engine hesitation, stutter light loading (1 Viewer)

[AZ 80]

Ok, guys my first question in long time. 94 Cruiser hesitates under light load, happens even at times on freeway with cruise control on, not all the time but occasionally after stop sign start to pull out into traffic and it sputters, hesitates, then after almost stopping takes off like nothing happened. I've changed the fuel filter ran two tanks of techroline concentrate thru and seemed to help some, but still having the issue. pretty sure its fuel. where should I start? Fuel sock? fuel pump? injectors/ efi? relay?
166k original miles on most everything.

Frosty

 

[js93cruiser]

try a tune up using oe cap rotor plugs and wires...after that i would clean out your throttle body, put some "marvel" mystery oil in your tank, tha stuff does wonders...also try a fuel pressure test...

 

[cybrstar]

I would try the fuel sock as well. The fuel sock is just like the fuel filter. Under light load, minimal fuel is pumped to the injectors. If the fuel sock is clogged then it might cause hesitation IMHO..

Also when I bought some crappy gas my engine was sputtering in first gear. Changed to only Shell/Cheveron and seems to run better.

If you didn't do a tune up yet, maybe wanna start there too. Check for any cracks in the vacuum hoses, or the air filter tube to the TB. Look at your spark plugs. If they look white then that means that you are running too lean.

Don't think that it is the Fuel pump because when you put Techron in the tank you said that it doesn't usually sputter.

Good luck

 

[corsair23]

Another known trouble spot is the wiring harness under the throttle body...Usually hear of the problem with the chaffed/burned wires in the harness causing problems under load as the engine shifts and grounds out the wire(s)....

At least worth a peek

 

[AZ 80]

best bunch of folks own a cruiser

Thanks guys yeah the rotor cap and rotor go in this weekend, will do the tune up I'll check wires and the harness too. then to fuel pressure. appreciate the comments. I'll let you know what shows up and how it works out.

 

[warpdriv]

When you go into the tank and RR the fuel sock, look very close at the connectors on the fuel pump. Mine were corroded so bad it was effecting how the engine ran.

 

[RescueU]

When you go into the tank and RR the fuel sock, look very close at the connectors on the fuel pump. Mine were corroded so bad it was effecting how the engine ran.

Curious to learn what you found when inspecting the fuel sock and the condition of the connectors at the fuel pump. Also...the level of effort if/when you drop the tank to address these 2 inspection/R&R points.

Good luck.

 

[wilkins.g.1]

AZ 80,

Did the Rotor and Rotor Cap fix your issue? I'm having the same problem and having trouble tracking it down.

Thanks,
Guy

 

[Polar Bear]

AZ 80,

Did the Rotor and Rotor Cap fix your issue? I'm having the same problem and having trouble tracking it down.

Thanks,
Guy

I had a similar problem around christmas. Did the plugs, cap, rotor, fuel filter, pcv & grommet. Didn't fix my problem, but I found an intermittent failure in my throttle position sensor and replaced that too.

When that improved but did not fix it, I took it to the dealer who said the ECU was providing conflicting data. Found a used one on mud and saved myself $1800.

That finally fixed my woes after a nearly 3 month long ordeal of hair tearing.

 

[AZ 80]

follow up

Well, guys the tune up was good for the ole beast but alas not the answer. I ran some BG44 through and that seemed to help for a while. Now the hesitation happens a on every third trip out. I pulled the harness apart and looked over every wire by the EGR and could not find any obviously worn or shorting. I covered that all back up with Heat temp tape and fit it all back into the tiny slot it came from. (whew) I purchased new pump and sock and was to install this weekend but the wife decided to fill the tank up even after I warned her last weekend that I was going do this job. "I thought the pump was somewhere else" was her response. oh well, I guess next weekend. Still no codes. Checked the Intake hose (replaced in last 2 years, but looked anyway) Have not run each a every vacuum line (not looking forward to that)
My next guess injectors and a third fuel filter. Then I will look into the OBC. If it keeps increasing in frequency then I'll bring it to the dealer. Although their mechanics have a real tough time if there isn't any codes for them to go on. Boy I sure miss the old guys that could tell by listening and driving where took look. Anyone know a good cruiser mechanic in greater Phoenix area?

 

[plumber3dad]

Fuel tank level shouldn't be an issue cause you don't have to drop the tank to replace it. There is an access panel under the rear passenger seat and carpet right to the top of the tank. Been there man. had to replace the tank on mine 2 days after I bought it. Luckily, a buddy had a spare from a buddy who rolled his after a trip to MOAB Driving home of all things slee rack all f-ed up and stuff slung all over I-40 I'm sure it was a terrible. Anyway be careful to not booger up the banjo fitting on top of the pump. Really easy though maybe 1.5 hours with a friends help and some sockets. Good luck with it Mine is acting up too.

 

[firetruck41]

Have you checked your air intake hose for cracks? Sometimes they are not easily visible.

 

[kidglove13]

x2 on the cracked rubber intake tube, which is probably hard palstic now and not rubber anymore

 

[Polar Bear]

x2 on the cracked rubber intake tube, which is probably hard palstic now and not rubber anymore

I'm pretty sure he said he replaced it 2 years ago. if thats the case its probably still good. Intermittent problems are a nightmare.

My ECU in the 97 was bad and later I found out it had solder joints inside that were cracked- not broken. So under a light load it would sputter and almost die, but full throttle would change it to closed loop mode and it ran fine. Weirdest part was that the longer I drove it, the better it ran. I could only account for this by guessing that the warmer the ECU got, the more thermal expansion happened in the ECU metals which closed the gaps in the joints enough.

Hunting down problems like this can be real frustrating. Good luck!

 

[AZ 80]

ok so far

Yes I checked the intake hose and it is all good.
Today I changed out the fuel pump and the "sock" (in a 94 it's really just a fine mesh screen covered nylon basket) So far it looks like it did the trick. Test drive showed more get u and go and idles smoother as well. Everything looked clean and new inside the tank. Changed the frame mount fuel filter again. ( if you have never done it please take the advice of "slotting" the engine side mounting tab) I will run it this week and let you know if the intermittent issue reappears.
Thanks for all the input.
I really appreciate everyone trying to help a guy they never met.
Ahh, faith in my fellow man restored. At least on Ih8mud!!!

 

[AZ 80]

Series 80 Stutter

Well my smooth runnings came to and end, it started doing it again. now it doesn't completely die it sorta fires, like it wants to run, and does it for a longer time period of time/distance. The CEL code came on (I thought yay, at first, but it is just EGR valve) Anyone think it might be a speed sensor or something similar?
I ask this, because, the first times it did this the cruise control was on. This last week twice it happened the shifting was erratic, higher revs between gears than normal. Other wise there has been no discerning pattern, it did it on slight incline one time and it's done it more often after a stop, and you start to accelerate, going straight or turning right or left. Next step the dealer will start his guessing game that cost $k's or maybe an Exorcist

 

[LINUS]

Have you gone over the air intake tube ( really pulled it, cleaned & inspected it?), and checked all the vacuum lines? How clean is the MAF inside?

Have you had the throttlebody off & shot it clean in all this?

Are you getting any color on the spark plugs?

How was the electrical connector for the fuel pump? Any corrosion whatsoever? I know that little connector can bring you to a dead stop if it's not in good health.

Is this only an issue when changing the engine load & the air/fuel meters (MAF, TPS) are in action - or is the motor stumbling while at an even load on the motor?

 

[AZ 80]

Linus, thanks.
Connectors looked great.
I sprayed MAF cleaner through it. It looks clean and all seems to move freely.
Intake hose less than two years old, I will pul it completely off again (might tear when I do) but will do
Have not had the throttle body off to clean.
Will go thru your list to best of my abilities. and try again.
Plug color was fine when this started this and changed them out.
This seems to happen under full load and even slight load. Not usually when even on load (except those two times on cruise control) It happened today on way back from airport, going up freeway onramp, very slight incline. It did the hesitation stutter thing for 1/4 mile even after we leveled out, then smoothed out ran fine for next 18 miles home. I floored it, let off, accelerated slowly (light load) during that 18 miles trying to get duplicate it. and ran without issue. I wish I could discern a pattern. If I had to make a guess I would say light loading. But it has happened when i have floored it too to merge into traffic.

Thanks

 

[firetruck41]

I haven't read through the thread recently, but did you check the wiring harness back among the firewall? Common to have a short there that will manifest as intermittent, and changes with acceleration, turning, etc (basically when there is body vs frame movement).

 

[Polar Bear]

I had an intermittent problem with misfiring years back in my old Tacoma. I spent several hundred dollars in parts chasing the misfire, smoked my catalytic converter in the process, only to find out that the spark plugs which I had so carefully inspected, cleaned and regapped turned out to have a hairline crack in one of them.

The hairline crack was shorting, and voila- problem fixed. The crack was so fine, it was almost invisible.