pray4locust

2001 honda civic ex automatic. completely stock for now. my car recently popped up a p1129 code. It idles rough and hits what seems to be the revlimit at about 3000 to 4000 rpms in every gear while driving. When i come to a stop it drops to about 600 rpms or lower and even dies out some times. I cleared the code (after documenting the freeze frame). It only seems to do it after reaching operating temp.

I have changed the map sensor (since it wasn't very expensive) and i am going to remove the iacv to check it tomorrow (gasket is on order).

I am looking for any suggestions. If you have had this problem and fixed it please post I am in need of serious help. I don't have much time to work on it as i work alot so simple suggestions first please.

MelJ

Have you checked to see if there are any leaks? The sensor could be functioning properly giving the PCM the info that something isn't right with vacuum. Cleaning the IAC seems like a place to start though. Just keep the vacuum thing in the back of your mind.

pray4locust

I meant to add that i was going to do that. Thank you though, those are exactly the kind of suggestions im looking for.

pray4locust

Ok. So after searching at five different parts houses for an iacv gasket (which apparently doesn't exist) I settle for some gasket maker.

I also find that the screws holding the iacv on are Phillips head screws. I personally hate when company use Phillips head screws on something that needs to be tightly secured.

Instead of stripping the screws in attempt to remove them, I settle for removing both lines connected to the valve and cleaning them and the ports. I also cleaned the slot on the inside of the intake on the throttle body.

I also checked for vacuum leaks (I even used the old garden hose trick.) And found none.

I cleared the code and did thirty minutes of driving (highway and city) and also let it idle for thirty minutes. The code has not reappeared. I did everything I could to make it come on. It is running perfectly now.

I will post again tomorrow to see how it acts after a cold soak.

pray4locust

Sorry its been a couple of days.

Wednesday the car ran perfectly. It had a cold soak and there were no problems. Thursday however on my way to work it popped up the code again and started acting up. I have cleaned it two more times and still no fix. Any suggestions?

pray4locust

I read somewhere to try an idle relearn on my car. Clear the code, idle for ten minutes, then drive. This worked for two days and the drive to work this morning. On my way home I stopped for fuel and after filling up the code popped up again and the usual symptoms returned. After thinking about it I think that a fill up has caused this before but since it was already messed up I didn't put too much thought into it. Someone please help!!!! This is very irritating!!!

lazlong

Filling up the tank wouldn't cause P1129.

Put a scan tool w/data feed on it and see if your getting 1.1V or less. If not, you have a bad wire/connection.

If you don't have access to a scan tool, check the grounds and check over the wire harness real good- especially where it goes thru the firewall, at the sensor connection, and the ECM/PCM..

pray4locust

thank you for replying.

I'm sorry for not specifying about the fill up. What i meant by that was that when i remove the fuel cap it seems that there is pressure behind it which is leading me to believe that the problem is somewheres in the fuel delivery system. i.e. fuel pump, fuel filter, injectors. Maybe something cannot stabilize the pressure fast enough after release?? I don't know why that would have anything to do with the map sensor, but i'm starting to get desperate. I unplugged the iac valve on the ride to work today and it seems to me that there is a studder in acceleration. Maybe the computer is trying to compensate for a dead cylinder?? I will check spark plugs and connecting equipment tomorrow but for the most part i am at a loss for what it might be.

i checked the wires and everything seems fine. I borrow a scanner from a freind. The scanner is new and one of the more advanced ones and it seems that the ecm is fine but i cant get rid of this danged map problem.

MelJ

That's depressurizing the fuel system. That hiss is any pressure remaining in the system when you take the gas cap off.

pray4locust

i was told to replace ect sensor beacuse that is the only thing that could cause my civic to go into limp mode but no dice.

I thought that maybe the pcv valve could have gone out causing the manifold to build pressure so i cleaned, and checked it but no dice on that either.

im starting to think that maybe my catalytic converter is plugged up and my secondary o2 sensor is bad. maybe this combination of the two things is not throwing a cel but is building manifold pressure and causing that cel to pop up.

ALL suggestions are welcome at this point.

MelJ

You can test the ECT if you wanna be sure that's the issue. I'd think that the car would throw a code for the circuit voltage being too high or low though. You should have 5 volts between reference voltage and a ground. Same with the reference voltage and return line. Should read 5 volts. I don't know how tech savvy you are, but the test itself isn't too confusing.

pray4locust

I changed the Ect with a brand new one. Voltages are fine and it is producing accurate temp readings.

Do you think that the cat problem is viable?

frex19500

i have a similar problem but mi engine lamp is not on, the revs are going up and down when the car is stoped, fluctuating in iddle to 700 and 500 i´ve went to a place and they cleaned the throttle body an the IAC , injectors and change the spark plugs, the car was fine for 3 days i was so happy, but now is again with the same sintoms, i guess they didn´t clean it well, but i guess the problen is on the IAC. i have a 2001 civic EX,with MT

pray4locust

I have cleaned the iac, throttle body, had a pressurized fuel rail and injector clean, and I changed the plugs and coils.

The more I read about plugged cats the more it sounds like a viable answer. I am getting new exhaust system this weekend and I will update whether the problem is fixed or not.

And you may also want to check your Pcv valve. I have the haynes Manuel so pm me if you need pictures and instructions.

jim1123us

I'm having a similar problem with my 02 civic ex. My plan is to attempt to pull the cat off tomorrow and see if it's blocked. If I'm not successful I'll throw in the towel and bring the car in. Any pointer on dropping the cat?

pray4locust

I dont know if you know but there is a way to bypass the second o2 sensor and run no cat. That is what i will be doing. They sell "test pipes" which is a basic bolt on pipe to replace the cat, but i am bringing mine to a muffler shop and getting complete new exhaust.

The weird thing im starting to notice is not only how rare this problem is but that it is only for the civic ex. If the exhaust change doesn't fix the problem im probably going to start looking for the problem with the differences between the ex and other model civics of the same year.

lazlong

Go out there right now and hit the bolts with penetrating oil. I probably won't help but, it never hurts. Your probably gonna have to cut them off anyways. Also it's a good idea to buy new springs for the bolts.

pray4locust

well sadly there is no fix.

just got back from the muffler shop. I had the cat removed and a new muffler put on. the car sounds great and a little bit of a power increase but the cel still comes on does the same things. I also put my o2 bypass mechanism on and there are no problems with that.

I guess my next move is to check out the egr valve. I unplugged the egr valve while the car was running on there was no change and the cel stayed off. While it was still unplugged i restarted the car and still no change and the cel stayed off.

im still at a loss for what this might be.

lazlong

Stupid question: Did you change the MAP sensor? Or at least see if it was reading correct to the comp?

pray4locust

Lol. Yes I changed and tested the map sensor. That was the first thing I did.

lazlong

^^ Yeah, I figured as much. Try cleaning the EGR.

jim1123us

Sorry to hear removing the cat did not help. I spend the morning attempting to pull the cat off mine, but despite the penetrating oil, I only managed to break one nut free. After hearing that your trip to the muffler shop did not work i'm not sure what my next move will be.....

pray4locust

i bought the gasket for the egr valve today and will be cleaning the egr tomorrow. I have had to clean the egr on another vehicle before. i had a 95 blazer and there was a carbon rock keeping the valve wide open but it caused the vehicle to idle more drastically.

I also changed to a cai today and it takes the cel a while longer to come on now which is making me think it is the egr.

pray4locust

Still no fix!!!!!!

I took off the egr valve and cleaned the hell out of it and the ports on the motor. The car still does the exact same thing. And yes the egr did have ALOT of buildup. Im thinking maybe the egr itself is not working but my tester broke today so i will pick up another when I have time.

I pulling my f'ing hair out over this. The next thing im going to do if the egr tests fine is to remove and check EVERY vacuum line.

pray4locust

FINALLY FIXED!!!

It was the cam timing. Apparently when the timing belt was changed it jumped two teeth on the cam sprocket. After a complete tear down i realized this and now its running like a top.

If anyone has any questions at all pm me.

special thanks to www.justanswer.com. this was an extremely helpful site.

korrakenpo

I have a 02 Honda Civic LX with a 185k, i experienced the same problem map sensor code p1129. Just wanted to say thanks because your post saved my car. It was the cam timing on my timing belt as well. My car kept stalling and losing power. I had taken my car to the Honda dealership and the first tried to say my car needed a new engine and that they would buy it for 500 bucks. A whole two months no mechanic could figure it out. Something so simple right in front of my face...

car runs like a champ now..

Thanks man.

pray4locust

I am extremely happy that I could help. When I first had the problem I looked everywhere online but no one ever finished and said what the problem was. I am glad that I helped someone along the way.

shehzad

I had the same exact problem. Keeping this in mind I Opened my timing covers and found the timing off about two notches because of the rubber seal from the lower TB cover. Put new TB new water P/P and run it for about 40 mile. No more P1129 yet. The Engine run with more power and quiter. THAKSSSSSSSSSSSSS.

pray4locust

I actually just sold that car, but never did gave that problem again. If both of your timing marks are right now you probably won't have any more troubles. I paid $3500 for that car two years ago, put 60000 miles on it, and just sold it for $5000. Gotta love Hondas

crisrx77

I had this code pop up after I cleaned the throttle body. Also p0507 turned out that you have to get the throttle reprogrammed any time you mess with the throttle body. It was causing the ECU to go into limp mode and would stumble and not wanna shift gears when applying aggressive throttle like when your merging on to the freeway or passing cars.