RTH HG rebuild --> running rough

Joined
Sep 21, 2017
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Boulder, Colorado
Hey all,
I recently (lol ok it was like 2 months ago) did a head gasket rebuild on a 95 FZJ. It mostly went smoothly, but now the engine is running very rough, to the point I didnt even try to drive it. was hoping you all could offer advice on the order with which you'd go through stuff. Here are the symptoms:

1) starts pretty quick (yay)
2) runs rough. RPM all over the place (but centered around a normal idle). Engine shaking in its boots. Loud.
3) revs, but doesnt help the rough running
4) leaving the computer control over the timing, it is also all over the place. Runs the best when retarded, but like around 14* (!)
5) RPM will eventually drop and it will die (unless revved)
6) no codes (waaaat)

Checks I've already done:

1) I'm 99% sure I set the timing gear right when I put it all back together.
2) I pulled the dizzy and checked the worm gear orientation and re-installed

Order of operations going forward:
1) check that the spark plug wires arent touching/crossing each other. I was pretty tired by the time I re-installed those. I've read charge can jump between plug wires if they're too close and lead to timing issues (also vvv easy to do)
2) check for vacuum leaks with the ole carb-cleaner method (easy) --> maybe double check the egr valve?
3) double check all vacuum lines (easy)
4) check compression? (the problem is I cant get the engine to warm up, so presumably readings will come back low)
5) pull valve cover and double check I set up the timing right. but again, i triple checked this before.


'preciate the help!
 

LINUS

Waiting for the Great Pumpkin
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I’m not sure what to make of “it mostly went smoothly” involving the repair.

Did the motor idle & run smooth post-rebuild, and now it has fallen to crap - or has it basically been poor since the rebuild?

If it was great, then I’d be looking at the basics - new PCV valve or check/clean it - then look into the fluids just to make sure your gasket is holding.

If you’re still good, then yeah - the ignition system & esp a new fuel filter if tou never changed it.

A smooth-ish idle but crap running is real indicative of a plugged fuel filter, so if yours is old, start there.
 
Joined
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gotcha, sorry for the unclear wording. I just meant that there werent too many hiccups while I was putting it all back together.

It didnt run smooth ever, after the rebuild. It idles very very rough.

I didnt replace the fuel filter (one of the few things that fell through the cracks in terms of ordering parts in time). The coolant still looks clean, but since I havent been able to drive it, it's barely been run. Dunno how long it takes for oil to foul the coolant.

*edit*
and the PCV valve is new.
 
Joined
Mar 27, 2015
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Westminster, CO
 
Sounds like timing may be off. Are you sure you're not a tooth off on the mechanical timing marks? Especially if you have to retard it that far, it's usually like 3 deg btdc with the paperclip in.

I'd look at your valve adjustment while looking at the timing.
 
Joined
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Sounds like timing may be off. Are you sure you're not a tooth off on the mechanical timing marks? Especially if you have to retard it that far, it's usually like 3 deg btdc with the paperclip in.

I'd look at your valve adjustment while looking at the timing.
Yeah I just really remember being very careful setting the timing and checking and rechecking before putting on the valve cover. And I didn't remove the chain from the gear....

I didn't check the valve clearance but I believed the shop did... I'll double check the receipt.
 
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Ok, well I've continued poking around (before taking the valve cover off due to laziness). Heres a video of it starting up, and me scrolling through real time data. Its very weird that its getting a 0v for one of the O2 sensors. I wonder if its a fuel delivery problem making it run super lean? Anyway, Just curious what people think. If no one has any insights I can pull the valve cover the next time its nice here. Which might be in a week! Vids in here.
 
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Feb 7, 2009
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Make sure all your fuel injectors are plugged in and in correct order check timing
 
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I did double check the order of the injectors. That's a good tip! But they're all in order, sadly. That would have been convenient. The timing seems unlikely because I remember being SO nervous about getting it right that I did it like 3 times. But I can double check.
 
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Olathe, KS, USA
 
You've got a massive tick. Could be exhaust leak, check you intake hose for tears. It looks old.

It acts like big vacuum leaks, but the tick mother's me most.

Unscrew the oil fill cap while idling.to see if it instantly.dies or makes no difference. If no difference, then I would look at vacuum leaks.

Did you do VC gaskets, spark plug tube seals, dizzy o-ring?
 
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Ooh ok ok I like this list of checks. The intake is brand new, as are all rubber components of the valve cover, and the dizzy o ring.

When you say take the oil cap to see if it dies, is the "it" the ticking sound? Also it could be an exhaust leak since getting all those nuts to torque spec was hard, especially near the fire wall.

I did check around for vacuum leaks with wd40, but could take another run.
 
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Possible you cross wired the ignition wires at the distributor?

Miss a electrical plug? Perhaps IAC motor connector at the throttle body.
 
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Ooh ok ok I like this list of checks. The intake is brand new, as are all rubber components of the valve cover, and the dizzy o ring.

When you say take the oil cap to see if it dies, is the "it" the ticking sound? Also it could be an exhaust leak since getting all those nuts to torque spec was hard, especially near the fire wall.

I did check around for vacuum leaks with wd40, but could take another run.
I'm not sure what the ticking is, it could be exhaust, but it pronounced.

Taking off the oil cap while running introduces a whole bunch of unmetered air and it should cause the engine to nearly die. If it doesn't make it worse, the computer is already compensating for other massive vacuum leaks.

Did you remember to remove the retaining bolt on the timing gear on the cam?

Did you tighten the VC bolts?
 
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I'm not sure what the ticking is, it could be exhaust, but it pronounced.

Taking off the oil cap while running introduces a whole bunch of unmetered air and it should cause the engine to nearly die. If it doesn't make it worse, the computer is already compensating for other massive vacuum leaks.

Did you remember to remove the retaining bolt on the timing gear on the cam?

Did you tighten the VC bolts?
Awesome, this is an easy test for big vacuum leaks. I love it. I'll do it soon.

I tightened the VC bolts to torque specs. Yeah, I pulled that retaining bolt. A good question though, would have been easy to forget.
 

Tedward

95 LC
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If there is a unmetered air getting in the ecu will add fuel. It can add fuel up to about 30% of the 'normal' air fuel ratio.
Normal is some ratio/amount that would be about correct at sea level in a new motor. I am making some of this up as I don't remember what I read and what I assumed. I think this is close to real and can be found in a fsm.

Anyway, you can use the obdII ecu info to see if any or what percent of fuel the ecu is adding. The air fuel ratio changes a little all the time but something like 15 percent difference from the norm is a problem. There is a percent of fuel added that will eventually cause a cel, like 25% or something.

I know a little about this because when i rebuilt the motor it had a leak that made the motor run rough until i found and fixed it. I did not tighten the lower intake plenum to the block. This leak made the motor run lean and the ecu compensated with as much fuel as it could.

So, maybe you have a massive air leak?
 

ScubaSteve80

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Did you label you valve shims when you took them out? If you didn't label them and put them back with the incorrect lifter bucket then you will have the knocking you are referring to. Look at 55:30 on Otramm's video to see what I am referring to. This is a very common mistake a lot of people make. Did you label them or put them back the way they came out?

 
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The head was handled by a machine shop. I delivered with the cams reinstalled after pulling the head. My understanding is they would have installed everything back the way it came out (they did a valve job and valve adjust, so I'm assuming they did it... Correctly....). For reinstall I just pulled the cams again and, you know, plopped it on there.
 
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Start with figuring out which cylinder it is by killing one cylinder at a time by either removing spark plug wire or injector connector. Next check compression if you haven't already. Still think at the end you're going to have to remove the valve cover to inspect.
 
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