Engine RPMs go Up and Down - Urgent please

89 Honda Civic 3 door hatch 1.6 lit. - Only when car is driven for 20 minutes or so, and kept either in Park or neutral, the RPMs go high and low, in a repititive fashion. Just like the car is in park mode and someone is accelerating and releasing in a cyclic fashion.

This started to happen about 3 weeks ago. Otherwise the car drives very well.

what rpm is it movin up and down thru..when idling mine sometimes moves about 100-200 up or down. i kno its from a vacuum leak somewhere..i just need to find it

Sounds like a vacuum leak, or your EACV. Do a search and youll learn tons as this is a common problem on these cars.

Between 1200 and 1300 RPM. Normal is 900 RPM.

When it happens, opening the hood seems to be a bit hotter than before (not sure). Thought it was a vacume leak somewhere. Is there a test I can do to confirm.
My mechanic friend says it is fuel related. Mine is automatic, it simply revs up, otherwise (if manual) it would have stalled.
ANY suggestions as to how I can confirm between fuel and vaccum issue.
Thanks.

Well since its an auto when its in drive there is a load on the engine and it wont surge up and down like if it were just idling. Are you throwing any check engine lights? look under the passenger side carpet and look in the little hole on the ecu, are there any blinking lights? if so, how many? count the blinks, if there is more than one code it will pause in between, then repeat.

like frodo said check for codes...if the system can't maintain proper fuel pressure it would cause the syptoms you have, but these cars have fuel pumps that just won't die...any fuel odor around the car?

My mechanic friend did some tests and said its my Fuel Injectors gone bad. They are costly @ $400. Mine has two of them. Dont have this kind of money. Any advise.

Should I take a second opinion?

What kind of freaking solid gold injectors is he talking about?! thats crap..if you think its your injectors go pull a couple from the junkyard and call it a day, they arent hard to install.

That's good to know FrodoGT. Roughly what would be the cost of a FI be, used and new.
Sounds like it may be affordable to me, in which case I will try installing it myself (if you say it not too hard) - Have any instructions? diagrams?
Thanks.

Doe sit do it whwen the car is cold or only when it's warm ? if it only does it when it's warm it could be cause by a dirty FITV (fast Idle throttle valve) use take it appart, and wash it with break cleaner.

The FITV is for cold idle...the EACV or IACV (same part) is for warm idle. Also, d series dont have a FITV..b series do

Have you checked for ecu trouble codes yet?

if the mechanic said it was injectors I would definately just use junkyard ones. You don't wanna spend all that money to find out that the injector wasn't the problem. It sounds doubtful if the problem only happens when the engine warms up. You should check the codes yourself. Do a search on checking for engine codes. Its easy. The mechanic might be trying to take advantage of you at that price, lol. Sounds like dealership prices. Replacing them is self explanatory if you just look under the hood

yeah you just disconnect your fuel line from the pump and leave it attched to the fuel rail. then unbolt the fuel rail and pop out your injectors. shouldnt even take you an hour to fix. you could try cleaning them but the car is old so you might as well just buy some new ones off of ebay or junkyard them..pm me and ill send you the shop manual if you dont have one

where you been kunundrum?? havent seen you on here in ages

yeah you just disconnect your fuel line from the pump and leave it attched to the fuel rail. then unbolt the fuel rail and pop out your injectors. shouldnt even take you an hour to fix. you could try cleaning them but the car is old so you might as well just buy some new ones off of ebay or junkyard them..pm me and ill send you the shop manual if you dont have one

where you been kunundrum?? havent seen you on here in ages


His car is dpfi, so no fuel rail. Before even replacing the injectors (they rarely ever go bad on these cars) do as Frodo said, his advice is gold; even better than your mechanics'. Clean your IACV, its not hard at all, take it off, get some carb cleaner and soak it clean. 30 mins tops and your problem is likely to go away, try it out before doing some costly repair.

my bad lol

The FITV is for cold idle...the EACV or IACV (same part) is for warm idle. Also, d series dont have a FITV..b series do

Have you checked for ecu trouble codes yet?

I'm sorry but you are wrong. My a6 had a FITV. When I first started the car the idle was 1500-1800 rpms then it would drop to the steady 1200rpms. The gauge was off so it was more like 1300-1500 then drop to 900-1000. Of course, Moe has a dpfi and my a6 was mpfi...

Anybody knows how I can access the Hayes Manual online, to fix this?

Anybody knows how I can access the Hayes Manual online, to fix this?

Free Service Manuals: http://hondatech.info/

The manual wont have the actual cleaning of the IACV or FITV, but it will show you the locations. Here are some helpful links that will probably solve your problem:
http://honda-tech.com/zerothread?id=1575913
http://honda-tech.com/zerothread?id=1575913

The two sensors are located in different locations on your dpfi manifold, the IACV i know for sure is on the right side of the manifold, to the right of your pcv valve; the FITV i'm not sure for dpfi. Both these sensors can be cleaned. Good luck

THanks CRXperiment

Yeah, I am wrong...its been awhile since i cleaned the one on my b16 out.

I used to clean the EACV with a Q-tip. I'd unbolt it from the Manifold and wipe the guey crap away from the mesh "screen." I know it's located different on the dpfi but you could probably do the same or use some kind of cleaner maybe?

im goin home this weekend to work on the legend but when im stuck with that ill definately be cleaning my b16s iacv and fitv..its been havin problems forever with the idle ive checked the hoses and adjusted the throttle cable but never even thought those would be my problem

CRXperiment..those links are pure gold..

I think the problem is you need a new oxygen sensor

You guys are the BEST. IACV is the culprit here. Took to a different mechanic and while the car was doing its RPM crap in park mode, he removed the hose that connects between the IACV and the box that leads to the air intake, and the car stopped reving up. HE puts the hose back in it, and it starts acting up. I am going to give hell to the other guy who proposed the $400 fuel injector kit change option.
The mechnic says the IACV is required to be changed and the new / refurbished (dont know) will cost roughly $50 to $60, and his labout another $30, so I am looking at roughly under $100 which I can afford. Seems like cleaning the IACV is not an option. He is going to order the IACV today and will get it fixed tomorrow.
THANKS all, if I dont hear from you on this thread, else let me know if the above seems not the route to go.

That's great but you still could've probably have cleaned it up and used a new piece of hose that didn't have dirt in it and been okay.

Turtle, one thing I dont understand, is that when the mechanic reconnected the hose the problem started, but it (problem) also went away, when he blocked the hose (still connected) by pinching with his finger and thumb. Going by that scenario, why would putting in a new hose make a difference??

Not sure but there may be restriction where the hose leads out of the EACV. So the hose may not be the issue but where the hose is connected. The mechanic probably did clean it out and decided it best to just replace it. If you never clean them they get nasty from carbon build up...

Seems like cleaning the IACV is not an option.

Yeah but you can DIY easily just for the heck of it. What do you have to lose? Hes going to get you a used unit anyway, at least try to fix this one yourself and if you mess up horribly then to hell with it, have your mechanic replace it. If you do a good job, which i'm sure you will, you'll save 100 bucks. This is not that hard of a job, all you need is a 12mm socket, a ratchet, and some carb cleaner. I dont know why you think cleaning it is "not an option." Just my 2 cents.

I agree with crxperiment...carbon buildup is the only problem that part has...it isn't under any high pressure from friction or anything...the money your spending is totally a waste..you take the part of and spray the crap out of it with brake cleaner and all is fixed

Thanks to your input - I luv ya all. My problem indeed was the IACV, but an interesting one:
My Mechanic had another 89 Honda Civic DX sitting in his yard. He proposed to take the IACV out of there, and try it on mine. Right in front of my eyes, when he removed (from my car) the two coolant hoses and the two bolts to let lose the IACV, Lo and behold what I see - A 3" to 4" black electircal tape was dangling from the inlet hole. Another 3" was all wrapped up and blocking the outlet hole. The inlet hole screen was missing (not broken, but missing). How the hell this happened. Those tapes could not have been sucked like that??? Dont know if the previous owner did anything ?? Can anyone explain.
I paid $60 (parts and labor) to my Mechanic to let me swap the units. We decided that since the screen was missing and the unit was not in a good shape, I will keep the one that came from the other car. He put mine in the other car, and it was working till I left the garage. In his honesty, I did whatever I did.
After the repair, you should hear my engine - It sounds like a brand new car.
Cheers ALL for a job well done.

nice job..
idk what that tape deal was..good thing you fixed it tho..i cant stand ghetto jobs lol probly was the guy that owned the car before you

From what you are talking about, I had this exact problem on my 88 Civic Hatchback, 1.5 L. Mine was a Manual and this RPM jumping would happen when I was sitting still at an idle. It was very frustrating and hard to explain. I was worried it was going to be all kinds of problems.

I found through another post on this site, that others had this problem. The problem I had was that my throttle cable was a little too tight. If I put my foot under the accelerator and pulled it toward me(off the floor) the revving would stop(I did this when I was sitting still at a red light or something). All I did to solve the problem was loosen the throttle cable just a little bit and I haven't had this problem again.

Hope that helps.