1800-200k sputter, 1991 B2600i ideas?

ive been dealing with this funny problem. When my truck is in the 1800-2000rpm range it sputters and such, i know that i have a clutch switch issue because the idle raises whern its in gear and the clutch engaged...could these 2 problems be connected? Anyone else have this issue? the ecu is newer has an 03 sticker on it. New distributor/plugs/wires recently. Oversized kn filter but stock maf and intake tubing, timing verified by digital timing light...confuzeled! Almost feels like it dosent fire on all cylinderrs or something?.......any ideas or fixes would be appreciated. Oh yeah , cleaned the maf awhile back...no change....but the problem does get worse with a 3" intake tube setup

If it's doing while you are under load (driving down the highway), I doubt the clutch switch is causing your problems. When it fails, it won't make contact telling the computer that the clutch has been depressed (disengaged). So if you are in gear driving down the highway, it shouldn't make a difference. But, I would definitely get it replaced. It should only be $10 or $15 are you local dealer.

As for the sputtering...
Does it stop doing it above 2000 RPM?
Does it do it when accelerating? Steady Cruise? During Deceleration?
Does it do it when you are parked and rev the engine to that range?

Is there much difference in sputter in 1st gear at 1800-2000 RPMs versus being in 4th or 5th Gear at 1800-2000 RPMs.

Have you checked the terminals on the MAF connecter. They are notorious for getting corrosion....

I notice it pulling away from a light the most, under power. But it doesn't just do it then, it does it in all gears(accelerating). Smooth at any other rpm. Sometimes if I let the clutch out at a much lower rpm and let it out slowly and be under load lower then 1800 or so it won't do it but its rare. I've cleaned and used dielectric grease on the maf connection as well...but I'll check again, you never know. I feel dumb on the last one I haven't tried with the truck sitting still. Doesn't seem to happen under a quarter on the temp gauge( just remembered).

after digging through a bunch of threads again....found a post i had either not read or just missed....fixed the upper clutch switch and it only does it every once in a while now....at least its alot better...ill update more when i get the other part figured out,,,i wasnt engaging a circuit needed to compensate for load apparently..so i think the stumble is from the circuit switching modes or something....fun with computer controlled engines lol



FYI, the upper switch (and the brake light switch im guessing) can be fixed with a pen spring if its simply the spring has failed...carefully bend the tabls back on the rear of the switch, if the contacts are good just replace the spring. I know the switch is inexpensive but has been a pia to get in my area recently so i just fixed mine

i was wrong...driving in normal traffic patterns it still does it....im testing the tps switch now to see if it is working properly....i can sit in my driveway and make it do it now no load...bring the rpms up to about 1800....step on it and it still does it...almost seems like its only got 2 injectors firing?.... grasping at straws now ...im out of ideas

Well, funny you should mention "2 injectors." The injectors are fired in pairs by the ECM. So if 1 & 3 or 2 & 4 are dropping out, then that is a tell tale sign of a bad ecm. If you can pick up some noid lights at your local auto-parts store, they will confirm if the injectors are indeed dropping out. Your computer has been rebuilt, but its not uncommon for them to fail again depending on the quality of the repair job.

Also, other have experienced loss of power at high RPMS when the ignition condenser starts going bad. So you might look at that too. I haven't seen it myself, but I doubt a weak spark due to a bad condenser would feel like two injectors dropping out. But it's only a 10 or 15 part... so even if it's not bad, you're not out much money and it will probably last another 20 years. The condenser is the smaller black box on the bracket with the coil. The larger one is the igniter module.

ill look into it, thanx scotch for all the help..... after checking the tps switch (good ) and cleaning the connections at the maf again just to make sure it started doing it worse...at all rpms under 2k.... so i cleaned the contacts in the cap (a little funky..only been like 1000 miles? wtf?) ripped an end of a spark plug wires double checking the gap on my plugs...(all within .02 of .44...made them all even) fixed the wire...test drove and no sputter... but it did the same thing to me last time i thought i fixed it....sunday im going to pull the ecu if i have time and put it under the magnifying glass and look for stains etc.....getting alot of small problems fixed on the way but feel like im beating my head on the wall

In the distributor cap? If so, do you have a gasket on it? Or let me ask, a gasket that is in good condition? It may be missing altogether. Saw a truck like that two weeks ago. Maybe you're getting some moisture or debris in there. Here is a thread with a few details on it....

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Hang in there. You'll get it sorted out and running smooth again!

2003 was smack dab center in the chinese faulty capacitor plague. Open that ecm up and check for "Bulged out" or "Domed" caps.

No gasket...makes sense though....I'll order one from the dealer....makes me want to check my resonator oring and such as well...its gonna snow today so it may have to wait to fix it....major help guys...thank you tons