Trying to pinpoint a slight miss on my 97 FZJ80. Took to local mechanic. He hooked up to Snap-On diagnostic tool. No codes. However, there is some sporadic miss on cyl 1 & 2 then the miss jumps to cyl 5 & 6, then back to 1 & 2. Sometimes there’s no miss. Cyl 3 & 4 don’t ever show a miss. Less than 7000 miles ago did new short block, rebuilt head, pretty much everything new around motor incl plugs, plug wires, distributor cap and rotor and coil. Anyone ever seen this? It’s runs great down the road with plenty of power. The slight occasional hiccup at idle drives me bonkers. Some have suggested fuel injectors be serviced. I hate to throw money at it if there’s another culprit that’s less work.
1FZFE Slight Miss at Idle (2 Viewers)
- Thread starter Indiana80
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
- Thread starter
- #2
I did not touch the injectors when engine work was done.
mingles
GOLD Star
Did the main engine wiring harness get replaced? What is the harness condition where it passes by EGR?
- Thread starter
- #4
I had the shop wrap it in heat resistant tape when they did the motor work. They did not mention the condition of the harness nor did I inspect it.
I've had a very slight miss at idle since I've owned the truck. Doing research it seems like it is very common and most people experience it. Some weeks will go by and I don't notice it, and then will notice it for a while. It is strange.
Would love to know what causes it and how to fix it for good though, so if anyone has figured it out, please post.
Would love to know what causes it and how to fix it for good though, so if anyone has figured it out, please post.
- Thread starter
- #6
If the miss was caused by an electrical problem (ie melted harness), wouldn’t that trigger a code in the diagnostic tool?
You might be surprised...
ppc
M Go Blue
More than likely would not cause a fault code. The codes are related to well defined conditions. A random short would not be considered well defined.
- Thread starter
- #9
My tube looks good, but I’ve not pulled it for a thorough inspection. Will check that and the condition of the harness. Thank you.
I had the weirdest thing happen to me the last time I changed the engine oil. After I refilled with new oil I started the engine to circulate the oil to regular pressure to verify the level and it wouldn't idle for anything. Off idle it would run ok but no idling at all. After a lot of head scratching and poking around I put the fill cap back on the valve cover and it ran fine.
Turned out I had a massive vac leak with it open . First time I've ever seen that on any engine but it happened. Try looking for a vac leak that is a big source of rough idling.
Turned out I had a massive vac leak with it open . First time I've ever seen that on any engine but it happened. Try looking for a vac leak that is a big source of rough idling.
devo
SILVER Star
Isn’t the miss from lean fuel while the engine is at idle, controlled by the ECU?
My ‘97 has idled this way for years. Smooths out anytime I use the throttle.
devo
My ‘97 has idled this way for years. Smooths out anytime I use the throttle.
devo
- Thread starter
- #12
I don’t know. Maybe all 1FZFEs do this? It’s not terrible, but you feel the hiccup in driver seat.
As far as lean condition I would make sure I have a new NTK or oem O2 sensor, it makes a nice difference on these engines.
You can also read your fuel trims with a multimeter. You didn’t say if the shop was reading that.
You didn’t say what plugs or wires you used, denso or ngk only.
Anytime I hear rebuilt head I cringe, seen a lot of machine shops cut the valves excessively which causes a premature burnt exhaust valve but since you say it’s random in between 1&2, 5&6 you should be fine.
I would be disconnecting the egr vacuum hose at the valve and drive it. Egr vacuum ports can get carbon up on this engine. That could cause the vsv not to be able to bleed off the vacuum properly which would leave the egr on at idle. With it disconnected, a few drives will cause a check engine light, cheap and easy way to rule it out.
You can also read your fuel trims with a multimeter. You didn’t say if the shop was reading that.
You didn’t say what plugs or wires you used, denso or ngk only.
Anytime I hear rebuilt head I cringe, seen a lot of machine shops cut the valves excessively which causes a premature burnt exhaust valve but since you say it’s random in between 1&2, 5&6 you should be fine.
I would be disconnecting the egr vacuum hose at the valve and drive it. Egr vacuum ports can get carbon up on this engine. That could cause the vsv not to be able to bleed off the vacuum properly which would leave the egr on at idle. With it disconnected, a few drives will cause a check engine light, cheap and easy way to rule it out.
- Thread starter
- #14
Thank you.
O2 sensors are new Densos. Plugs are NGK. Wires are from Mr T.
Mechanic used the multi-meter on plugs for injectors 1 and 2. Injector 1 tested 13.8 and 2 at 14 (Ohms, maybe?). He said they were within spec.
Regarding the head, the machine shop milled down just a fuzz and checked for trueness end to end. The head was milled down within less than the max allowable. I have the thickness amount removed on the shop’s invoice. They used a Toyota OEM valve grind kit. The only thing they noted was light scoring on a cam lobe that was all / or mostly polished out. Oil pressure is great. I checked it with a manual gauge.
For the EGR vacuum port test, just disconnect the vacuum tube and if CEL comes on, the EGR vacuum port is the culprit? Sorry, I’m not an engine mechanic, but I know vacuum leaks can cause all kinds of issues. Note: vacuum lines are all new, as well.
Side note: when I went to pick up the truck at the shop the mechanic showed me the read outs on the Snap-On diagnostic tool. There was a read out that showed Advanced Timing read outs ranging from 5.5 to 7 at idle. Not sure if that’s good or bad. Mechanic also said the diagnostic tool can show flow levels for each fuel injector, but he couldn’t remember how to find that test on the machine- he’s an old school guy.
Egr test is, disconnect vacuum hose. The lack of misfire will tell you if that is the problem. With it disconnected the check engine light will come on but it isn’t a big deal. You can clear it by pulling the EFI fuse for 5 minutes.
It’s good to know that they barely shaved the cylinder head. What I’m referring to is the valves. It’s called valve margin, New is 1mm and limit is .5mm. Like I said since the misfire varies it is probably not the problem.
The Toyota scanner, techstream didn’t tell me hardly anything on my 96, then again I didn’t pull the oldest version of techstream out. So you are lucky the Snapon scanner is telling you misfire data. He might have it on an engine scope, that would make more sense. Toyota didn’t give us much misfire data in 96-98.
- Thread starter
- #16
Dumbass question here, but am I correct to assume any misfire indicates a problem? I’ve never watched one of these tools show real-time firing info. It was pretty cool. We ran the vehicle at idle and watched the screen with the machine plugged into the OBDII port. It would show all cylinders firing correctly, then 1 only, then 1 & 2, then 5 & 6, then no miss. Exactly how I can feel the slight hiccup in driver seat. No check engine light, no codes. My only concern at this point is that I don’t want to cause engine damage running like this. Do you see any long-term harm with this? My local mechanic said the miss is so slight he wouldn’t be concerned about burning up a piston. He’ll tear into it if I ask, but I don’t think he knows where to start.
The misfires most likely won’t cause engine damage, more of an annoyance. When it misfires under load that is when real issues happen. But the 1fz properly running is smooth as glass at idle. What is MAF reading at idle?
gonzopancho
SILVER Star
My 97 lx450 did this. Turned out to be a stuck EGR valve. Even though it tested good, replacing it fixed the issue.
COYS
SILVER Star
My 97 did this seldomly at idle.
By consequence of replacing original MAF with the Wits’ End version + new OEM tube, haven’t felt it since. Also replaced o2 sensors with OEM and Denso (one of them is NLA) all as PM.
Engine hasn’t been touched yet.
By consequence of replacing original MAF with the Wits’ End version + new OEM tube, haven’t felt it since. Also replaced o2 sensors with OEM and Denso (one of them is NLA) all as PM.
Engine hasn’t been touched yet.
- Thread starter
- #20
Opening my thread back up with an update. Putting in refurbed injectors, replaced VSV, vacuum lines, cleaned up all vacuum ports on upper intake, replacing fuel pressure regulator while in there. Figured I might as well replace spark plugs. Pulled the fairly new Denso OEM plugs and all 6 had a black residue and smelled like fuel. The O2 sensors are newer Denso units. What else could cause overfueling? We’ll see how it runs when everything is buttoned back up.
