Komi

I have a 88 non-turbo rx-7 'n' the idle goes between 1400 'n' 1800 with almost no vac (don't have brakes) after the engine warms up.


- I've checked the vac lines 'n' they all seems ta go where they're supossed 2 (replaced a bunch that were gettin' old 'n' hard).

- TPS is set correctly.

- Just replaced the exhaust manifold gasket 'n' there are still leaks right now but not between the O2 sensor, but can't find exactly where. (a lot of white smoke).

- its prolly not the ECU cuze I grabbed 2 at the junkyard 'n' tried em with no change.

- My timin' can be off 40 degrees EITHER way (yes I can rotate it about 80 'n' no change in the engine).

- Its not throwin' ne codes.

I'm still new ta rx-7s 'n' can't seem ta find why its doin' this. Any help would be extremely appreciated as I can not find out why its doin' this. It feels like a vac leak but I have found none. Although there is a quiet high pitched sound comin' from the passengerside of the engine (I believe) but I'm gonna wait a couple posts b4 I go ahead 'n' start takin' off the intake manifold.

lax-rotor

iTrader: (1)

look up oscillating idle. and are you positive that you've CORRECTLY set your idle when your engine was warm?

sidewayz_FC

my car had an oscillating idle from 1400 to 1800ish, by bacv valve was out, is it only doing it until it warms up or is it constant

Komi

as fer the idle screw it can be in all the way or taken out with no change. I could have a problem with the BAC valve however I have taken 1 from the junkyard (I understand that it could be bad 2) but it does fire.

It does have the erratic idle up until it does fully warm up to.

sidewayz_FC

your sure its not a vac leak? i had a bolt missing on my throttle body when i bought the car, and idle screw inputs wouldnt do anything, and neither would a/f adjustments. get a can of starting fluid and go to town.

Komi

I didn't find ne missin' bolts that i think would do it, i don't have the hose fer the BAC valve bolted onto the throttle body (cuze i've been regularly takein' off the throttle body) but it doesn't look like it would leak air in it. I'm gonna take some pics later. also ever since I have changed the gasket the engine will occasionally die but I tightend the bolts, ran it, 'n' tightened em down as hard as I could without breakin' em. When I use the starting fluid I'm not gettin' ne reaction from the engine.

"...as far as I can tell, the 1500rpm is the point at which a fuel cut is issued. Ground (or short) the initial set connector, and set the idle speed. Too high and the 1500 fuel cut comes into play. If this doesn't fix the problem, then it's most likely a vacuum leak somewhere."

I read this in another post 'n' I need it explained a lil so I can try it. I'm not eliminating the possibility that it could be a vac leak somewhere that I can't find. Where was the bolt that you were missin' SideWayz 'n' where did u spray?

Komi

I just took off all of the intake manifold 'n' found that the wire for the O2 sensor was torn. That was prolly it after I replace the exhaust gasket. I'll be back in bout 2 or 3 days 'n' tell u guys how it goes.

Thanx fer all your help :-D

Sideways7

iTrader: (7)

I don't think a problem with the O2 sensor wire would cause this. Try checking the TPS. Also, spray some starter fluid around to make sure. Just because you replaced all of the vac lines doesn't mean there isn't a vac leak.

Also, try speaking normal English and you will get more helpful responses.

'88fc

First off, you said lots of white smoke? That is usually burning coolant.

Second, you said you have no power brakes, thats a vacum leak. Disconnect the line from the brake booster and plug it, even though you think you have no leak, you migh have a bad booster.(seen it a few times)

Third, if it won't idle right when it is cold the O2 sensor isn't the problem, the ecu will only look at the O2 when it is in closed loop(warm)

Fourth, you sound like a redneck crossed with I have no idea what.

dipsherry

look at the idle screw had same problem when i first bought my 7

helghast7

iTrader: (6)

why you say coolant leak for white smoke how much wsmoke we talking? mine puffs a little white smoke but only in the first few minutes, cold start, or are you talking about all the time?

Aaron Cake

iTrader: (1)

Keep in mind that if you are going to set the idle with the screw, there is a procedure to follow. The engine needs to be totally warm, the initial set coupler jumped, and the timing must be correct. The FSM and Haynes manuals have this procedure. Don't just go turning the idle screw because the ECU will try to compensate with the BAC and you will never get the idle set right.

It sounds like your issue is one of the following, in this order:

1. Vacuum leak
2. Bad/maladjusted TPS
3. Sticking or otherwise failed BAC valve.