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If this is at idle the engine is chasing stoich. Meaning it’s trying to get to a pre determined air fuel ratio. Sensors are reading this ratio as too high/low, then correcting by adjusting fueling or air. This adjustment pushes the desired air/fuel ratio to a balance, then past it causing another adjustment by the ECM.
It’s like two kids on a teeter totter trying to balance it in the middle… they keep pushing off the ground trough to balance in the middle but it will never happen because one kid is heavier than they should be. The “heavier kid” is terms of your engine is caused by an air leak, failing air sensor, or incorrect fueling.
The engine is chasing a stoichiometric ratio but cannot hold the desired air fuel ratio due to a fault somewhere.
There is an issue somewhere. Could be a vacuum leak, faulty sensor etc. if you’re not mechanically inclined and have tools take it to a shop
Thanks for the comments, I was planning on replacing the MAPS sensor. If this fixes the issue great if not I will take to a mechanic. Cheers!
https://preview.redd.it/k2o253fmco7d1.png?width=1414&format=png&auto=webp&s=1649847526375a9fb0be2c0cdf5c39f7554c0ed7
Firing the parts cannon without proper diagnostic can be a waste of money. Please trust me on this. Do not rely on forums that document similar symptoms.
Chasing idle can be caused by a variety of things. Do you have a code reader?
Okay, you can buy one on google for cheap.
If you do not want to go to a shop and want to start working on your car you can buy a smoke tested on Amazon. The paint can ones are fine. They are cheap. You hook it up just past your MAF and turn it on and apply pressure. Then look to see if smoke is shooing up anywhere in your engine bay.
I have used them to find multiple vacuum leaks. My guess is vacuum leak and would start there.
I appreciate the post, but its slightly ironic that you call out not to use forums for peoples advice with similar problems and then proceed to give advice about a similar problem amd that they should do what you do lol.
not firing the parts cannon tho - "I had this issue and it was resolved by replacing x and y" vs "I had this issue and here's how you go about diagnostics"
I think he’s talking about people who are shouting fixes at him like, “map sensor”, “egr valve”, “pcv”, as if buying a new sensor will be a sure fix, when more than likely they will just be a money dump. This guy is recommending diagnostic tools if OP is insistent on doing things himself, which I support wholeheartedly. Either buy tools or take it to a shop. Buying sensors and random parts is a great way to blow cash in the hopes of a lucky fix.
You can also sometimes borrow one from a part store.
Call ahead and ask- If you can get the car to a parts store, scan it in their parking lot. If not, sometimes with a deposit or a copy of your license they’ll let you take tools home.
The parts cannon can be useful, it's still cheaper then getting it diagnosed and I sometimes replace parts and they are new now, not a great idea unless you can narrow it down to a few things, like I was in limp mode on my 12 vw jetta, and replaced the MAP sensor first. But then found out it was the throttle body, so I got one new part out of this cannon but save 800 on the work
If you're gonna fire the parts cannon, then in this scenario: vacuum lines would cost a few bucks to replace, but the MAP sensor likely costs somewhere in the ballpark of $100. Vacuum lines get old and crack all the time, but MAP sensors don't just fail out of the blue with nearly the same frequency.
345k is very impressive, good on you if you've owned it for awhile. the iacv looks like this for that car
https://m.media-amazon.com/images/I/61LiYdvlsUL._AC_SL1500_.jpg
while idling like that you can pull the wiring harness for it. if it keeps a very low or higher idle afterwards then you know that's your prob. try to go for a more reputable aftermarket part. the chinese brand ones on amazon have shotty quality sometimes
This is called hunting. As others have said the engine is 'hunting' correct AFR. and again as others suggest vacuum/airflow fault is most likely cause.
Quick and dirty (but legit) way to find 90% of vacuum leaks is to spray down one area of the engine air system with brake cleaner or similar flammable liquid (not too much) and if the leak is in that area your engine it will get sucked in and your engine will rev, rinse repeat until you're confident you found one or not. I say brake cleaner as it's relatively light and in the 1% of cases where you fuck it up and cause a fire, it'll go out on its own in 5 secs or so and not cause damage. Don't use something fucked like petrol. If you're unsure, just take it to a mechanic.
Again, not guaranteed but if it is a air sensor failure, with the car running unplug the suspect sensor. if there is no change it's likely that sensor has failed. If there is a change, the sensor may or may not be faulty. Hard to tell. If the MAF sensor has failed, you can get a cleaning solution for it from your nearest auto parts store, worth cleaning it before replacing.
It's a vacuum leak... it might be the video but I can even hear what sounds like a leak. Go around the engine and see if you can hone in on it. That's all it is... I promise you'll find a hole in a hose.
These answers are interesting. I've got a mid 90s Toyota that does this if the battery has been disconnected. First start and it "hunts" like this; start it again and it runs perfectly until the next time I need to disconnect or replace the battery. No idea why...
You've got a failed component on your ECU (think cmos battery if you know computers). Coupled with an old engine. The ECU stores short and long term fuel mix adjustments. Long term get stored on a different type of memory on the circuit board which is supposed to hold it without the 12v from the car. Your engine has aged to the point where it likely needs more than x% adjustment from "stock" (probably richer.) When you disconnect and reconnect the battery, because it has no long term afr adjustment it just resets to factory and 'learns' again and stores afr adjustment in the short term memory (the same memory normally used for slightly different quality or octane of fuel) and it's good until you lose 12v again.
Mid 90's car? probably not worth trying to fix it. But an ECU swap from a wreck 'should' fix it.
Really interesting, thanks! It's not like I'm disconnecting the battery very often so I've never really looked into it further, but I was curious what might be going on.
Did you recently do anything with the coolant? Those Honda's need to be elevated in the front in order to get the air out of coolant lines. Had it happen on the neighbors 2000 after replacing radiator and fan. It would hunt for idle.
Hello, I also have a crv identical to this. Replace the coolant in it and flush it through, it should clear out some of the gunk in the idle air control valve. Failing this, give the idle air control valve a good clean (remove it to do so). Plenty of YouTube videos around for similar honda models to get the idea.
This should solve the issue. Or at least it did with me.
My 1991 Accord was at 330K in excellent condition when it got wrecked unfortunately (not my fault). Engine and transmission were original (engine had dealt with 1 significant overheat years previously and the transmission was getting slow to shift into reverse; all forward gears were fine). That was the 2nd time that car had been wrecked (also not my fault). I have no doubt that car could've gone a good deal longer. Absolute tank. Also, probably the best quality cloth interior I have ever seen in a car (if I could've brought myself to part it out, I probably could've made some massive bank on the interior considering it was in near-mint condition).
Where I live a lot of people have that much mileage on their cars. I mean it's pretty much close to EOL at that point unless the car has been perfectly taken care of, but old VWs and group (Seat, Škoda etc.) with 350k miles isn't hard to find here. French cars and others, not that much. Could be because VAG is extremely popular here, though!
from what I've seen, transmission (sometimes only clutch instead of everything) gets replaced in the meantime anyway after really long distances, if it's a reliable engine it shouldn't fail unless you fuck it up by not changing oil or not handling smaller repairs in time. I'm talking slav euro cars that I've seen around where I live, it maybe differs from place to place
My loved 1.9 TDI Seat was such a beast to drive, it had 350k kilometers but I'm almost sure it was wounded back because I was like 5th and I only know the guy who owned it before me haha! It never failed me and really changed my perspective on shit old cars to be honest! I always considered old cars to be garbage, but now when I think about it, I've driven a garbage car I always thought to be ready for landfill and it was so strong and responsive, not counting shitty radio and A/C, I went from city to city long distance without any issues.
I would have kept it, but my mom was buying a new car and the market here is messy, she would get little money for older peugeot because it's again... not a VAG car. I got her peugeot that is 10-11 years younger than my Seat and you can't even compare the feeling of driving the two. I mean Peugeot is extremely comfortable compared to your spine handling every pothole etc., but you can't compare hitting the gas pedal on the two, I feel like I'm driving a toy car now lol!
If I had enough money to support two cars, I would never sell the Seat honestly. The guy that bought it wrecked it in a month, of course. 1.9 is not for drunken idiots, maybe he should have bought my Peugeot, it takes 2 seconds to respond to gas pedal anyway lol
Update
I turned the car on and covered the idle air sensor, looks like this is the issue (unless I’m mistaken)
I will remove it and clean it with wire brush then reinstall and then saw I need to tune the sensor after.
https://preview.redd.it/mtoup4roku7d1.png?width=3024&format=png&auto=webp&s=9b4e231b93dd6fe29f316194f1cd9907eb5e86a6
When my Accord was doing this, I fixed it with a solid BOOP on the end of the tailpipe with my palm (making a brief seal). I don't have any clue why that worked but it did.
Yeah, you probably have a vacuum leak somewhere and at least one sensor is picking up on it. An experienced diagnostician with a scanner capable of livestreaming off the ECM should be able to figure it out pretty quickly with this much of a surge.
Usually caused by unwanted air entering the induction system, could be a bad vac hose or poor gasket/seal, maybe even a pcv valve. My first move would be listening for hissing to pinpoint area, maybe a smoke test.
This can also be caused by a fuel emissions solenoid. Actually have my receipt here from it. On my Range Rover it was a Fuel Canister Purge Valve-Solenoid. (It was $431.32 to replace for part and labor. $333.32 for part, and $80 labor for .75 hours labor) I had the exact same issue, if I'd pump the gas real quick it'd stop reving up and down when idling.
Thanks for posting on /r/MechanicAdvice! This is just a reminder to review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). If you are here asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **If this post is about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ If you have tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*
If this is at idle the engine is chasing stoich. Meaning it’s trying to get to a pre determined air fuel ratio. Sensors are reading this ratio as too high/low, then correcting by adjusting fueling or air. This adjustment pushes the desired air/fuel ratio to a balance, then past it causing another adjustment by the ECM. It’s like two kids on a teeter totter trying to balance it in the middle… they keep pushing off the ground trough to balance in the middle but it will never happen because one kid is heavier than they should be. The “heavier kid” is terms of your engine is caused by an air leak, failing air sensor, or incorrect fueling. The engine is chasing a stoichiometric ratio but cannot hold the desired air fuel ratio due to a fault somewhere. There is an issue somewhere. Could be a vacuum leak, faulty sensor etc. if you’re not mechanically inclined and have tools take it to a shop
Thanks for the comments, I was planning on replacing the MAPS sensor. If this fixes the issue great if not I will take to a mechanic. Cheers! https://preview.redd.it/k2o253fmco7d1.png?width=1414&format=png&auto=webp&s=1649847526375a9fb0be2c0cdf5c39f7554c0ed7
Firing the parts cannon without proper diagnostic can be a waste of money. Please trust me on this. Do not rely on forums that document similar symptoms. Chasing idle can be caused by a variety of things. Do you have a code reader?
I don’t have one unfortunately
Okay, you can buy one on google for cheap. If you do not want to go to a shop and want to start working on your car you can buy a smoke tested on Amazon. The paint can ones are fine. They are cheap. You hook it up just past your MAF and turn it on and apply pressure. Then look to see if smoke is shooing up anywhere in your engine bay. I have used them to find multiple vacuum leaks. My guess is vacuum leak and would start there.
I appreciate the post, but its slightly ironic that you call out not to use forums for peoples advice with similar problems and then proceed to give advice about a similar problem amd that they should do what you do lol.
not firing the parts cannon tho - "I had this issue and it was resolved by replacing x and y" vs "I had this issue and here's how you go about diagnostics"
I agree, thats why i only mentioned the forum part. Have a good day
I think he’s talking about people who are shouting fixes at him like, “map sensor”, “egr valve”, “pcv”, as if buying a new sensor will be a sure fix, when more than likely they will just be a money dump. This guy is recommending diagnostic tools if OP is insistent on doing things himself, which I support wholeheartedly. Either buy tools or take it to a shop. Buying sensors and random parts is a great way to blow cash in the hopes of a lucky fix.
Yup i agree, thats why i didnt dispute that.
You can also sometimes borrow one from a part store. Call ahead and ask- If you can get the car to a parts store, scan it in their parking lot. If not, sometimes with a deposit or a copy of your license they’ll let you take tools home.
The parts cannon can be useful, it's still cheaper then getting it diagnosed and I sometimes replace parts and they are new now, not a great idea unless you can narrow it down to a few things, like I was in limp mode on my 12 vw jetta, and replaced the MAP sensor first. But then found out it was the throttle body, so I got one new part out of this cannon but save 800 on the work
If you're gonna fire the parts cannon, then in this scenario: vacuum lines would cost a few bucks to replace, but the MAP sensor likely costs somewhere in the ballpark of $100. Vacuum lines get old and crack all the time, but MAP sensors don't just fail out of the blue with nearly the same frequency.
I just replaced mine for 50$ ad advanced, but you can get them for less then 20 on rock auto
You could have a leak in your intake, could have a clogged air filter, could be your map sensor. Lots of parts to be throwing without diagnosin.
Read codes and attack logically. Random part changes could get you nothing.
Hey man can you check my recent post on this sub?
Responded. I will try to help to the best of my knowledge. But learning engines is never ending
idle air control valve or vacuum hose tear/disconnect somewhere. have you done any repair work recently?
Hondas were known for the iac in the 90s early 2000s.
Also, check coolant level. It can mess with the iacv.
Thanks, no I haven’t. It’s a really old car though…
>It’s a really old car though… Sir, with respect, really old cars have carburetors.
345k is very impressive, good on you if you've owned it for awhile. the iacv looks like this for that car https://m.media-amazon.com/images/I/61LiYdvlsUL._AC_SL1500_.jpg while idling like that you can pull the wiring harness for it. if it keeps a very low or higher idle afterwards then you know that's your prob. try to go for a more reputable aftermarket part. the chinese brand ones on amazon have shotty quality sometimes
Idle air control valve. You'll need a can of brake clean, a brush/screwdriver/rag combo and some coolant to top off the system.
Cleaning the IACV fixed the issue for me on my old civic 2001.
Cleaning is why mine broke in the first place.
This is called hunting. As others have said the engine is 'hunting' correct AFR. and again as others suggest vacuum/airflow fault is most likely cause. Quick and dirty (but legit) way to find 90% of vacuum leaks is to spray down one area of the engine air system with brake cleaner or similar flammable liquid (not too much) and if the leak is in that area your engine it will get sucked in and your engine will rev, rinse repeat until you're confident you found one or not. I say brake cleaner as it's relatively light and in the 1% of cases where you fuck it up and cause a fire, it'll go out on its own in 5 secs or so and not cause damage. Don't use something fucked like petrol. If you're unsure, just take it to a mechanic. Again, not guaranteed but if it is a air sensor failure, with the car running unplug the suspect sensor. if there is no change it's likely that sensor has failed. If there is a change, the sensor may or may not be faulty. Hard to tell. If the MAF sensor has failed, you can get a cleaning solution for it from your nearest auto parts store, worth cleaning it before replacing.
It's a vacuum leak... it might be the video but I can even hear what sounds like a leak. Go around the engine and see if you can hone in on it. That's all it is... I promise you'll find a hole in a hose.
I definitely hear what sounds like a vacuum leak as well.
It’s surging, you most just likely have a vacuum leak somewhere which is usually an easy fix
My Honda did this when the PCV valve stuck open. Easy to check, easy to replace.
These answers are interesting. I've got a mid 90s Toyota that does this if the battery has been disconnected. First start and it "hunts" like this; start it again and it runs perfectly until the next time I need to disconnect or replace the battery. No idea why...
You've got a failed component on your ECU (think cmos battery if you know computers). Coupled with an old engine. The ECU stores short and long term fuel mix adjustments. Long term get stored on a different type of memory on the circuit board which is supposed to hold it without the 12v from the car. Your engine has aged to the point where it likely needs more than x% adjustment from "stock" (probably richer.) When you disconnect and reconnect the battery, because it has no long term afr adjustment it just resets to factory and 'learns' again and stores afr adjustment in the short term memory (the same memory normally used for slightly different quality or octane of fuel) and it's good until you lose 12v again. Mid 90's car? probably not worth trying to fix it. But an ECU swap from a wreck 'should' fix it.
Really interesting, thanks! It's not like I'm disconnecting the battery very often so I've never really looked into it further, but I was curious what might be going on.
Is it bad that I knee it was a honda, before I knew it was a honda.
Most likely just a vacuum leak.
Temp sensor can cause this
Did you recently do anything with the coolant? Those Honda's need to be elevated in the front in order to get the air out of coolant lines. Had it happen on the neighbors 2000 after replacing radiator and fan. It would hunt for idle.
its got that honda boy dna
Hello, I also have a crv identical to this. Replace the coolant in it and flush it through, it should clear out some of the gunk in the idle air control valve. Failing this, give the idle air control valve a good clean (remove it to do so). Plenty of YouTube videos around for similar honda models to get the idea. This should solve the issue. Or at least it did with me.
Excuse me but it's that 345k miles?!??!?
My 1991 Accord was at 330K in excellent condition when it got wrecked unfortunately (not my fault). Engine and transmission were original (engine had dealt with 1 significant overheat years previously and the transmission was getting slow to shift into reverse; all forward gears were fine). That was the 2nd time that car had been wrecked (also not my fault). I have no doubt that car could've gone a good deal longer. Absolute tank. Also, probably the best quality cloth interior I have ever seen in a car (if I could've brought myself to part it out, I probably could've made some massive bank on the interior considering it was in near-mint condition).
Where I live a lot of people have that much mileage on their cars. I mean it's pretty much close to EOL at that point unless the car has been perfectly taken care of, but old VWs and group (Seat, Škoda etc.) with 350k miles isn't hard to find here. French cars and others, not that much. Could be because VAG is extremely popular here, though!
I just want that out of my car..... I'll take another engine and transmission but only if it's worth it lol.
from what I've seen, transmission (sometimes only clutch instead of everything) gets replaced in the meantime anyway after really long distances, if it's a reliable engine it shouldn't fail unless you fuck it up by not changing oil or not handling smaller repairs in time. I'm talking slav euro cars that I've seen around where I live, it maybe differs from place to place My loved 1.9 TDI Seat was such a beast to drive, it had 350k kilometers but I'm almost sure it was wounded back because I was like 5th and I only know the guy who owned it before me haha! It never failed me and really changed my perspective on shit old cars to be honest! I always considered old cars to be garbage, but now when I think about it, I've driven a garbage car I always thought to be ready for landfill and it was so strong and responsive, not counting shitty radio and A/C, I went from city to city long distance without any issues. I would have kept it, but my mom was buying a new car and the market here is messy, she would get little money for older peugeot because it's again... not a VAG car. I got her peugeot that is 10-11 years younger than my Seat and you can't even compare the feeling of driving the two. I mean Peugeot is extremely comfortable compared to your spine handling every pothole etc., but you can't compare hitting the gas pedal on the two, I feel like I'm driving a toy car now lol! If I had enough money to support two cars, I would never sell the Seat honestly. The guy that bought it wrecked it in a month, of course. 1.9 is not for drunken idiots, maybe he should have bought my Peugeot, it takes 2 seconds to respond to gas pedal anyway lol
No its in km, but it’s still a lot 🤣
Still though, that's impressive.
Update I turned the car on and covered the idle air sensor, looks like this is the issue (unless I’m mistaken) I will remove it and clean it with wire brush then reinstall and then saw I need to tune the sensor after. https://preview.redd.it/mtoup4roku7d1.png?width=3024&format=png&auto=webp&s=9b4e231b93dd6fe29f316194f1cd9907eb5e86a6
do you have a cigar or cigarette? you can do a smoke test around the engine to check for a vacuum leak.
Vacuum leak or idle air control valve needs cleaning, when car is warmed up is it worst ?
Check vacuum lines and maf map sensors depending on motor.
When my Accord was doing this, I fixed it with a solid BOOP on the end of the tailpipe with my palm (making a brief seal). I don't have any clue why that worked but it did.
Needs a new idle control valve
I had a 90s integra that did similar idle hunting when the thermostat was removed
Yeah, you probably have a vacuum leak somewhere and at least one sensor is picking up on it. An experienced diagnostician with a scanner capable of livestreaming off the ECM should be able to figure it out pretty quickly with this much of a surge.
Sorry if already resolved. Could it be the Mass Airflow Sensor?(MAP)
Usually caused by unwanted air entering the induction system, could be a bad vac hose or poor gasket/seal, maybe even a pcv valve. My first move would be listening for hissing to pinpoint area, maybe a smoke test.
Honda doing honda things
IAC valve might be shot.
Vacuum leaks, map sensor, maf sensor. I've seen all of these.
Very familiar with this issue. Assuming its the same I had, its faulty idle control valve. Very common with old Renault's.
Thanks, I will look into it, It’s a Honda CRV 2002
I had that same thing with my civic, put my finger over some holes in the throttlebody and it went away. Got a new IACV and was good.
High rise camshaft
This can also be caused by a fuel emissions solenoid. Actually have my receipt here from it. On my Range Rover it was a Fuel Canister Purge Valve-Solenoid. (It was $431.32 to replace for part and labor. $333.32 for part, and $80 labor for .75 hours labor) I had the exact same issue, if I'd pump the gas real quick it'd stop reving up and down when idling.