miss/stumble/chug @ or below ~1400 RPMs on my 92

[yosh18981898]

Yeah the title says it all.

1992 5-spd 4x4 sport. 117,000 miles

Runs excellent once I get past 1400. It has a homemade high-flow intake (completely leak proof) and flow master exhaust with high flow cat connected to the y-pipe by a reducer made by me (also leak proof). It's got a somewhat erratic, although smooth, idle (much like a mild performance cam). The problem is much more noticable when the engine is cold...

I have:

1) Changed spark plugs
2) Tested wires to be good (replaced 9 months ago)
3) Run SeaFoam through the intake
4) Cleaned MAF
5) Scanned computer and got nothing on both KOEO and KOER tests.

The secondary resistance on my ignition coil is a bit out of range, they measure about 14,000 ohms while the Hayne's manual specifies 5,000-11,000 ohms. Could this be it?

Could it be fuel related?

O2 sensor (even though the comp doesn't say the O2S reading is out of range)?

Please post any ideas

 

[MrShorty]

1) When you say, "Scanned computer and got nothing on both KOEO and KOER tests." Does nothing mean the computer didn't respond at all, or does nothing mean you got all pass codes from both tests? Nothing at all is a fault condition that should be investigated.

2) Would it be difficult to put the stock intake back on? I wonder if something about your intake is causing some confusion to the computer. If the problem goes away with the stock intake, but is present with the new intake, then your intake is going to need a further engineering to get the problem to go away.

 

[yosh18981898]

I scanned the comp and got the 111 pass code on both the KOEO and KOER tests.

The truck has previously run great with the intake it has now. I kind of destroyed the old air box by drilling it too much :thumbdwn:

From the searching I've done, others have had fixed similar problems by gapping their plugs at 0.050, instead of the factory 0.054. I just replaced the plugs gapped @ 0.054 and I don't really feel like doing it again, especially since it has run great with 0.054 plugs.

This all started last winter when a spark plug wire went bad and I drove around with a dead cylinder for ~1000 miles before figuring out that it was the wire. All that unburned fuel coming out the exhaust, in turn, trashed my stock cat. I wasn't about to fork over $200 for a stock cat when I could get a universal high flow 2-1/4" cat for $40 and a little welding to make an adapter to mount it on Ford's goofy oval Y-pipe opening. I know for sure that the adapter doesn't leak and that the exhaust system flows more freely than when I had the stock cat and muffler. The truck revs very quickly, like 1500 to 3500 in a split second.

Ever since then, I've had that annoying little chug (it's not anywhere near a full blow miss) getting off of idle. Sometimes it's barely noticable, sometimes it's very noticable.

I have been running the fuel tank down to almost empty alot lately, I was thinking I might have got the fuel filter clogged up with all the crap at the bottom of the tank. I have a new fuel filter but I can't get Ford's stupid "not-so-quick" release open to get the old one off. YES I have the special tool for 5/16" and 3/8" lines but it does nothing when used as desribed in the Haynes manual. I'm thinking I might need the 1/4" one, does anyone know for sure?

Also, could it be the O2S? I'm still on the stock one at 117,000, and it was in there while I was driving around with a dead cylinder for ~1000 miles, getting coated in unburned fuel. However, the comp doesn't say it's bad and it's a realtively expensive part to go throwing money at if it's not going to fix it.

Anyways, those are my thoughts...

 

[yosh18981898]

C'mon I need answers/suggestions/ideas!!!!!!!!!!!!!

back to front page

 

[410Fortune]

fuel filter can definately cause a slight miss, you might consider the sea foam treatment, some in the tank some through the manifold vacuum. then replace the fuel filter.

I did not see you say you have cleaned the MAS and re-set the computer?

02 sensor will usually throw a code. Typically they last 60K< but of course they can go much longer.

 

[yosh18981898]

I cleaned the MAF, but I did not reset the comp. The MAF looked pretty clean though. I will try reseting the comp.

Also, I will try sea foam through the fuel tank as soon as I get a tank of gas. I have vowed not to buy more than $20 of gas at a time until it gets below $2.40 a gallon. Right now it's $2.499 and falling fast

Any other ideas?

 

[yosh18981898]

Sorry guys I haven't been home since last post so I haven't been able to try anything yet...