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Misfire issue, need help

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Old 09-30-2018, 02:59 PM
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Misfire issue, need help

So recently I went and bought myself a 1991 toyota 4runner v6 3.0. And it had some small issues with it. It always had a misfire but at the time, wasn't anything serious.

Drove the car for about a week. And the misfire got worst, and worst. Until one time I drove it for about 30 mins and the car chugged and died at a stoplight.

Once that happened we started to investigate and try to find this issue.

The person that put this engine in really threw it all together. Such as a aftermarket fan is their, but the wires are not connected.
Their is a knock sensor on top of the engine, but not plugged in correctly or mounted, its just hanging their.
Bunch of vacum leakes that we plugged up
And many more.

Anyways, we replaced the 1AT sensor, aka the air flow sensor. And that didn't fix the issue.
We smoked the engine to see where the vacum leaks where coming from, and one hose had a major leak. So we patched that up. Still misfires.

After that, we checked the timing on the distributor and everything was on the mark, weirdly enough, putting it on the CORRECT timing made it miss more then putting it just a little foward.

We did a check engine light test. And got back error code 24, 25, and 52. Listed below are the error codes and what they are.Trouble codeFault locationProbable Cause24lntake air temperature (lAT) sensor-circuitWiring, lAT sensor, ECM25Mixture control -continuously leanWiring, injector, H02S, ECTNAF sensor, intake/fue/lignition system, ECM52Knock sensor (KS) -circuitWiring, KS, ECM
We fixed the intake sensor, so thats gone. We still have 25, and 52. But I don't even know if those are causing it to misfire, what do you guys think?
The car also backfires. As misfire is causing it.
NEW PARTS!
Added spark plug wires
Added Spark plugs
Added new hose's on certain parts that where rusted, cracked, etc.
I also did two fuel injector cleaners. Still nothing.
Did a fuel injector pressuare check (i think its called that?) And it came back good. Around 40psi if i remember correctly.
I also disconnected the battery and checked that, cleaned up the connections a bit. And made sure it was good. Left it their for like 25 mins. Oddly enough, I started the car up and it ran perfectly for about 1min or so. After that it ran really bad again and started
to misfire. We thought doing that would reset the computer or something in that matter.

We also did a compression check, all are good, coming in at 175 all around and one is 165.

I'll be adding pictures here in a bit to show you what it looks like, it was clearly just thrown together
I'm asking for ANY Experts help in fixing this vehicle. This is my only vehicle and need it to run.
Thank you!

Pictures:
https://imgur.com/a/U3tG9hX
As you can see, I added some new parts. And if you look close, you can see I plugged up a lot of vacum leaks on the left side of the engine.

QUICK UPDATE:
Fixed the wires.
Fixed the Knock sensor
Fixed the crankshaft
Fixed the timing
TPS was on backwards, some how? Fixed that.
Fixed all those grounds that literally didn't do much because it wasn't a ground.
Fixed the 02 sensor that was not plugged in, and rusted.
Fixed the coolent leak. Hose wasn't clamped down all the way to the TPS sensor

After all of this, their is still a misfire. Anyone know what it might be?
Thanks!

Another quick update.
Ran out of options and brought it to a dealership that I work at, that is a toyota dealership.
Payed $65 and got these results

FROM THE TECH:
Someone has destroyed this vehicle. EGR has been removed and plugged off.
Many vaccum lines have been plugged off
PCV does not work, plugged off
Vehicle runs really poor. Fuel pressure is within spec. If I pinch the return line vehicle runs better.
Codes for TPS and knock sensor.
So many things wrong with this vehicle
Maybe we should start with fuel filter in case volume is low
Could also be fuel damper
We would need to remove intake plenum to inspect/replace
A good start would be knock sensor with new wire, Fuel filter, fuel dampner, intake boot, and pcv stuff.
---------------------------------------------------------

So with all of that being said. Its running rich, you can smell fuel like crazy, and its blowing a lot of smoke. SO should I start with the fuel filter and dampner and see if that fixes it?
Also, for some reason the knock sensor is still coming up as a code, even tho its been installed correctly. I'll double check that.
TPS sensor has a code and im not sure why. It only had a code after we messed with it and put it in the correct position.
Intake boot is a temp fix, and is fine for now.
With the PCV stuff is that a huge issue? Same with the EGR. Or should I start with the Fuel filter and dampner. I can't see it being the knock sensor thats making the engine flood itself, or so it seems.

Also here is a list of parts I need. Would anyone be kind enough to link me to some OEM cheap parts if possible? Thanks!

Fuel Filter
Knock Sensor
Sensor wire for knock
Air surge Gasket
Intake manifold gasket
Fuel gamper set
TPS sensor.

Thank you guys for all your help. Hopefully in the following days I can get her back on the street!

Last edited by NBAProfessor; 10-10-2018 at 03:46 PM.
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Old 09-30-2018, 03:00 PM
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https://www.troublecodes.net/toyota/...up-or-4runner/ Link to the codes, didn't get posted as I wanted it to.
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Old 09-30-2018, 07:39 PM
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You have a lean code (25) but afterfire (back fire in tail pipe), this leans towards an exhaust leak before or at the oxygen sensor (false reading) or possible just a bad o2 sensor.

Hook the fog machine to the exhaust piping and have a look.
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Old 09-30-2018, 07:46 PM
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Originally Posted by Co_94_PU View Post
You have a lean code (25) but afterfire (back fire in tail pipe), this leans towards an exhaust leak before or at the oxygen sensor (false reading) or possible just a bad o2 sensor.

Hook the fog machine to the exhaust piping and have a look.
Do you think this could cause the misfire?
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Old 09-30-2018, 07:55 PM
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Originally Posted by NBAProfessor View Post
Do you think this could cause the misfire?
Inaccurate oxygen sensor signals, yep. It has a kind of burbling quality to it, rich smelling exhaust with lots of carbon on the pipe. If the exhaust is hot enough you'll get an after fire (big bang) due to incomplete combustion.

You'll get similar symptoms with an injector that leaks fuel into the intake, but that's abit harder to check. It should also set an over rich code if it's beyond the trim limits.. Yours is stating lean so could be both..
(Edit)
How old is the oxygen sensor?

Does the outside appear clean? (O2/sensors compare ambient and exhaust gasses to determine the signal levels

Last edited by Co_94_PU; 09-30-2018 at 07:58 PM.
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Old 09-30-2018, 08:18 PM
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Originally Posted by Co_94_PU View Post
Inaccurate oxygen sensor signals, yep. It has a kind of burbling quality to it, rich smelling exhaust with lots of carbon on the pipe. If the exhaust is hot enough you'll get an after fire (big bang) due to incomplete combustion.

You'll get similar symptoms with an injector that leaks fuel into the intake, but that's abit harder to check. It should also set an over rich code if it's beyond the trim limits.. Yours is stating lean so could be both..
(Edit)
How old is the oxygen sensor?

Does the outside appear clean? (O2/sensors compare ambient and exhaust gasses to determine the signal levels
Yup does have a rich smell to it. Thats interesting tho. I'm into older cars (70's) and all this sensor tech is amazing how it can stop a car from running to me. And Im not sure. I Just got the car off craigslist a month ago. So its probably old, or never been changed.
So what do you suggest I replace. If their is a leak in the exaust, which their might be. Someone messed with it and put a new exaust on....

And im not too sure. I'll check when its daylight. It might be dirty. Do you mean like oily or do you mean like just dirt and stuff?

Last edited by NBAProfessor; 09-30-2018 at 08:23 PM.
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Old 10-01-2018, 01:51 AM
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Here is a short video that illustrates the operation of an oxgen sensor..


First check for leaks upstream of the sensor (smoke/fog test). If you find any replace the gaskets or repair the holes.

If there is no change.

Measure the voltage on the VF diagnostics port. (Details in the service manual, and a few threads discussing it also)

If the sensor looks fouled, or old (they have a lifespan this is listed in an FSM or possible from the sensor manufacturer also). OR the sensor output isn't meeting spec. It's time to replace it.

Since its a new to you vehicle with unknown history (no receipts), it would be considered part of a new vehicle time up to replace it not "throwing parts at a problem". So just order one regardless unless it's bright shiny new once you get eyes on it.
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Old 10-01-2018, 03:34 PM
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Originally Posted by Co_94_PU View Post
Here is a short video that illustrates the operation of an oxgen sensor..

How an oxygen sensor works.

First check for leaks upstream of the sensor (smoke/fog test). If you find any replace the gaskets or repair the holes.

If there is no change.

Measure the voltage on the VF diagnostics port. (Details in the service manual, and a few threads discussing it also)

If the sensor looks fouled, or old (they have a lifespan this is listed in an FSM or possible from the sensor manufacturer also). OR the sensor output isn't meeting spec. It's time to replace it.

Since its a new to you vehicle with unknown history (no receipts), it would be considered part of a new vehicle time up to replace it not "throwing parts at a problem". So just order one regardless unless it's bright shiny new once you get eyes on it.
Little update. Replaced the o2 sensor and its still running bad. Just ordered a throttle position sensor to see if thats possible why? Did another reset on the ecu and for some reason the check engine light just does a constant blink. Instead of giving me like 2 blinks, pause, 2 blinks, etc.
What else do you think I should do? And do you know why my engine light is doing that? Thanks!
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Old 10-01-2018, 04:03 PM
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The constant flashing of the CEL indicates no fault codes. I took a look at your pictures- you’ve got a lot going on under the hood and none of it looks like it’s helping your situation. I wouldn’t keep firing parts at it. Start with cleaning up that engine bay.
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Old 10-01-2018, 08:35 PM
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Originally Posted by mholme View Post
The constant flashing of the CEL indicates no fault codes. I took a look at your pictures- youíve got a lot going on under the hood and none of it looks like itís helping your situation. I wouldnít keep firing parts at it. Start with cleaning up that engine bay.
Looking at pics finally..

Holy crap man, start with all those shenanigans!

Knock sensor needs to be screwed it.

Engine bay is no place for electrical tape.

Random grey wires hanging over fender go, and start, where?

Loose plug wire on the distributor.

Duct tape belongs on heating ducts not intake piping, and even then they use proper stuff not the trashy fiber tear easy stuff we make art out of.

Probably some stuff overlooked, lots of mouse nest going on there.
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Old 10-01-2018, 09:08 PM
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Originally Posted by Co_94_PU View Post
Looking at pics finally..

Holy crap man, start with all those shenanigans!

Knock sensor needs to be screwed it.

Engine bay is no place for electrical tape.

Random grey wires hanging over fender go, and start, where?

Loose plug wire on the distributor.

Duct tape belongs on heating ducts not intake piping, and even then they use proper stuff not the trashy fiber tear easy stuff we make art out of.

Probably some stuff overlooked, lots of mouse nest going on there.
I would do that right away, but I need it to run as its my only way to get to work. I understand that none of that helps But I need this misfire to go away first then I'm gonna start fixing that stuff. Knock sensor will be first. The only reason duck tape is on the intake is to hold the vacum leak temp until we buy the OEM part. They wanted 90$ for it, crazy lol.
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Old 10-01-2018, 09:55 PM
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Originally Posted by NBAProfessor View Post
I would do that right away, but I need it to run as its my only way to get to work. I understand that none of that helps But I need this misfire to go away first then I'm gonna start fixing that stuff. Knock sensor will be first. The only reason duck tape is on the intake is to hold the vacum leak temp until we buy the OEM part. They wanted 90$ for it, crazy lol.
Your misfire isnít going to go away if you donít fix the root cause of it. All the hacks going on in that engine bay is crazy, to say the least. Possible vacuum leaks, suspect wiring. You have a lot of work to do before you can confidently drive down the road. Get it cleaned up and start fresh. It stinks to have to clean up someone elseís mess, but if you want it reliable, thatís what you have to do.
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Old 10-02-2018, 05:33 AM
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Originally Posted by NBAProfessor View Post
...They wanted 90$ for it, crazy lol.
The reason you come to YotaTech is to learn about alternate sources. $42: https://www.rockauto.com/en/catalog/...take+hose,6344


Originally Posted by NBAProfessor View Post
I would do that right away, but I need it to run as its my only way to get to work. ...
Hardly anyone has the luxury of owning a "project" vehicle AND a reliable DD. But your truck (as it is now) is going to strand you somewhere on that 75 mile journey. Figure out public transportation, get another job, borrow a recent-model Camry. Otherwise, you'll always be cutting corners ("I need it to run to get to work."), and glancing nervously at your gauges.

I know you're posting from a phone, and thumb typing is way above my pay grade, but please take care. Every time you misspell a word a few folks have to spend time trying to figure out what you meant. Eventually, if your posts are hard to read, they'll all give up.
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Old 10-07-2018, 08:09 PM
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Originally Posted by Co_94_PU View Post
Looking at pics finally..

Holy crap man, start with all those shenanigans!

Knock sensor needs to be screwed it.

Engine bay is no place for electrical tape.

Random grey wires hanging over fender go, and start, where?

Loose plug wire on the distributor.

Duct tape belongs on heating ducts not intake piping, and even then they use proper stuff not the trashy fiber tear easy stuff we make art out of.

Probably some stuff overlooked, lots of mouse nest going on there.
QUICK UPDATE:
Fixed the wires.
Fixed the Knock sensor
Fixed the crackshaft
Fixed the timing
TPS was on backwards, some how? Fixed that.
Fixed all those grounds that literally didn't do much because it wasn't a ground.
Fixed the 02 sensor that was not plugged in, and rusted.
Fixed the coolent leak. Hose wasn't clamped down all the way to the TPS sensor

After all of this, their is still a misfire. Anyone know what it might be?
Thanks!
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Old 10-07-2018, 09:03 PM
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You set the TPS adjustment correctly? Have you read your spark plugs? Are they gapped correctly? Timing set at what? Whenever possible, you should use OEM parts, especially for the ignition system. A good set of DENSO wires/cap/rotor are not that expensive.
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Old 10-07-2018, 09:27 PM
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Originally Posted by mholme View Post
You set the TPS adjustment correctly? Have you read your spark plugs? Are they gapped correctly? Timing set at what? Whenever possible, you should use OEM parts, especially for the ignition system. A good set of DENSO wires/cap/rotor are not that expensive.
TPS adjustment should be set correctly. Spark plugs are good. Gapped perfectly. Timing im not too sure, I'd have to ask the mechanic, but he says its set perfectly? Brand new wires for spark plugs, and cap for distributor. The cap was inside the truck when we got it so we threw it on. And it still ran bad. Has no cracks. We also tried the original one that was on it, also had no caps. No idea why they had 2 to begin with. I don't have the truck currently a mechanic is trying to fix it but hes stumped too. Thank you for the reply!
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Old 10-07-2018, 09:56 PM
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Maybe they had two distributor caps because of the same issue you are currently trying to fix. If you’re having a constant misfire, your mechanic should be able to pull/change the plugs and get an idea of what’s going on during the ignition process, even isolate the cylinder(s).

I don’t know what brand plug wires those are in your pictures, but like I said, these old Toyotas like OEM parts. And as mentioned before, one of them doesn’t even look seated. Cheap chain store parts are often bad right out of the box or fail quickly when heat cycled. I’m not trying to say throw parts at it, but sometimes you have to go ground zero and climb up from there.
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Old 10-07-2018, 10:14 PM
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Originally Posted by mholme View Post
Maybe they had two distributor caps because of the same issue you are currently trying to fix. If youíre having a constant misfire, your mechanic should be able to pull/change the plugs and get an idea of whatís going on during the ignition process, even isolate the cylinder(s).

I donít know what brand plug wires those are in your pictures, but like I said, these old Toyotas like OEM parts. And as mentioned before, one of them doesnít even look seated. Cheap chain store parts are often bad right out of the box or fail quickly when heat cycled. Iím not trying to say throw parts at it, but sometimes you have to go ground zero and climb up from there.
So should I try buying a new distributor cap? also would you be able to tell me which one doesn't look seated? Thanks! u
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Old 10-07-2018, 10:33 PM
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I wouldn’t buy anything yet, other than a new intake hose. Let your mechanic do the work you’re paying them to do. The plug wire directly to the right of your oil fill cap doesn’t look seated. Maybe it’s the angle of the picture, maybe it isn’t. I don’t know off the top of my head what cylinder it is, but it’s worth checking. Get rid of the taped intake and insure you have no vacuum leaks. Good luck.
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Old 10-08-2018, 01:13 PM
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Originally Posted by mholme View Post
I wouldnít buy anything yet, other than a new intake hose. Let your mechanic do the work youíre paying them to do. The plug wire directly to the right of your oil fill cap doesnít look seated. Maybe itís the angle of the picture, maybe it isnít. I donít know off the top of my head what cylinder it is, but itís worth checking. Get rid of the taped intake and insure you have no vacuum leaks. Good luck.
The mechanic says hes stumped. He said hes gonna try one more thing, but he says he has no clue what it might be.
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