rough idle and soft acceleration

ndiiorio

Registered User
i was having problems with my fuel pressure and maf codes and now that is fixed. what is happeneing is with or without the chip. it has a rough idle and when i acclerate slowly it seems like the engine is working too hard and feels very rough. this happens only up to about 1500 rpms and then everything seems to smooth out. doesnt matter hwat gear or how fast but when im slow with acceleration and the rpms are low is when the problem occurs. the only other thing i noticed engine wise is that my tensioners seem to be moving with the rough idle, ive never noticed them to move before. its mostly on the sc pulley and one real low on the passenger side. do i need new tensioner springs and is this causing the rough idle? spark plugs and wires are new, fuel pressure is at 43 at idle, new computer and new maf. i have no codes and no cel. mods are on my member page.
 
rough idle seems like a miss maybe overly rich fuel. Are you sure the fuel pressure regulator isn't leaking into the vacuum line attached to it? Maybe a bad injector?
 
injectors are new with less than 200 miles on them so i dont suspect them, i dont believe the fuel regulator is leaking, when i remove the vacuum line from it the idle doesnt change. ive searched for any vacuum leak and i couldnt find one. it doesnt smell like it is running rich but i havent ruled that out.
 
If this is a change in performance, make sure you check all the electrical connections. Dis, coil pack, crank/cam sensors.

Do you have a tool to run engine diagnostics? If you have a code scanner and the manual for it, it should walk you through how to do a cylinder balance test. It's a test you can run after you do a Key On Engine On test.
 
alright... on the first test i got a code 92 which is rich at the o2 sensors, i did the test two more times and i didnt get it, im assuming the first time i did the wot part a little weak. i did the cylinder test and it is telling me the #2 cylinder is weak. i pulled the spark plug, it looked a little fouled, i tried to clean it and put it back in. same result on the test. im going to have to get a new plug to satisfy the test for me to make sure it is not something else. i know its not the wires as i switched it with another and still got the same result. if i get a new plug and i still get the 20 code for the #2 cylinder where do i go from there? how can i check the injector for it being clogged? what is the voltage supposed to read at each injector? thanks
 
I would do a compression test. But that's because I have compression gauge to test with.

I would put a new plug in gapped the same as others. (you may need to pull one of the other plugs to verify this. Then test. Still same cylinder... then find a similar length plug wire for there and swap them and test again. Same issue? Got to do a compression test.
 
put in new spark plug, swapped the wire and still the same. i found a small leak at the underside of the collar nut. after trying to tighten it i ended up taking it apart. the leak was at the threaded area for what the collar nut presses up against when tightened... i didnt know until i was blowing it off with some compressed air and saw fluid come up through the inside. I seald that and put everything back together. gained about 2 on my vac. gauge and it smoothed the idle a little. im gonna buy a compression tester tomorrow and see what i got. after the fix i can hear the noise a little better, sounds like its coming from the sc. it has less than 200 miles on it, was s-ported and rebuilt by magnum powers. i heard some people say there are some spring loaded and some are different is this true? what noise am i hearing? its not at all consistent and it comes and goes. ahhhhhh
 
o.k. the leak will cause the rough idle...Shouldn't have an impact on the cylinder balance test.

I'm not sure where you are describing the leak is coming from. the collar nut presses against a raised lip on the SC top. That lip is created from a another large nut screwed onto the SC top with an o-ring seal. That inner nut requires a spanner wrench to back off. If it's leaking from there, you'll want to first see if you can tighten it. the other place to leak is if the SC top flange isn't sealed against the flange from the lower SC Tube. There needs to be a semi-flexible seal inside there, either the factory teflon tape replacement, or a reusable teflon gasket, or use of RTV to take up any gaps in the seal of the top to the tube.

Spring vs something else means the coupler in the sc snout. The shaft attached to the pulley is coupled to the rotors in the supercharger via either a solid coupling, or a spring coupling. It has some clearance in the coupling that can eventually get excessive and cause a rattling noise.
 
Because you found a leak in the IC system, I would recommend getting a set of teflon IC tube gaskets and installing them......

They seal very well and are re-useable, so long as you don't over tighten them.....

This will rule out any leaks in that area......

What kind of noise are you hearing from your SC.....

They will make a rattling noise when the solid coupler starts to wear a bit....

Later models of the SC had spring loaded couplers in them....
 
oh... and pull the cable off the battery and let is sit for 10 minutes to clear the adaptive memory of the computer before trouble shooting further after fixing the leak. adpative memory will have adapted to your vac leak and it takes time to re-learn once you fix something. Better to start from scratch.
 
have the teflon gaskets that why i had such a hard time finding the leak. on the sc top is where the leak was. it was on the nut that keeps the collar nut from sliding off. i was able to turn it about a quater turn. i had resealed that to fix the leak. im going to do a compression test today and see what i have, and reset the computer.
 
oh the noise in the sc sounds like there is something loose inside the snout but it doesnt do it constantly and when idle is increased it goes away. i havent checked the oil in the sc but im guessing if it is low that might be part or all of the problem. i didnt think it was the sc at first it sounded like a rattle in the engine somewhere but when the idle smoothed out a little it was easier to tell that is where the sound was coming from.
 
Fuel pressure shouldn't be that high...with vacuum hose attached it should pull the pressure down to about 37 psi when idling. Are you sure that hose is connected properly and coming from a location that gets a vacuum and a boost signal ? Should be on the return plenum side.

David
 
The noise from the supercharger is a result of an uneven idle. Did you find the cause of #2 being weak?
 
not yet, i still have to pick up a compression gauge. the store by my house didnt have one so i have to go to the other side of the island... and while it is only 15 miles sometimes that trip can take over an hour, im hopefully going over today after work so i should know soon. since i fixed the vacuum leak the idle has not been so bad and the sound isnt consistent with the idle. it comes and goes but it is something that just started with the rough idle.
 
i did the compression test and i got between 150 and 160 for every cylinder. im going to recheck the gap on all the plugs and then reinstall.

if i still get the same results is this going to be an electrical problem... coil pack, dis, etc...?
 
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