Engine Cut Out and High Idle

I have learned from this forum that there are many knowledgeable car guys that have help with my '95 Riv. Well my '88 Olds Toro has been randomly suffering from engine cut out while I am driving. It usually happens when I remove my foot from the accelerator, mostly at speeds under 10 mph but occassionally in the +10-40 mph range. If it is not cutting out, it is racing at around 2500 revs (as I am driving say 35 mph @ about 1500 rpms, I lift up on the gas pedal, shift into neutral and the rpms go to 2300-2500). When I come to a complete stop in drive or neutral, the idle does return to 750 in about 15 seconds ands stays there. I replaced the throttle position sensor with no luck. The onboard diagnostics computer is not throwing any error codes. Anybody have any ideas? Tx, Ren

OK so I'll think out loud about this one.

Do you have an OBD-1 compatible scan tool? See http://forums.corvetteforum.com/c4-scan-and-tune/885608-1987-oldsmobile-tornado-with-obd-1-read-out.html.

Is your check engine indicator on?

You will probably need a scan tool to get the basic info needed to fix this. Sure we are helpful but the questions that have to be asked to make this fix will likely require some scanning. Running scans will tell you which sensor (if any) is dead so you don't waste $$ replacing stuff that is good. Might try to find an Actron CP9145 or CP9185 used. Like this

http://www.bonanza.com/listings/Actron-s-Super-AutoScanner-OBD-I-II-Scan-Tool-CP9145/66538591

you will have to get the OBD I cable from Actron. At that price you might as well buy new, actually - check Amazon.com or call around. Alternatively look locally for a garage that is closing or a mechanic who is updating his or her tools - in metro Detroit that should be do-able and you'll be helping them out by buying the good used tool. I'm thinking $75 or less cash.

Another thought - When was the last time you replaced air filter, and do you know if there is a mouse nest in the air box?

What you probably want to do is connect the scanner and take a log of a test drive where you experience the cutout or racing. Racing at around 2500 RPM sounds like a sick MAF but that is ONLY a GUESS. And why you expect anything to be normal if you are driving at 35 and put the car in neutral - well I am sure it has an explanation but I have no clue what it might be. However, it is what leads me to think the MAF may be ill, as if it is reading somewhat, then the PCM then has to put in default values for fuel injection and throttle position so you don't stall. If you have a scan that shows the air flow values that would tell you right off.

1) I currently do not have the OBD-1 scan tool. I will try to locate and buy a good used one.

2) the air filter is a K&N and is clean

3) As far as why I put it in neutral At 35 mph, it just felt different the way it was driving even though in "Drive" the rpm read 1500-1600 but it jumped to 2500-2700 when I took my foot off the gas pedal and put it in neutral. I was just confirming that it was acting up. In fact I really have to apply the brakes quite a bit firmer when it races and I keep it in Drive but once I come to a complete stop the idle does return to normal, both in drive and neutral.

Maybe I should get a can of MAF cleaner?

Thanks for your help.

There is a problem with K&N filters fouling the MAF if the instructions for oiling and what not are not followed EXACTLY. Actually, that may be the bulk of your problem.

anyway... If you are going to clean the MAF, its best to get both MAF and TB cleaner, and a new TB gasket. Pull the TB and clean it, use an aluminum pie plate or some such as a cleaning tray. While you are in there clean the air passages to the idle air control. You may want to pull the IAC to do this - if so you want to search for the posts on this site about cleaning and resetting it. This may also be a cause of problems (sticking IAC) but I have not heard of an IAC doing quite this.

Pulling the MAF, cleaning the TB, adn cleaning/replacing the MAF and IAC are all what I'd put on the "deferred maintenance" list. In maintenance by the book so to speak teh GM mechanics are supposed to clean this stuff in high mileage car "emission service" but usually don't go much further than connecting the car to a BG machine or some such.

Anyway...

If the MAF is fouled the TB is more fouled. And on these cars you can't really spray the TB clean, all it does is pile the gunk lower in the air intake, which is then a real pain because of the idle air control ports.

At your car's age you *may* simply want to replace the MAF sensor if it is dodgy. But you need the scan tool to tell.

So what I would do:

- get a replacement TB gasket, they are easy to get but you may have to get it mail order (rockauto.com)
- pull the K&N and either reinstall the old air box or wash it and re-oil it exactly per instructions and reintsall. Do not overoil it under any circumstances.
- pull the TB and clean it including the backside.
- using TB cleaner clean the intake area, you may need some red rags to stuff in the intake hole temporarily to catch the TB cleaner and the loosened gunk. If you have been running a K&N for a while I guarantee you ti will be foul in there.
- using the TB cleaner clean out the IAC air passages. Check this site for how to clean and reset the IAC - you may need to replace it.
- while the TB is out remove and clean the MAF, you may need to replace it (scan tool read before you work will tell)
- clean the excess oil out of the air horn (the air intake tube from the air filter to the TB)
- reassemble, while you are at it check for breaks in the electrical harness to the MAF and IAC.

Other input?!?

Thanks for all your input and time Albertj. If you ever get to metro Detroit I'd like to buy you an adult beverage of your choice. I will whittle away at your suggested steps after I get a new compressor on my '95 Riviera this coming week. Also, I went with the K&N that fits inside the OEM airbox. It is really clean.

A note on K&N filters.A K&N filter wont need to be cleaned on a passenger car for YEARS! If its red its treated.If it becomes WHITE it needs to be treated.There are street cars out there with more than 70 thousand miles on one treatment.So no one has to clean the filter hardly ever!
Remember,IF ITS RED IT AINT DEAD!

p.s if the filter gets dusty and little flecks of dirt, bird feathers and what not,just find an old paint brush and gently brush off the debris.
Oem type K&N filters are more prone to gathering debris on account of them being enclosed.With an open air filter debris just swirls around and gets deposited allover rather than on just the filter.....

Your IAC motor could be acting up as well, but that may be due to your MAF problems. (IAC = Idle Air Control)

rivren wrote:

Thanks for all your input and time Albertj. If you ever get to metro Detroit I'd like to buy you an adult beverage of your choice. I will whittle away at your suggested steps after I get a new compressor on my '95 Riviera this coming week. Also, I went with the K&N that fits inside the OEM airbox. It is really clean.

Clean is great, but if overoiled the oil can form an aerosol of sorts that partly covers the MAF.

Albertj, Good point.

A big thanks to Albertj & Deekster_Caddy for your great insiteful suggestions. I installed a new, regular air cleaner, drove the car with no improvement. I cleaned the MAS and TB, drove the car with no improvement. I installed a new IAC today, drove the car all day and never had a cut-out. I kept re-creating the situations that usually produced a cut-out/stall and never had a problem. I think it's fixed. Now I can replace the compressor, drier and expansion orifice tube to get the air running. Thanks again for everyone's input.

rivren wrote:

A big thanks to Albertj & Deekster_Caddy for your great insiteful suggestions. I installed a new, regular air cleaner, drove the car with no improvement. I cleaned the MAS and TB, drove the car with no improvement. I installed a new IAC today, drove the car all day and never had a cut-out. I kept re-creating the situations that usually produced a cut-out/stall and never had a problem. I think it's fixed. Now I can replace the compressor, drier and expansion orifice tube to get the air running. Thanks again for everyone's input.

Thanks for posting your results. I had not heard of a bum IAC doing this but in combination with the other cleanings it sounds like you fixed it.