1988 Grand Marquis, bombed smog test followed by stalling issue...

I was given a 1988 Mercury Grand Marquis by some family members, and when I went to get the smog test some weird things happened. First of all, my family members drove it about six hours to get it to me and had no issues. Second of all, they did some routine maintenance on it prior to giving it to me, (oil change, air filter change, etc.) And thirdly, the vehicle has been registered in California since it was purchased, so it has never failed a smog test, and the most recent one was about six months before they gave me the car.

So, I drove the car up to get the smog test before I registered it, (about three miles), and it seemed to be driving alright. (I'm used to driving a 2005 Tacoma with less than thirty thousand miles on it, so I'm a little new to driving older, almost "clunker" cars, but it seemed okay.)

I parked and talked to the technician, he told me to bring the car into the garage. I pulled it in, parked, and shut the engine off. He told me I could leave it running, so I started it back up and got out. He walked me through the cost real quick, took the registration info, then the car stalled. He started it up, hooked the smog test gear up to it, and started the test. It seemed like he had to have his foot on the gas during the idling test, and when he took his foot off the gas at the end of the test it stalled. He ran the test twice, I think, and it failed both times.

He then moved the car further into the garage and performed the test where he screws the thingie on the gas tank, (I'm not mechanically inclined nor do I have knowledge whatsoever of what the smog tests are...). Anyway, after that, he went to back the car out of the garage, but it stalled every time he shifted into reverse, so he revved it up, slammed it into reverse real quick and peeled out. When he parked, it stalled.

He then printed off the results which he said were probably the worst he had ever seen. I don't know what they mean, but the numbers recorded at idle are:

HC (PPM) MAX: 120
HC (PPM) MEASURED: 5273
CO (%) MAX: 1.00
CO (%) MEASURED: 9.64

And at 2500rpm:

HC (PPM) MAX: 140
HC (PPM) MEASURED: 5031
CO (%) MAX: 1.00
CO (%) MEASURED: 9.64

It seems like a pretty big disparity, and it seems strange to me the HC was worse at idle than at 2500rpm, but I don't know anything about it.

Anyway, I then had the same problem as he did, with it stalling at idle, (but only after it tried to rev itself up a few times), and it stalling whenever I shifted from park to reverse or tried to get to drive. In order to go anywhere I had to rev it up, ram it past reverse and into drive real quick and step on the gas real quick, otherwise it just died. It would start right back up, but if it idled for more than a few seconds or I tried to shift, it would die unless I used the technique I just told you, which I'm sure is really bad for the transmission. It's also terribly scary and unsafe to drive since at every stoplight and stopsign, the car would die, and I would just have to hope no cars pulled up behind me, because every once in awhile using the above technique I would accidentally be in reverse when I hit the gas instead of drive. I also noticed that when driving it would rev itself up a bit every now and again, particularly noticeable at lower speeds like 5mph or so. I never got it over 15 or maybe 20mph driving it home because I wanted to be prepared to pull over at any given moment.

Anyway, I did some research online, and apparently it could be any number of things. From my research I feel the most likely culprit is the Idle Air Control Valve, but I wanted to check with some people more knowledgeable than I before I put any money into it. I can't afford a mechanic, (hence why I got a free car), so if this can't be fixed cheaply by myself the car is going to end up on Ebay with no reserve. =/

Sorry for the long explanation, I just wanted to give as much info as possible. Anyone know if replacing the IAC Valve could fix one or both of the problems? I'm really hoping replacing it it would be enough to fix the stalling problem AND the emissions problem, but maybe that's too much to ask?

It could be the IAC, which IIRC is on the intake manifold and positioned at a 45* angle, an easy replacement that I did on my '86 when I still had it. There may also be a vacuum leak somewhere....there is a plastic junction, it's "C" shaped and white in color which is near to the steering column. If you can hear it hissing, replace it.

The bad results might be from having just started it - it was still in the startup "loop" in the computer control and that would definitely make it more polluting. Check the spark plugs and plugs wires, as well as the cap and rotor, if your family didn't replace those they could contribute to stalling also.

Post back after you've checked everything --