Rough Slow Speed

[ekcheah]

My Suzuki Sidekick 1.6 auto 16v fuel injection 1996 runs very rough between 1000 - 2000 rpm. The engine is smooth at idling speed (900rpm) and also beyond 2000rpm. The engine is practically running rough ( power looks like coming on and off) in the range 1000 - 2000rpm. This is during first and second gear. Very uncomfortable and embarassing ride at this range. I have changed the spark plugs, ignition cable, air filter, fuel filter, distribution rotor and cap. Please help !

[jtgh]

is your check engine lamp on?

how does it run cold, try to go to 2500 in 1st and 2nd cold.
report results.
cold is rich.

if you had a vacuum leak , off idle will be horrible, hot.

hot engine goes to closed loop , full ecu servo with OXY and MAF sensors. Cold your car runs with a TPS only.

does car BUCK or BOG.?

buck = ignition , very violent in nature.

bog = lean Air fuel mix at that RPM. Loose of power but smooth loss unless it back fires thur throttle body to air cleaner , cough cough, more like a hicup.

talk to use.

[ekcheah]

dear jtgh,

All check lamps are out when the engine starts - hope that's what you meant.
When cold, the engine runs slightly better. As advised, i have run the engine at 2500 rpm in first and second gear when cold. Same roughness with exhaust sputtering between 1000 and 2000 rpm more pronounced when the gas pedal is depressed. At 2500 rpm for both gears, roughness reduced but can still hear the exhaust sputtering. More of BUCK , ignition not very violent.

When gear is in neutral or parking , the engine is smooth throughout from 900 - 5000 rpm exhibiting none of the symptoms described above.

Thanks and hope you can help identify the cause of the problem. Very embarassing when I have passengers .

[jtgh]

not spark, if you can do that (spark plugs love to misfire under load ,but yours are new)
I presum pulling plugs they look white or slate gray/white (not black with oil or gas carbon,etc)

you have a lean engine: is my guess.

EGR stuck open (pull , look , clean) ( drive with clean valve and vacuum hose plugged to prove Egr VSV is not stuck open too, and ignore P0400 DTC during test.)
vacuum leak (any)
if above checks out.

coked MAF ( clean with CRC MAF CLEANER, do not touch parts inside, very fragile)
Clean it 3 times , soaking 10min between spary blasting it.

spray from front and behing MAF.

check all hoses,even the MAF to TB big hose for leaks
pinch all vacuum lines for leak test, (idle should not drop)
do not pinch ISC air hose or PCV air hose (supposed to leak)
do not forget to pinch Brake booster hose.

powerloss


keep in mind, 16Valve engine HATES air leaks, will go lean for any leak.
the faster you go , the less the leak is , in relation to main induction so top end performance will be better. Off idle will be very bad.

most likely the problem can be fixed with out spending money.
or at least find the real bad part and not replace good ones.

we can find it.
jerry

[ekcheah]

Thank you jtgh for the procedures I need to follow. Will work on it this weekend and report back to you. Appreciate your time to help me .

[jtgh]

one other test , hot , try wide open throttle, up a hill .

engine fails under load hot, but how about WOT ?

how is that? ( wot , is rich , and max gas usage if good its not the pump or injection)

the EGR valve stuck open is infamous for causing flat spots , and is only a tad stuck open. remove and remove all carbon under valve seat.

I put my bet on EGR, (leaking exhaust in to induction all the time)
if you had air leak , tad off idle would be horrible BOG.


you get some effect cold so forget MAF, forget it is only used hot.

i say now , EGR , or then it must be air leak anywhere in induction system. this car is lean, you dont smell burn gas fumes
the exhaust my stink, a bit cuz it is hot as a pop corn you know what. Back firing up thur TB is possible. poping exhaust because too much air in there causes muffler explosions.
you are lean. due to leak or stuck open EGR.

i hope the lowers the labor to find it.
bless everyone for Christmas.

[ekcheah]

jtgh, you were right on the MAF - I cleaned it and the roughness was still there. There was no leak on the induction tubings, leaving as you suspected the EGR.

The EGR valve is situated in a position that I just do not know how to get it out to clean it or lean the valve seat or even to replace it. How do you get it out. Not much working space. Do you need to hoist up the car and dismantle it from beneath the engine ?

[jtgh]

book says, remove EGR, no help at all.

egr on yours is rear of intake manifold.
anything allowing access there would help.

lifting tranny tail shaft my cause a little forward movment. gently.

there are ways. to help.