Idle miss, 84 toyota truck, 2barrel, no computer

Asked by Apr 28, 2014 at 12:37 AM about the 1984 Toyota Pickup 2 Dr Deluxe 4WD Extended Cab LB

Question type: Maintenance & Repair

I am a mechanic. Spent 1 hour looking at WEB , marlincrawler, toyotatech, etc - too many suggestions, some erroneous. I have matched compression and 'compression rise' characteristic. Excellent spark 25KV, through all plugs. have swapped wires, plugs, even reversed distributor AND... ALWAYS #3 practically dead at idle, seems to go away at 1500 plus RPM. I saw a lot of people  on web with this problem. I personally think it is VALVE related. How smart are you on this ? I'll be troubleshooting tomorrow. THANKS. carltonlovejoy@yahoo.com 512-858-7609

3 Answers

16,155

you have compression,spark and gas. and it's misfiring at low rpm only - valve sticking sounds like a possibility ( I'm sure you haven't mixed up wires so firing order must be right )

1 out of 1 people think this is helpful.

remember my issue. Valves are perfect - never stick, are not burnt,, and are set correctly. Here's the real neat and terrible fact : This is a free running problem (no load) .. like I say, you can unplug #3 cylinder and get NO RPM decrease ! , this is during idle or when you just rev the non-loaded engine. When you drive under load it is fine . How did I prove this ? I drove the truck 'as is', THEN I drove with #3 cylinder wire removed, THEN I felt what a truly DEAD #3 would be. Then thinking that Under Load, it was working ok , I went up a 30 degree grade , in 4th gear, at 1000 RPM - not a single stutter, putter, or anything - just smooth ..AGAIN demonstrating it was working under load. Incidentally, under acceleration feels , is, perfect too. So back to square one. WHY is it at idle or revved (with no load besides engine itself) does this #3 contribute NOTHING, it's amazing to unplug the wire and nothing changes with the engine rev ... whereas any of the other wires 2,3,4 cut down idle speed to almost vehicle not able to idle ! You can hear at the exhaust tip constant putter. This is truly going to answered by a 'mastermind' or luck ? It has every mechanic .... so far .. baffled. It must be so simple though Incidentally, data not put in the first report is that 'the compression rise characteristic' of #3 is identical to 2,3,4.

16,155

no load at low or high rpm=dead BUT with load at low or high rpm=fire I'd have to see that to believe it , I'll ask some buds if they have any ideas but for now I can't believe this is possible. Hope someone reading can believe it and help.

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