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PostPosted: Wed Nov 21, 2018 10:56 pm 
LE Member

Joined: Sat Nov 17, 2018 7:00 pm
Posts: 1
Location: Kansas
Year and Trim: 1989 Bonneville LE
1999 Bonneville SE x 2
New to the form. Thanks for the acceptance. I've been around a while and done a few things including all my own maintenance for 50 years. The Bonneville affliction started with a 93 that ran up to 385K before the tranny learned to slip and slide. Presently one 99 nearsighted Bonneville is able to see 400k very clearly, with original engine and trans. Rod bearings as an easy preventative were done at 200k and 300k. Also at 300k did a timing set and oil pump for giggles. Rod bearings again at 400k and it should be good to go another 100k, no tranny issues what so ever and pan comes off looking pretty nice and clean inside. Other Pontiacs include an 88 Fiero and a 99 Firebird, both needing new homes being out of space. And I have an 89 LE, why I joined, seeking some input.

The 89 LE has 2 issues, starting and cooling fan operation.

Starting - Current status
Cold crank - Hold key to crank and it will do just that with little to no fire. But if you crank for 1 - 2 seconds and wait 15 seconds, then it will instantly start. Too rich, right? The 15 seconds allows for vaporization. It will also start if crank 1 second, stop, and crank again for 1 second. Sometimes it takes 4 tries of these short crank cycles. Once running all is good.

Starting - Earlier status
Difficulty starting hot or cold but replacing idle air control motor (IAC) helped tremendously. I suspect this is still involved but have tried 4 of them, some work better than others even after reset procedures. It idles perfectly with the one on there now. It would not surprise me if this is still the culprit or more like it, what controls it.

Warm crank - It always starts and tends to mostly fire right off if cranked momentarily and let go of the key. If holding the key on a bit long you would quickly sense that it tends to go into a crank but no or little fire mode.

The 2 wire coolant temperature sensor, intake air temp sensor (IAT), and as mentioned the IAC, along with crank sensor have all been replaced. I have added ground wires everywhere, i.e., battery to block, block to chassis, battery to ECM housing (behind glove box on right) with no change. Battery tests good although getting close to weak on the scale at 7 years of age but no issues with crank. Fuel pressure holding normally, around 40 as I recall, when starting. Showing 180k (yes put in rod bearings at 155k when acquired car). Fuel pump replaced not long ago and fuel pressure regulator. Regulator hose is dry inside. I have removed and unplugged the fuel evap cannister hose in case it was saturated with gas and causing a rich start. No change there. No vacuum leaks detected checked by pinching off all hoses and also spraying Gumout (don't do this at home) around potential areas with no change in idle.

Cooling Fan
The LE model with AC has only 1 fan with the usual 2 speeds. They come on with the AC, although it is finally low on R12 (not a typo) so cycles off pretty soon. Fan comes on when pulling codes with a paper clip, normal from what I have read. Fan is off when start a cold engine. But it comes on when the temperature gauge is only 1/4 of the way to normal operating temperature. And it never shuts off running on high (I think it is high when first comes on but not sure). Swapping relays has made no difference and don't see how they would since they function and are not stuck open or closed. The 2 wire coolant temperature sensor has been replaced with 4 different ones, so likely not the problem. Temperature gauge sender, single wire, replaced, no change with the fan as expected. Wire inspections (what I can see) reveal protective covering and no chafing on exposed insulated portions.

The car runs great although only gets 23 mpg with a lot of city highway where my 99 Series II will always get 30 if I try to conserve and can squeeze 33-34 driving 55.

At this point I suspect the computer (ECM) for maybe both the fan start issues and possibly low mpg but do not know how to test it. The replacement cost is too high for just trial and error on an old car even if in great shape.

Any wisdom, thoughts, or encouragement would be greatly appreciated from some of you experts.


Sorry for being long winded but felt you need the whole story to sort through from your end.

If I have violated protocol and should have posted this somewhere else, just point me in the right direction.


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