I swear this mini-van is possessed.

ManglerYJ

Well-Known Member
Joined
Mar 20, 2005
Location
Lexington, NC
I have owned this 1999 Oldsmobile Silhouette now for 6 months and have had all sorts of little gremlins in it. It all started with the hood catches failing which caused the hood to fly up and take out the windshield at 45 mph (testing out the brakes that I freshly replaced) Before we could even get it on the road, I had to install hood-pins to replace the faulty catches. Then, the smaller repairs started. First ones were more of personal convenience repairs:

1: replaced the rear blower motor that only worked some times
2: replaced the rear hatch struts (kept hitting my head on the darn hatch)
3: Repaired some torn seats and installed some lumbar "cushion" (pool noodle) to replace what had worn out.

Drove for a while and started getting a random "Low Coolant" light. Sometimes it was actually low, other times not. Replaced sensor. Kept driving and the only time it would come on would be a true low coolant situation. Periodically still losing coolant, even though it's not leaking anywhere obvious. Took it to Walt's Radiator in Lexington to have it checked and there was a crack in a tee in the heater line. Replaced tee and connector. Now things start getting expensive.

Freon was low in system so I added two cans. Got back and forth to Raleigh on a trip and A/C ran like a champ. Day later, no A/C. On way home from Raleigh, check engine light comes on at a rough startup and motor shakes at idle with no power. Code says cyl 5 misfire. Limp home from Raleigh and wife suggests we fill it with fresh gas. We do, and a few days later while rounding a corner, the check engine light goes off and stumble goes away. Drive for a month or so, have A/C compressor replaced (it's starting to get warm out!).

Saturday, I drive it to drop off my daughter at a friends house and another hard startup causes check engine light again and rough idle. Again, Cyl 5 misfire. Van still had plenty of gas so I haven't filled it yet, but still running rough with CEL.

Even though we know the history of the vehicle (bought it from good friends who had the motor replaced about a year prior to us buying it), my wife is about done with the van already. Aside from the obvious problems we've had, it's a perfect vehicle for her so we REALLY don't want to get rid of it because we won't get back a third of what we have in it, but the repairs are getting old quick.

Any suggestions of things to check without throwing parts at it? First thing everyone has said is change (in this order): plugs, wires, coil pack, fuel injector, O2 sensor (no idea why), PCM, etc. Without the ability to test parts, I HATE the idea of just blindly replacing stuff until the problem goes away. I did trace the plug wire end to end and put a piece of wire loom over it that I had laying around to see if by some chance it was touching something and grounding out. I also checked both ends to make sure they were clipped in properly.
 
Most common misfire problems on those are plugs wires or coils in that order. Plugs are cheap enough I'd throw an autolite single or double platinum in at least that cylinder, or replace all six if they're old (not sure if they were replaced with motor). If that doesn't fix it swap a wire between 3 and 5 for example and see if the skip follows. If yea buy wires if no swap coil pack and retest
 
Oh.... and did I mention that I'd love to kick the engineer who stuffed that motor underneath the windshield in the nuts. Twice.


Seems like to get to the rear spark plugs you have to remove the motor mounts and roll the motor forward. Anyone done them on that generation Silhouette/Transport/Montana/Venture?
 
Oh.... and did I mention that I'd love to kick the engineer who stuffed that motor underneath the windshield in the nuts. Twice.


Seems like to get to the rear spark plugs you have to remove the motor mounts and roll the motor forward. Anyone done them on that generation Silhouette/Transport/Montana/Venture?
At work I usually unbolt the exhaust from the rear manifold so I can move it over and do them from underneath but I'm using a lift, LOL. I'm not sure if swinging the engine forward will help since it'll lift in the rear. The entire coil/module bracket can be removed there are three connectors, two bolts to the upper plenum and two nuts down by the exhaust manifold. All can be reached from the top with the right combo of extensions and wobbles. Once the coil pack is out of there there's a little more room to work.
 
At work I usually unbolt the exhaust from the rear manifold so I can move it over and do them from underneath but I'm using a lift, LOL. I'm not sure if swinging the engine forward will help since it'll lift in the rear. The entire coil/module bracket can be removed there are three connectors, two bolts to the upper plenum and two nuts down by the exhaust manifold. All can be reached from the top with the right combo of extensions and wobbles. Once the coil pack is out of there there's a little more room to work.


A lift sure would make it easier. I may try swapping wires as you said and see if it switches cylinders. That is a no cost approach. I hadn't thought about removing the coil packs for more room. Thanks!
 
I would think a clogged fuel filter would give a misfire on all cyls or a random misfire condition, but it was something that crossed my mind when "mentally troubleshooting" it.

I was thinking in your post where you mentioned turning a corner and the stumble went away. Perhaps there's a piece of trash partially blocking fuel flow? I'm just throwing out ideas, good luck with the repair.
 
Go ahead and replace the intake gaskets. Get the high end Felpro set. That's where your coolant is going. My uncle runs 3 of these vans to haul people to a local military base for work. Been done to all 3. Rear blower motors in two of them, and one had an oil pressure sending unit bust and blow oil everywhere. They're good running and riding vans otherwise and they get pretty good mileage.
 
Go ahead and replace the intake gaskets. Get the high end Felpro set. That's where your coolant is going. My uncle runs 3 of these vans to haul people to a local military base for work. Been done to all 3. Rear blower motors in two of them, and one had an oil pressure sending unit bust and blow oil everywhere. They're good running and riding vans otherwise and they get pretty good mileage.


I really can't complain too bad (although my post pretty much is a b!tch session!) because the milage is really good for a 16 year old van with 240,000 miles on the body, transmission, etc. That was the factory compressor and the factory rear blower motor that I replaced, it just sucks that it all hit at once. Considering the age of the vehicle and the fact that it doesn't leak a drop of ANYTHING on my concrete driveway, I'm pretty impressed.

How hard of a job is the intake manifold gasket? I did a head gasket on a 1999 Sunfire and I swear it was the last head gasket I will ever do. I was much more mechanically inclined when the people building vehicles had the same size hands as me.
 
Everything is a pain in the ass in a van...you know it'll be a fun time when you need a funnel to put brake fluid in it!

My neighbor did them for my uncle. Only charged him 250 labor. It's a helluva job though. There's a lot of stuff going on with those motors.
 
I thought the Radiator shop fixed the missing antifreeze! If Not, then as Croatan Kid, says "intake gaskets". Had that happen to my 350, which are Famous for bad gaskets! I also started getting a misfire on # 5, which is where the gasket was bad.
It can also cause engine to run erratic. Another misfire problem I had, under high RPMs, & towing, was due to my in-tank fuel pump, dying. Engine was simply running out of fuel. A Good clue to this, om GMs, is the fuel gauge will be acting faulty!
 
So, oddly enough, I am leaning towards fuel filter now. The flashing check engine light changed to a solid CEL and rough idle went away a couple days after running some Lucas Fuel System Cleaner in the tank. A day or so later, the solid CEL went away as well. Occasionally still we get Low Coolant lights that come and go, but a check of the coolant level says it's OK. Temped to just bypass that low coolant sensor all together.

Wife has decided that the van will be replaced within 6 months, so I'm not sweating it too bad.
 
Probably an injector then. A fuel filter won't affect just one cylinder. You'd have a random/multiple misfire code (p0300) or lean codes and be really down on power. It could still be an ignition problem since they can come and go with temp or humidity and it coincidentally went away while running the cleaner.

If it doesn't come back though I'd put money on a fuel injector being dirty.
 
I had worked on one of these 3.4L v6 engines in a Montana. The coolant system on these engines suck. If you keep getting that light for low coolant, it most likely that you still have trapped air in the system. There are two bleeder screws (i believe 7mm or 8mm head) one on a stand pipe on top of the water pump and on on or near the thermostat housing. As for cyl 5, if i remember correctly it is the one in the rear bank passenger side, it has been a failure point for faulty head gaskets. I am not saying that you are one of the lucky ones to have a blown head gasket, but definitely get that plug pulled out and see what kind of story it tells you.
 
So the story continues.....

The other day we had another rough start, then blinking check engine light. Since the other times, the problem seemed to go away with attention to fuel, I changed the fuel filter. Sure enough, fires right up and blinking SES goes away. I will see if this takes care of the problem. If so, @flatbedtoy nailed it.
 
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Is this the 3.4L or 3.8L? I thought the 3.8 was the one with the intake gasket problems. May not be the only one though. In my own experience just a couple weeks ago, the flashing SES light leans toward a bad plug wire. I replaced plugs and wires, and the problem instantly went away.
 
They both had issues with intake gaskets, it's just much more difficult to change them on a 3.4. The 3.8s were usually just the upper intake halves warping.
 
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