Loss of power and backfiring?

[Dog in Da Cruiser]

Hi there, Ive been having a couple issues with my 97 80 series. A couple days ago I noticed that sometimes usually accelerating from a stop, or even just moving under 30 or so MPH, the vehicle seems to experience a loss of power sometimes between 1200 and 2700 RPM's, Ill have to mash the peddle to the floor and shoot the RPM's up to 3k in order to get moving. Also occasionally ill start the vehicle and ill get a rough idle that is somewhere between 300 and 500 RPM's, the idle is rough enough to shake the vehicle and physically feel it, it goes away if I restart the vehicle or just give it a tiny blip of throttle. The rough idle is occasional but has happened to me when the vehicle is both warm and cold. Today as I was driving home from work at about 20 MPH, I noticed a popping or backfiring sound and the RPM's would jump between 1k to 1200 while applying no extra throttle. Ive not gotten a single check engine light during any of this. Im not sure if its worth noting but the previous owner deleted the EGR, Ive had this vehicle for about 5K miles and Im just now experiencing these issues. I read a similar post about this and I think that ill start by replacing the spark plugs and o2 sensor but other than those im not sure what else to do, any advice is appreciated. Thanks!

Also I have a video of the vehicle backfiring or popping, if you would like to hear it or know what it may be feel free to send me a message and ill shoot you the youtube link!

 

[devo]

I’m throwing in the TPS?

 

[Fj80oregon]

There was a post recently with similar symptoms and he had a broken spark plug that broke at the porcelain and was causing it to backfire.

 

[ToyotaWeapon]

Check the Intake Duct Tube between the Air Cleaner and Throttle Body. Take it out completely and check for cracks or leaks. High mileage or older Landcruisers heat and vibration underhood can crack the rubber intake parts resulting in air leaks and poor performance including stalling and popping.

ToyotaWeapon

 

[DIRTBIKEUSA]

Sounds ignition related.

 

[Dog in Da Cruiser]

Check the Intake Duct Tube between the Air Cleaner and Throttle Body. Take it out completely and check for cracks or leaks. High mileage or older Landcruisers heat and vibration underhood can crack the rubber intake parts resulting in air leaks and poor performance including stalling and popping.

ToyotaWeapon

Thanks for the advice, tomorrow I will rip it out and check it, a few days ago I did soak it all down with carburetor cleaner while the engine was running and I didn’t hear the RPMs fluctuate at all but it definitely needs a thorough check.

 

[Dog in Da Cruiser]

Sounds ignition related.

I thought so too at first, a couple days ago I replaced the plugs and wires but that hasn't seemed to change anything.

 

[DIRTBIKEUSA]

If everything outside the engine checks out, look into checking valve cam clearances.

 

[robnicko]

When changing the plugs and wires did you check inside the distributor cap incase its leaking oil in there?

 

[BILT4ME]

I really hope you didn't spray carburetor cleaner all over under the hood.
Carb cleaner will melt plastics, etch paint, and can attack some rubber products.

There are many things this could be. Personally, I would do the following:
Inspect intake tube
Install new OEM plugs, wires, cap, rotor.
Inspect valve cover for vacuum and oil leaks, particularly around the spark plug seals and oil cap.
Then check all vacuum hoses
New PCV valve and hose.

Prior to starting, with key in the RUN position, do you have a CEL?
If not, it's possible that your PO removed the bulb since he defeated the EGR. So you may actually be throwing codes, you just don't know it.

Get an UltraGauge to monitor your truck. Maybe it's an O2 sensor acting up and you can't monitor it.

 

[LandCruisinMy93]

Oh boy. Immediately my mind goes to an ignition/timing issue. Whether it is that the timing is off or the cap and rotor, plugs, plug wires are bad....but it have also seen stuff like this caused my ground wires coming off. Had a 2003 3.5l altima that would start, idle low and then backfire and die...trouble shot for days and found 2 grounds broken off the engine. Reconnected them and it ran fine. 1989 Honda civic motor swapped, customer had video of the thing shooting fireballs out the exhaust and a slough of issues...wiring harness grounds also. The kid didn't think he needed to attach all grounds. Some aren't daisy chained.

The last thing that comes to mind is utterly plugged catalytic converters.

 

[BILT4ME]

I really hope you didn't spray carburetor cleaner all over under the hood.
Carb cleaner will melt plastics, etch paint, and can attack some rubber products.

There are many things this could be. Personally, I would do the following:
Inspect intake tube
Install new OEM plugs, wires, cap, rotor.
Inspect valve cover for vacuum and oil leaks, particularly around the spark plug seals and oil cap.
Then check all vacuum hoses
New PCV valve and hose.

Prior to starting, with key in the RUN position, do you have a CEL?
If not, it's possible that your PO removed the bulb since he defeated the EGR. So you may actually be throwing codes, you just don't know it.

Get an UltraGauge to monitor your truck. Maybe it's an O2 sensor acting up and you can't monitor it.

Fuel injected engines don't backfire unless wiring is shorting out or there is a major fueling issue.

 

[Dog in Da Cruiser]

I really hope you didn't spray carburetor cleaner all over under the hood.
Carb cleaner will melt plastics, etch paint, and can attack some rubber products.

There are many things this could be. Personally, I would do the following:
Inspect intake tube
Install new OEM plugs, wires, cap, rotor.
Inspect valve cover for vacuum and oil leaks, particularly around the spark plug seals and oil cap.
Then check all vacuum hoses
New PCV valve and hose.

Prior to starting, with key in the RUN position, do you have a CEL?
If not, it's possible that your PO removed the bulb since he defeated the EGR. So you may actually be throwing codes, you just don't know it.

Get an UltraGauge to monitor your truck. Maybe it's an O2 sensor acting up and you can't monitor it.

Nope lol just carb cleaner around the intake hose and I made sure to give everything a wipe down with a damp rag afterwards.
I just put in OEM plugs and wires.

Now I feel really dumb, just went outside to the driveway and checked. Looks like I don't have a CEL light (can't believe I missed it every time I've started the truck). Plugged in my OBD reader and got a P0340 code which from my five minutes of searching looks like it is a cam position sensor which is built into the distributor assembly. Do you think that this could be part of the problem or an unrelated issue?

 

[BILT4ME]

Nope lol just carb cleaner around the intake hose and I made sure to give everything a wipe down with a damp rag afterwards.
I just put in OEM plugs and wires.

Now I feel really dumb, just went outside to the driveway and checked. Looks like I don't have a CEL light (can't believe I missed it every time I've started the truck). Plugged in my OBD reader and got a P0340 code which from my five minutes of searching looks like it is a cam position sensor which is built into the distributor assembly. Do you think that this could be part of the problem or an unrelated issue?

I absolutely think this could be it.

The cam sensor will assist in adjusting timing and basically the ECU has no idea what the timing should be doing and adjusts it randomly and could cause backfire or severe loss of power

 

[Dog in Da Cruiser]

I absolutely think this could be it.

The cam sensor will assist in adjusting timing and basically the ECU has no idea what the timing should be doing and adjusts it randomly and could cause backfire or severe loss of power

I did a bit more research and I believe that the only way to buy a new cam position sensor is if i buy the full distributor assembly. Now before I spend a couple hundred bucks on a distributor, by any chance are you able to explain to me why the car would lack power in the lower RPMs and then when the RPMs increase to about 3k and above the power is back. Im still new to turning wrenches on my vehicles and understanding mechanical systems like these, but to me it would seem that if the cam sensor assisted and effected timing, would it not do that throughout the whole RPM range from idle to redline? Therefore a faulty cam sensor would mean a loss in power no matter the current RPM. Why does the issue seem to "disappear" once I go above 3k RPM.

Im not sure if my question makes any sense and/or the answer is very simple, but I don't entirely understand.

 

[BILT4ME]

I did a bit more research and I believe that the only way to buy a new cam position sensor is if i buy the full distributor assembly. Now before I spend a couple hundred bucks on a distributor, by any chance are you able to explain to me why the car would lack power in the lower RPMs and then when the RPMs increase to about 3k and above the power is back. Im still new to turning wrenches on my vehicles and understanding mechanical systems like these, but to me it would seem that if the cam sensor assisted and effected timing, would it not do that throughout the whole RPM range from idle to redline? Therefore a faulty cam sensor would mean a loss in power no matter the current RPM. Why does the issue seem to "disappear" once I go above 3k RPM.

Im not sure if my question makes any sense and/or the answer is very simple, but I don't entirely understand.

Yes, your question makes sense.

This is why it's very important to PROPERLY diagnose the issue.
Step one was to read the code.
Step two is to get the FSM and go through the procedure to confirma that is the problem.

I understand why you're asking that.
If the sensor is supposed to give a reading to the ECU, the the ECU will adjust the timing accordingly. If the sensor it "stuck" in one place, then the engine will have one "sweet spot" that it runs well.
If the sensor is giving random, erroneous readings then the ECU will continuously adjust the timing advanced and retarded to compensate and may make it so you have no good running places on the RPM range.
If it gives no reading then the ECU will have a default timing to allow it to limp.

If the inside of your distributor is coated in oil that could be a cause of the failure.

Also check the plug in connection on top of the distributor, as those are known to have wire breakage from people leaning on it. Unplug it and replug and inspect those wires.

 

[CharlieS]

I did a bit more research and I believe that the only way to buy a new cam position sensor is if i buy the full distributor assembly. Now before I spend a couple hundred bucks on a distributor, by any chance are you able to explain to me why the car would lack power in the lower RPMs and then when the RPMs increase to about 3k and above the power is back. Im still new to turning wrenches on my vehicles and understanding mechanical systems like these, but to me it would seem that if the cam sensor assisted and effected timing, would it not do that throughout the whole RPM range from idle to redline? Therefore a faulty cam sensor would mean a loss in power no matter the current RPM. Why does the issue seem to "disappear" once I go above 3k RPM.

Im not sure if my question makes any sense and/or the answer is very simple, but I don't entirely understand.

I'm in the camp of making sure the basics are taken care of, and following the FSM.

Idle issues I've found have been largely vacuum leaks. Spraying stuff around the engine bay wasn't ever helpful for me, but smoke testing was very effective.

Have you made any changes or modifications before this started? I always like to go back to the things I've messed with to make sure I didn't inadvertently cause the issue (and I have many times).

Like for example, is there any chance that when you put in the new plugs and wires that you might have swapped the spark plug leads on either the distributor or the plug end? If you're firing a plug in the wrong part of the cycle, I could see it backfiring.

I know this is some sort of bias I have since I chased a similar sounding issue with bogging at low RPMs, but between putting in a new TPS (and they do go bad) and adjusting both the throttle and accelerator cables I was able to eliminate a very similar sounding behavior. The FSM has a procedure for properly adjusting the TPS that isn't difficult. The throttle and accelerator cables are a little less precise, but the FSM addresses how to adjust them. It is surprising what a small amount of adjustment can do for throttle behavior.

 

[Dog in Da Cruiser]

I'm in the camp of making sure the basics are taken care of, and following the FSM.

Idle issues I've found have been largely vacuum leaks. Spraying stuff around the engine bay wasn't ever helpful for me, but smoke testing was very effective.

Have you made any changes or modifications before this started? I always like to go back to the things I've messed with to make sure I didn't inadvertently cause the issue (and I have many times).

Like for example, is there any chance that when you put in the new plugs and wires that you might have swapped the spark plug leads on either the distributor or the plug end? If you're firing a plug in the wrong part of the cycle, I could see it backfiring.

I know this is some sort of bias I have since I chased a similar sounding issue with bogging at low RPMs, but between putting in a new TPS (and they do go bad) and adjusting both the throttle and accelerator cables I was able to eliminate a very similar sounding behavior. The FSM has a procedure for properly adjusting the TPS that isn't difficult. The throttle and accelerator cables are a little less precise, but the FSM addresses how to adjust them. It is surprising what a small amount of adjustment can do for throttle behavior.

I believe the only things I have done inside the engine bay so far was a new power steering pump, new drive belts, and a new fuseable link all of which have been replaced a couple thousand miles before these issues arose.

When I was doing plugs and wires it was in response to this issue, but it never hurts to double check and see that I've got them all in order.

I will look into the TPS as well as the cables, thank you for the insight.

 

[Dog in Da Cruiser]

Yes, your question makes sense.

This is why it's very important to PROPERLY diagnose the issue.
Step one was to read the code.
Step two is to get the FSM and go through the procedure to confirma that is the problem.

I understand why you're asking that.
If the sensor is supposed to give a reading to the ECU, the the ECU will adjust the timing accordingly. If the sensor it "stuck" in one place, then the engine will have one "sweet spot" that it runs well.
If the sensor is giving random, erroneous readings then the ECU will continuously adjust the timing advanced and retarded to compensate and may make it so you have no good running places on the RPM range.
If it gives no reading then the ECU will have a default timing to allow it to limp.

If the inside of your distributor is coated in oil that could be a cause of the failure.

Also check the plug in connection on top of the distributor, as those are known to have wire breakage from people leaning on it. Unplug it and replug and inspect those wires.

That makes so much more sense, thank you.

I just got my FSM so I'll give that a look and see. I will also check for oil in the distributor, as well as the plug on top of the distributor.

 

[Albatross80]

One more thing to check before you throw the parts at the problem. And it's easy, fast and free to do.

Air, fuel spark and COMPRESSION.

Rent a compression gauge from the auto parts store and check all the cylinders. If two cylinders that are next to each other have wonky/low compression you likely have a blown head gasket between cylinders.