91 Metro 1.0 3cyl. automatic engine idles high then low in park and sputters up hills

[doug2060]

My 91 metro has idled high since I got it but now I have a problem. When I first crank it, it's fine but after driving a while I will put it in park and it will idle high then low over and over. It started after I was going down the highway at 60mph and it started cutting out real bad but I could still drive it at about 20mph but if I got it past 30 or 35 it would start again. When I would take it up a hill it would get worse. I parked it and let it cool down a few hours and it was fine. I even drove it about 100 miles in one trip with no problems. Then it started again while I was going up a fairly steep hill. I checked the spark plugs and the one on the end near the transmission had a lot of white build up the other 2 were fine but were a bit white but good and not anywhere near as bad as the last one. I replaced them all anyways. The car has new plugs, wires, dist cap and rotor button. I can drive it all day long without a problem and then it will start doing this. Usually going up a hill or at high speed and gradually gets worse until I turn it off and it cools down for about an hour then I can drive it another day or two befor it starts again. I'll start checking the intake and see what I find there. Any help is much appreciated.

PS- The check engine light does not come on when this happens...

[doug2060]

Compression checks out good.

Timing set to specs

idle still high but it was when I got it and can't be lowered anymore than it is. (are they normally high idler's?)

I also tightened up on some throttle body screws and bolts. (not much looseness but worth trying.

I also tightened up on the exhaust manifold which was somewhat loose (not much but not at spec) and had a missing bolt at the end where the bad spark plug was I described earlier (I did replace it).

Still doing it...

[spy1309]

White spark plug means that u are running on the leans side, also your engine will run hotter than ussual.
Missing a bolt on exhaust might create problems for you because during the exhaust pulses air might be drawn inside and pushed inside exhaust pipes tricking the O2 sensor that you are running leaner than you actually are.
In my oppinion fix that manifold and get a new gasket installed before you do anything else.
Is known that a hot engine runs on the lean side coupled with your leak you engine runs extra lean after a long trip.
End of the story get the leak fixed first.

[brivers]

Idle adjusted all the way down? Sounds like you have a vacuum leak. Check all your hoses and anything associated with the intake manifold, including gaskets and brake booster. If you take a can of either and spray around components while engine is idleing it may show you the leak when engine rpms change. Good luck.

[DOCTORBILL]

We all need more information about your Metro.....

Do you have a Chilton or Haynes Manual to help you (ha!) ?

How many miles on the engine?

Do you have a Catalytic Converter? Is yours full of melted crap?

Are there any vacuum leaks? What is the Vacuum reading?

Is your "Check Engine Light" working?
Does it come on when you turn the key?
If it is burned out, you'll be missing important messages from the ECM.

Is/are your O2 sensor(s) OK?

Could your engine Temperature Sensors be going bad?

Could your Intake Air Temperature Sensors be going bad?

Does the engine overheat?

If the problems shows up when the engine gets hot, it may be related to one
or more temp sensors.

Are there any computer connections to the Automatic Transmission (anyone?)
I'm thinking about the Idle Control Module.

Could the Throttle Position Sensor be going bad - worn contacts?

Many of the above small sensors and parts can be obtained at your local Pull-n-Save lots.

Also, how about Carbon in the EGR Valve and galleries? Mine was completely
plugged up from the Exhaust Manifold, thru the EGR back into the Throttle Body.

Is the PVC Valve working? (A $5 item that regularly goes bad).

Intermittent problems could easily be caused by bad contacts/wires - these will drive you crazy!

That's all I can contribute....anyone else? Crvett69?

DoctorBill

[RossT]

Yep, I vote for vacuum leak too. I use carb cleaner to find them.

[DOCTORBILL]

I put this together to test for Vacuum Leaks...



The Propane makes the engine idle faster if it is sucked into a vacuum leak.

Less chance of starting a fire and is easily directed and turned off.

For what it is worth....

DoctorBill

P/S - Its not really patented...I'd just like to think so.

...and I've never really tried emptying a $2.50 can of propane into a Gopher or Mole tunnel,
but this summer I may do so...then ignite it. Gophers and Moles were invented by the devil.

[doug2060]

All my vac lines are fine. Everything is good and the thing runs fine for days at a time with no issues the suddenly goes ape sh*t until it cools off for about 30 min. to an hour. I'm thinking the catalytic converter. I haven't looked at it yet. Are there any o2 sensors after the cat on a 91? What if any negative affects if I were to gut it (other than destroying the environment)because I can't afford to buy one at the moment? I haven't had any trouble with it lately until I had been driving for a couple hours earlier this week then started to go up a steep hill and it did a little sputter but then straightened out. The car has nearly 150k...

[91Caprice9c1]

Check your fuel pressure and look at your fuel pump relay for signs of burning.

-MechanicMatt