1987 GMC Safari running problems

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  #1  
Old 11-25-02, 08:30 PM
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1987 GMC Safari running problems

Greetings to all. I have a 1987 Gmc Safari van, V-6 engine, auto tranny, air conditioning, approx 112,000 miles. I just bought this about 3,000 miles ago. Ran great when I bought it. Now it's not running so good so I thought I'd bring the symptoms through here and see what comes up. It has always started good, starts quick and idled smooth. It still starts good and idles smooth, but if it is not warmed up good and I drive it, it will run rough until it warms up. Then it develops a "stumble" at lower rpm's under load. If I rev it up when it is in park, it runs smooth. If I am driving up a hill or under load it will run rough and possibly mis-fire. If I am driving and it starts running rough, and I step on the throttle hard, it seems to run smooth, but when I return to cruising speeds of 55-60 mph the rough running returns. Just prior to when it started running bad, if I let it idle when it was warm, the check engine light would come on, and then when I resumed driving it would go out again. The check engine light does not come on now when it is running bad. Tonight I put some injector/carb cleaner in it as well as some gas line anti-freeze into the tank in case there would be some water or ice in the lines. Sooooo, any suggestions? Any inherent problems with this type of machine? And also a couple of other general type questions. There is a product called Iso-Heat, which is a gasline antifreeze and contains isopropyl alcohol (which is basically rubbing alcohol), can I just use straight rubbing alcohol? What would it do to an engine? Anxiously awaiting replies, thanks in advance and Happy Thanksgiving to all.
 
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  #2  
Old 11-25-02, 10:37 PM
knuckles
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When was the last time this thing was tuned up?

These vans are good for secondary igntion problems. Check/replace spark plugs, spark plug wires, distributor cap & rotor.

These vans are also good for vacuum leaks. Check the various hard plastic & flexible rubber lines for cracks, breaks, etc.
Repair any cracked or broken vacuum lines.

Let us know where this gets you & we'll go from there.
 
  #3  
Old 11-26-02, 06:16 PM
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A couple more questions about the van

First of all thanks for the reply. I checked the vacuum lines and they all seem good and sound. I checked the cap and rotor as well and they both seem good. I think I will replace the plugs and wires and cap and rotor this weekend just to be safe. Now for the couple of questions.

I know the plug wires can be tested with an ohmeter, do you know what the readings should be? Does the reading vary by length of wire?

One thing I forgot to mention, the van was low on oil when I checked it a week or so ago. After I put in the oil to the fill line, the gauge wouldn't work right. The pressure showed up over 80 pounds. Tonight, when I was checking the vacuum lines, I checked the connections on what I think is the oil sending unit. Everything looked tight and clean. When I started the van up the gauge still seemed to be malfunctioning, and it still ran the same. THEN, on the way home from working on it...I had to accelerate hard, and the van seemed to run out smooth again, like it did when I first bought it. Then I noticed that the oil gauge was working. If this, or any, sending unit is not working, will it send signals to the computer and cause the vehicle to run bad? Thanks again. I hate to be so long winded about this, but I guess the more info I provide the better chance I have of getting good feedback.
 
  #4  
Old 11-27-02, 09:55 AM
Joe_F
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The sending unit only operates the dash gauge, it has nothing to do with the computer.

Again, as mentioned by Knuckles, do a full tuneup with quality parts. Sounds like this has not seen service in a long time. First place to start.

Let us know what you find.
 
  #5  
Old 11-30-02, 01:13 PM
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Back to the basics.
Check your fuel filter.
Check your base ignition timing. Contrary to what you'll read here it does make a difference. (Check the GM Manual under Drivability Symptoms)
Additionally you may want to yank your EGR valve and see if it's carboned up. (Use a new gasket when you replace it.
 
  #6  
Old 11-30-02, 09:20 PM
Joe_F
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Check your base ignition timing. Contrary to what you'll read here it does make a difference. (Check the GM Manual under Drivability Symptoms)
---

I resemble that statement . Lol. Base timing is a different animal than most folks typically try to set. Many folks are timing it the old fashioned way...when vehicles had vacuum advances. Truth is that does nothing.

Shouldn't have to alter base timing either unless there is a factory modification or other problem. Stretch in the timing chain at this point is always a possibility too.
 
  #7  
Old 12-01-02, 12:50 AM
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Joe, I agree on most of what you say but I beg to differ on this point.
In my '90 GM factory manual, page after page tells you to check your ignition timing. You have said a hundred times to do what the OEM says. Well?????

I can tell you from experience on my '89 Burb it makes a very noticeable difference in Open Loop idle and WOT acceleration.
 
  #8  
Old 12-01-02, 08:30 AM
Joe_F
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Yes, follow the OEM.

Check your BASE timing and set it to what? Factory spec as shown on the underhood sticker . Most OEM manuals tell you to do that....so we agree .

That I agree with. However, many folks simply believe they can rotate the distributor as with old cars and "tune it by ear". Years ago, you could do that. Now, it requires disconnecting the timing connector and a different procedure. Most times if you have to change the timing from something other than factory spec, there is something wrong .

What did you change the timing to?
 
  #9  
Old 12-01-02, 01:58 PM
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Long story short...
Had camshaft problems which threw out a knock sensor code. Engine self tests EST and could not create a knock, computer thought it had no control of EST and let go of timing. Bright light - no power. When base was advanced from O (OEM Spec) to 8 BTC, it could cause a knock and correct it. Idled like crap in closed loop!
Took a couple of weeks to figure out.
Made me really miss my old Pontiac.
 
  #10  
Old 12-01-02, 04:38 PM
Joe_F
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As noted, there were other problems .

I can tell you when I got my 79 400 Trans Am, the timing marks and pointers were colored yellow, so I knew that someoe had been in there before I got to it. Sure enough, the timing was bumped up to about 22 degrees..factory spec is 18. Cranked it back down and it hot started better .

I can tell whoever timed it did not have an advance dial type timing light because 18 is at the end of the physical scale. However, using an advance light puts the timing at zero with 18 degrees advance dialed in and the vacuum advance disconnected.

Dollars to donuts, Pontiac provides more driving excitement .
 
  #11  
Old 01-21-03, 07:13 PM
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1987 gmc safari running problems, fixed

The problem turned out to be a clogged catalytic converter. I came up with the trouble code for a bad oxygen sensor and deduced that the converter must be plugged. Took it off and sure enough, one end was black and clogged. Runs like a new vehicle now. Thanks to those who replied and I hope this helps someone else.
 
  #12  
Old 01-22-03, 03:55 AM
Joe_F
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I hope ya changed the sensor and also gave the vehicle a good tuneup and servicing or else the new converter will meet the same fate .
 
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