XJ40 ( XJ81 ) 1986 - 1994

rough running after head gasket change

 
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Old 12-12-2018, 04:34 PM
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Default rough running after head gasket change

Hey all. You'll be glad to know that my head gasket change was a qualified success. I refer you to the last entry in my thread "94 no start." I reassembled it and not surprisingly had a coupe of hiccups, one being a leaky injector causing Very hard starting. The other was fairly scary (in terms of the cars' future as seen at the time). I had a piece of the intake cam gear literally Break off and fall into the various gears and chains down below it. I believe that the gear was previously cracked judging by the color of the metal in the crack. I am not really too surprised since this car has a rebuilt title and was abused beyond being totaled. Anyway, the ruckus as that gear chunk was being chewed and tossed around was, as I say, scary. When I installed the replacement gear I rechecked the timing and all seemed good at that time.
Time passed. Not a little, Not a lot. I now have a rough idle. currently the best way for me to describe it is this- If the car had a carb and a choke plate, I would say that the choke is sticking shut. It runs "good" cold, as it warms it gets really rough as if it was flooding except that open throttle does not help. I have unplugged the injectors one at a time and found that cylinder #2 makes the least difference when unplugged seemingly indicating a problem there. I changed that spark plug, and then all with new (the ones in it did not look wet or even very dark), I swapped that plug wire, and then all with known good ones, along with the cap and rotor. I then swapped that injector into cylinder #3 and installed a 7th injector from my bag of tricks. No difference. I checked compression, got 150# cold on all, I have 40 pounds of pressure in the fuel line ahead of the rail. Since it Seems to be temperature related I swapped the temperature sensor (the 2 pronged one) but got no change there either. I don't think its the thermostat since the temp gauge on the dash is acting normally. I have not done a thorough vacuum leak search, but I doubt that is the issue either. I would suspect a sticky valve, but not with good compression (?) As a humorous aside, I have code FF44 now. The car is thumbing its nose at me. Gah!
Where I am now is that maybe when that gear chunk went loose, it knocked the lower chain off a tooth. I suppose that this would be easy enough to check on the timing mark. But I didn't do it yet.
I surrender the podium, thank you for your time. As always Comments and potshots are requested.

the missing chunk is dead center of the photo. Cant imagine how this happened!
 
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Old 12-12-2018, 07:24 PM
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Well Jerry that certainly is the $hits after all that hard work. Commiserations!

When you say she runs OK whe cold, like, how OK? Can you rev her up normally-ish before she gets warm?

If so, this suggests that the mechanicals are probably just fine and you have an issue when she goes into closed loop, like too much fuel (choke analogy symptom) followed up with a too rich message FF44 from the o2 sensor ..so maybe grounds not clean, corrosion on ecu pins, relay pins dirty, MAF plug etc ....Worth checking for vacuum leak around the throttle body and intake piping too because crazy as it sounds, air (vacuum leaks) make the car run rich rather than weak as the ECU tries to compensate by upping the gas delivery times ...

Anyway, not much help but at least those suggestions might give you something to do tomorrow rather than going to the mall, right?

good luck with it

Larry
 
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Old 12-12-2018, 08:33 PM
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Yes, it runs more or less normally cold. Only once it warms... I forgot to put in there, I also swapped maf sensor, and checked those connectors at the time. Will check the other connections (happily) instead of shopping. Thanks.
 
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Old 12-13-2018, 12:21 PM
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I spent the morning wiggling things and reflowing the solder in the crimp ring on the injector grounds' group. Installed New star washer under the 2 grounds there. Must have done something as I was able to climb that one pesky hill around the corner And take it out on the highway. It's not what it was though, still somewhat rough. Once it cools I will clear the code, wiggle more things and try twisting the distributor. I know. But I'm going to try. I think I will also look into sending a spare set of injectors off for fresh ones to swap to see if I still have a leaker. Thanks Larry, as always. I should know by now, check the connections!
 
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Old 12-13-2018, 12:28 PM
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Quick addendum- I pulled the 2wire plug on the O2 sensor and see one of the!terminals pushed back almost out of the housing!!!! Gah!
 
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Lawrence (12-13-2018)
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Old 12-13-2018, 06:47 PM
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That'll do it, had a Range Rover with almost permanent check engine light fault we chased forever - same problem.

Larry
 
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Old 01-24-2019, 07:34 PM
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Ill just put in here to "close" this problem. I changed the fuel filter (which had previously been left alone since its connections were rusted up) and sections of its tubing, changed the fuel pressure regulator (which was probably good), and installed reman injectors. It seems to be better. I have to assume the filter let something loose or that I knocked something loose in the lines by moving them around with the head gasket change.
 
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Don B (01-28-2019)
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Old 01-25-2019, 05:05 PM
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So now running normally Jerry?

Larry
 
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Old 01-25-2019, 05:37 PM
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Yes. I didn't test drive but let it run to warm and through the gears. Spring will tell.
 
 
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