So on Christmas Eve my wife's 91 240 started acting up as we drove home.
We recently had the fuel pump changed due to failure. The car ran fine after but exhibited hard starting in the rain and when cold. We'd have to crank the starter holding it and pump the gas until it would eventually start, run rough, then smooth out after a couple of minutes and be fine. This time it just started running very rough and almost stalled repeatedly.
We took it to our mechanic and 220- later we had a new O2 sensor and a car that still runs poorly.
It starts up now when cold right away, idles high for about 20 seconds and then the idle slows and hunts and seems like it's going to stall.
If I unplug the AMM it will start and run steady but a bit rough. The last time I plugged the AMM back in and restarted the idle stayed high and did not drop.
Tomorrow I will inspect for vacuum leaks and clean connections.
Also, when I changed the air filter last night the air breather box was loaded with almonds and dog treats that somehow made their way from the inside of the car to the air box.
Any help would be GREATLY appreciated.

thanks, Kirk S.

Hi All,

Just an update for anyone interested. It appears it was the AMM after all.
I should have trusted my instinct on this one but didn't have a spare to
check with. After thorough IAC and throttle body cleaning I still had intermittent issues. This morning it ran horribly upon starting. I unplugged AMM
and it idled o.k. I then plugged back in and it ran o.k. with a few idled issues
while on the way to the bone yard. 50- later (including warrantee) for a very clean looking AMM and the difference in performance was immediate and vast. Knock wood but she seems to be running better than ever.

Thanks for all the help!

Kirk S.

Now make sure the preheat hose to the airbox is either blocked off, removed and plugged or the airbox thermostat is working properly. I remove and plug this hose as I do not need to worry about visual inspections.
Also get another AMM for future reference.
Dan

The preheat hose is plugged.
I have a smog test coming up, I usually block it off down below and
then attach hose for inspection. They don't check underneath. The
thermostat was open but the hose was off. I think it had more to do with
age and perhaps the debris from the rodent fiasco.

Thanks for posting back the final resolution!

I found that the thermostat flap itself, once removed, makes a nice plug. It's also satisfying to force something into that blasted hot-air intake side. Heh heh.

Glad you got it worked out! How's the 84?
--
1990 740 Turbo, on its way to stock specs, maybe beyond

My bad AMM did something similar, but worse. Started, high idle for a few seconds, then idled at 200, 1500, 200, 1500 and usually died after a few oscillations.
It can cause wacky mixture.

Before looking at that, I would unplug the IAC and see if it makes a difference. I would lean towards a vacuum leak before replacing parts.

Good Luck!
--
1990 740 Turbo, on its way to stock specs, maybe beyond

So I unplugged the IAC connector and it idled fine, plugged it back in and high idle followed by hunting idle. Does this narrow it down to a bad IAC?

thanks, Kirk S.

Hi,


Try cleaning the idle valve. Instructions in the FAQ.

A piece of rodent generated debris may have entered and jammed the control valve.


Goatman

I just cleaned the IAC and there was a bit of gunk in there and idle was immediately better. I also discovered a very loose spark plug. I'm pretty surprised the mechanic didn't even look at the plugs or even disconnect the AMM or IAC for troubleshooting purposes but....
I generally do all this stuff myself but my wife needed the car a.s.a.p. and I didn't have the time to troubleshoot.
I'm crossing my fingers that it was a dirty IAC.
Next up is the 84 wagon that was running perfectly but died on my wife when she got in it to pick me up at mechanic's after dropping off the 91.

Cheers and thanks for the tips, Kirk S.

T,


Please tell about the 84! I really like those engines. I was thinking about buying another car just for the engine. I am about to take a trip to the oil company on 1st street, hopefully I can fuel up with some E85. My Bosch injectors I scored with quad ports from a Volvo S80 improved drivability, but the mixture remains in error for open loop. It was really bad last night at 20 degrees.

Happy New Year!
Goatman

First off, the update on the 91. Replaced the plugs (one was loose as I mentioned earlier), cleaned the IAC valve, put a bottle of techron in and filled up with 91 gas, seemed to be idling better and driving fine. Half way to the pick a parts the check engine light came on. No change in how it was driving though. I picked up a brand new appearing IAC valve and bellows for AMM/throttle body, put them on and it appears to be running fine, though the check engine light came on again.
Not sure where to look next. Do I still suspect the AMM? I saw one at bone yard that appeared almost new and very clean on the inside. I hid it in case I need to go back and pick it up for 50.00.

Thanks, Kirk

p.s. The 84 died and I haven't gotten it going again. I just tried another fuel pump and same no start. Cranks, getting spark, I can hear the fuel pump but no go.
It has 320k on it and was running perfectly. Wife got in to pick me up at mechanic where I'd just dropped off 91 and it died. Mechanic gave me a ride home, felt the fuel pump as I cranked and told me it needed a new pump. I put one on that I picked up at bone yard and same thing.

"Do I still suspect the AMM? I saw one at bone yard that appeared almost new and very clean on the inside. I hid it in case I need to go back and pick it up for 50.00."

You need a spare to trouble shoot and have a known good spare on hand, I would grab the like new AMM.
Dan

I think it's a good time to start new threads. I've had no-start issues with my 84. Bought it from a guy who thought it needed a fuel pump for a song. I replaced the fuses and drove it away.

Definitely pull the codes on the 91. It may tell you the AMM is a likely bad part. Or it may save you that $50.

Please start threads for both so the board can see the new issues and help you with them.

Happy new year!
--
1990 740 Turbo, on its way to stock specs, maybe beyond

You're right, I should start new threads as this is getting a bit confusing.
Didn't want to start troubleshooting the 84 until I had a clear head on the 91.
Mechanic didn't see a code for AMM but I'm having some serious trust issues with him on this last episode so.
What diagnostic tool do I need to check the codes? I feel inferior asking but
I'm used to the older non code bricks.

Happy New Year! Kirk

You need no tools, just the FAQ. Print the 3-5 pages of FAQ on pulling the codes.
It's ODB1, it uses a flashing LED to flash codes like 1-1-3. There's a socket and an electrical bullet connector you can switch between two sockets to pull different types of codes. It's pretty easy, but the timing is a little hard to pull off. Don't be afraid to check them twice.
--
1990 740 Turbo, on its way to stock specs, maybe beyond

Thanks, will do today or tomorrow.

Hello,


As I said earlier, the procedure is listed in the 700/900 FAQ on this site.


Goatman

hi check engine code. use 700/900 faq.

goat

I checked the engine code and it's giving me a 1-1-3 fuel injection.
No codes on the ignition side.
I cleaned the throttle body which was a complete mess and now the idle is high, steady but high. Throttle position switch is not clicking like it's supposed to.

thanks, Kirk S.

I've actually never read the codes before since my 84 and 87 don't have the
diagnostics and I'm more familiar with them.
For some reason I'm still thinking AMM. When I unplug the connector to it it idles smoothly and consistent. Plug back in and it's much better since replacing the IAC but still hunts a little and doesn't seem perfect.
Could be a trip to the bone yard Sunday to pick up the AMM I stashed.

Kirk S.

Hm. I can't say! I think that's a bit odd. Make sure that the throttle stop set-screw is adjusted right and your throttle plate is shutting completely. Also make sure the throttle body is clean. Some people use the set-screw to increase idle if something like the IAC isn't working.

Being methodical is key! Good Luck!
--
1990 740 Turbo, on its way to stock specs, maybe beyond

I'm going to inspect today in daylight for vacuum leaks and check out the IAC as well. When this last round of issues started the check engine light came on and mechanic replaced the O2 sensor. It looks like he didn't even look for vacuum leaks as the hoses all look pretty untouched. I suspect AMM or IAC but need to be methodical on this I suppose.

thanks, Kirk S.

Can you swap in a known-good Idle Air Control? The IAC would be my first suspect.

Its location is close enough to the block to get some warming as the engine heats up, and that may loosen up sticky residue inside it.

Older cars with carburetors and accelerator pumps benefit from pumping the gas pedal on a cold-morning start. With FI engines one runs the risk of having too much fuel from multiple start attempts, which must burn off after the engine starts. It can run rough from a too-rich mixture during that time.

If the check valve in the fuel line is failing, the fuel delivery system can lose pressure overnight. In that case it is necessary to turn the key on and off several times to pump up the fuel to the needed pressure.

Hope this helps.

Bob

:>)

I replaced the plug wires as that was my wet weather hard start suspect but that was minutes before we took it to my mechanic that diagnosed the O2 sensor. Haven't had a hard start since we got it back from mechanic so I don't know if it was the wires or the O2 sensor.
I don't have a known spare IAC valve but that was something that was also a suspect in the back of my mind.
I'm hitting the local parts yard tomorrow or Sunday for other items and will keep my eyes open.
I should also mention once warmed up it seems to run o.k., not perfect but o.k. and at freeway speeds it seems fine.

thanks, Kirk S.