I have a 94 2.0 626 with a standard transmission.

Car had several OBD-I trouble codes:

15 - Oxygen sensor or circuit
16 - EGR valve position sensor or circuit
17 - Feedback system
28 - EGR control solenoid or circuit

Had the EGR and position sensor replaced. Started experiencing a very rough idle once hot. Mechanic couldn't fix it.

Took it to another and he got the idle more smooth but now it fluctuates by about 500 rpms. Check engine light is back on.....more codes to follow.

Any thoughts?

 

How old are your wires ??? How old are the spark plugs ??? Or is the dizzy not placed corectly??

 

Two things that are somewhat common on that car for the rough idle and surge. Sticking Idle Air Control Valve and leaking intake manifold gasket. Gasket tends to leak on the underside area and is not always visible from above. Did you get any new codes back yet?

 

My 98 626, 5 speed, 2 liter engine, has recently developed this problem as well. Once the engine is hot (after having been driven for a bit), and I turned it off, it would not idle after I turned it on. The car would just stall. To continue driving, I'd have to keep the rpm high (at least 1000 rmp) and get in gear to get moving. Once the car is moving, it's OK. If I had to stop, it would stall. The mechanic diagnosed it as a faulty fuel pump, put in a new one for $350 labor included. Was this a fair price? He said he had to drop the fuel tank, since the pump is inside the tank. Now the car does not stall like before, but the idle rpm is still very low, and the engine acts as if it is about to stall.

 

$350 is probably not bad price as labor for pump R & R is listed at 2.6 hrs in Mitchell plus cost of the pump. Question is, was that part of the original problem? I cannot think of any failure that the fuel pump might have that would create that kind of problem at idle without creating even worse problems at higher rpm/speed/loads. Not stalling anymore. You sure the base idle speed has just not been jacked way up so it would at least seem to be improved?
I guess the point is moot as the repair has already been authorized, completed and paid for so that is that.

Sounds like you probably have a problem with the IAC or Idle Air Control Valve. Also referred to as BAC or Bypass Air Control. This valve performs two separate but similar functions. When engine and coolant are cold, a passage is open in the valve to allow bypass air past the throttle plate to elevate the idle speed for cold operation. As the coolant warms up and is circulating within the valve, this passage begins to close off until it is completly blocked. At this point the engine computer takes over and opens another passage with an electrically controlled duty cycle motor. Target RPM is maintained by opening and closing this valve as needed depending on varying presence or absence of loads on the engine. It is this portion of the valve that is probably stuck closed or mostly closed.

First off check to see if the throttle cable has been adjusted up too tight in an effort to compensate for the stall. It should have a small amount of play and at least not be tight as a piano wire when throttle is closed. If that is ok then at a hot idle, disconnect the connector for the IAC valve. If it is working correctly then RPM should drop quite a bit and perhaps even stall. If there is no change in engine speed then valve is not operating and will probably need to be cleaned or replaced. The IAC valve is located on top of the throttle body. Just locate the air cleaner and the large diameter black hose that runs from it to the engine. Where that hose connects to the engine is the throttle body and IAC is right there on top. Two wires in the electrical connector are Blue w/ Orange stripe and Green w/ Red stripe. Resistance of the valve motor should be around 8 ohms. Drawing below may give a better idea on location. IAC is #8 in the identifier.

[IMG]local://upfiles/1377/22061AAD63524761998C3402C93A54FE.gif[/IMG]

 

babyhuey,

Thanks for the explanation. I'm not sure that the fuel pump replacement was necessary. The mechanic said that it was about to fail, and I have been going to him for routine maintenace for many years, so I kinda trusted him. But what you said now made me doubt him a bit, since he never told me anything about the IAC, which he should have. I'll look into that myself, just don't have much free time right now.

Thanks again,

 

I have the same problem Idle flucuation on a 94 626 2.0L w/AT, I took apart the IAC and cleaned the springs and plastic piston looking thing and it made a differance.

I still have a high idle even when warmed up its around 1500rpm and will bounce to 1900rpm and back it was around 2500 before I cleaned the IAC. On the highway (at 75mph) it'll go from 3000rpm to 2600rpm then right back up to 3000, it does this pretty consistantly and is more anoying than anything. But the high idle is killing the MPG and is a pain in town.



"then at a hot idle, disconnect the connector for the IAC valve. If it is working correctly then RPM should drop quite a bit and perhaps even stall. If there is no change in engine speed then valve is not operating and will probably need to be cleaned or replaced. The IAC valve is located on top of the throttle body."

I'll disconect the wire conector when I get home and see what happens.

 

I disconected the wires from the IAC and nothing changed, That means The IAC is probably bad since I already cleaned it out once and got rid of some carbon and white scale. I have the other TB from the old engine I'll try that next.

FYI I priced new IAC's at a few places they run from 499.99 (auto Zone) to nearly 800 (JC Whitney) or a whole TB assembly for 1300. 00.

BUMP all that

I'm going to the junk yard in town they have one 95 sitting in there hope it has a AT.