I have a 2000 XJ8 with a misfire barely runs. Has new heads 10k Miles ago.
Compression in 2 Cylinder testes 0 Compression in rest of cylinders test between 150-160.
Codes ARE:
-P0300
-P0304
-P0306
-P0308
-P1313
-P1314
-P1316
-P0335
-P0560
Any help in appreciated Thanks

 

Here is a quick rundown of the codes:
P300 Random misfire = usually caused by vacuum leak
P304 Misfire cylinder 4
P306 Misfire cylinder 6
P308 Misfire cylinder 8
P1313 Cat Convertor damage
P1314 Cat Convertor damage
P1316 Injector circuit malfunction
P0335 Ign/Coil primary/secondary cylinder 2
P0560 Vehicle voltage malfunction

Based on everything you see I think you need to start with some basics.
First verify good tight connections with engine compartment connectors.
Two erase all codes and start fresh.
Three make sure the battery is either new or has been removed and fully charged.
Four Pull the ignition amplifier for cylinder 2 and swap it with a different cylinder. pull the number 2 spark plug and put a couple of teaspoons of oil in the cylinder thru the spark plug hole. If that cylinder has been dead the raw fuel running thru it could have caused bore wash.
Once you have done all that fire it back up let it run or if its running fair take it for a drive and pull the new codes.
We can continue from there

 

Thank You so Much
I will try this tomorrow morning and let you know.
Do you think that it could be a intake leak and the compression could be passing thru the intake valve. I don't thinks its Head gaskets either because they were replaced as well as the heads 9k miles ago and their is no sign of water in the oil or moisture in the exhaust.
I will try every you suggested in the morning Thanks.

 

I think your misfires are the result of a vacuum leak. I think the dead cylinder is "bore wash" the code showing bad ignition primary/secondary would mean that cylinder wasn't firing at all. The raw gas will wash away the oil film and the compression will drop to zero. If you do a search for Bore Wash in the forum you will find it is common to the nikisil coated engines.
Once you make all of the checks get a can of Brakekleen or starting fluid. While the engine is running spray the base of the intake and see if the engine rpm changes or smokes. If so vacuum leak.
Another common vacuum leak area is the intake snorkle downstream of the MAF Sensor. Check the underside and all around the wrinkles for cracks. At the snorkle to the throttle body make sure the gasket ring is in place and that the snorkle is tight.
You will have to repair misfires and then run it awhile to see if the CAT convertor code will go away. If you haven't run it to long in a lean condition it will burn clean.

 

I put a table spoon of oil in cylinder 4 and 8 they tested 5lbs of compression. The piston looks good and the valves look clean and are working. I sprayed starting fluid around the intake and found no leaks but i do hear a noise when its running souns like pssshhh noise of air. Im lost

 

Good you are making progress. The sound is probably your vacuum leak.At least you have eliminated the manifold. You will now need to start looking at each vacuum line and find the source.
Start with the intake snorkle and spray around it.
Next try the Part load breather line on the valve cover drivers side.
Then the fulll load breather line on the valve cover passenger side.
It is imperative to find and eliminate the the leak before we continue troubleshooting.

 

Am I missing something here? We have an engine with only 5 lbs compression in two cylinders after adding oil and are concerned with vacuum leaks? It would appear that there are bent valves to be addressed first.

 

RJ if you look at the original post and the codes thrown only the number 2 cylinder was dead and the codes showed it was not firing at all primary/secondary ignition failure. I think bore wash is the problem with number 2. all of the other codes and random misfire show vacuum leak. and from his post he can hear it. If it was out of time with the new heads it would bend more than one cylinders valves.

 

Yeah, I agree with Vern, assuming the facts are right. I would try and fix the bad coil first, then look for the look for the vacuum leak. Since it is a AJ27 engine and the amps are in the coils, just swap the coil in cylinder 2, (the second back from the front on the right hand side) with another coil, reset the codes, do a hard reboot and see what you get.

 

Ok Adding oil in cylinder 4 and 8 does not make any change in compression still at 5 lbs for those 2 cylinders. The piston looks good no hole and the compression ring is fine. There is no water in the cylinders and no water in the oil so that elimantes the head gasket being bad. The heads were resurfaced and new valves, timing chain tensioners and cams along with all gaskets were replaced 7200 miles ago total cost was 5700$. I tested some areas for vacum leaks found nothing. I have came to thr conclusion that there is a stuck exhaust valve on those 2 cylinders because around 2-3 rpm every thing smothes out and it runs better. May i be right? Any more advice is appreciated. Thanks all.

 

"compression ring is fine"
How do you know that? Xray or something?

And, The question is why there would be two "sticking" valves. New valves should certainly not be coked up or dirty.

BTW, it is possible (arguably unlikely with two banks bad!) to have a bad head gasket without oil and water mixing. And the "wssh" sound you mentioned could very well be a cylinder leak. Usually, the compression tester hose has a quick connect that can be plugged into an air chuck. I would turn the engine until the troubled cylinders' valves were closed and apply compressed air to see if I could find the leak. Even if it is out of the exhaust or intake valves, you will hear it. Or use a smoke machine injected into the spark plug hole.

 

Have you checked the valve lash????????????
There are shims installed and if they were not set correctly when the heads were rebuilt, the fault could be there.

I had another shop send me a 4.0 XJ8 for poor running after the heads were machined and reinstalled. They could not figure out why it ran so poorly. The valve lash was not checked because the machine shop SAID it was set properly.

There was NO CLEARANCE on several valves and I had to reset everything because NO ONE CHECKED!!!!!!!!!!!!!!!!! and just installed the heads!!!!!!!!!!!!!!!

When I assemble an engine I don't take ANY ONES WORD FOR ANYTHING!!!!!!!!!!!!!
I check it myself.

bob gauff

 

Sparken i know the comp ring is fine because i added 4tablespoons of 20w50 in the dead cylinders and they were still 5lbs if the comp rings where bad it would at least be better then 5lbs. The heads were installed by a BMW shop in portland,or and it ran great when they where installed a family freind was driving it home and it all the sudden started missing firing. So im pretty lost i am going to do a cylinder leak down test tomorrow.

 

Woah! Do you mean this happened on the trip home from the re-assembly of the heads? I missed that part. I thought you said heads were 10,000 miles ago.

 

No it happened 7000 miles after the install of the heads.

 

OK. I guess you will know more after the leakdown test. Keep us posted!