Hey Everyone! My new to me 89 Lesabre with the pre-series I 3800 has a stalling problem that is not throwing a CEL. I bought the car a week ago and noticed that when the car is cold (sitting overnight) it can be a real pain to start. Lots of cranking and eventually it catches. At idle it runs ok, the idle jumps up and down a couple hundred RPMs. I assume that to be the TPS, possibly pertain to this issue?

A few days ago it tried to stall on me and threw a CEL, code 41 cam pos sensor. I replaced that with a duralast one and the code never came back. The old sensor looks like something had been rubbing against it before. The cold start issue stayed the same. The following day I upgraded the magnavox ignition to a delco system. Idle smoothed out a but after that but still had the hunting going on.

Now today in the morning it was a pain to start, but this time stalled after I got it running. I restarted it, and it stalled after a few seconds. I had to hold the gas down a hair on the 3rd start after it started. After holding it for a minute it was fine. Almost stalled when I put it in gear but recovered from it. I went out to lunch and it was a repeat of this morning.

So with no codes to work with, anyone ever experience this? I'm a bit stuck and not sure where to start. Thanks!

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1989 Buick Lesabre T-Type-140K
1987 Buick Lesabre Custom-152K

First check that all spark plugs and wires are not broken. It's easy and only takes a few minutes. Then make sure the voltage at idle is above 13. Most auto parts stores will test your alternator for free.

Most likely causes are low fuel pressure or ignition coils/wires/plugs. With the cam sensor problem you had, I also recommend removing the sensor and checking the magnet on the cam sprocket, which you can see or feel through the hole for the sensor. It sounds like the magnet partially broke off.

I also recommend getting a PC based OBD-1 scan software if you have a laptop. You can see for yourself what the computer is seeing. Easier than probing around with a DMM and chasing ghosts. I can direct you to some good info if you are interested; best investment I've made for a car in a long time. The OBD-1 systems are sorta bad at telling you when a sensor is bad, so actually seeing the readings is a better tool than a field diagnostic, and no dirty hands. The software will work on all OBD1 computers (and works on our '95 OBD1.5 park avenue)

For the most part, anything that can cause hard starting will also cause other drivability problems. Here is a long list of "possibilities" derived from the service manual for the '89.

Hard starting
With the hard starting issue, I would check for fuel pressure before and after the initial prime. The fuel system should maintain some pressure overnight so that the fuel pump doesn't have to pump long to bring it up to about 40psi on the first prime cycle. You might also have a bad injector or dirt buildup in the fuel rail, but only if you notice any misfiring during normal driving as well. Make sure the fuel filter isn't 22 years old... If it's not a fuel pressure issue, it could be a timing issue. You need a timing light, a pencil, some cleaner, a protractor and a silver sharpie to make your own timing marks to know for sure. The '86 & '87 engines were prone to hard starting when the nylon cam sprocket was failing; your engine doesn't have that nylon part but if the timing chain has jumped it can cause hard starting. This would not be a common issue. More likely is that the magnet on the cam sprocket has been damaged or fallen off. This requires a mirror to look through the sensor hole to check the condition of the magnet. If it's broken, it may have hit the old sensor and isn't strong enough to trigger the sensor on time, which will throw your timing off. Timing is (almost) everything to a good fire (except fuel and oxygen)

Poor Idle

Idle may be the Mass Air Flow sensor (MAS). It may be dirty, or the element may have oxidized if it was hit by anything. Check that it is free of any soot (use a soft brush and MAS cleaner to lightly brush the carbon off). Also, check that all the air ducting and vacuum hoses and gaskets are sealed properly. A bad MAS can cause all of the hardest to diagnose drivability issues like misfiring and hunting for RPM, stumbling on sudden throttle changes, etc. Also, if the coolant temp sensor is off bad enough it can cause hard starting. Use a DMM to measure resistance to check the sensor. The EGR valve may be stuck open and would cause hard starting and rough idle. The TPS could cause this issue if the internal spring is broken and it is allowed to 'float', or if the signal voltage adjusted too high at idle the car will idle high. This wouldn't normally cause hard starting or hesitation BUT it can. The best way to test is using a DMM and testing the sensor. I think it should read .5v at idle and 5v at wide open

Hesitation
Dirty or corroded ground wires to the ECM; just check the connectors and clean as needed. Most common problem is a bad ignition coil or plugs/wires. Fuel pressure, MAS, TPS, can all cause hesitation as well. (TPS might have a broken arm and not change with the throttle)

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Boost addict


The Fleet:
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'97 Camaro - Top swap
'05 STS - V8, AWD, her DD
'92 Trofeo - Fair weather DD
'99 Montana - top swap 3800
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'92 Bonneville SSE
'87 LeSabre T-type
'67 LeSabre

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'97 LeSabre - Top swap

RIP:
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I have a '95 Bonneville that has the OBD-1.5 system.
What PC-based scan software do you recommend for my laptop?
Do I need to buy any hardware other than a cable to connect 16-pin OBD connector to USB connector?

I had poor idling issues with my '87 Olds 88, I cleaned out the idle air control and that fixed it. However cold starting was never a problem, stalling with the engine warm was my problem.
On several European cars I've come across bad engine temperature sensors that will go to maximum enrichment if they went open circuit (constant flooding) or lean right our if shorted - like starting a carburettor engine with no choke.
Worth a look along with all the other suggestions posted.

Roger.

Definitely the IAC or idle air control valve. When the rpm's are jumping up and down it means it clogged or sticking. Pull it off and soak it in a good cleaner.