect, the voltage on Injector 4 is significantly lower then to the verify the issue then run another wire from either another injector or from the battery to see if the voltage comes back up. There must be some voltage as you say the injector clicks but not as loud as the others. Also the injector has been flow tested. Again as you have had all the injectors cleaned then unless you marked the injectors and put them all back in there original positions then you have swapped injectors and the problem is still in the same cylinder so it is wiring. The positive injector wire seems the logical culprint. Good luck. MichaelZ
You say earlier the plug in cylinder 4 looked the same as when you put it in. If the injector was firing and there was no spark the plug would have been wet with fuel. Makes me think it's injector related. Either faulty injector or the wiring to it, yet you have checked that too. I'm at a loss mate but I'll be following this with interest to see the eventual outcome. Best of luck
Take the plug off #4 injector and put the multimeter across the terminals of the plug. Do you see any voltage?
Will definitely try the multimeter trick, however a mate ran my multimeter on his car battery and melted the leads will buy some new ones tomorrow. In the mean time, would it be wise just for testing to run another cylinders injector plug to the #4 injector and try the screw driver trick? I mean logically #4 injector should pulse and if functioning should make some normal loud twaks. It'll be out of sync with the spark I'm guessing though.
Do not swap injector leads Definately do not swap injector leads. The injector leads are sequential and only go the the correct injector from the ECU. Also remember to leave the injectors plugged up when you do the voltage check as I described in my previous response. If you disconnect the injector and use the multimeter into the connector you will always read correct voltage even if you have a corroded wire. Good luck. MichaelZ
You can just run a pair of cable straight from the battery to the injector terminals to see if it seems to fire properly. Suggest you do this first. Then look at the power to the injectors
Just on this, you can run any injector leads to any injectors. Swap the whole lot around if you like. Injector phasing is only an issue at low revs and light loads. It will start as normal since the injectors are triggered as a group on cranking anyway but will pretty quickly run crappy when cold and require throttle to keep it going. As engine speed increases itll run allright Perfectly acceptable method of testing injectors and wiring and will do no harm at all. E
