Sudden undrivably rough idle, stalling and a long story

Power/Fuel
,
1

1996 / 2.2 L4 / 186k / Upper engine rebuild 30k ago

Car was driven on a errand by my mother. Upon trying to leave for home, the car started running very rough, and stalling. From the description she gave on the phone, it sounded like a plugged up exhaust. I told her to get some fresh gas and ease it home after.

When I checked the car for codes, I got 2. A P0300 and a P0122. Okay, so the throttle position switch has taken a dump, that’s easy enough. The car has 186k miles, but my constant nannying usually soothes her, so surely that’s all, right? God, I wish that turned out to be true.

I pulled the plugs, and #4 was gas fouled and sooty, #2 and #3 looked lean, and #1 was partially wet fouled. There was also gasoline in the oil. When the car would run, it would run the gambit from idling semi rough then stalling out and refusing to restart, almost like it was flooded, to idling scarily bad and no pedal response, to running too high of an idle and idle searching.

Since I have:

Replaced the TPS
Replaced the IAC
Replaced the CTS
Replaced the MAP
Replaced the ICM
Replaced the FPR
Replaced both ignition coils
Replaced plugs and wires
Replaced the fuel injectors (thanks to those that helped me)
Replaced the PCV (I was desperate)
Replaced the fuel filter
Checked the pintle on the EGR (looked good, cleaned)
Checked for Vacuum leaks (as best I could)
Checked the Fuel pressure (40 PSI) (drops to 20 after shutoff)
Checked for exhaust restriction (ran open exhaust manifold)

That brings us to today. New injectors just in, and the engine will run, but rough and loud. It almost sounds like the firing order is off slightly (Im using 1342 or from L to R 4132) and throttle control is almost non existant. It also shuts off when its warm almost like its flooded. No codes are showing. (despite discovering a sensor in back being unplugged and the O2 sensor being unplugged at times)

I’m close to summoning the devil to make a pact.

2

what do you mean, there was gasoline in the oil?

3

Gasoline diluted motor oil is most often caused by a leaking fuel pressure regulator, severe engine miss, or fuel injectors not pulsing closed. I’d check those things in that order and see what happens.

4

I know the first post is rather long, but you can see where i have tried those things already.

5

Do you own a compression tester and a vacuum gauge? I would like to see compression readings and vacuum reading at idle.

186K on original timing chain?

6

I dont own either, but i can rent them for tests. Yeah, its the original chain for sure. At this point other than the pistons, crank, cam, its the only original rotating assembly part that is… lol

I guess i should mention, i was also thinking timing chain at some points, as when the engine is idling, i hear a metallic “snapping” sound from somewhere in the front of the engine. With the erratic idle, or high idle at times, it was very hard to hear until now.

I’ll see about renting those today.

7

Tried to rent a compression tester, both they had were broken or unusable. I pulled all 4 plugs, they were brand new, about 10 mins of engine running time. All 4 are sooty now. Ill just order both tools from Amazon.

8

Hate to say it, but I wonder if those o-rings are still leaking…

9

My guess, I don’t think you’ve got the injector problems completely solved yet. Ask your shop if they have the capability to do an injector balance test.

10

I doubt it. The engine is clearly running rich, and all 4 being uniform kinda points to it. The plugs arent wet fouled, so it could be weak ignition, off ignition, bad compression etc.

I ordered several diagnosis tools i didnt have before, so all of us will know soon lol

I… dont have a shop?

11

Had some time to work on the car today.

The Compression Test:

    #1     #2    #3    #4

D 180 200 200 210
W 225 215 220 210

Does this indicate a problem with cylinder 1?

I did a spark test, and all 4 cylinders had healthy spark with the engine running. I’ll do a vacuum test tomorrow.

An odd tidbit today, I went to test fire the vehicle, and I had the plugs out. I decided to clean them before I installed them. Plugs 1 and 4 had carbon embedded in them, wouldn’t really clean. While plugs 2 and 3 simply cleaned by being sprayed with cleaner. You’ll remember, that cylinders 1 and 4 have been problem children this whole time.

I also “tested” the injectors while they plugs were out, they didn’t fill up as before, and only the finest mist sprayed out while cranking. I don’t think the O rings are leaking, and as far as physical function they are working as intended.

12

I would have done a quick engine vacuum test first, it’s quick and easy.

The difference in compression for cylinder #1 is no cause for concern. The compression readings seem high across the board, much higher than I would expect to see for this engine. Compression skewed high can mean excessive carbon buildup on the pistons or camshaft timing off.

13

I only did the compression test first as i already had the ignition system disabled, and had the plugs out to check them.

The valves only have 30k on them, and not carboned. The cylinder walls when i checked during the upper end rebuild at that time, were in great condition, and the piston tops, anyway seemed fairly clean. But if im wrong, and its entirely possible, would the cam timing being off be from a worn cam, or a stretched chain? The cam and chain are original to the motor, above that, fairly new. Would that timing difference be enough to cause a rich condition, or an erratic idle?

Today im also going to check the crank position sensor if i have time. The only areas i can think of that might be causing the problems are timing, vacuum, and ECM.

14

Vacuum test is done. With the engine running poorly, and stalling after a few minutes in intervals and running so rich, I couldn’t get the engine up to full operating temperature, but I got it as close as possible before the test.

I got a vibrating “steady” reading of 7- 8 in. on the dial. This did not change in any range from approx. 1500-2000 rpm. The vehicle doesn’t have a tachometer, so I had to just play it by ear. Sadly today was the best its ran in a while.

With the rich condition, stalling, and at times high idle with a side of general ill running… Im thinking heavily its a vacuum leak(s).

The metallic snapping/clunk sound I recorded today. Its coming from the cylinder 1/timing area. The better the engine runs the less the sound is present. The link is not a download, its a simple video link. Just copy and paste, as it wont work as an embed here.

15

I’d want closer to 18" of vacuum at idle. Your rich running is the result of a low vacuum reading from the MAP sensor, telling the ECM the engine is under a load and to add fuel.

Compression higher than expected, vacuum lower than expected, rattle noise from front of engine. I’d be pulling the timing cover next.

16

That low of a vacuum reading, and needle activity usually indicates a manifold leak, so yes it should be from 18-22 inches of mercury. And as i indicated above the symptoms indicate low vacuum, from said condition.

If the timing chain or guide IS having issues, that would throw off the timing, but i cant fathom how even preignition or a change in cam rotation would cause a very low vacuum condition?

17

Way back in February of 1998, GM had a TSB (87-61-21A) regarding timing chain noise in the 2.2 engine. They blamed excessive wear due to lax maintenance, though your engine has enough miles that it may just be time for a new chain and/or tensioner.

If you do determine a timing chain replacement is needed, the TSB gives a tip that may be helpful (please forgive the all caps, I just copied/pasted from the TSB):

AFTER REMOVING THE TIMING CHAIN, TENSIONER, AND SPROCKETS, INSPECT THE CUP PLUG BEHIND THE TIMING CHAIN FOR SIGNS OF OIL FLOW (SEE FIGURE). THE CUP PLUG HAS AN ORIFICE APPROXIMATELY 1MM (0.039IN.) IN DIAMETER. IF THE PLUG APPEARS DRY OR THE ORIFICE APPEARS TO BE BLOCKED WITH DEBRIS, INSERT THE PULLER END OF SLIDE HAMMER J 6471-02 OR EQUIVALENT INTO THE CUP PLUG AND REMOVE IT.

AFTER CLEANING ANY DEBRIS FROM BEHIND THE CUP PLUG, INSTALL A NEW CUP PLUG, GM P/N 14033197, INTO THE OIL PASSAGE. IMPORTANT: THE CUP PLUG MUST BE REPLACED WITH GM P/N 14033197. THIS PLUG HAS A SPECIFICALLY SIZED LUBRICATION HOLE FOR THE TIMING CHAIN. IF ANY OTHER PLUG IS USED, THERE MAY BE A REDUCTION IN ENGINE OIL PRESSURE TO THE VALVETRAIN OR A LACK OFLUBRICATION FOR THE TIMING CHAIN AND TENSIONER COMPONENTS.

Cam timing can affect manifold vacuum, though it seems like it would have to change quite a bit to get your results.

18

Thanks very much for the heads up on the TSB. Yeah I’ve always been taught that the links in the chain wearing out or jumping a tooth always retarded the timing, and that if the timing is retarded you have low compression, not high and not a 11 in. plus drop.

19

If you had a manifold leak that caused you to lose that much vacuum you’d be able to hear it hissing a block away. And it should run better as you open the throttle.

Ignition timing has a small effect on engine vacuum. Camshaft timing has a large effect on vacuum and compression.

20

Well, usually true but the engine is running so loudly and badly and with the clanking its hard to hear anything else. Indeed it does have a big effect, but again when the chain is worn or its jumped a tooth, the timing is retarded and causes low compression along with low vacuum. I have low vacuum but not low compression.

Its entirely possible the chain is damaged, and is at least worn. But, i hope you can understand why im trying to do everything in my power to prove it isn’t. I think you naturally underestimate how much I dont want to have to remove the chain lol.

We will know fairly soon, as im making a smoker to smoke test the engine in a day or two. If the smoke test doesn’t show a massive vacuum leak somewhere, I’ll have no choice but to inspect the chain. At worst, I’m out 15 dollars in materials, and at best the problem is solved and I can put the chain off till later.