Not the typical idle issue?

[802cb7]

So I figured its time to post this because I've tried everything. I'm pretty mechanically inclined, and have been around cars my whole life, I enjoy the technical stuff. Anyway, I've had this issue since i bought the car (2 months ago). The car idles just a hair under 1,000 rpm, I've tried to adjust it only to have it shake and shudder now like its set way too low, even though it still sits around 850-900 rpm? What really bothers me is not being able to have a normal take off from a stop light because of this. I sort of have to rev it a little and let the clutch out slowly. which only seems to work part of the time. Its embarrassing and makes it look like I dont know how to drive a standard! (been driving stick since 1999) the car will buck and chirp etc, not real bad but enough.

What I've done so far:

bled the cooling system (according to hynes)
changed plugs
plug wires
air filter
pcv
new thermostat
cap
rotor
fuel filter
I use fuel injector cleaner every 3rd fill up
changed MT fluid
cleaned iacv
cleaned FIT
adjusted FIT

I'm sort of at a loss on this one guys. I've tried everything I can think of. I've done a bunch of searching, but still nothing. Its just strange, its like the computer wants it to idle slightly high. Which could be a vacuum leak I suppose?

[802cb7]

Oh, and another thing. This one REALLY stumps me. When I changed the distributor cap I went for a drive and HOLY crap! The car actually felt pretty quick and fun to drive. I did my normal loop where I cruise around, and noticed at many spots where the car had seemed just "OK" in the past, was greatly improved. Like it was not just my butt dyno fooling me. This was an actual improvement. The car revs quicker, excellerates better, all in all just more fun.

So here is where I'm really stumped. I get home, shut the car off, and go to bed. Come out the next morning all excited to drive the car again just to find out its right back to normal. By normal I mean, just doesnt feel quite right for a 2.2L 16v. Like its just lacking in something, something is being held back, like the clutch is slipping which its not. I know my car is 24 years old, I get that. but its been very, very, very well taken care of. I did a test, I took the cap and rotor off again, then reinstalled. The same thing, car was awesome! Any ideas guys/girls?

[johnl]

Oh, and another thing. This one REALLY stumps me. When I changed the distributor cap I went for a drive and HOLY crap! The car actually felt pretty quick and fun to drive. I did my normal loop where I cruise around, and noticed at many spots where the car had seemed just "OK" in the past, was greatly improved. Like it was not just my butt dyno fooling me. This was an actual improvement. The car revs quicker, excellerates better, all in all just more fun.

So here is where I'm really stumped. I get home, shut the car off, and go to bed. Come out the next morning all excited to drive the car again just to find out its right back to normal. By normal I mean, just doesnt feel quite right for a 2.2L 16v. Like its just lacking in something, something is being held back, like the clutch is slipping which its not. I know my car is 24 years old, I get that. but its been very, very, very well taken care of. I did a test, I took the cap and rotor off again, then reinstalled. The same thing, car was awesome! Any ideas guys/girls?

Well that all sounds too weird to not be a coincidence. I suspect you might have an inlet leak somewhere, maybe some hose, maybe a gasket, maybe some component exposed to inlet vacuum...?

Or a wild guess, are you sure the distributor is tight, and that it didn't move when you were messing with the cap?

[802cb7]

Well that all sounds too weird to not be a coincidence. I suspect you might have an inlet leak somewhere, maybe some hose, maybe a gasket, maybe some component exposed to inlet vacuum...?

Or a wild guess, are you sure the distributor is tight, and that it didn't move when you were messing with the cap?

The distributor is marked in white out so I know it didnt move. I actually had that same thought and checked for tightness. All is fine with that. I'm going to look for a vac leak I guess.

[802cb7]

so I check for vacuum leaks all over. Couldnt find a single one. There is no arcing of the plug wires as well. I did however notice a wicked loud sound coming from under the air box. What is that? It did go away after a while. Anyway, I also reset the idle. Which did help. I guess my question is when adjusting the idle where exactly is 650 rpm on the tach? Pretty sure I'm doing the procedure right.

[Granite CB7]

Thoroughly clean every ground in the engine bay especially the ecu ground on the thermostat housing. I worked on an h swapped cb with poor grounds it ran slower than the stock motor. Cleaned all the grounds and it seriously woke up. I was shocked because I was out of ideas trying to fix it. I'm not saying this is the problem but its a step in the right direction.

[802cb7]

Thoroughly clean every ground in the engine bay especially the ecu ground on the thermostat housing. I worked on an h swapped cb with poor grounds it ran slower than the stock motor. Cleaned all the grounds and it seriously woke up. I was shocked because I was out of ideas trying to fix it. I'm not saying this is the problem but its a step in the right direction.

funny you should mention that. I recently did my thermostat and forgot to tighten that ground, car ran only to about 2k the fuel cut. I fixed that. I will go out and clean all the grounds. I also rebled the cooling sytem (AGAIN), and now have a perfect idle. I also decarbonized using the water trick. My idle sits perfect. But i still have this skip in the engine and performance feels low. iTS NOT TERRIBLE , just not all there . at idle its purrrrssss. then every so often a slight skip in the engine. I've dont just about everything i can think of.

[802cb7]

so grounds are all clean and tight. Just as I figured, it was one of the first things I did when I bought the car. Battery is clean and terminals tight. Dont know if this matters, but about a month ago my battery light would come on for a split second and go out. This would happen 2-4 times a day. Hasnt happened since. I'm at a loss. Really want to feel the power of this car again.

[802cb7]

ok, so upon more investigation I noticed a bolt for the distributer was extremely loose. which means someone has been in there before. More investigation shows the distributor was very retarded. I moved it to the middle, but dont own a timing light, or really know how to do that. Either way I've been messing with it all afternoon on different settings and the car still feels the same. Maybe I'm crazy?

[johnl]

ok, so upon more investigation I noticed a bolt for the distributer was extremely loose. which means someone has been in there before. More investigation shows the distributor was very retarded. I moved it to the middle, but dont own a timing light, or really know how to do that. Either way I've been messing with it all afternoon on different settings and the car still feels the same. Maybe I'm crazy?

The ECU will adjust ignition timing to match it's maps, but if the 'base timing' (i.e. the rotational position of the distributor) is too retarded the ECU may not have enough scope to reach more advanced timings as required (or retarded timings if the base timing were too advanced). If so then this means that in some circumstances the ignition timing will be more retarded than it's supposed to be, but in other circumstances it will be OK.

I think this will be why you are finding that the base timing can be changed without much obvious affect on how the engine is running. You should set the base timing with a timing light to ensure that the ECU can actually adjust the timing to full advance (or retard) as needed.

To set base timing you need to find the blue electrical connector under the dash, and insert a piece of wire into the two connections to 'short' it out. The ECU will then go into 'diagnostic' mode and stop adjusting the ignition timing, allowing the base timing to be set with a timing light (in 'diagnostic' mode the timing is only affected by the distributor position, the ECU doesn't 'fiddle' with it). Once done remove the wire and the timing should be correct. The 'diagnostic port' (i.e. blue connector) is I think in the passenger side foot-well, maybe hidden under the carpet (I'm having trouble recalling, it's been so long since I had to use it).

I suspect this may not cure your problem, but it might, and even if it doesn't it means you can move on to checking other things...

[802cb7]

i found that blue plug, but i was expecting a female plug, not a male. One thing I've been meaning to ask: If I unplug the IACV and the engine doesnt die thats good right?

[ahdiofreak]

I believe so. Do you have an external ignition coil? Did you change the coil?

[802cb7]

I believe so. Do you have an external ignition coil? Did you change the coil?

No, its an internal coil. Also, forgot to add this which might help. When I start the car, the rpm will jump to the cold start idle and drop really quick to the point where the whole car will shake then it jumps up again to around 1,500 and will do the cold start process normally. How ever, if i start the car and just go without warming it up it almost dies, shakes so bad and is very hard to drive, I have to rev the shit out of it just to start off.

[SEgirl]

I'm finding this discussion very interesting. I have a 93 SE sedan with 320K miles and thought it ran fine. However, when I got another SE with 220K miles, I couldn't believe the power that it had. Both cars were completely stock, everything under the hood was the same. I guessed the difference was that my first SE had quite a bit more miles, but after reading this thread, I wonder if it's something else. It does feel like something is holding it back/weighing it down, when accelerating.

It also does idle high, around the 1K mark, but it's done that for a long time.

[johnl]

i found that blue plug, but i was expecting a female plug, not a male.

It should be a two point female plug. That you found a male plug is a mystery to me...

One thing I've been meaning to ask: If I unplug the IACV and the engine doesnt die thats good right?

Well, yes, but it doesn't necessarily mean that the 'base idle' speed is correctly set. With the engine at correct operating temperature, and no auxiliaries in use (i.e. no parasitic loads from the AC or heavy electrical loads through the alternator from say the headlights etc.) the idle speed should remain unchanged when the IACV is disconnected. If not then the 'base' idle speed needs to be (in theory ought to be be) adjusted at the throttle body. A small change is probably insignificant, but if it's a big change in idle rpm (when the IACV is disconnected) then it should be looked into.

The IACV allows additional air inflow at idle (bypassing the butterfly valve, which in theory has no part to play in idle air flow, though in practice some air does pass the edges of the butterfly flap) to account for idle rpm drop caused by parasitic loads. If the ECU detects a fall in idle speed then it increases the amount of air flowing through the IACV until idle speed is at spec. If the base idle speed is very low then it may not be able to do this adequately, i.e. may not be able to increase flow through the IACV enough to bring idle to spec (though I'm not sure of the limitation of the IACV, i.e. I don't know whether it can flow enough air to allow idle to be correct even if base idle air flow at the TB is very low or zero).

Note that the idle air 'bleed screw' at the TB is what sets 'base' idle air flow. It's an adjustable screw that constricts / deconstructs an air passage in the TB casting (the bleed screw is the large 'plug' with a slot for a screwdriver blade, don't confuse it with the butterfly 'stop' screw on the side of the TB). In theory, all airflow at idle passes through the idle air bleed orifice in the TB, unless the ECU is causing additional air is being passed though the IACV to keep idle rpm at spec. In practice there is always some air passing the edge of the butterfly valve, and this quantity can change depending on the temperature of the TB casting, i.e. how much the casting has expanded or contracted due to changes in temperature (the butterfly itself will also expand contract, but to a much smaller degree since it's steel and not aluminium, and exposed to lesser temperature changes than the TB casting)

The bleed screw doesn't do anything to the butterfly valve, which is set very nearly completely closed (at 'zero' throttle opening) and should never be changed (i.e. never adjust the butterfly stop screw to alter idle speed). Theoretically the butterfly valve should be completely closed at zero throttle opening, but in practice it's isn't (not quite) to prevent the butterfly valve being jammed shut when the TB casting contracts as it cools down (as the TB casting cools the aluminium body contracts, and can 'capture' the edge of the butterfly valve disc if clearance is too tight). If the butterfly valve is opened in an attempt to increase idle speed, then this might have a significant affect on the TPS at idle, though I'm not sure if this would have significant consequences.

Over time the idle air passage in the TB can become obstructed with crap, which can mean the bleed screw needs to opened a bit to increase flow (by turning the screw counter clockwise), or, that the passage needs to be cleaned out (if the base idle speed is unresponsive to changes in bleed screw rotation). There is an O ring at the bleed screw which can fail and allow air to bleed in past the failed seal, or allow the screw to back out with vibration and cause idle speed to increase (if the bleed screw turns with little resistance then the O ring may need replacing, or it can be sealed using a non hardening gasket goo, but not silicon, which will both seal and stop the screw from backing out).

If base idle speed is too high then the IACV can do nothing to lower it. Base idle speed is set with the 'diagnostic' plug 'shorted' out with a piece of wire (as for setting base ignition timing), which temporarily prevents the ECU trying to adjust idle speed with the IACV.