T4RFool
New member
I know, the 4runner had been down for 6 months now and I still have no idea why.
Backfire/Studder under acceleration
- Thread starter T4RFool
- Start date
I know, the 4runner had been down for 6 months now and I still have no idea why.
PitbullRescuer
New member
How did you check the injectors? I've been telling you for a month now I think it's an injector. I thought you said you replaced an injector?
T4RFool
New member
I have not replaced any injectors. I used a multimeter on them and removed spark from each individual injector and they were all missing/hesitating. That gave me the impression that it wasn't injectors unless they were all clogged equally. That's why I moved onto the ECU thinking that it was more probable that the ECU was not acting normal. Now that its not the ECU *shrug*. It's hard to say what my next move should be because what else is there. Clogged catalytic converter?
It seems like it should be an injector problem but when I removed spark from each cylinder it still ran the same consistently after each cylinder was tested. If it wasn't so consistent across every cylinder I would have sent them all in to be cleaned but they all performed the same. It seems like something is causing the injectors to miss at the same time, like they are all cutting out at the same time.
It seems like it should be an injector problem but when I removed spark from each cylinder it still ran the same consistently after each cylinder was tested. If it wasn't so consistent across every cylinder I would have sent them all in to be cleaned but they all performed the same. It seems like something is causing the injectors to miss at the same time, like they are all cutting out at the same time.
spectre6000
New member
How's the oil been? Has the engine ever seen particularly high revs? You've gone through pretty much everything on the top end of the engine, but I don't think a single thing has been mentioned about the bottom end... What if something is messed up internally and it doesn't start to get nasty until it gets spinning fast enough for whatever is out to start affecting things? I can't think of any sensors down in that part of the system that would throw codes, but something being far enough out of whack could potentially cause things to get pretty funky in #3 without any related codes...
What I'm thinking at this point, and bear in mind I'm grasping at straws, is maybe a high RPM event or some manufacturing/maintenance defect might have either sheared or seriously loosened one of the rod bolts on the #3 rod at the crank. As RPM increases, the forces acting on the remaining rod bolt cause it to bend and effectively screw up the timing and such on that cylinder, throw things out of balance, etc.
Not a happy thought, but mayhap one with some merit...
What I'm thinking at this point, and bear in mind I'm grasping at straws, is maybe a high RPM event or some manufacturing/maintenance defect might have either sheared or seriously loosened one of the rod bolts on the #3 rod at the crank. As RPM increases, the forces acting on the remaining rod bolt cause it to bend and effectively screw up the timing and such on that cylinder, throw things out of balance, etc.
Not a happy thought, but mayhap one with some merit...
T4RFool
New member
if that were the case, then that is a serious problem that is far beyond my mechanical skills. I was thinking about maybe taking the catalytic converter off next but that idea has me worried.
To answer your questions though, the engine hasnt ever been high rev, after it warms up it'll hang out around 600-700. Oil hasn't ever been an issue either, I've never had to worry too much about checking oil because every time I have its never been low or abnormal. I've always thought that I had a good motor up until this all started.
spectre6000
New member
I can't think of a way a cat would do that without throwing a code...
Again, I have to be honest. I've not had a chance to tear into one of these that deeply. Oftentimes you can get to that part of the engine by removing the oil sump and maybe a windage tray (depending on if/how it's installed). That would give you a clear view of the guts, and with overhead cams there shouldn't be much between the windage tray and the crank. You might need to turn it over from the top side to get a good look at everything, but that will give you clear and concise knowledge that anything in the bottom end is good or bad.
There are a few possible scenarios:
1) Nothing's wrong on the inside, you get an oil change, you learn something cool about your engine.
2) The #3*end cap is loose with a loose nut or something. You thoroughly inspect and replace what needs replacing, get an oil change out of the deal, and you learn something.
3) The #3 end cap is loose, it's taken the crank journal and rod with it. You get an engine rebuild (or a new crate engine while that's still an option... or a DIESEL!). Expensive, but it'll be like brand new! Since most of us are going crazy replacing suspension components and such, the only true mechanical wear liabilities are the engines, transmissions, and transfer cases. Replace those and it's a brand new truck (since you've probably already replaced damn near everything else with aftermarket stuff anyway).
Again, I have to be honest. I've not had a chance to tear into one of these that deeply. Oftentimes you can get to that part of the engine by removing the oil sump and maybe a windage tray (depending on if/how it's installed). That would give you a clear view of the guts, and with overhead cams there shouldn't be much between the windage tray and the crank. You might need to turn it over from the top side to get a good look at everything, but that will give you clear and concise knowledge that anything in the bottom end is good or bad.
There are a few possible scenarios:
1) Nothing's wrong on the inside, you get an oil change, you learn something cool about your engine.
2) The #3*end cap is loose with a loose nut or something. You thoroughly inspect and replace what needs replacing, get an oil change out of the deal, and you learn something.
3) The #3 end cap is loose, it's taken the crank journal and rod with it. You get an engine rebuild (or a new crate engine while that's still an option... or a DIESEL!). Expensive, but it'll be like brand new! Since most of us are going crazy replacing suspension components and such, the only true mechanical wear liabilities are the engines, transmissions, and transfer cases. Replace those and it's a brand new truck (since you've probably already replaced damn near everything else with aftermarket stuff anyway).
T4RFool
New member
I wish I knew how to do half of the stuff you just described lol I also wish I had a garage where I could just start tearing it apart and it didn't need put back together within a few days. So what your describing here would require dropping the oil pan correct?
spectre6000
New member
Yup. You could spread it out over a few days too if you wanted to. It's more or less sheltered from everything but a flood by virtue of being on the bottom.
Again, I don't know what needs to be removed before you can get to the oil pan without going outside and crawling underneath my 4Runner, but if it's easy to get to your cost would just be the associated gasket kit and you could probably have it apart and back together within an hour or two (assuming things turn like they should and there's no crazy weird engineering design decisions that went into the engine there).
Also just a disclaimer, that's a grasping at straws idea. It may be right, may be another total waste of time... It's really hard to diagnose engine problems using text only...
Again, I don't know what needs to be removed before you can get to the oil pan without going outside and crawling underneath my 4Runner, but if it's easy to get to your cost would just be the associated gasket kit and you could probably have it apart and back together within an hour or two (assuming things turn like they should and there's no crazy weird engineering design decisions that went into the engine there).
Also just a disclaimer, that's a grasping at straws idea. It may be right, may be another total waste of time... It's really hard to diagnose engine problems using text only...
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T4RFool
New member
At this point I'm grasping at straws, any and all ideas I am considering. I'm doing a lot of reading right now on valve float, weak valve springs and worn valve seats. All the symptoms I'm having can be exhibited by weak valve springs and worn valve seats. That idea is also beyond my mechanical know how though. From this point, everything that could cause this problem seems to be much more expensive than anything I've done so far and I've already put around 500 into it and haven't fixed anything.
PitbullRescuer
New member
Assuming you have a 4WD, dropping the pan is a b*tch. You have to drop the front diff to get to it. Not fun, not easy and not sure how much you would really see at that point either.
Very possible it's an issue with the heads. A bad valve seat could cause a misfire. It's a compression problem so it makes sense. However, it might actually be more cost effective to drop a good used engine in it than to pull the heads and have them rebuilt.
Very possible it's an issue with the heads. A bad valve seat could cause a misfire. It's a compression problem so it makes sense. However, it might actually be more cost effective to drop a good used engine in it than to pull the heads and have them rebuilt.
nevada
Senior Member
someone with more knowledge may chime in and correct me, but valve float at 2500 rpms? i would be really surprised if it would happen that low.
T4RFool
New member
The first time this ever happen though was at 5000rpm and has settled at 2500rpm
curtperry
New member
I would recommend that you have a look at the service manual and refer to the trouble code that you have.
Section DI-138:
DTC No.
P1300
DTC Detecting Condition
Condition
(a) is repeated 3 times consecutively during 6 con-
secutively IGT signals while engine is running (a) IGF signal is
not input to ECM for 2 or more ignitions
Trouble Area
Section DI-138:
DTC No.
P1300
DTC Detecting Condition
Condition
(a) is repeated 3 times consecutively during 6 con-
secutively IGT signals while engine is running (a) IGF signal is
not input to ECM for 2 or more ignitions
Trouble Area
- Ignition system
- Open or short in IGF and IGT circuits from igniter to ECM
- Igniter
- Ignition coil
- ECM
spectre6000
New member
curtperry: All of those things have already been addressed if I recall correctly....
Everyone else: You might be onto something with the valve/intake issues. It goes back to the intermittent fuel suspicion (the original guess as I recall). It's correct that valve float occurs at higher RPM with healthy springs. A broken valve spring could cause the same basic symptoms as valve float at a lower RPM. It wouldn't necessarily progress so much as just happen though.
What WOULD progress would be a sunken valve seat. The heads are aluminum, and valves seats love sinking in aluminum. It also wouldn't throw any codes save the associated misfire.
Start with a valve cover gasket kit and take it down that far. Just follow your manual (you have a manual right?) and you'll be able to see the valve springs and anything amiss should be pretty obvious. A sunken valve seat (where the metal around the valve seat gets soft and the pressure from the valve spring essentially uses the valve itself to pull the seat into the softened metal of the head OR it can fall out and clack around like hell in a situation called a dropped valve seat) may appear as one valve stem zeroing higher than the others (you may need to actually measure). A dropped valve seat (will be clacky and loud as hell) will appear as a valve that doesn't rise all the way (and clacks like hell). That said, a head shouldn't be that hard to replace either AND it's not something that necessarily MUST be new. It would probably be better to do so while these sorts of parts are available from the manufacturer though... Tearing down the top end is not hard to do (none of this is really, just have your manual handy and stay organized).
A history of poor oil change intervals and overheating events can contribute/cause this to happen. Ring any bells there T4RFool? Fit the PO's MO? How long have you had this thing and how much of its history do you know?
At this point, since you've done just about everything on the top end (is there any easily accessible stone that hasn't been turned over? What has NOT been actually REPLACED?), don't bother putting it back together until you find the culprit (save putting it back together to remember how things go together if there's going to be time between fiddlings). If you take it all the way apart and still haven't found the problem, sell the parts off on eBay one by one and you're down to a replacement engine regardless.
EDIT: Have you done a compression test? I don't remember seeing that, but it's one of the first things you usually look at. The tool is cheap and it can be done in 30 minutes or so.
Everyone else: You might be onto something with the valve/intake issues. It goes back to the intermittent fuel suspicion (the original guess as I recall). It's correct that valve float occurs at higher RPM with healthy springs. A broken valve spring could cause the same basic symptoms as valve float at a lower RPM. It wouldn't necessarily progress so much as just happen though.
What WOULD progress would be a sunken valve seat. The heads are aluminum, and valves seats love sinking in aluminum. It also wouldn't throw any codes save the associated misfire.
Start with a valve cover gasket kit and take it down that far. Just follow your manual (you have a manual right?) and you'll be able to see the valve springs and anything amiss should be pretty obvious. A sunken valve seat (where the metal around the valve seat gets soft and the pressure from the valve spring essentially uses the valve itself to pull the seat into the softened metal of the head OR it can fall out and clack around like hell in a situation called a dropped valve seat) may appear as one valve stem zeroing higher than the others (you may need to actually measure). A dropped valve seat (will be clacky and loud as hell) will appear as a valve that doesn't rise all the way (and clacks like hell). That said, a head shouldn't be that hard to replace either AND it's not something that necessarily MUST be new. It would probably be better to do so while these sorts of parts are available from the manufacturer though... Tearing down the top end is not hard to do (none of this is really, just have your manual handy and stay organized).
A history of poor oil change intervals and overheating events can contribute/cause this to happen. Ring any bells there T4RFool? Fit the PO's MO? How long have you had this thing and how much of its history do you know?
At this point, since you've done just about everything on the top end (is there any easily accessible stone that hasn't been turned over? What has NOT been actually REPLACED?), don't bother putting it back together until you find the culprit (save putting it back together to remember how things go together if there's going to be time between fiddlings). If you take it all the way apart and still haven't found the problem, sell the parts off on eBay one by one and you're down to a replacement engine regardless.
EDIT: Have you done a compression test? I don't remember seeing that, but it's one of the first things you usually look at. The tool is cheap and it can be done in 30 minutes or so.
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curtperry
New member
He did mention ruling out the igniter but did not say how AFAIK. There is a procedure for testing this. One thing that was not mentioned was "Open or short in IGF and IGT circuits from igniter to ECM". So checking the condition of the wires/connectors between the igniter and the ECM would be a good idea.
Not to discount the great ideas that have already been given, but I think he has already thrown enough parts at it and should instead try some proper diagnosis. The service manual provides a diagnosis flow chart for the code and that avenue should be exhausted before getting too deep into the engine. It might save him some trouble.
T4RFool
New member
There is one incident that rings a bell but I guess I cant deny that it may be the cause even though it happened years before this whole problem started. About 3-4 years ago I had a rather unpleasant incident up in the mountains of Colorado. I went through a short but deep enough water crossing that caused my clutch fan to grenade. The unfortunate part is that the fan grenaded into my radiator causing irreparable gouges and holes. I had to coast it down the mountain without a motor basically, starting it only to get the brakes juices going and to go up the few incline that there were. Needless to say the motor was hot but I was extra cautious bringing it down and stopped several times to let it cool down. After I got it down the mountain I replaced the radiator and tore it open to make sure I hadn't cracked anything. I never considered that there could have been damage to the valve, I popped a new radiator in and it ran just like it did before and I figured that I was in the clear. I never even considered it could be the cause of this current problem because it happened so long ago and driven it a lot since then.
T4RFool
New member
I have looked over and double checked any and all wires under the hood and most under the dash, I have spent close to a day using the mulitmeter to look at everything that I could check. I haven't really mentioned it though because there wasn't any results, I have checked/replaced everything that would cause the p1300 code. I wouldn't have bought an ECU unless I had checked everything else first.
spectre6000
New member
3-4 years is a long time for something like this to incubate... There's a possibility it may have been a contributing factor, but it wouldn't likely be a major cause in my mind. It did start at higher RPM and progress lower and lower so it's possible, but I wouldn't beat myself up over that.
Before we go any further, you may still try the cat if you truly think that could be at fault, and just cut it out and rev the **** to see if it'll pull past 2500 RPM. The lack of back pressure won't be very nice to your exhaust valves, but it won't do any damage for a single pull or two. At this point, I'd be calling it inop until you can figure out what's going on.
I've never seen a sunken valve seat in a modern water cooled engine in person (to be fair I've never spent that much time with modern water cooled engines), but I've seen it countless times in the VW/Porsche 2.0L TIV heads (in fact, I probably have two or three of those heads with sunken valve seats in my storage unit back in Dallas). That doesn't mean they don't happen, just that I don't have any direct experience with them. I wish I could take a picture to show you what it looks like, but a 2K mile round trip for a photo seems a little silly when Google images is right there (hell it's probably shorter to just drive to your house and eliminate the textual diagnosis nightmare). If you pop the valve cover over the appropriate bank and remove the cam, you should be able to lay a straight edge across the valves (which will all be closed). If one is high, there's your culprit. Cost: 1/2 of a valve cover gasket kit.
Again though, if nothing turns up I wouldn't bother putting it back together at this point as everything on the top end has been eliminated (in my mind with my memory, you may know of a stone you haven't turned). Inspect each part as it's removed for any signs of ANYTHING that seems marginally suspect.
Before we go any further, you may still try the cat if you truly think that could be at fault, and just cut it out and rev the **** to see if it'll pull past 2500 RPM. The lack of back pressure won't be very nice to your exhaust valves, but it won't do any damage for a single pull or two. At this point, I'd be calling it inop until you can figure out what's going on.
I've never seen a sunken valve seat in a modern water cooled engine in person (to be fair I've never spent that much time with modern water cooled engines), but I've seen it countless times in the VW/Porsche 2.0L TIV heads (in fact, I probably have two or three of those heads with sunken valve seats in my storage unit back in Dallas). That doesn't mean they don't happen, just that I don't have any direct experience with them. I wish I could take a picture to show you what it looks like, but a 2K mile round trip for a photo seems a little silly when Google images is right there (hell it's probably shorter to just drive to your house and eliminate the textual diagnosis nightmare). If you pop the valve cover over the appropriate bank and remove the cam, you should be able to lay a straight edge across the valves (which will all be closed). If one is high, there's your culprit. Cost: 1/2 of a valve cover gasket kit.
Again though, if nothing turns up I wouldn't bother putting it back together at this point as everything on the top end has been eliminated (in my mind with my memory, you may know of a stone you haven't turned). Inspect each part as it's removed for any signs of ANYTHING that seems marginally suspect.
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PitbullRescuer
New member
Spectre, you can't see the valve springs with the valve covers off. 5VZ uses bucket lifters, which go over the valve springs. With the cams in the head its hard to get a good look at the valve train. Your idea is a good one just won;t work for this application.
