What we have here is a 1992 Volvo 740 wagon non-turbo.

Problem Description:

The car starts fine cold. The intermittent problem occurs after being driven, then parked for a while, and then trying to restart. It turns over, sometimes sputters a bit, then dies. In order to get the car to start in this scenario, you must depress the gas pedal ~1/4 inch, and it starts right up, every time.

The Volvo mechanic pulled a Air Mass Meter code, cleared it, then after the problem reoccurred, pulled the same code again. So, we replaced the Air Mass Meter. This DID NOT fix the problem! argh.

Additional Information:

When the car starts the idle seems to be too low. ~500, then rising to the normal 800-900 RPM. It seems to me that the solution to this problem is the solution to the start issue. Most cars startup with a high idle, then idle down...but not this one.

Could this be the idle air control valve? heat trap?

I have already cleaned the throttle body.

Thanks for any help.

 

Perhaps you need to adjust the throttle linkage better?

 

Intermittent problems are the most difficult to diagnose.

Once the problem is happening in front of the tech, he can reasonably determine, through diagnosing, what the issue is with some certainty.

If the problem will not occur while he is looking at it, then it's a game of forensics and speculation. It it does happen while your tech is looking at it, and he still can't fix it, time to look for a new tech.

The symptoms you describe could be anything from a split in some obscure vacuum hose to frayed wire in any number of harnesses. The most likely scenario is it's something to do with the fuel system.

Any/all info regarding observations while the problem is happening would be invaluable in helping to diagnose the issue.

When the problem occurrs:

1. Do you see smoke from the exhaust when it starts?
2. What was the exact code your tech pulled?
3. Does it absolutely run perfect except for this issue? Any other symptoms?
4. How many miles on the odometer? How long since most recent tune-up? Compression good? Etc. etc.

 

Here is some more information:

Most often, when the car starts up (doesn't stall), the RPM seems to hesitate up to/around 500. Then shortly after rises to the normal 800-900. When the car has the stall issue (on start-up), the car doesn't actually start-up, but just dies.

I believe this symptom is key to understanding what is going on here, but am unsure what is wrong. I believe most cars on start-up rev above 1000rpm, then settle down to operating RPM. So, this car seems to be behaving backwards.

Other than this problem the car is in sound operating condition (119,000mi). That is, runs great, doesn't burn oil, etc.

Could this be an Idle Air Control (IAC) valve issue? Has anyone had an intermittent problem similar to this that replacing this solved?

 

Thanks for emphasizing that even when you car starts and runs, that it lingers for a bit at 500 rpm before idling at normal 950 rpm (I didn't catch that fact the first time I read your post).

I think you're right; that is the critical clue, because it means the problem is always there; it's just worse at some times more than others.

But here's where your ears will also give you some clues. This is a hot-start only problem right? So when you start the warmed up car (and it runs..) does it seem like it's running rich? i.e. does the idle lope along coupled with some black smoke out the exhaust? Once you get it started, do you have to rev it up to clear it out (acts like the plugs may be partially fouled)?

Or does it sound like one or two cylinders are just not firing for a brief time?

Or does it just run at too low of an idle rpm, albeit fairly smoothly until it warms up to the point where the idle speed come up? If it's this one, then yes, your IAC could be the culprit. What you're doing by opening the throttle slightly is effectively what the IAC is supposed to be doing; letting some controlled amount of air bypass around the closed throttle plate into the engine. Have you tried cleaning the IAC with de-gunker (like you did with your throttle body)? Also keep in mind the IAC is controlled by some control unit which is reacting to input from various sensors (i.e. a feedback loop), so, as I said before, it still could be any number of things.

Systematically diagnosing the problem takes time, skill, and most importantly the knowledge to understand how the system works. That's how you recognize what components of the system are not working properly and repair them as necessary.

Or you can shotgun it and throw parts at it; somtimes your lucky, but most of the time you won't be.

Let us know what you find...