# Hesitation on acceleration- running out of ideas



## AP100684 (Apr 1, 2009)

Preface to everything - I am a noob with limited mechanical knowledge and skills.

96 Sentra hesitates and stumbles on acceleration and idle 'falls out' a little when coming to a stop. No check engine light. Used to do this pretty consistently while driving. Cleaned MAF, Throttle body, and IAC, also replaced spark plugs, wires, and have run approx 10 gallons of BG44k treated fuel. No longer have issues with idle falling out. The first 150 miles post-repairs I experienced absolutely no hesitation on acceleration. Now, it will hesitate on acceleration for approx 15 minutes at a time and magically clear up and remain good for a couple hours. I'm stumped by this irregularity. Maybe whatever is getting clogged intermittently in fuel system and after 15 mins BG44k fuel eats it up???? What are some things I should check? TPS? MAF sensor? Cat converter (would that even make sense?) Fuel filter? (replaced less than a year ago). Any and all ideas appreciated.

(PS Have been plagued in the past by the dist cap and rotor button falling out but I AM POSITIVE it is in there securely)


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## jdg (Aug 27, 2009)

Ya did everything I would've done EXCEPT replace the distributor cap and rotor.
The button might be in the cap securely, but what about the rest of the it?


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## AP100684 (Apr 1, 2009)

hey thx jdgrotte. I'm not really sure what you mean by the rest of it? both rotor and dist cap are relatively new (less than 3 months).. is there something in particular i should be looking out for? maybe ignition coil? whatever is causing this is driving me absolutely crazy.


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## STEALTHY SENTRA (Sep 1, 2009)

I suggest checking for intake leaks,check condition & gap of plugs,check condition of all vacuum hoses(cracked,brittle,burnt)egr valve.*jdgrotte would u agree?*Hope this can help clear-up problem.


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## jdg (Aug 27, 2009)

STEALTHY SENTRA said:


> I suggest checking for intake leaks,check condition & gap of plugs,check condition of all vacuum hoses(cracked,brittle,burnt)egr valve.*jdgrotte would u agree?*Hope this can help clear-up problem.


Well...ya...of course. It's the "intermittent" nature that kinda gets me.
I would think that the normal stuff (MAF, TPS, etc) would set a code if anything was going bad in those areas. But if all of us GA16DE owners know anything, it's that the crank sensor won't always set a code and will cause all sorts of crap! Then again, same thing with the MAF. But the CPS is cheaper than a MAF.
And I'm just talking to hear myself talk at the moment trying to figure what I'd change out first if it was me... Heck my '98 200SX is still up on blocks waiting for warmer weather so I can put the head back on without freezing my nuts off.


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## AP100684 (Apr 1, 2009)

hey guys, really appreciate the thoughts. i was looking for clues today and noticed oil in the bottom of 2 spark plug chambers, covering the plug threading. Could this be causing my problem? Not sure the effect oil has on plugs. The valve cover looks to be shot- with at least one gasket thing cracked and protruding a little. Consensus is to find a b13 replacement?

Follow up q: could over-tightening the valve cover mess up these tube seals? not sure if i did something wrong putting the vc back after i changed the tensioner.


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## lukesSX (Feb 17, 2010)

It could be a problem if the plugs are really oil soaked. If not, then it would probably just shorten the plugs life. I would just get a new gasket, torque it down correctly, and that will most likely fix the oil problem.


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## smj999smj (Jan 1, 2006)

Yes, the oil in the spark plug wells could be the cause of your problem, creating a short. The spark plug tube seals are individual seals and overtightening the valve cover should not have caused the tube seals to leak. IIRC, the valve cover bolts are shouldered so overcompressing the vc gasket is impossible. Regardless, you need to get a new valve cover gasket and spark plug tube seals and replace them and get all of the oil out of the spark plug well. Brake cleaner, a rag and compressed air usually works best. Also need to clean the end of the spark plug wires and make sure the boots of the wires haven't bloated due to the oil contamination. If they have, you'll need to replace the wires.


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## AP100684 (Apr 1, 2009)

thanks guys! have replaced the valve cover, gasket, and tube seals. oil leaks no longer an issue, but i do still need to clean out the residual stuff inside. will do that today. ALSO, i replaced the distributor with a questionable 25$ junkyard find. No longer have the very obvious (and abrupt) hesitation problems. Instead, now I have noticeably sluggish acceleration when starting from a stop. What would you guys check first? Fuel delivery? TPS, MAP, MAF? I have no engine codes..


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## skeeter123 (Apr 30, 2010)

Sounds like the distributor timing. Did you put it into "timing mode" to set the timing and idle speed? I think the 96' were to be set to 15 deg.
Hope this helps.


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## AP100684 (Apr 1, 2009)

skeeter123, hopefully that's all it is. I played with an old timing light today just to see how it works. i found the timing indicator but couldn't see the degree markings clearly enough to feel comfortable adjusting it. maybe the bulb was too old or dim but i'm going to have a shop do it so i know it's done right.. hopefully they know about timing mode... will update.


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## skeeter123 (Apr 30, 2010)

Timing mode involves taking the TPS sensor connector off, and revving the engine in a particular way; you can look it up in the FSM.... Couple of things I found useful:

Use some white fingernail polish to mark the proper spot on the flywheel's timing mark.
Once you've set the distributor timing, scratch a deep mark across the metal from the engine to the distributor so you'll have a reference in case you have to move it again sometime. Also, using my scratch-mark as a reference, I've advanced mine a little to get some extra oomph out of it; you can get away with advancing the timing a bit more than spec if you use higher-octane gas; test it out by flooring it and making sure there's no knocking.


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## AP100684 (Apr 1, 2009)

Going to have a mechanic friend help me adjust timing tomorrow morning. Is going into 'timing mode' common knowledge among mechanics or should I let him know? Also, ignition timing spec under my hood says 8 degrees +/- 2, is there an advantage to having it set at 15 degrees instead? 
THANK YOU skeeter123, smj999smj, lukessx, jdgrotte and stealthysentra


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## lukesSX (Feb 17, 2010)

It should be common knowledge, but the procedure for doing it varies on different model cars. He will probably have access to some kind of manual which will tell him how to do it if he doesn't already know. Advancing or retarding the timing can give you more top end or bottom end. You have to remember though that you'll gain more in one area, but you'll also lose more in the other depending on what you do. I've never set one at 15 degrees so I'm not sure what it will do, but I'm sure someone else will know.


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## skeeter123 (Apr 30, 2010)

When I say a little bit, I mean 2-3 degrees. 

From FSM for 1996's, for GA-engines its 8deg +/- 2; for the SR's its 15deg +/-2.
see:

http://www.********.com/FSM/Sentra/1996/EC.pdf

for procedure for timing mode / idle speed adjust.

The +/- 2 deg is because it is pretty hard to see it, even with white paint on the mark and in the dark of night... you're sort of offset from the timing indicator when looking at it from above, have to gestimate that you're at the right spot. That's why I suggest making the scratch mark , then adjusting a bit from there to see if you get a little more pep w/o any knocking. If the ECU detects a knock, it will retard the timing quite a bit, ruining your performance.

Or this link, which apparently doesn't get filtered:
http://www.aubreyandcharles.com/ServiceManuals/


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## jdg (Aug 27, 2009)

lukesSX said:


> I've never set one at 15 degrees so I'm not sure what it will do, but I'm sure someone else will know.


I tried both of my B14's at 15BTDC last year. Pinged like somebody was doing drum rolls on the intake with a hammer! Performance went in the crapper, but only because the knock sensor was working overtime and the ECU was killing the timing. Then again, I was running regular unleaded. Never did try it with premium. I'll save that for this summer sometime.
I've got both of mine set for 10BTDC, or at least as close as I can get it. Runs fine for me.


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## smj999smj (Jan 1, 2006)

When I went to Nissan's training center years back, the instructor there said most Nissan engines "wake up" with an extra 3 degrees of advance over the factory recommended setting.


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## AP100684 (Apr 1, 2009)

Just had mine timed to 10. Peace of mind achieved.. for now...

In other news im burning oil like crazy and the car still struggles on acceleration from a stop. This sluggishness is very different from the hesitation i was feeling pre-distributor & valve cover swap. I realized today (like a dummy) that when I swapped the valve cover I didn't inspect the PCV at all. Maybe this is an issue? No stores within 100 miles have the part on-hand, so hopefully tomorrow we'll see.


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## AP100684 (Apr 1, 2009)

pcv thoroughly cleaned and working. not the cause. when i press the gas pedal after coming to a stop 60% of the time it won't respond as it should... resulting in painfully slow acceleration until 2nd gear or so. Fuel pressure?


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## jdg (Aug 27, 2009)

Since you were burning oil, how about the plugs being all crudded up now?


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## camoy (Apr 28, 2004)

OP i have read the thread a couple of times but didn't see where you listed the mileage on your car. What is that mileage? If it is over 100K have you ever replaced the upper timing chain tensioner? That thing can wear down to metal and allow for enough slap in your chain to wear the idle sprocket which in turn could allow your chain to wiggle between half a tooth forward or backwards when the car is running. This will also cause the hesitation and poor acceleration.


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## lukesSX (Feb 17, 2010)

I would do a compression test and see what you're getting and also check for small vacuum leaks.


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## AP100684 (Apr 1, 2009)

Just wanted to state an official end to my problems. The initial hesitations and jerkings were solved by swapping out the distributor (maybe a bad coil?). The post-distributor issues I had (terrible responsiveness and massive oil burn) were actually my fault. The aluminum valve cover I used as a replacement had a crack in the tiny little rectangular gasket thing within the valve cover gasket (don't ask me what it's called). ANYWAYS, after replacing that tiny little piece of plastic everything is back to normal- no more burning oil and clean, steady acceleration. 
Thanks for you guys' help and patience


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## jdg (Aug 27, 2009)

AP100684 said:


> The aluminum valve cover I used as a replacement had a crack in the tiny little rectangular gasket thing within the valve cover gasket (don't ask me what it's called).


That's exactly what I call it 
Ya, the distributor could've been half a dozen different things inside it...bad bushings, bad pickup, bad coil, bad wiring, bad ju-ju...I like the last one personally.


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## smj999smj (Jan 1, 2006)

"PCV baffle" gasket or seal, is what it is.


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