Pronounced engine miss, suggestions?

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KevinGn_WV

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I could lie and say its on my 92 Yukon, but I wont. Its on a 92 K2500 I just bought and I dont feel like joining another board since you guys/gals seem pretty smart.

I just bought this truck and though the body, frame, and most everything else is in great shape, I got it cheap. Cheap because of this miss.

So heres the basics. 350/auto/TBI. 225k on the clock, and no idea if this is the original engine, rebuilt, reman, jy or what, I just dont know so Im assuming its an untouched original.

I started with the obvious, plugs, wires, cap, button. It had the cheapest bosch in it which I replaced with APP25 Autolites. The old ones were black and wet. All of them. Three of which were not much more than finger tight. It also had Bosch Magna core wires, and the cap & button, IDK. The wires were probably ok but I wanted to be sure. The contacts inside the cap were horriblely knicked and all had what looked like an almost white, slightly grey looking buildup that looked like oxidation or corrosion.

Heres the interesting part. The button was rusted onto its shaft and I actually had to break it off, the sand smooth the shaft before the new one would go on. Also, inside the dizzy was rusty looking. What I think is the magnetic pickup? that sits on top of the pickup coil has a coating of rust. Its not rusted solid. it wiggles around and I shot it a couple times with MAF cleaner. Removed the pickup coil, and cleaned the contacts and the mating surface, although I did forget to coat the mating surface with di-e grease. Big issue?

Put it all back together, and very little improvement if any. It has a pronounced, rythmatic miss at idle. (which leads me to believe its ignition related) In gear, either R or D its worse, obviously, however as the revs come up it "seems" to smooth out.

It holds good oil pressure and I dont hear and ticking or thunking. The SES light has not lit up at all, but I do know it works, as it lights when in the key-on, not running, like all the other lights in the cluster.

The temp gauge does not operate. I know the temp helps control timing and so forth, so possible this is part of the problem?

No vacuum leaks found. PCVs rattle and are not clogged end to end. EGR is not stuck, though I didnt test to see if its operating properly.

I do not have a way to scan or test the system. Its in my garage which is now buried in 2 feet of snow. What do I need to purchase to "scan" the system? Price range? And where to purchase locally if possible. We have all of the major parts stores.

Thinking of things as I go here so bear with me. The dizzy is not loose, but I cant say the previous owner didnt move it thinking they could adjust the timing. Though not likely. Dizzy shaft didnt seem to have any play in it. Moderately strong fuel odor after shutdown, with the cleaner off. Normal?

Thanks in advance for any help, advice, and/or suggestions. Ill be bored and stuck in the house for a few days.

EDIT: Afterthought...I was positive the damaged components I replaced would correct the issue.Now thinking the actual problem caused the issues I found?
 
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SunlitComet

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Sensor for coolant temp on dash and one used by the vcm are two different ones. The one on side of block is for the dash. You would need a OBD1 scan cable and software for pc-based one or a similar hand held device from a parts store perhaps. Less then $100 for sure. If concern about fuel smell you can shine a quick flashing led or strobe light down the Throttle body to see how the injector spray pattern looks. What were the plugs wet with anyway?
 
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KevinGn_WV

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They were all wet with fuel for sure, one had an oily look but Im not convinced yet it was oil, but rather wet carbon buildup, and that plug I remember I backed out with just the socket and extension it was that loose. If im allowed to post pics Ill go take some of what Ive found.

I appreciate the reply.

EDIT: I just backed it into a snowbank and floored it, def running rich.

RE-EDIT: Stuck it in a snowbank and ran it pretty hard to get it out. Got back inside and its blowing oil out of the pass side pcv, which ironically is right above the oil fouled plug. Pulled that pcv and it idled up a little, pulled the whole vacuum line and it idled up significantly. Dont know if this is normal or not. And this point Im thinking and have some internal problems. Bummed to say the least.
 
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KevinGn_WV

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I replaced the MAP and IAC to no avail. Pulled off the valve cover on the passenger side and oil return were clogged with sludge. Cleaned them out and so far, no more blowing oil. All of the lifters except one I could wiggle just a hair. Not sure if thats normal. Also found these things: Ground from passenger side frame rail is broken off. Not sure where that is supposed to go to body or block but Ill find out. And...there isnt a cat or O2 sensor. None. But Im not getting a SES light. How is this possible and could the absence of these cause the miss? If I unplug the ECT or MAP nothing "seems" to change except the SES light does come on.

Seems like its not sure where it wants to idle. If I just start it, it stumbles. Blip the throttle and it idles up some and smooths a little. Rev it up pretty good for 5-10 secs and it idles up and actually idles decent until I put it in gear. IDK. I just dont have the money for diagnostic stuff and nobody seems to scan these ilder trucks.
 

Jerky Arm Ape

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I'm not familiar with the obd1 diagnostic system so I'm not sure it should produce a code for the absent converter or O2 sensor.
Although the computer does use the front 02 sensor (s) to adjust for proper idle.
 
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KevinGn_WV

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Looks like I can get an innova for under $200 but if im reading correctly only the 3120 or 3140 will work? Im looking at amazon as i have a prime account so if theres another/better for the money please let me know.
 
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KevinGn_WV

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I didnt get a chance to ohm test the ect but when I unplugged it, the engine tried to die. Unhooked the egr with no change, and no vacuum from the port either. Is this vacuum under load? Also with the egr unhooked I pressed in the diaphram and it tried to die. Seems to be running a little worse now that Ive done all of this stuff but I probably fouled the plugs. Although now when I give it a little throttle it also tries to die then as well. Re-ran and cleaned all grounds. Ground from alternator to core support looks like it got hot at some point and melted the insulation for a few inches. Cooked the ecm maybe?

And speaking of the alt, the in dash voltmeter is twitchy. Its at 14 until you throttle it and it drops, then kind of twitches down.

O2 sensor....confirmed, there isnt one anywhere. Looks like exhaust work was done from the driver side manifold down and there is no cat, also confirmed. Someone at work suggested tps. Need to test that as well.

I need some clues where to go with this thing. I cant keep throwing parts at it.
 

OR VietVet

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Have you ran a compression test at all? If so what were the results, both wet and dry?
 

sgtpoliteness

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No O2? I suppose if there isn't one it should stay in open loop. Ohm check the ECT. Remember, resistance should decrease as temp increased. I'll check Alldata tomorrow and post the resistance-to-temp specs.


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---------- Post added at 08:42 PM ---------- Previous post was at 08:38 PM ----------

Also, you don't need a scanner. You just need to jump two of the pins in the OBD connector. I can't remember which. You'll then count the number of times your engine light blinks. This will give you a fault, if there is one. Try googling some combo of your model year and blink codes or something. Again, I'll look at Alldata tomorrow.


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---------- Post added at 08:44 PM ---------- Previous post was at 08:42 PM ----------

FYI, I custom built a TBI setup from a '94 C1500 into my '77 Cherokee when I had it so I'm at least comfortable with TBI. :)


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KevinGn_WV

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Thanks for the replies. Havent run a comp test yet, I dont have the gauge. The ECT looks like it was recently changed, probably the PO trying to fix this miss but Im going to replace it anyway. I have no way of knowing what temp the coolant is at and I cant run the truck inside the garage for very long and working on it outside is not an option. I have severe nerve damage, cant feel my fingers as it is and cold air just causes lots of pain. Im too old for lots of pain.

Im wondering now if all of the stuff Ive replaced or unplugged the ecm is saying WTF?? And hasnt reset. I drove it to the gas station and put gas in it but with the road conditions we have had I barely hit 35mph and that was probably briefly.

On a side note, just to get up away from my garage was a task and it did go over 35 in theory...Im positive it made it to operating temp lol, and once it hit WOT throttle, it ran pretty smooth and felt quite strong. Not exactly real world conditions though.
 

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