#4 Not firing at low RPM

etdavenport · 08-16-2009, 11:31 PM

Hello!!

I am new to the Suzuki 1.6L 16v and I am having a little trouble with a recent purchase. When Purchased the car, it had a rough idle. After a Full tune up [plugs, wires, cap, rotor] it ran fine for about 100 miles. then back to rough idle.

Symptoms:

Cylinder #4 is not firing at idle. I pulled all the plug wires while running one at a time to verify this. But at about 1500 RPM it will start firing again. [verified this in the same manner] So i assume it is getting gas, and i know they are all getting spark. Could I have a possible clogged injector? I did notice a bit of oil around some of the plugs when I pulled them[ not much but it was present], and a small hint of blue smoke when it first started cold. [hasn't done that again since i purchased it. Valve guides?!?! seats?!?] And I have not had opportunity to test compression. It tuns like a top at normal RPMs, just wont idle when it warms up.

If you have any input please let me know. I am a newbe to this engine and EFI all together. I am going to start by cleaning the injector or possibly swapping it with another for a test to see if that's all it is. Can injectors be intermittent like that? Am i looking at a larger problem here like valve guides, broken springs etc?] I payed $400 for the car to begin with so, if I have to a full rebuild would not be a bad idea, but I would like to avoid it if possible.

Thanks!

jtgh · 08-17-2009, 11:59 AM

Quote:

And I have not had opportunity to test compression.

if it cant pump air. its not going to work.

but you can hear the injectors click,
1/4"tube to ear (ar a $3 stethoscope) and press other end to injector side.
listen to them all, all must sound alike.
assumes spark is perfect. (tune up was good action !)

1; motor good.
2: injectors good. (if #4 is dead injector after swap, ECU bad)

id workin a new fuel filter too. wont want to have marginal fuel pressure (flow)

etdavenport · 08-17-2009, 02:14 PM

I tested the compression today. #1 was at about 30psi, #2 130psi and 4 and 5 both at 170psi. The injectors all sounded the same so i did not even try the swap. Im assuming that whatever the compression problem is in cylinder # 1 [most likely rings?], it is just not getting enough compression to operate at low rpms.

I did the filter as part of the tune up and even drained all the old gas. I bought this thing after it had been sitting for a long time.

Taking into consideration the compression in the first 2 cylinders, is the ECU still a possibility? Can low compresion cause the sympoms I am describing? I even went as far as dumping a half a bottel of 100% petroleukm in the motor and the idle is almost normal now, with the occasional miss.

And lastly. IF I am going to crack this thing open to do rings and possible valves, shouold I jsut rebuild the whole car? The kit is extreamly cheap, but is it a lot of extra work? It seems to me jsut looking at the size of the block, rebuilding it would be the better rout, instead of just doing the rings.

Oh and i never posted my vehicle...

1993 Suzuki Sidekick 4dr
1.6L 16 Valve

MarkB.NV · 08-17-2009, 03:09 PM

I'd suspect a cracked / broken piston for a reading that low (bad rings are usually something like 50-70 psi, but that's based on my own modest experience).

Next step - do a wet compression check. Just squirt a teaspoon of oil into spark plug hole before doing the check on that cylinder. See if the compression comes up and by how much. If the wet test shows a much higher compression for #1, then it points to bad rings.

Then check the valves. If you have no valve clearance, the valve may not be closing all the way - letting gasses escape and causing the low reading for #1.

Before planning a rebuild or other serious work - I'd double check that you don't have a stuck valve on #1. No clearance -or the valve is getting hung up and not closeing. (if the no 1 cylinder swallow a screw/nut/rock -it could have damaged the valve or seat - preventing a good seal). What did the no 1 spark plug look like?

noisey jack · 08-17-2009, 03:49 PM

If it start missing when it get hot it could be valve clearance to tight ? did you cheque the comp. when it was hot or cold? also cheque wet and dry...

etdavenport · 08-18-2009, 12:27 AM

plug looked the same as the others. slightly black on the end. I tried the oil trick withe the compression and my stupid gauge decided to die right then, Needle valve quit working so it wouldn't hold a reading, but it didn't look like it changed anything while watching the needle..lol I visually checked the valves. Nothing look awry from the top, but i have no idea what the seats or sleeves could look like. I did happen to try something that kinda worked, and I am wondering what this could mean. I dumped a can of that engine restore crap into the motor oil and the compression in #1 came back up to 130. Could I have a blown Head? the reading going from 30psi to 130 just with a can of crap is very odd... The vehicle was low on coolant, but I haven't had it long enough to see if it holds water. No bubbles or any of the obvious signs of a blown head, but that doesn't mean anything. I may just crack the head and peek at that gasket.

ranger88den · 08-18-2009, 05:44 AM

Put #1 on TDC and put a compressed air-to-spark plug fitting (I think Lisle makes one), pump it up, and see where the air comes out of. good luck

jtgh · 08-18-2009, 11:37 AM

these facts above are all on the instructiion sheets fo the vacuum test guage and the leak down tester. (sorry for stating obvious )
you have dead cylinder. you did not say your location so i cant tell if your motor is subject to freeze damage. nor when the car last run perfectly. 2 important bits of information.

the the compression test wet and dry as the above poster said and the poster that said pressure the cylinder and listen for the leak. (is right on the mark) be curious.

you can do that,later test with block dry and thermostat out so you can listen inside the water jackets for leaks there, with a rubber tube to your ear. "stethosope" again.

you listen in side #2 with a hose to see if the leak is going into #2 . (pressure on 1)
we menition this , as a precaution for :
is it just a bad head gasket
or
is the block or head cracked.
warped head.
warped block.

ONce head is off, check the deck for warpage using a steel rule and feeler gages
do same on head.
the wet compression tests will warn of leaking valves is oil , can not improve the compression.

examine the head carefully. some time a bad valve guide can get really bad and do very bad things , spring and valve.

if you think the head gasket is ok, before and after head off, id have head pressure tested., if not outright overhauld.
cycle crank moving pistons up and down and look with a very bright light for cranks in bores.

you dont know what you got, so take extra readings like prev.postes say.
cheers

Nor'Easter · 08-18-2009, 01:18 PM

The first post mentions a problem with #4 cylinder. Then a compression check shows a problem with #1 cylinder. Is the 30# compression reading at #1 cylinder a typo? Where is the problem? #1 or #4????

One of your plugs would look a lot different if you had low compression like that and that cylinder would NOT run or fire although it may still show spark with a timing light or pocket spark checker.

So what is it? Post #1? ..or post #3? They are completely different with different problems.

jtgh · 08-18-2009, 04:08 PM

it may have more than one problem.
in fact, never seen a 93 with out piles of problems due to neglect.

he might have confused #1 and 4 ,by looking at Dizzy wrong.
the compression guage is not fibbing. dead cyl. or more.

i can only assume he read the sheet of paper with the gauge and used w.o.t, FOR ALL TEST.

many forget it.