Jump to content
  • Sign In Changes:  You now need to sign in using the email address associated with your account, combined with your current password.  Using your display name and password is no longer supported.

 

  • If you are currently trying to register, are not receiving the validation email, and are using an Outlook, Hotmail or Yahoo domain email address, please change your email address to something other than those (or temporary email providers). These domains are known to have problems delivering emails from the community.

Stutter/hesitation at low RPM

Precise1

By Precise1,
in The Garage

 Share

Recommended Posts

Precise1 NPORA Old-Timer

Precise1

Posted
Posted

Ok, first off, YES, I am searching!!! Just a LOT of threads to pick through with our glorious search engine...

 

95 manual with 128k. Drove it for 3 years/20k miles without a problem, haven't touched anything under the hood. It was tuned up 4 years ago (PO) and passed Cali smog last year.

 

For the last month or so, I would get an occasional hesitation, almost always only in first gear when first getting rolling, and only then when warm or warmed, parked briefly, and restarted. No biggie, just annoying, feather the throttle and it would handle. It's been getting more frequent, sometimes affecting second gear shifts. Today it was worse, hard to keep running at low rpm, blubbering on attempted acceleration with the same effect shifting to second and third gear, even after shifting, but seems to run fine 2k rpm+.

It feels like a fuel issue (too much or too little) but I won't swear thats it...

 

I have changed the inline fuel filter 2 weeks ago, thinking that may be it. Nope. Battery has 12.4 volts and cranks strong. I ran the ECU codes several times. Mode 3=55 every time(NP), Mode 4 said it isn't the TPS (was my guess). I will relocate the ECU tomorrow so I can do the real time diagnostics on the way home (hope I make it).

I will check the usual: Plugs, wires, cap, rotor, vacuum lines, exhaust leak b4 the O2 sensor, MAF... Then I get into wiring (gods I hate that!!).

 

Anyone have any experience with something like this? Any info/tidbit/suggestion I don't know or may be missing? Thanks all !!

 

Of course, this happens in winter with a week of rain forcasted..

 

B

Link to comment
Share on other sites
GrimGreg NPORA Old-Timer

GrimGreg

Posted
Posted

I think you are on the right track, like you mentioned start with the cap and rotor. Clean your MAF and throttle body, since it never hurts even if it isn't causing the trouble. Given the time since the last tune it might be time for some new plugs or at least an inspection and regap (if you are REALLY cheap, me, if I go through the headache to pull a plug, I'll replace it).

 

See what those things do for you, no fix, start checking things like the engine temp sensor, O2 sensor, testing for bad injectors, etc.

Link to comment
Share on other sites
Precise1
NPORA Old-Timer

Precise1

Posted
  • Author
Posted

Well, I got home late and it was getting dark when I started poking around. I prefer not to trouble shoot in the dark as it is too easy to miss something... I'm tired and lazy too.

 

The intake tube looks fine and I cleaned that MAF 2 years ago (<12k miles) but it cant hurt to be done again.

It's my daily driver, but rarely sees more than 20 miles a day.

 

No obvious cracks or loose vacuum lines. I forgot to mention yesterday that when I was doing the diagnostics and I had it running, at one point the CEL would come on right when I first touched the gas petal and would stay on unless I let off or pressed it slightly more. I wish it would just give me a damn code!!

 

Hmm, I didn't think about cleaning the throttle plate. Good one.

I somewhat suspect suspect the O2 sensor, TPS or MAF, in that order. Tomorrow should be dry and I'll try to get to work early so I have some day light time.

 

Thanks for the input, I'm off do so some research. :beer:

 

B

Link to comment
Share on other sites
Precise1
NPORA Old-Timer

Precise1

Posted
  • Author
Posted (edited)

Ok, after doing much research and finally getting time to start working on the truck, here is a lesson on 'Start with the basics' or KISS...

 

I had checked the battery and ground:ok

Replaced the inline fuel filter:ok

 

Yesterday I started by checking the timing. It was close, a little retarded but not bad. It was jumping around a little bit though. I pulled the #1 plug. A little used, but good gap and color so no worries there.

Then I pulled the dizzy cap. Dirty and corroded with rust and ash under the rotor which had burn marks on and around the top contact as the photo shows. WTF?

A look at the cap showed crusty pins and NO center graphite contact. As a matter of fact, the contact support cone was burned away into a crater with only the spring showing and that is recessed a bit. With the approximately 1/4" tall cone and 1/4"+ graphite contact, I can only assume that there was a 3/8-1/2" gap between the electrode spring and the contact point on the top of the rotor. The spark was arking across this gap to fire the cylinders... Damn, who says Pathy's aren't die hard runners??

I had a VERY hard time removing the rotor, it was corroded onto the dizzy shaft. Trying not to pry too hard and mess things up, I broke part of the rotor plastic upper with leverage, but then noticed a crack down in the shaft body and was able to pry the plastic off leaving the metal core adhered to the dizzy shaft. This did not budge with pliers, even after rapping it a few times to try to break it free. Not wanting to pry on the shaft, I tried heat instead.

WARNING!!! The zinc alloy (or whatever it is) of the rotor core heats quickly and will start to bubble and melt under the heat of a propane torch. Just as I figured it was worth starting to pry on, I noticed it was melting and deforming. A quick twist with a screw driver bent and pulled it right off.

I put a block of steel I keep in the freezer in the top of the dizzy shaft to cool things down so it didn't degrade any seals/whatever down there, and when it was cool, sanded the corrosion off. I installed the rotor and cap and fired her up.

Today when I drove to work, I noticed that the start/warm up/idle was smoother, acceleration was better with no hesitation/stutter at any time, even on the way home when it would before like after stopping at a store.

 

Who'da thunk it!!! By spending $30 on one of them new fangled physical contact electrode distributor cap and rotor units, I think I gained 15HP, 4MPG!!! Will technilogy ever cease to amaze me??? NO !! :D

 

B

 

 

Hmm, can't seem to upload the photo and to busy to mess with it now... Maybe later...

Edited by Precise1
Damn site software
Link to comment
Share on other sites
Chriskaw440 NPORA Old-Timer

Chriskaw440

Posted
Posted

Hmm, can't seem to upload the photo and to busy to mess with it now... Maybe later...

 

 

I havent been able to upload any photos either no matter what I try and I am a graphic designer....me thinks the admin needs to check things out to see what the deal is......

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing
×
×
  • Create New...