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1989 Buick LeSabre Cold Start Problem


prginocx
07-20-2004, 09:00 PM
Hello everyone I am new to the forum.
Car has 79k miles and has been well maintained. Oil / filter. New Serp belt, New alt / Battery, new fuel filter, new plugs, new wires, Air filter element, New PCV valve (Pain to insert), New 02 sensor, all in the last year. Bought vehicle used from a grampa with 72k miles.

Great running car, Starts first time when warm, after 2-4 cranks every time. Runs well, seems to have power enough (I don't drive it normally it is the wife's car).

Problem is very repeatable. AFter being off for over 5-6 hrs or longer it won't start on the first try. EVER. Crank 10 Revs and it won't start. You always have to turn the key off and crank again, then it catches right away. I do hear the fuel pump coming on for about 2 seconds. I do have fuel pressure at the injector manifold rail (Just bought the gauge, Will measure soon). 2nd cranking it starts and It also seems to take a second to idle up to choke RPM, I assume this is the delay of the IAC closing / opening. After the faster Idle is achieved it stays that way for about 4-6 minutes, then idles and runs great.

I have verified the TPS adjustment to .4 volts when butterfly is closed. It was off a tiny bit. I have verified spark on one cylinder during this cold crank no start condition. As you can imagine this is a difficult problem to troubleshoot, cause each test / check must wait about 5-6 hrs for the problem condition to re-occur. I did replace the temp sensor. I realize I'm being picky to work this issue, but I'm afraid it will grow into a real issue and leave me somewhere. I did run some fuel injector cleaner stuff, made no difference (As expected). I have replaced the air filter. There was some debris clogging the intake upstream from the filter and I removed that stuff.

Any pointers would be appreciated. Is there any other maintenance items I should know about ? Thank you.

rustbucket
07-21-2004, 08:25 AM
Wire up 2 wires to a small 12V light bulb and take off an injector connector and plug your test lamp in the connector. It should flash as you are cranking. It verifies the ECM is pulsing the injectors.
Also, the IAC operation sounds funny, perhaps it is sticking. When you turn on the key, it is supposed to go to full open (or closed, i forget) to acheive fast idle for starting. Then when it starts, the computer moves it to acheive the idle it wants. You may want to take it off and clean it up. (dont try to test it by leaving in plugged in and turn on the key while not mounted, Parts and springs go flying!)

yogi_123rd
07-21-2004, 02:05 PM
I too have experienced this problem in my 90 Lesaber and I am very interested as to what causes it. Exactly as you have said, the first turn of the key you can crank and crank and it does not fire. The second turn of the key is always an IMMEDIATE start.
For what I observed, the problem only occurs in temperatures below 60 degrees.

yogi_123rd
07-21-2004, 03:04 PM
I've had a few more thoughts on this problem. I've always thought it was an electrical problem, but you seem to have tested that end. If it's not electrical, there's no gas getting to the cylinders. You mentioned a possible sticking IAC. Hmmmm. What if no AIR was getting into the manifold. The air flow in the throttle body consists of a main bore (for acceleration) and a 1/4 inch bypass bore hole (air bypasses the main butterfly value) for idle which is regulated by the IAC valve.
If the IAC valve is stuck shut, no air can enter the maniford. Fuel injection just injects fuels into the manifold, not the cylinder. The pistons will not be able to suck the gas into the cylinder.
While looking in from the outside of a throttle body may look relatively clean, they are typically grundgy with heavy carbon and oil buildups. The crap comes from blow-by introduced thru the PCV and it gets everywhere.

Since you have reproducable problem, start the car and use liberal amounts of carberator cleaner directly into the bypass hole for the idle system/IAC. You should see that hole off to the side when looking into the throttle body's bore and before the main butterfly valve.
You should know by the next cold crank if that was the problem. At the very least your idle problems may go away.

prginocx
07-22-2004, 07:36 PM
I've had a few more thoughts on this problem. I've always thought it was an electrical problem, but you seem to have tested that end. If it's not electrical, there's no gas getting to the cylinders. You mentioned a possible sticking IAC. Hmmmm. What if no AIR was getting into the manifold. The air flow in the throttle body consists of a main bore (for acceleration) and a 1/4 inch bypass bore hole (air bypasses the main butterfly value) for idle which is regulated by the IAC valve.
If the IAC valve is stuck shut, no air can enter the maniford. Fuel injection just injects fuels into the manifold, not the cylinder. The pistons will not be able to suck the gas into the cylinder.
While looking in from the outside of a throttle body may look relatively clean, they are typically grundgy with heavy carbon and oil buildups. The crap comes from blow-by introduced thru the PCV and it gets everywhere.

Since you have reproducable problem, start the car and use liberal amounts of carberator cleaner directly into the bypass hole for the idle system/IAC. You should see that hole off to the side when looking into the throttle body's bore and before the main butterfly valve.
You should know by the next cold crank if that was the problem. At the very least your idle problems may go away.


I have since verified the fuel pressure at the rail (37psi) during the cold crank no start. I'm going to look into cleaning the intake manifold upstream from the throttle butterfly. It does have black gunk accumulation. I did find one of the nuts missing from the three holding the ECM onto that aluminum bracket. I also cleaned and squeezed all the connections inside the "Brick". I wire-brushed the surfact under the nuts to assure a good connection. One of the torx screws holding the cover on was missing so that is replaced. REset the computer, cold crank problem is still there, but I believe the car seems to have al little more acceleration now. Plenty of get-up-n-go for a grandma car, HA !

sallisonbrown
07-22-2004, 09:07 PM
I had the same basic problem but it was on my old 89 pontiac with the same engine/tranny combo. I never figured it out but did figure out how to get around it.

Never, never, never put your foot on the gas when you go to start the car! If someone else tried to start it and depressed the gas it would crank and crank. Once turned off and then back on it would generally start but not the first time!

Can't hurt to try and doesn't cost a cent to try it. Let me know if it works for you.

Steve

shadow28
07-27-2004, 11:54 AM
My 90 lesabre did the same thing at 100,000 mark.

I used about 2 cans of gumout in the intake and did a can of sea foam thru the vacum line.

car runs like new now I have 170,000

Jed Rule
07-27-2004, 07:19 PM
Had the same problem on an old Olds 98, same engine. I had to cycle the key on/off twice to get it to start when temp was below 30. Then I found updated prom addresses this problem. Immediate fix. Inquire at the dealer, it's not expensive.

prginocx
07-30-2004, 05:31 PM
I did throughly clean the IAC valve cone and the seating area. There was a lot of black residue on that area. However the cold start problem still exists. I'm going to look into the new ECM prom deal.

yogi_123rd
08-01-2004, 12:12 PM
To err is human, but it takes a compter to really screw things up.

I'm just guessing here and thinking out loud. If the
car has evidence of spark, gas, compression and the car still don't start. Is it timing??? Is the correct cylinder getting the spark? How exactly does the electronic ignition module know which cylinder to send the sparK to. In reading up, it just says the ECM uses the crankshaft position sensor and the camshaft position sensor to figure out timing. If the previous poster, Jed, is correct, then it must save the next cylinder number to fire into the prom and use it on a restart. A bad prom and this info would be lost.

I'm really interested in what this problem resolves to be.

rustbucket
08-02-2004, 08:22 AM
On th 87, the manual says below 400 rpm (ie when cranking) the ECM does not control the spark, it is done by the ICM. When it goes above 400 (started), the ICM tells the ECM to take over and it can do the spark advance, etc. The ECM does control the injectors, and it says below 400, it is pulsing them all. Did you do the injector test with the light bulb?

prginocx
10-07-2004, 11:58 AM
My manual says to adjust the IAC cone so the tip of the cone is about 1.125" from the o'ring seal seat. This adjustment is done with the IAC removed after a normal engine shut down. The valve is spring loaded and can be adjusted in or out by twisting it on its threaded shaft. After exploring the area the cone valve extends into I realized there is a ton more room for the valve to extend into this area. It was in no danger of bottoming out, which is what the manual warns about with the 1.125" limit.

I can perform a cold start fine with the IAC removed and this area plugged up, so I figured the IAC wasn't limiting the airflow enough to give plenty of fuel upon cold startup. I adjusted it to about 1.20" and now I can start cold. I've waited to post to really try it out over a couple weeks and it starts on about the 3rd or 4th crank cold which I figure is about average. Car seems to idle normal.

P.S. During routine maintenance I checked the CV boots and at 90k miles they are fine, look almost untouched. How come I had to replace the boots on my wife's Honda at 90k miles ? I thought Japenese cars were so much better ?

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