1989 S10 Blazer miss

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Hello All,
I've got a 1989 S10 Blazer 4x4, 4.3L, auto, TBI, with approx. 175K miles on it. Last week, my wife, on her way to work, ran over a rock. Since then, the engine has developed a miss. I'm not saying the cause
of the miss was hitting a rock, but I thought it might be relevant. The miss is especially noticeable under a load. I have tested the coil and distributor pickup, both are OK. The vacuum tube where the PVC valve attaches to the bottom ot the TBI was clogged. Cleaned that and now have vacuum there. Replaced the PVC valve and air cleaner just because it was time. This week I'll replace the plugs, check plug wires, and throw a bottle of Techron in the tank. Nothing so far has eliminated the miss. I need help with this. What is the next thing(s) I should be checking? EGR? IAC? Would LOW back pressure cause this? (I found the muffler was loose where it attaches to the cat.) By the way, there is no service engine light illuminated (bulb works). I have not checked for codes because of this. Any help appreciated and welcome. TIA
Leyton at Tahoe
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Describe the miss, please. H
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A code can still be stored even if the light is out....K
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You won't get a misfire code on a 89 vehicle.

-
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Very easy way to find which cylinder is Missing
Start up the Cold Engine
immediately start touching the EXHAUST manifold NEAR each plug
if the Manifold is warm near a certian plug Than that Plug is Firing. if it is cool( cold) then that plug ISNOT FIRING!! Now u need to check that PLUG as well as resistance of That plug wire . also look for a Carbon Arc in the Distributor cap where that plug wire fires from.
ONLY TRY this on a COLD ENGINE .
I have used this method Since 1953
L8ndeb wrote:

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Thanks for the responses. A little update. I did hook up my code checker and only got the "12" code. "No reference pulses to ECM". It was getting dark, so just for sh-ts and giggles I started her up and looked under the hood. I found a small arc from the plug wire to the exhaust manifold around number 5 cylinder. Also, the spark was very yellow. So, I thought my next move will be to replace the plug wires and the coil. Right move??
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12 is normal with the engine not running..new wires otta fix everything..don't waste money on a new coil
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you've found your problem. Now pull the plugs while you're at it, read 'em, and put everythng back together with new parts as indicated <so far, the wires-- checked the dizzy guts out yet?>
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snipped-for-privacy@gmail.com wrote:

read
Here's an update on my nightmare. Thanks to all that have responded to date. I replaced plug wires, coil (just for good measure), plugs, fuel filter (because it was time). Fired it up and the miss was still there, but sounding worse, like another cylinder was not firing. I took off the EGR valve thinking it may be clogged, but it was not. I cleaned it up alittle and replaced it. I started to pull plug wires while it was running to isolate the bad cylinder, and it was #5. The car also started to backfire occasionally throught the TBI (just when starting). Thinking it might be a timing problem, I loosened the distributor locking bolt a little to turn the dist. while it was running to see if it help. It did not. I looked at the old plugs again, and all looked normal except #5. Alot lighter color than the rest. Like it has a lean condition in that cylinder. I said screw it, I have had it for the day. Got in to drive home, went about 500 yards, the car sputted and stalled. Would not restart. Had to tow it home. Tomorrow I will do a compression check on #5, and to a static check on the timing to eliminate a timing chain problem. I will also check for any engine codes, and report back what I find. As usual, any comments/suggestions appreciated.
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Hate to mention this now, but my 91 developed a miss a few months ago..got worse the more I drove it...no codes showing....As it turned out the bushing in the Distributor had worn itself out of round....see if you have any slop on the rotor shaft and check for an unusual wear pattern inside the cap...K
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ken wrote:

round....see
Hi Ken,
Thanks for your reply. I probably should have mentioned in my last post that I did remove the distributor cap, cleaned all contacts and reassembled. I did not see any unusual wear. I doubt if it is there, but I'll check for bearing wear today.
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The distrib had just a little wobble on the shaft (170K miles)
any is too much......
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Good day all,
In what seems like day 42 of this fiasco, I did a compression check on all cylinders, and pulled the distributor. The results of the compression test were 118 psi in for the lowest reading, 125 was the highest. Seem to be within tolerance. The distributor shaft has no play, however, it does not turn freely. It takes from some to moderate effort to turn it. Also, I discovered the insulation on the wires from the pickup to the advance are cracked. Can there be voltage leaking or arcing from that? Lastly, when I pulled the plugs to do the compression test, all plugs (3 days new) were carbon fouled except #5. It looked like it either had not fired, or was not not getting much fuel. It had a LIGHT odor of gas while the other plugs had a HEAVY odor. As usual, I welcome comments or suggestions.
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Make sure you have spark at all your cylinders...Yes the cracked insulation could be a problem having too much resistance if corrosion is in the wires....Also Pull your valve covers turn the crank manually make sure all your valves move...A stuck exhaust valve will cause carbon build up fast...Heres a stupid question but have you checked the timing? S Cook Re: 1989 S10 Blazer miss Group: alt.autos.4x4.chevy-trucks Date: Sun, May 22, 2005, 1:08pm (CDT-2) From: snipped-for-privacy@aol.com (L8ndeb) Good day all, In what seems like day 42 of this fiasco, I did a compression check on all cylinders, and pulled the distributor. The results of the compression test were 118 psi in for the lowest reading, 125 was the highest. Seem to be within tolerance. The distributor shaft has no play, however, it does not turn freely. It takes from some to moderate effort to turn it. Also, I discovered the insulation on the wires from the pickup to the advance are cracked. Can there be voltage leaking or arcing from that? Lastly, when I pulled the plugs to do the compression test, all plugs (3 days new) were carbon fouled except #5. It looked like it either had not fired, or was not not getting much fuel. It had a LIGHT odor of gas while the other plugs had a HEAVY odor. As usual, I welcome comments or suggestions.
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Last post of the day. Thanks to all that have responded. I have checked for spark at all cylinders. It is there. I have checked timing, it's within a degree or two of what the emissions sticker says. I did pull a valve cover today (drivers side because of the #5 plug being the only one NOT fouled), expecting the worst, but all valves are opening and closing. I'm also wondering if maybe the pickup is somehow screwed up for number 5 since it is the only one that is not fouled. I'm beginning to lean more and more towards the distributor. BTW, can anybody tell me where the fuel pump fuse is located? It is not marked on the fuse panel. (1989 TBI) The reason I asked is I disconnected the feed and return fuel lines from the TBI, then turned on the key expecting a spray of gas, but got nothing. The Haynes manual says there is an override by way of the oil pressure switch. If the fuel pump does not come on with the key, once 4 LBS of oil pressure is built up, the pressure switch will energize the pump. So.....I'd like to check the fuse to see if it is blown. As usual, I wecome any comments and suggestions.
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if the s10 is like the full size, the fuel pump fuse is in the engine compartment next to the fuel pump relay, under a plastic cover.
-Bret
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The fuse is 10 amp ecm located in the fuse panel near the emer.brake pedal. Bobby
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I also should have mentioned that there is a spark at #5. Pulled wire and grounded it. Nice purple spark.
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Update 5/21: Today I did a compression test on #5. 105psi and held. Then I did a static check on the timing. (Checked the rotor to see it was pointing on #1, pulled the #1 plug to make sure the piston was up, and looked at the timing mark and it was within 2 degrees from TDC.) Looked to be a degree or two from being right on. When I pulled the plug from #1, it was carbon fouled. These are new plugs. They have 500 yards (haha) on them. I then pulled the wire connectors to the TBI to make sure they were clean, they were. I then started the car, started hard, same heavy miss. BTW, still had intermittent backfire through the TBI during starting. While the car was running, I connected the timing light and checked timing, was about 5 - 6 degress from TDC without the timing connector under the dash being disconnected. I also connected the light to each plug wire one at a time to see if there was a spark going through them, there was. As of now, I don't have a clue what to do next. One thing I would like to know, would the "vehicle speed sensor" cause this kind of problem? We have had a flashing brake light code 9 or 10 for about a year. Lately, the brake light has been lit continously. Anyway, I need recommendations other than driving it off a cliff. Thanks.
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BTW, tomorrow I will check the compression on all cylinders. I thoght I would also pull the valve covers and see if what's up in there. Any other suggestions welcome.
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