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Discussion Starter · #1 ·
Alright, I have this annoying stumble that's been consistent for 2 days now.

First time it ever did it was when I took a trip out to Centralia, PA. Did it a couple times when getting on the gas from a stop, and by the time I got home, it was gone.

Didn't reoccur until I had to drain/flush/refill the tranny. Put some drygas through the fuel, seemed to have fixed it. Alright, so perhaps it was just a little water in my fuel.

I just took it in for emissions on Tuesday. When it went in, it was A-OK. Got it back, and it now has this nice little stumble coming off from each and every stop. I nearly had it stall on me coming across an intersection last night, so I took a small drastic measure and went and bought a new fuel filter and put in a paper filter, just to make sure.

Helped a little bit, but not much. This morning, I took the Throttle Position Sensor off, sprayed it out with contact cleaner, put a little dialectric grease on the foam ring, bolted that back up, and moved onto the Idle Air Control. Removed that, sprayed it out with degreaser and contact cleaner, wiped it down, and also used a little degreaser on a rag to clean out the port for the IAC in the throttle body. It was pretty nasty, so I figured I might have found my culprit.

Left for work, got about a mile down the road, and it starts doing it again. By now, I'm real annoyed. I've run down the list of things in the shop manual, and everything seems fine so far.

Anyone have any ideas? My mechanic thinks plug wires (they were brand new last June... :? ). I still haven't checked the MAP sensor on the manifold.

BTW - Vehicle is a '92 3.2 SOHC/Auto.
 

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If i were you Zack, i would go ahead and pull the plugs/wires/cap and check to see that none of the connections are fouled. A buddy of mine has a '00 F150 that has 2 fouled plugs, and it stumbles a little bit just like you are describing. His truck has a warning light and alarm that goes off when they are stumbling, so its hard to just ignore it.

I would just figure on going ahead and checking that stuff first, even if it was brand new, and especially if you are already in there to check other sensors.
Good luck with it, oh and sorry to hear about possibly not going to VT...Hope that situation works itself out, too.
-J :wink:
 

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Discussion Starter · #3 ·
Well, I'm not going to VT. I'll be sticking up north for a while. Just can't afford it.

Anyways, as far as pulling the plugs and wires? I wish that was a simple 30 minute job (P.S. - There's no distributor on this engine... :wink: ).

We're going to check the plug wires tomorrow, and I might just go as far as actually pulling the plugs. The plugs and wires were all done last June when we did the valvecover gaskets. Unfortunately, I have to do the valvecover gaskets again this year. What a stupid design.
 

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(edit)- sorry.. noticed you mentioned it was while accelerating from a stop, skimmed through it too fast... probably a different problem all together...

ok... so is the engine "stumble" happening just as you come to a stop?

I have had an issue like this for ages... comes and goes... From what I have learned.. it has to do with the idle control change from coasting idle to curb idle... when coasting (when there is input from speed sensor) it is supposed to aim for an idle of ~1000rpm- something to do with decel emission control... (keeps fuel mixure closer to optimal during engine braking i *think*)... but then when there is no input from the speed sensor, it's supposed to drop the idle down to ~750(curb idle)... at this point, my engine "looses" it and often stumbles far below the 750 mark, then hunts up and down again to recover... with the AC on, it sometimes dies, have had it die a few times without the AC as well.

I think I have the same 3.2 as you in my early 95 rodeo. (built in 94, sold as 95).... maybe we have the same problem?

I've tried.
1. spark plugs, wires.
2. oxygen sensor.
3. fuel filter.
4. lots of gas treatment, both water and seafoam through brake booster line several times.
5. idle air control valve(motor)
6. throttle positioning sensor.
7. cleaned out throttle body very well, (including IAC port)

only thing left to do, is fix my EGR- which throws a code occassionally, (could theoretically be causing the problem)... was also thinking about replacing the coil packs.

if we have the same problem.... i'd love to find the solution. has been pestering me for ages..
 

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Discussion Starter · #5 ·
Yeah, our problems are a bit different.

Today, I checked for arcing between the wires and coils, tested the cat... still can't find anything.

Really at a loss here.

It seems as if it's loading up on idle, and upon acceleration, it just doesn't have the spark to ignite it, or at least thats what we're thinking.
 

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My 92 Pickup 2.6 has recently stumbled now and again at lights. Two days ago truck stranded me at work. It would turn over and over as if no gas. Fuses and relays good. Pump would energize perfectly w. direct connect to a battery. Tried alternator replacement (from tips here and elsewhere), but still wouldn't run. They finally found an inline connector that was corroded where the wires enter the plastic connectors. Less than ten dollars, but already got that alternator, too. OH WELL, it had a ton of miles on it, so couldn't have hurt. Anyways, the stumble is now gone. I don't know if it's the new alternator or not - but maybe that corroded connector between the fuel pump and the relay was the culprit for the stumbling prior to the complete failure?
 

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Discussion Starter · #7 ·
Thing is, the fuel's getting there. It's pushing the unburned fuel out when it catches (black smoke), so my belief is that the problem lies within the ignition.

I've got a brand new set of plugs and plug wires that are going on tomorrow. Maybe tonight if the truck cools off.
 

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A stumble accelerating from a stop sounds like an O2 sensor problem. Especially when you've eliminated the more obvious things like plugs, wire and fuel.

When my O2 sensor was failing it did the stumble upon acceleration, but would run fine after I got it up to speed.
 

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I have the same truck and problem and haven't been able to fix. I've replaced spark plugs, fuel pump, fuel filter, O2 sensor, PCV, cleaned TBI & IAT & EGR... what have I missed?
 

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did you check your intake manifold gasket? spray carb cleaner around where the intake manifold meets the head and look for bubbles/the idle dropping or rising sharply if ti does it means its sucking in the carb cleaner.

Its easy to check and from the little ive learned about the 3.2 the IMG can cause all sorts of bizzzare problems, and you might as well check it before the big stuff.
 

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ive got a similar problem with my 95.5 rodeo 3.2 also. if im just lettin the engine idle it will go from 1000rpm to below around 700 and stumble back up, you can really feel the stumble just sittin there. anyways im curious what the problem could be also, cleaned throttle body, new plugs and wires about a half a year ago, egr is clean. maybe a few injectors going bad? anyones input is appriciated. maybe il put some new spark plugs in it again. ive got NGK's in it now, anyone know a good plug to run in these? thinkin about maybe some basic Acdelco's or Denso. thanks
 

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NGK's are about the best your gonna find for your trooper.

When a engine stumbles and hunts for an idle Its almost always a IMG going bad. Or a Idle control valve that has become so dirty or weak that it can't do it's job fast enough. Stuff like that usually degrades over time and leaves you feeling like "there's no way that could be the problem, I cleaned it out once." But a replacement is the best way to fix the problem. I'd go after the IMG first then I'd check for a EGR leak at the gasket or the stem. Then I'd replace the IAC. In that order.

As for the stumble, I really can't help you there. I wish you the best of luck.
 

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I'm suprised someone with more knoweldge than me has not chimed in. Our 2000 3.5 was doing exactly all of the mentioned symptons and I did the whole plug, sensor thing to no avail. Finaly BIG SWEDE said to check the intake manifold gaskets and I believe he said the 3.2 was similar any way I pulled the intake and both gaskets were cracked. New gaskets and it runs better than it ever did before. Hope this helps DAVE
 
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