Author Topic: 22re tachometer jumping with misfire/backfire 2500-3000 rpm  (Read 258 times)

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87funner

  • Offline Dusty Trails
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So I have a 1987 22re manual trans that previous owner said has a unknown "racing cam in it and a header installed when the previous owner rebuilt the top end.  He deleted all of the ac hardware under the hood as well.
The first problem I had with it was a week after I owned it I decided to check the oil. It was full when I bought it but empty a week later. The dipstick was dry. I was pretty surprised by this as I didn't notice any smoke until after this was discovered. At night getting on the freeway with all of the headlights behind me I could see a lite puff of smoke in between gears. Surprisingly what fixed my oil loss problem was changing the oil to Royal Purple High Mileage 10w 30. After that I have stuck with the same oil brand and had to top it off with a half qt once or twice between oil changes. So this will come into play a bit later.
I've had the truck about a year and I decided to add a bottle of techron fuel system cleaner in my last tank of gas. I'm not sure if it is just coincidence but at the end of that tank of gas problems started. Coasting down a hill at about 2600 rpms I gave a tiny bit of throttle. Less than a 1/4 inch and the tach started bouncing iratically all over the place and the engine started missing and backfiring pretty bad. If I gave it more throttle or backed off completely it ran like like nothing was wrong.
So over a week this got worse and worse. It now occurs on exeleration and pings at times through the 2500-3000 rpms. It's very exaggerated with lite throttle coming off of a coast.
So things I've done and tested so far are: plugs which were surprisingly clean, wires, ignition coil. The old one failed the secondary test at 13.2k ohms. I checked for vacuum leaks with starting fluid and the idle stayed steady although I did find some questionable lines that I replaced. The large hose that comes off the the bottom front side of the throttle body under the idle adjustment screen had evidence of what I believe was clean oil in it and a drop did drop out of it. Next I pulled the throttle body which was pretty clean from the front side. The backside was caked with about 1/8" baked on oil. The upper intake is overcome with about a 1/4" of baked on super black oil.
So I cleaned up the throttle body  and tested the TPS (throttle position sensor). The step where I tested IDL - E2 with the 0.85mm gap at the throttle stop screw would not test open or infinite. I was reading .13 at the lowest as I tried moving slowly from 0 gap to WOT at the stop screw.
I want to correct the problem before I take apart and cleanup the upper and lower intake. So my plan is to throw a new TPS on and get it dialed in. Then throw it all back together. I want to test my compression and vacuum pressure on the manifold. Hopefully those values may help in diagnosis.
One thing did just pop into my head is that the oil pressure gauge drops pretty quickly at idle by about half.  I'd say it drops just below the 1/4 mark.
I am definitely a home mechanic but I learn quickly. If I find a good accurate video on YouTube or repair manual I can usually figure out how to do it myself. Any advice and experience you've gone through may help me figure this one out. I look forward to hearing from you guys.
87 4Runner
22RE header and cam 31's

Allison

  • Offline Dusty Trails
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check out the afm? disturber timing? efi timing

Slabzilla

  • Offline Rock Master
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The oil pressure drop is pretty normal, the gauges aren't that accurate. Good call on the TPS.  I'd check the EGR might be stuck open or the PCV valve may be clogged or need of replacement.  The carb/injector cleaner might have clogged your injectors after it broke loose stuff from the fuel filter under the intake manifold.
'85 Xtra-cab, 4.5" Downey Off-Road lift, 12-15 KM2's on American Racing Baja's, 4.10's, 4.7's, Downey Off-Road CAI, Marlin rear bumper & sliders

 
 
 
 
 

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