scout206

Hello..
I have changed out most electrical components recently but still have a rough idle and shake after driving for awhile. Usually starts up fine and the
condition appears after some driving. Rough idle, doesn't die but feels like its
going too.
I am considering 2 possibilities... The IACV or/and the timing belt.
I just ordered a new belt as I really can't say for sure if it has ever been changed. 215.000K on the car.
I have read that the IACV doesn't begin to function until the engine is warm and as I never notice a rough idle on cold starts I am thinking about ordering
one but also don't want to waste 200 bucks!
Thanks for any info!

ezone

You have a couple old threads with similar concerns listed.
Still the same issues now?


Is this condition always present after warmup, or does it actually run correctly sometimes too?
A clear answer to this might lead me to much different answer.


Timing belt-- pull the upper timing cover and check cam/crank timing. If it is still "in time", the belt isn't the cause of your problem (even if it does need changed, it would have to have jumped time to be a cause.)
For a much quicker check, I might put a timing light on it and see if timing is off by 20 degrees or more. That would be an indication of a timing belt jump.

IAC? Does the engine simply idle at too low RPM, way below normal idle speed?

There's a difference between rough, and slow.

Poopies

iTrader: (4)

As far as the timing belt goes, if you're in doubt, change it out!

Before you change out the IAC valve, you should try removing and cleaning it with some throttle body/carbuerator cleaner first. You can even use brake cleaner. It's a hell of a lot cheaper than going new!

Here's just one of the DIY articles available for a D-series engine similar to yours.

http://www.superhonda.com/forum/f94/...r-iacv-144463/

scout206

Thanks for both replies.

I have ordered a belt so I will be checking that soon. I'll try to remove and clean the IACV first. This rough idle only occurs after the engine warms up and it really is there every time you are in idle at a stop or decelerate in
neutral to a stop. If I had to choose between slow and rough I guess it's rough and causes a noticeable shake in the steering wheel. As to the RPM I would say it feels lower than normal rather than higher.

When the engine is cold and warming up it's fine and has no shake in the steering wheel. It runs and drives well with no issues under load other than a mild vibration in the gear shifter... It's a problem with a warm engine at idle.

I was somewhat optimistic it could be the IACV after reading it didn't start working until the engine was warm. Just thought that if it is idling ok before the IACV starts to operate.. then maybe it's the cause of the problem.
I would guess that if it was a timing belt problem it would be present under both cold and warm idle conditions..

I'll let you know if I have any noticeable improvements after cleaning the IACV.

Thanks!

scout206

Hello,
I removed and cleaned the IACV today.. it is called the EACV in my Haynes
manual. I didn't know how to physically test the unit to verify it functions, just cleaned the screen and the interior coolant chamber. Can I put 12V to one of the 2 blade connecters and observe any movement inside the hole
beside the screen?

Have to say, no noticeable change in the warm idle. It's as if it at can't
hold a set RPM and also has a vibration you can easily feel on the steering wheel.
I am now considering ordering a new EGR valve as they are known to cause
(Haynes +Rock Auto) rough idle conditions when faulty or leaking.
That would at least eliminate that suspect. Any EGR experts out there?
Thanks

ezone

Block the EGR passages to disable it. One could remove the valve, cut a piece of thin cardboard the shape of the gasket but without any holes for the passages, and put it back together.


If you remove the EGR valve and see that the pintle is stuck open, that kinda verifies it's a problem.

The controls that operate the valve could be causing it to stay open.

scout206

Just came back from a quick night time search for the EGR valve depicted
on Rock Auto for a 1991 civic with a 1.5... Couldn't find anything looking like that yet but I found numerous online posts from other people looking for the same part on the same car lol. One post said if you have a 1991 base civic with a manual transmission it doesn't have a EGR !?!
That seems kind of strange when they list that very part for a 1991 base civic with a 1.5 on Rock Auto...
I'll try a more extensive search in the daylight....

Poopies

iTrader: (4)

Nah, you've got one. Check out part 8 (in the picture, not the list) in Honda's e-store here:

http://estore.honda.com/honda/parts/...n=&b=E++03&dl=

I'm assuming you have a 4 door DX 5 speed.

scout206

It's a 1991 base model, 2 door + hatchback, 1.5L with a 4MT

ezone

Would help IMMENSELY if you tell where you live, because he cars are equipped differently to meet regulations for the market they are to be sold in, USA or Canada.


I'm taking the liberty of using the info I have available to post that you are in:
British Columbia, so I must assume the car was made for sale in the Canadian market.

Don't rely on aftermarket catalogs. Always use a factory catalog FOR YOUR COUNTRY when possible as first and most reliable choice.




Fishing through a Canadian parts catalog here shows the 3 door (hatch) Standard model as being the only one that has a 4 speed manual trans. (Same for US STD models.)

All other versions including DX are shown with either 4 speed automatic or 5 speed manual, no 4 speed manual trans is listed.
If you have a DX, try shoving that shifter over for one more gear LOL.

Further, I didn't see any EGR listed for a Canadian market car.


Correct me if this info is wrong?

Poopies

iTrader: (4)

Part 15 on the diagram then.

http://estore.honda.com/honda/parts/...n=&b=E++03&dl=

@ezone, does the e-store list ALL the variants?

ezone

I think e-store is for USA only (did not look LOL).

Try this link instead http://www.torontohondaparts.com/


EDITS:
e-store says American Honda at the bottom of the page, and
I didn't find an EGR on that car in the Canadian catalog

scout206

Ok, sorry about any USA/Canada confusion.. I purchased the car new in Canada. Just had a long chat with the Honda parts man at the local dealer and he confirmed, No EGR. He said the problem is most likely with the
TPS and he confirmed what I read about that component on Rock Auto.

http://www.rockauto.com/catalog/more...563&cc=1168433

If you have a defective TPS Honda will only sell the complete throttle body
for BIG $$. As this sounds like the TPS may be my next suspect... I've ordered one for now. I expect I'll have to remove the throttle body to change this part. Has anybody here done it before?

Thanks

ezone

2 issues you face:

1) (Without looking, assuming they are all alike here) I don't think those are rivets holding it to the throttle body, I think those are really screws that had the heads broken off. (Anti-tamper, breakaway screws, similar to what holds the ignition lock to the steering column.) If those were really rivets in there, the screws you get with the new sensor wouldn't have threads to screw into, right??

You can use a small chisel to start them turning loose, you could hack a slot in the head for a screwdriver, you could just grind the whole mess off. Just don't booger the threads for the new screws.



2) It must be adjusted precisely. You will need a way to read output voltage.
TPS needs to be adjusted to 0.50V at fully closed throttle.

There is very little room for error here. (That's why the factory only sells it with the whole throttle body!?!)


From troubleshooting for code 7:

Turn the ignition switch ON.

Disconnect # 6 hose from the
dashpot diaphragm and connect a
vacuum pump to the diaphragm.

Apply 20 in. Hg to the diaphragm.

Measure voltage between C7 (+)
terminal and C12( - ) terminal.
(I'd backprobe at the TPS connector with a regular voltmeter for this step)

Is voltage approx. 0.5 V at full
close throttle (applying vacuum to
the dashpot diaphragm), and approx.
4.5 V at full open throttle?
NOTE: There should be a smooth
transition from 0.5 V to 4.5 V as
the throttle is depressed.

scout206

Thanks for the heads up on the TPS adjustment topic. Are you coming to Vancouver anytime soon? lol
Ok I talked to a shop about this TPS and they said they would not be comfortable with drilling out the screws and mounting a new TPS but that
they could adjust it if I installed the new one. I also ordered an oxygen
sensor just because that looks a lot easier to replace.
The shop said they can do a diagnostic on the car for about 120.00 so I am considering that option also.
I had another clue today other than that this condition only happens with a warm engine.
Lights on or off, or heater on or off directly affect this rough idle condition.
When you turn the lights on the rough idle and shaking becomes worse, turn the lights off and it certainly improves but it's still present...
Any new ideas????
Thanks

ezone

There's a difference between poorly running engine at idle, and a simply too slow idle speed. Either can cause the roughness to be felt inside the car.

You sure of which may be the issue here?

Slow can feel rough, just because it's too slow.

What's your RPM @hot idle? (use a real tachometer)

scout206

I don't have a tach at the moment. I'll look into that.
I'm sure if I buck up for the diagnostic service they will check that.
Right now I just have the 2 clues...
It doesn't happen will a cold engine and when the warm engine has a
rough/slow/shakey idle it instantly becomes worse if you turn the lights on??
I have a O2 sensor and TPS ordered atm and also have not seen any check engine light on the dash.
Thanks

ezone

With a cold engine, the fast idle system increases the airflow to support the cold running engine (may or may not raise idle RPM but most do). This is always true on any engine no matter if it uses a carb or fuel injection. The engine simply requires a lot of extra air (and extra fuel) to maintain a given RPM when cold.

By the time the engine has reached its operating temperature, all fast idle controls are supposed to be turned off/disabled so the engine is running at its "base" idle RPM or programmed hot idle RPM (depending on the systems used, and many older Hondas used 2 separate idle speed control systems )

Your base idle speed may just be too slow, or the idle speed control can't raise it enough to reach and maintain the specified idle RPM.


If the idle speed is already too slow, and you add more load to it (electrical stuff operating is still an additional load) but the idle speed control system can't do it's job, then the engine speed slows even more and gets even shakier.


Guessing, because I can't see what's actually going on there...

scout206

Still guessing also...
I starting to wonder about the fuel injectors, fuel pressure regulator, weak fuel pump... Changed the firewall fuel filter a few weeks ago, no change.
I may to try to disconnect the injectors while running to confirm a
drop in the RPM on each cylinder...
I bought a Oxygen sensor socket and just waiting for that part.
The mystery continues...
Tnx!

smatcivic

Any update on your progress in figuring out this problem. I've been battling the same issue on my 91 civic. Some days are better than others, but it drives me crazy.

scout206

Sorry to report that I do not have any updates. I have been busy with metal work on another vehicle I own. I still have the same issue previously described. I was just checking in to see if anyone had any new ideas..
I may have to buck up for a diagnostic visit one day.
It hasn't died at idle on me yet but I would sure like to know the cause.
I was thinking about maybe trying change a map sensor out if I get my
hands on another one..
also...
I did replace the O2 sensor, no change.
I did test the main and aux fuel injectors for resistance and also the intake air temp sensor.
all 3 were within the allowable resistance range posted in my Honda manual

scout206

update...

Yesterday the car was doing its usual rough idle when warm and then for the first time ever the check engine light came on. I just checked the code and have a code 8. TDC sensor. My manual lists some continuity and resistance checks at the distributor connectors but it looks like this is may be a new distributer fix... Hoping this is the cause of this long term problem and not something new..

Effin Daniel

any new updates? I've been having this problem for over 3 months now and have been following tons of feeds on this site and finally made my own account