1998 Land Cruiser Rough Idle (1 Viewer)

[66kid]

Hey guys, new to the forum here but have been browsing for years finding helpful information on cruisers. I have a 1998 Land Cruiser which currently has 256,xxx miles and has started having some issues. A while back I had done some work which included replacing the starter. I then replaced the fan clutch shortly after due to a wobble from the bearing and while I was in there decided to change the timing belt and water pump. This all has been done within the last 10k and recently it has not been running well and has a intermitant popping sound and hiss coming from the driver side of the intake manifold. I should also note I changed the intake manifold gasket when replacing the starter which lead me to believe they may have not been torqued properly so after retorquing the problem is still there. I scanned with my BlueDriver which provided the codes P0300, P0301, P0302, P0305 and P0307 although there was no CEL. All arr misfire codes for one bank except P0302. After replacing spark plugs which were overdue and checking coils I am still having the problem. At this point I am at a loss as to what could be causing the issue.

 

[xeuxaz]

Did you replace the intake manifold gasket?

 

[66kid]

Did you replace the intake manifold gasket?

Yes I replaced the lower intake manifold gasket at the same time I replaced the starter.

 

[xeuxaz]

Derp. You mentioned that. Any chance a vac line is bad or cracked after reassembling?

 

[66kid]

Derp. You mentioned that. Any chance a vac line is bad or cracked after reassembling?

I'm pretty sure all the vac lines are original and most are split towards the end so that could definitely be the issue. Are there others besides the ones that are on the airbox assembly?

 

[3_puppies]

Yes I replaced the lower intake manifold gasket at the same time I replaced the starter.

with OEM Toyota?
are they installed in the correct orientation?
torqued properly?

 

[66kid]

with OEM Toyota?
are they installed in the correct orientation?
torqued properly?

I believe they are in the correct orientation based on other forums I have read on here and the bolts are torqued to 13 ft/lbs evenly. I used a NAPA brand gasket rather than OEM.

 

[xeuxaz]

I'd carefully check all the vac lines, including the one for the fuel pressure regulator, etc. Maybe review this 2UZ-FE Intake Manifold diagrams..... - https://forum.ih8mud.com/threads/2uz-fe-intake-manifold-diagrams.783240/.

Also, from what I understand you want to stick with OEM only on that gasket.

 

[66kid]

Update after replacing some of the cracked vacuum hoses besides the large one connecting to the air box and checking the hose at the fuel pressure regulator. I noticed that the hose connecting to the fuel filter has a crack in it and the previous owner must have attempted to fix it with what looks like scotch tape. It's not leaking so I figure it must be a sleeve over another line. Tried to start and it will not idle unless giving it some gas then it runs fairly smooth but has what sounds like an occasional miss which fluctuates the rpm.

 

[xeuxaz]

Throttle body clean? MAF sensor clean?

 

[66kid]

Throttle body clean? MAF sensor clean?

I cleaned the throttle body about the same time as the starter replacement and cleaned the MAF several times since then. The MAF has been replaced with a Duralast when I was chasing down a sluggish acceleration problem a while back. (I know Hitachi OEM should've been used) This fixed that problem but could it have failed again causing this issue? I've tried to run it with MAF disconnected and there is no change.

 

[take123]

You mention you replaced the spark plugs. What about the ignition coils? You mention you checked them. How are the condition? I know ig coils are expensive. When were they last replaced?

 

[66kid]

You mention you replaced the spark plugs. What about the ignition coils? You mention you checked them. How are the condition? I know ig coils are expensive. When were they last replaced?

Ignition coils were replaced along with spark plugs due to the misfire codes on multiple cylinders. The old coils did not have any cracks in the boots or anything. They had been replaced before due to a few dead coils maybe 75k ago.

 

[xeuxaz]

If you were local to me I’d offer to let you swap some parts back and forth between our trucks to eliminate some variables.

Do you still have the old ignition coils? Maybe buy another MAF and return it if it doesn’t help. Sounds like a pain in the butt!

 

[Mike NXP]

I cleaned the throttle body about the same time as the starter replacement and cleaned the MAF several times since then. The MAF has been replaced with a Duralast when I was chasing down a sluggish acceleration problem a while back. (I know Hitachi OEM should've been used) This fixed that problem but could it have failed again causing this issue? I've tried to run it with MAF disconnected and there is no change.

This sort of seems like a big clue. I totally get using aftermarket parts sometimes and they probably will work just fine BUT you said you installed a new MAF and it fixed a problem you were having ( a different problem ) but now a similar run / idle issue is back.

I hate to just throw parts at stuff but maybe OEM MAF should be on your to-do list. Or maybe just putting the original ( cleaned up if you still have it ) back it for diagnosing. I don't think running without the MAF will help for troubleshooting. Otherwise it sounds like you have checked all of the other suspects off the list ( plugs, coils, intake gasket, etc.)

>> So what was up with the fuel filter / lines, is there a chance you need to look at that again or is it good to go.
>> What exactly is happening, as you idle you get an occasional popping / miss sort of noise? Can you post a video?

Rough idle is one symptom, and will relate to a handful of different suspects ( vac lines, MAF sensor, dirty throttle body, and so on)...... BUT missing / popping / backfire type of noises is another set of troubleshooting all together ( gaskets, valves, timing, plugs/coils, etc. )

PS - some vacuum lines have enough slack where you can just snip the cracked ends and re-install.

 

[66kid]

After swapping the newish coils with the old OEM coils on cylinders 1,2,5,7 it is running worse lol. No CEL or codes when scanned and still won't idle on its own. A/T oil light flashes when it's about to die then revs high to prevent it from dying. MAF air rate is fluctuating from 2.1-2.7 lb/min. My next step is go through each of the old coils and see if any of them are better.

 

[take123]

i had one LC where it was idling rough and had cel and vsc lights and I found the wire was chewed up on a knock sensor on the engine. Replacing the wire fixed it

Did you check condition of the engine wiring?

Do you have rodent issue?

 

[66kid]

i had one LC where it was idling rough and had cel and vsc lights and I found the wire was chewed up on a knock sensor on the engine. Replacing the wire fixed it

Did you check condition of the engine wiring?

Do you have rodent issue?

Unfortunately that may be the cause as it has sat for a while and there is signs of rodents. I think I have narrowed it down however to a coil and/or MAF sensor issue by switching coils around and using old ones I replaced before. My reasoning for thinking MAF sensor is when I run it with the MAF sensor disconnected it runs pretty good, but when I plug it back in it runs poorly. Earlier when I tried before changing the coils there was no change with it plugged in or unplugged.

 

[66kid]

Replaced the MAF sensor and did not change anything. Scanned again and the misfire codes are gone but there is a permanent code but doesn't say what it's for? Still running rough, checked o2 sensor voltages and am not getting voltage for sensor 1 in both bank 1 and 2. I assume there is supposed to be voltage there.

 

[hortandr]

Any updates 55kid??