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Stutter between 2500 and 3500 rpm


Kittamaru
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Hm... so what do you think I should look at first? I'm guessing O2 and/or Temp as was suggested (makes sense).

 

Is there any danger in running the truck with them disconnected for a period of time (long enough to warm up)

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Stupid update - last night the temp gauge never climbed more than 1/8th of an inch above the C line... and the truck ran fine the entire way home 0o'

 

Thinking its time to replace some elderly parts in this beasty - what all of this list is a "consumable"?

 

Thermostat

O2 Sensor(s)

MAF Sensor

Engine Temperature Sensor

Throttle Position Sensor

I'm going to wait for Beast to ship the FSM so I can scan it. Once I have that I'll, hopefully, have a much better idea of wtf I'm doing :D

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It's back again... I'm starting to think it's related more to something being wet than anything...

 

I have recently (as in, less than 2 months ago) replaced my Dizzy Cap and Rotor... should I take those off and look for moisture?

 

right now it's POURING rain, and it's stuttering from dead start up thru 65pmh :(

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mine used to studder on my old one for like a week. The problem ended up being that the clip that pluged onto the MAF was getting hit by my hood and was starting to get a short i wiggled it around and it worked fine after that. try that once.

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mine used to studder on my old one for like a week. The problem ended up being that the clip that pluged onto the MAF was getting hit by my hood and was starting to get a short i wiggled it around and it worked fine after that. try that once.

Mine also did this, the wire on mine actually ended up being broken.

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Mine also did this, the wire on mine actually ended up being broken.

 

o that would suck im glade mine never got that bad. Im sure it woudl have eventually i tried to only open my hood when i had to after i found out asbout the short. Defianly check that out and make sure its not that causes your studder

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My MAF appears in good condition. I tried wiggling it - no effect.

 

The stutter happens now even when in Neutral and I gas her hard... she chokes and then revs.

 

I called my mechanic - he said that, given I have 18 year old Plug Wires and my plugs have well over 50k on em (possibly even 100k) it's worth a shot to replace em - I planned to anyway. I just need to wait till after christmas (when I get paid next) so I can afford to...

 

Anyone have a recommendation on wires? I'm looking at the NGK's listed in my siggy :D

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I won't know about my gas mileage for a while... my gauge doesn't work right until I'm below 1/4 tank (bad sending unit, functions from 100-95% full, then from ~ 30% down to empty :(

 

I HAVE smelled fuel and something acrid... which has me worried. But the acrid smell and fuel smell started long before the stutter - I attributed that to it running rich due to the cold... was that an idiotic call on my part?

 

As for cleaning my MAF... I haven't. It hasn't been touched since the truck was built :P Something I should try?

 

The thing to remember - except for the "consumable" parts, and the K&N Air Filter... everything in/on that truck is original from 1990 :jig: Consider it good fortune and good craftmanship for everything to last that long

Edited by Kittamaru
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I won't know about my gas mileage for a while... my gauge doesn't work right until I'm below 1/4 tank (bad sending unit, functions from 100-95% full, then from ~ 30% down to empty :(

 

I HAVE smelled fuel and something acrid... which has me worried. But the acrid smell and fuel smell started long before the stutter - I attributed that to it running rich due to the cold... was that an idiotic call on my part?

 

As for cleaning my MAF... I haven't. It hasn't been touched since the truck was built :P Something I should try?

 

The thing to remember - except for the "consumable" parts, and the K&N Air Filter... everything in/on that truck is original from 1990 :jig: Consider it good fortune and good craftmanship for everything to last that long

 

I mention the MAF sensor cleaning because it can mess up the air readings and do stupid things to it, sputtering, idling funky, etc. There's a how-to somewhere on here. Mine was running slightly...off before I cleaned my MAF. Once I did that, it had a little more power and ran smoother.

 

I still think the smell of fuel constantly means it's dumping too much gas into the engine and not all of it is burning as it should, hence the sputtering issue. Or, like the mechanic said, it's not getting the correct amount of spark ignition it should, and not burning the normal amount of gas the engine is getting. It could go both ways.

 

Replacing the wires sounds pretty viable I suppose, that's something to try. If it improves, well there's your answer. If it doesn't...well...

 

IF your year truck has the temp sensor, I still have a feeling that might be it. It was incredibly intermittent. I went through this hassle with mine, replacing a lot of things that would, in common sense, fix the problem. The temp sensor was the last thing I had expected, then wham it totally gave out and I was stranded, and hit with a rather huge repair bill.

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Yeah... Original 18 year old spark plug wires :P

 

Replaced the Dizzy Cap and Rotor myself about 2 months ago - was damn proud of the fact too :D

 

I'll try to clean my MAF when it stops pouring hell and freezing ass outside :(

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Just a quick update - I am loosing mileage... I'm down almost a full 100 miles to the tank... now, part of that could be wintermix fuel (I ALWAYS get worse mileage in the winter, even if I never use 4x4) but DAMN. 100 mile / tank difference? It means I've been cut to almost 70% of my usual MPG (I can normally just squeak 300 miles to the tank without hitting reserve).

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Just a quick update - I am loosing mileage... I'm down almost a full 100 miles to the tank... now, part of that could be wintermix fuel (I ALWAYS get worse mileage in the winter, even if I never use 4x4) but DAMN. 100 mile / tank difference? It means I've been cut to almost 70% of my usual MPG (I can normally just squeak 300 miles to the tank without hitting reserve).

 

Holy hell, that's a serious decline in mileage

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I think a FULL tune up is required on this truck...do it soon before you waste a crap load of gas and/or it completely dies on you. Just a thought, has the timing belt ever been changed on that thing?

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Timing belt was done less than 25k ago, and was checked last spring.

 

Once I get my paycheck friday I'm going to start the repairs - plugs + wires, then I'll clean and/or replace the MAF. Then put it in for a full tuneup after the new year.

 

What gets me is that it started along with the cold :(

 

Parts/Sensors I want to replace:

 

o2 Sensor

Thermostat

Engine Temp Guage

 

Parts I want to clean/check:

MAF

Heater Core + Plenum

 

Parts I want to install:

Bypass + external Tranny Cooler

 

Anything else I'm missing? I mean... I'm basicly 4k overdue for the 150k checkup, just can't afford the damn thing :( If I could manage to save up two full paychecks I'd be grand, but that requires @!*% to stop going wrong.

Edited by Kittamaru
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Seems the truck is determined to prove me wrong - my gas guage is back up to 1/4 again and sitting there, and I'm currently at 200 miles... meh. This is frustrating.

 

If anything, my milage is a LITTLE lower... but I won't know for 100% till I next refill :(

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My truck has recently developed a stutter... speed doesn't matter as much as engine RPM and pedal depth. When it stutters, if I push further down on the accelerator it gets worse, let up on it (but still accelerating) it gets slightly better. I think it could be running VERY rich... but I don't know.

 

I ran injector cleaner, recent oil change and a recent fuel filter change. Air filter is a K&N with only a few thousand miles on it.

 

Any ideas or info you'd need?

 

PS - when it passes 3k the power picks up, and after 3500 rpm the truck surges and the stutter disappears. It doesn't seem to happen at ALL when the truck is cold, and is more prevalent in 2nd and 3rd gear without OD/TC lockup.

 

I had this same problem the issue is the EGR valve. After I installed the pacesetter headers a noticed the stutter.

 

Turns out, after a bit of online research that our EGR valves work off of negative pressure (back pressure) from the exhaust system which with headers and a upgraded exhaust system the majority of the back pressure is lost, at least enough that the EGR will not function properly. Our EGR valves kick in above 2500 rpm causing the stutter.

 

To test:

 

-In park, slowly rev the engine to verify where the stutter starts

 

-Disconnect vaccum line feeding EGR valve

 

-Slowly rev engine and see if the stutter is gone.

 

This was the solution in my case. You may need to plug that vaccum line and you may also have to adjust the fuel/air mixture.

 

A permanent solution would be to track down a positive pressure EGR and fab it up to fit; then again you could just put a block off plate in too.

 

Have you had much like with your NTK O2 sensor?

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I haven't done the O2 sensor yet... and if my EGR is bad it's bad... I haven't done anything to change the backpressure, except patching a long-standing hole in my exhaust (gasket blew between the Y-Pipe and Straight Pipe)

 

I also don't know what the EGR valve is (I think I do, not certain - is it that circular thing near my intake?)

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Anything else I'm missing? I mean... I'm basicly 4k overdue for the 150k checkup, just can't afford the damn thing sad.gif If I could manage to save up two full paychecks I'd be grand, but that requires @!*% to stop going wrong.

 

A Chilton manual, 'cause chapter 2 is called "Engine performance and tune up"... ;)

 

B

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That's a place to start, but generally, you want to keep the Haynes manual in the back of the truck for when you have to take a crap in the woods or something...

 

Check every 250 miles or weekly:

...

...

Brake and clutch fluid

ATF level

P/S fluid level

...

...

 

WTF, drive for 4 hours, pull over and check the brake fluid level? My ass, you stupid crack smoker!!

 

B

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