Spark and ignition experts I need your help

BrianSD_42

BrianSD_42

New member
so I've had a weird random, occasional misfire at idle for awhile now.

I had a local shop do an injector service and that seemed to solve the problem for about 1000 miles but then it came back. Always at idle.

Are my injectors too old? The quote below I found on another thread seems to imply injectors wear out over time.

Is it something else such as the computer?

I have already replaced Fuel filter, plugs and wires with OEM parts.

This only happens at idle, usually 600RPM

The orifice in the end of an injector is about the same diameter as a human hair. The astringent, abrasive character of injector cleaner enlarges this hole over a period of time. Since your on-board computer doesn't know this, it will continue to tell the injector relays to open wide and thus provide a rich fuel mixture. Then the oxygen sensor calls for the fuel supply to be cut back. Once that's at a minimum, the check engine light comes on. New injectors cost about $165 each - a little more than the cost of the fuel you thought you were saving.
Click to expand...

This comment is interesting because it seems to be what might be going on with my truck.

I've 230k original miles on my injectors and I keep getting a random 01,02,03,05 misfire CEL that only happens at idle and doesn't come back for hours or days later. It never flashes just throws the code at idle occasionally.
I've done the fuel injector service but if the issue is that my injectors are worn out then that's a bummer since they are way expensive.
 
Last edited:
Register to hide this ad
Your mechanic should be able to hook up some type of diagnostic equipment that does more than read live data to see the pulse rates/flow widths. If they are within spec, I'd rule out injectors. Ever had a fuel pressure reading done?

Does it happen in both P and N?

When your heads were rebuilt were all new gaskets used from the head on up? Maybe enough to let in enough air when the engine is not under load but goes away when it does?

Just spitting out ideas......
 
im going to take it back there.

I don't know what was tested. I know they did an intense fuel injector cleaning.

Not sure what P or N is. My knowledge is definitely limited on this topic. If you mean park and Neutral then yes it does as well.

Never happens on start up. Always happens after running 2+ mins or more and by that time the engine is warm. Usually it happens 10-15 mins after normal running but when I come to a light.

It does feel a bit rougher at 600 RPM then 800.
 
Last edited:
Just curious if the CEL will occur at 700 rpms in Neutral or Park, as opposed to D at 600 rpms.

I would guess not a vacuum or gasket leak then since it doesn't happen when dead cold.

I have had one injector that could not pulse correctly and ended up flooding the cylinder. But it was quite apparent. Otherwise a balance test or ohm reading has told me which one is dead.
 
Since it has to run for a bit before it happens it must be happening just when in closed loop mode. How old is your pre cat O2 sensor?
 
A fuel service will do nothing on a dirty or injector with flow issues. The fuel service are only good for injectors that not causing any drivability problems. They meant to keep clean injectors healthy.

I would find a doctor injector (Doctor Injector) or contact rc injector (Fuel Injector Cleaning). This is a better option for finding faulty injectors.

Now if an actual injector cleaning service company does not find a pintle or flow rate issues.
Your next is to find a good Toyota dealership or an independent shop that specialize in Toyota.

If you do go for a Toyota dealer ask for an MTD (Master Toyota Diagnostic) specialist to work your problem. Most dealerships will have 1 or 5 guys in this level; these are the guys you want working on your problem. I would even ask to talk with one before he works on it. So you can explain your issue with him or her.

If you decide to go with an independent. I would ask if they have a pico scope or a snap on versus.
With your problem I would check IGT signal when the misfire is happening. A shorted or missing IGT will cause a no spark on that cylinder or cylinders. If fuel and ignition are good, I would do a in cylinder pressure test to see if it's valve opening issue or other mechanical problems. The above test requires special test equipment that only top diagnostic shop will have.

If you wanna try. You can do a running compression test along with a vacuum gauge. And as far as testing IGT, good luck! A multimeter useless.

So my advise to you is stop asking people in here to help diagnose your misfire cause it's useless too! Unless you want to keep throwing parts at your rig on your dollar.

Btw, nice rig you got there!
 
Bad TPS would cause misfire or rough idle. Found that out on my old Tacoma.

In this case, an ohm test for the injectors might be something you might want to do, but I they're all firing then that's not really going to help you much.

Here's a video I made about testing the injectors:

https://youtu.be/drGaZNky2Q4


Again, probably not going to be your problem, but worth a shot an takes a couple seconds for each one.



Another thing you can try is to take the number 4 and 6 injectors out, ad swap them with a known "bad" injector. If the code follows, good chance the injectors are done, and you can order or rebuilt them.
 
Forgot to add that as far as I know, the 4Runners do NOT have any kind if sensor or the injector, so TP wouldn't really help out much there.

All it really knows is a misfire. No specific info as to injectors or spark plugs/wires/coil packs.
 
So my advise to you is stop asking people in here to help diagnose your misfire cause it's useless too! Unless you want to keep throwing parts at your rig on your dollar.
Click to expand...

Well the thing is I will go to the mechanic and they have done pretty good historically on my truck.

I haven't really thrown any parts at it although I realize my first post makes it sound a bit like I did.

In the past year I have replaced the fuel filter, plugs and plug wires with Toyota parts. This was more preventive and not related to this random misfire code.

The thing is the first time the code happened it disappeared for 6 months, then 3 then 2 then blah blah now it is happening every 2 days.

But even at every 1 to 2 days it still only happens at idle and far far from every time at idle. It literally happens once and I clear the code and it doesn't come back until the next day.

I just took an entire Sunday drive (about 150 miles) with many stops at idle and no code.

It certainly isn't a continuing misfire that can be "caught in the act" very easily.

The TPS does sound intrguing. If it doesn't cost too much I would consider just replacing it and hoping that solves it.

I also read this thread at Toyota Nation
http://www.toyotanation.com/forum/81-pre-88-toyota-pickup-hilux/327126-bad-tps-symptoms.html

Frankly if it is something relatively cheap like the TPS that would be great news.

Thanks for the advice all !

Doc - I took a look at the video. Wow you are hardcore. Your engine is in pieces.
 
Last edited:
Doc2012 said:
Bad TPS would cause misfire or rough idle. Found that out on my old Tacoma.

In this case, an ohm test for the injectors might be something you might want to do, but I they're all firing then that's not really going to help you much.

Here's a video I made about testing the injectors:

https://youtu.be/drGaZNky2Q4


Again, probably not going to be your problem, but worth a shot an takes a couple seconds for each one.



Another thing you can try is to take the number 4 and 6 injectors out, ad swap them with a known "bad" injector. If the code follows, good chance the injectors are done, and you can order or rebuilt them.
Click to expand...

should the injectors be tested hot or cold? i know the temp will affect the resistance but not sure how much.
 
BrianSD_42 said:
The TPS does sound intrguing. If it doesn't cost too much I would consider just replacing it and hoping that solves it.

I also read this thread at Toyota Nation
bad tps symptoms - Toyota Nation Forum : Toyota Car and Truck Forums

Frankly if it is something relatively cheap like the TPS that would be great news.

Thanks for the advice all !

Doc - I took a look at the video. Wow you are hardcore. Your engine is in pieces.
Click to expand...

A failing TP will NOT cause an idle misfire. But the symptom felt may feel like a misfire to some. When there is short, open, or dead spot during acceleration from a stop with the TP circuit, a bucking or sligth hesitation is felt. Most TP dead spot or open is within the first 30% of it's sweep and after 50% of its sweep. Again you will not see this with a multimeter. Again the multimete is not fast enough to capture a glitch that faster than 1s.

If you problem is this intermitten, I would find a good diagnostic technician.
The advise I give my customer is when the problem happen stop at shop right away & don't turn off the car. That way the problem can be recorded or captured during the misfire events for review.

other way is install a fly recorder that can be play back later to see where fuel trim data is at during the misfire is taking place.

But I do have to tell you that you have to be patient; for, catching an intermitten runnability is going to be hard.
It's best to daignose problems like yours when the problem is happening. otherwise you will end up paying the shop for a, "no duplicate problem concern."

AGAIN, take it to a good diagnostice technician that specialize in drivability concern. NOt to a bolt on, parts replacer, line techline that knows a thing or two about diagnosing.
 
AGAIN, take it to a good diagnostice technician that specialize in drivability concern. NOt to a bolt on, parts replacer, line techline that knows a thing or two about diagnosing.
Click to expand...


The thing is this problem occurs so rarely. Even now that it is occurring every few days it only happens once and it gone. I could drive hours and it is only that one period of a 5-10 seconds and it throws a code.

I'd be happy to have a pro-technician try to capture this but can that be done for less than $100?

I don't really want to pay several hundred dollars to troubleshoot a ghost misfire that occurs rarely and is hard to capture.

What I would like to do is have the mechanic check the easy things and take it from there.

This may sound like a dumb question but .....

what would be downside of just forcing the truck to idle higher, say at 1,000 RPM when in D at a stop? I realize in N the idle would be a bit higher than that if I manually changed it.

This problem never occurs at high idle.
 
Wasting gas for one with an idle at 1000 rpms. Not to mention the ECU wouldn't be thrilled with it.

I'd try just putting the 4runner in N every time you get to a long light, etc. and see if the misfire occurs.

I have heard of a TPS causing a car to run too rich or lean, but that was in a car without a MAF. If there was a minute glitch I would think the ECU would compensate for it. For $30 (found on Ebay with free shipping), a replacement wouldn't hurt the wallet too much, thought I am not fond of just throwing parts at a problem.
 
BrianSD_42 said:
The thing is this problem occurs so rarely. Even now that it is occurring every few days it only happens once and it gone. I could drive hours and it is only that one period of a 5-10 seconds and it throws a code.

I'd be happy to have a pro-technician try to capture this but can that be done for less than $100?

I don't really want to pay several hundred dollars to troubleshoot a ghost misfire that occurs rarely and is hard to capture.

What I would like to do is have the mechanic check the easy things and take it from there.

This may sound like a dumb question but .....

what would be downside of just forcing the truck to idle higher, say at 1,000 RPM when in D at a stop? I realize in N the idle would be a bit higher than that if I manually changed it.

This problem never occurs at high idle.
Click to expand...

If the problem is consisten at setting DTC that would be a good thing.
The Toyota tech stream can be set to recorded once a DTC is set. The technician can can review data 50% or more prior to DTC was set. That way fuel trims and other data can be reviewed.

Now as far as labor charges it really depends on the shop/tech. But in your case, someone at the shop should drive it home while the scan tool is hook up and have it set for DTC trigger to auto record.

A good shop shouldn't charge you more than a couple of hours of actual diagnostic time. Unless they have to start taking harness part or panel to further diagnose wiring fault, if thats the case.
 
LittleCaesar said:
I have heard of a TPS causing a car to run too rich or lean, but that was in a car without a MAF. If there was a minute glitch I would think the ECU would compensate for it. For $30 (found on Ebay with free shipping), a replacement wouldn't hurt the wallet too much, thought I am not fond of just throwing parts at a problem.
Click to expand...

The only way a TPS will cause a rich or lean condition is if it was replaced and not set correctly or a corrode ground circuit. Or is low 5v ref. due to corrosion on power side of the circuit.

NO, the ECU will NOT compensate for a glitch, specially on an OBD2 system. If the ECU see's it and don't like it, it will let you!
 
You must log in or register to reply here.

Members online

Total: 274 (members: 1, guests: 273)

Forum statistics

Threads
278,311
Messages
3,554,082
Members
248,016
Latest member
Advally Service

Share this page

Trending content

Back
Top