David923

A I just bought a 97 Civic DX auto and the car wont pass smog cuz it doesnt stay at a constant rpm it jumps around all the time just changed the o2 sensors,throttle body twice,air filter,and fuel filter and its better but same problem and there is no codes any ideas on what it can be?? plzz help
It did have codes1298 high input,p0135 o2 sensor, p0141 o2 sensor and p0501 speed sensor range/performance but it all got fixed changing a burnt fuse #15

David923

a couple of mechanics said that too much air is getting through and another said that to much gas was getting through and thats why it wont stay at a constant speed it works normal when i disconnect the tps...I have no idea what it can be????

gearbox

iTrader: (95)

tps is the problem. make sure when you get a new throttle body, its for auto trans and not manual.

David923

I did. Both the throttle bodys I bought were for auto trans...Can it be anything else??

CivicRage

David923

haha i know i read alot of threads its all the same..i do want to check my idle air control valve though i dont know how to check it??

David923

And I meant when I disconnect the MAP sensor it works fine...

gearbox

iTrader: (95)

well that makes quite a bit of difference. sorry i couldnt read your mind when you said tps but meant the map sensor. you guys would probably be more welcome over at honda-tech. and no, most of us here are not mechanics, we are amateurs who work on cars in our little bit of spare time. yet you somehow expect us to solve all your problems, for free on the internet, because you cant figure it out yourself and too cheap to visit a mechanic that can actually diagnose a car in person. if you think the forum is not helping, you are free to leave. nobody is forcing you to stay.

David923

i didnt say this **** dont work i said i read alot and there all the same any help or guess is appreciated cuz ive tooken it to mechanics and thats all they do as well but i dont have the money to keep taking it to a mechanic...so i got on this so gear box can u help ?? and how do i check the idle air control valve??

CivicRage

CivicRage

gearbox

iTrader: (95)

if that is how you expect to get help for a problem, by going around to forums and telling everyone how worthless they are, im not surprised nobody has bothered to say anything. you need to understand we are not trained mechanics, just regular people with other interests, one of which is cars, but not our main profession. so ofcourse you have to expect educated guesses and random comments. if many different mechanics could not solve your problems, how do you expect some group of online forum members to do any better except offer suggestions? im sure you are frustrated, but cars are complicated. thousands of parts, lots of things can go wrong, and nobody knows everything about how an engine works. have you tried hooking up your data logger to see what the throttle positions are, it should be 10% closed and 90% when fully open. is your throttle plate loose, is the gasket between throttle body and intake manifold leaking air, what about the iac gasket, etc. unfortunately with so many parts, you have to go thru and slowly eliminate parts. like i mentioned in your other thread, the tps sensor could have cracked internally and you would never even see it unless you take it apart and look. the sensor is plastic and has a strong spring loaded mechanism with a plastic key hole. the throttle body connector is metal, so it can easily crack the sensor over time and throw off the readings. if you have an older pre-2001 civic, there is also a fast idle valve that can go bad or get loose inside. it can cause erratic idle and stalling. we are trying to help, but you cant expect a quick fix. try checking the pcv valve too.

gearbox

iTrader: (95)

its somewhere in this thread if you want to clean it

https://www.civicforums.com/forums/7...e-up-mods.html

David923

thanks gearbox i wiill check all that tomarrow bcuz i cant see ishh rite now.... one question is there any possibility that the o2 sensors can be causing this?? bcuz when i changed the o2 sensors i still had p1298 eld high input and i think it might of damaged the sensors


also thanks civicrage but i already did change the MAP sensor as i said i bought 2 Throttle bodys with everything and still does the same thing...i hope its nuthin bigger

CivicRage

CivicRage

CivicRage

gearbox

iTrader: (95)

okay i see why you are upset after changing all that stuff and still having problems. from your info, i would say the tps is fine. the idle screw should not need adjusting, since it is controled by the ecu. since the ecu is probably fine also, it sounds like there is a physical problem with air delivery. possibly there is a problem with the throttle plate not sealing properly, and there is a different amount of air going inside than what the ecu thinks. so it tries to constantly adjust the iac to let in more or less air, which can cause rough idle because the air speed always changes.

some things to check with the intake which im sure youve done, but i will add it anyway: change the pcv valve, make sure the vacuum hose connecting the engine to the intake is not kinked or bent. also check the pcv hose line and be sure it is not leaking air. i know youre tired of the iac but it is also possible that the sensor has just failed. sometimes cleaning does not help and the sensor must be replaced. what happens if you unplug the iac with the engine on? if you unplug a working valve, the rpms should increase or fluctuate. if the valve is bad, nothing will happen when you unplug it. what happens when the sensor is plugged in and you use load-bearing accessories like the a/c? does the idle quickly drop and recover? or does nothing happen...

also, if the engine is running and you put your fingers to block the airflow going to the iac valve, the rpms should drop noticably. if they do not, you may have potential vacuum leaks at pcv valve or its hose, evap canister purge valve (if equipped with evaporative emissions control), intake manifold (possibly from crack in manifold or bad seal to the head, throttle body (check gasket between IM and TB), or brake booster hose.

also make sure the ignition timing is properly set.

since this has not been mentioned before, and since im guessing you dismantled the throttle body from the engine to clean it, you must perform the idle learn procedure to set the idle speed. with the engine warmed up after driving, turn the car off and disconnect the battery for a minute. reconnect, close the hood, and start the engine. make sure all accessories and lights are off, and do not press the gas pedal. let the car idle in park or neutral for 10 mins. shut off the engine, then restart and go for a drive. see if this fixes it. i remember on my auto, after cleaning the intake components and putting everything back, i had a jumpy idle until i performed the learn procedure. then idle is perfect at 700rpms.

CivicRage

David923

no i didnt replace it becuz it seems to be working fine and and the transmission feels fine... i checked for vaccum leaks (none) but my pcv valve is clogged bad man its a bitch to get to no space...well by checking this i ripped the hose have to get a new one lol...but hopefully that was the problem i doubt but hopefully lol

CivicRage

gearbox

iTrader: (95)

i can only try and comment on your problems compared to my own car, which is a newer gen than yours and some things will be different. most civic seem to be able to run just fine without any air intake from what ive noticed. the only sensor it has is air temp, and so long as its plugged in, it doesnt matter where it is. our engines do not need intake vacuum for any specific part to function like some other cars do (these cars usually have a MAF sensor built into the intake hardware). or if you meant the idle is more stable with the intake off, it does point to a map sensor issue, since that sensor uses incoming air pressure to figure out how much fuel to add.

you brought up headgasket, and the only way that would cause rough idle (and misfires) is if coolant was leaking into the cylinders. its really easy to check. just pull the plugs out and look for white residues on them. but even then, usually after the coolant burns off, the car will idle normally. im starting to think the mechanic may have not lined up all the timing marks exactly right. you have to go by whats most logical. if it started happening after the work you had done, chances are the work is to blame. compression check should only take 5 minutes, so not sure what his problem is not to do it. but i dont think the headgasket is bad. did he do a valve adjustment when performing all the other work?

which brand of oxygen sensor did he use, because that can cause issues too if its the wrong type (narrow/wide) or slightly different voltages. or if it was damaged during install which is VERY easy to do if youre careless (dropping it 12 inches off the ground, getting antisieze or other fluid on it, etc). i had a similar situation where the auto store sold me a secondary sensor (for the cat) instead of a primary and i had all sorts of problems with hesitation and acceleration lag. even if the voltage reads normal, hondas are very picky with their sensors and parts. ive seen a honda start misfiring with bosch plugs, yet go back to normal with ngk or denso. same with o2 sensors, they seem to prefer ntk (not ngk) or denso.

your map sensor, even when bad, doesnt seem like it would cause idle issues. i can check my sensor reading, however they are different motors and could have different operating voltage. you can probably find it in a haynes manual for your year of car tho. make sure the map sensor bolt is not tightened more than 3 ft/lbs and the 0-ring is not squished flat. whats puzzling is the check engine light should have come on if the idle is not steady or if any sensor is to blame.

gearbox

iTrader: (95)

also make sure the map sensor is getting 5V signal with the ignition on.

CivicRage

gearbox

iTrader: (95)

yeah usually valves should be adjusted around 100k miles or if they start to get noisy/tick. eventually it will start sounding like a diesel. if the shop was really cheap, they wouldve used a universal o2 sensor and spliced the wiring, and this will cause massive problems due to changing the wire lengths and possibly the voltages. hopefully they used a plug-in type otherwise youre gonna have a wiring mess to fix when you go to install the new sensor. make sure the map sensor is getting a full 5V, just to rule that out. but my bet is on the o2 sensor. the primary sensor is the most important because it determines how the engine runs. secondary is just there to tell the ecu that the cat is working.

CivicRage

CivicRage

gearbox

iTrader: (95)

oh man all this over an o2 sensor installed wrong. yeah you got lucky and can just unplug the whole mess and throw it out. then plug in the oem sensor to the factory harness when you get it. dont forget to do the whole ecu reset and idle learn over again so the new readings from the sensor can adjust. and make sure the new wiring gets clamped into the oem holders as it runs from the plug to the sensor hole in the exhaust. hopefully this fixes everything.

CivicRage

Let us Pray.

CivicRage