Intermittent Hesitation/Surge Problem

[fixkick]

Recently having routine maintenance done on my 97 Sidekick 1.6, 5spd MNL, 4 door Sidekick 16 valve engine.  Check engine light had been on in the car intermittently since I got the car in 2015 with 60k original miles on the clock. 
Never any drive-ability issues. Gas mileage 24-25 mpg which I felt was good as I do little interstate driving. Don't recall when it became "permanently" on but I got curious while car was in the shop.
Mechanic scanned and gave me codes for upstream 02 sensor and P0400 (EGR).  

Car needed a muffler and I decided to go ahead and take care of 02 sensor issue. 
Upstream was stripped out and could not be removed form the manifold. 
Exhaust shop had to create a bung hole in down pipe b4 cat to install. downstream was replaced as well.
Had the egr, egr switch tested by mechanic and he said all good. 
Cleared codes.  That lasted 2 days and engine light back on. P0400. 
Decided to get egr, switch and modulator to replace. Cleared codes.   (always do this last not first) VSV switch or MOD,  EGR MAIN IS GOOD GUESS, SURE. AND COMMON FAILURE.
At this point, noticed a slight hiccup at idle but no hesitation, etc good acceleration, etc.

Shortly after apparently got bad gas (RUST) somewhere and was driving on interstate. 
About 20 miles out, car started "bucking" like a slight power loss.
applied pressure on accelerator would responded and buck again intermittently.
trip and put Heet in tank, drove about 10 miles and fine.  (HEET is just alcohol , try better Chevron Techron, it has Benzine in it far far better to clean your muddy injectors)
Didn't have any other issues. 
Took to mechanic next day. 
light still on P0400. (400s can be easy or hard to fix doing my tests way less work and cost)

Had smoke tested.
Only came out at airbox. 
Checked and cleaned mass air flow.   all this good.
Asked to change fuel filter and when they pulled it was full of water - looked like mud. (means car has rusty tank inside , Red Iron Oxide mud)
Recommended I drop tank, etc. dump gas and replace fuel pump and strainer as well.  Did it.  (did he forget to look in the tank top  HOLE the Fuel pump rack came,out for fully rusted out tank this FIRST) using a FLASH LIGHT and look for 5minutes the whole inside even  mirror on stick to see top of tank inside, for rusted fully as many are.

While it was there I had them do plugs, wires, rotor button and distributor cap. )a time up) the cam belt is next 60k is belt.
Never done since I owned car but also never any issues (current mileage 97k). sure you did this after all it is misfiring for sure,  and that is spark or injectors failing. 99% of time


Drove car over a week and suddenly when driving back from errand about 5 miles from my house when I was accelerating at about 20-25mph, the stutter/hesitation reappeared. Continued to do so for a few blocks then stopped. (filter full of mud again?) You need to know that mud seen there lands also in the 10micro screen in the 4 injectors, never good that.
Many shops do not do this correctlly , with fueling the right way,  new tank, new filter , llines flushed, then have injectors pro cleaned (reverse flowed ultrasonic cleaning)
doing that backwards is just repeats with bad injectors.. ( a bad tank is A BAD TANK)



Called mechanic.
No help - slammed. 
Let car cool off and drove again a couple hours later. Initially no issue BUT appeared that once at operating temp for several miles - approx. 5, the issue would resurface. Continued driving, it would occur intermittently.  (is the front crank pulley  17mm bolt set to 94ft./lbs torque? or at 10, oops nobody reads TSB warnings, it seems. (use 5th gear, turn CW to set torque to spec)

Now it seems if car sits 10 -15 minutes and then you drive again, once you've gone so many miles or so many minutes at normal operating temp, the stutter hesitation occurs.  Speed doesnt seem to matter. 
Whether your're going 20mph or 60 mph.  On same note, it may not do it at all.

Car currently in different shop now and they are trying to diagnose. 
At $117 an hour, I need help and advice.
Most places won't even touch old cars.  P0400 code still when took in.  Never have been able to get rid of it.

See attached narrative I gave to mechanic shop.
The EGR can cause stalling just before stop signal,  this is bad EGR MAIN, always, #5 part...

97k,  so is a near new car,  that low, very very rare that. (I had 2 like that)
too bad really that the  mech never looked down the tank hole, with PUMP RACK removed, too too bad that..  wow, what  MISSED opportunity there..
that mud does not just come from thin air, the tank is bad. (or the fuel rack only rusted out, ??? but only looking matters.


EGR 400 fail is caused by 3 things, vacuum path failing or exhaust, (exhaust is always #1)  and #3 bad parts, EGR main tops that list ALWAYS.
P400 does not a lie the EGR system is failing and can so all the symptoms (not mudd related) stated about. for sure hot RPM below 800PRM hot engine. 750rpm is spec min.
the first thing to do is clean  out mono-port hole here, EGR port.
https://fixkick.com/sensors/EGR/90-95/SL...ge_12.html

then test the EGR main. 
the EGR main can be bad, that is  the device on the rear of Intake man. runner #4 EGR mIAIN.
on cold engine not running make sure the ring inside can be pushed, and make the valve open and closed with thunk.
test #2, is the stall test.. (best done with hand vacuum tool, no burns)


your car will not have part 36. your car has EGR map system , and works far better than other early ways..
To test EGR nothing works better than having a HAND VACUUM pump to connect to hose 23 , and hot  engine pump up say 10HG vacuum and the valve opens and
stalls, or RPM falls 800 to 400.. this one test, tells me (passing) that the EGR exhaust paths are not 100% bad,
this also is binary search method "diagnosis" , cutting the true possible causes in 1/2,   and 1/2 the labor, or MORE.
if guessing, just clean the mono port hole and buy a new #5  (far far less work if this fixes it)


all tests are here,  covering this GEN2 EGR yours is.
see the stall test, below... then the bark test.

https://fixkick.com/EGR-Gen2a.html

try to know that the path for ERG is long, and complex. but on this car less, by 3.
Tube 50 can clog;.
EGR main #5 can be bad.  most are at 100k miles ive seen..

the intake egr ports can be clogged, and the head tunnel EGR and the #4 exhaust port EGR tunnel clogged too.
that is why I do test first. to see what we have,
 
see the ring below (push here) if must move cold(hot you get burned ) and the ring moves 1/4" inward keys on pocket test this is JAM test 1.
then on the engine running test, hot , I apply vacuum to the missing vacuum nipple below, and engine stalls hot, 800 rpm drops to 400 or less or even stalls.. if yes ,this test passes
if the test fails, for stall test, remove hose from bark tube(cold running engine) and it is felt to go PutT PUTT every time #4 cylinder fires. (barking like)
if the Bark test if failing remove the egr main below and remove the carbon packup everywhere inside, even the bark tube can pack up.  if this test bark still fails then
the head or intake tunnels are packed up in carbon.
did you buy new MAIN below #5 part? please advise. if yes the ring moves free and stall test passes. if  not the bark tube most go putt putt.



bark failures,  are here,,  red arrow path , end to end, packed in carbon, I  can also start the engine below, 
the feel if the "IN" hOLE BARKS. the out port runs pipe 50 and the mono port injector egr.  



the head path is below (bark tunnel) I like naming them to focus clearly.



crazy S here..



and last this, most hard of all to fix. well the  above crazy S , hard too.





all 96 up have  mono-port EGR injection point , #1 must be cleaned from front to rear (facing bell horn) and at pipe 50.  this loves to clog up, "LOVES TO"


the #1 hole here i s 1/2 clogged up, and that is BAD. seen them 100% clogged, and that makes hole  Invisible, ( only seems so.)

good luck and do ask questions, I can fix this EGR no matter what with testing, for sure easy if tests FAIL HARD< as is so common.