Desperate: 99 Toyota Corolla "Lean Surge" (?)

Sep 30, 2017
Vancouver, BC Canada
Per the title, I am having some difficulty diagnosing an engine fault that would appear to point to the ignition coils. Per Haynes, the secondary resistance for these coils should be between 9,700 ohms and 16,700 ohms. Mine measure 12,300 ohms (each of the two coils) when cold, and 16,300 when hot. So, in the Hot condition, they are both just inside of the limits of rejectability. Let me explain further: there are two ignition coils on my '99 - and ea. ignition coil has two "towers" - onto which of each a high tension lead services a sparkplug. One coil caters for cylinders 1 and 4; the other serves 2 and 3. My fault codes are P0300, P0301, and P0304 - Random cylinder misfire detected; Cylinder 1 misfire detected; and Cylinder 4 misfire detected. The car would appear to faulter, just off-idle.... and only when beyond initial start-up / open loop operation. Truly, it feels like lean surge... cuz when you back-off the throttle when it surges, the surging reduces or ends. The pairing of the coils would appear to say that the coil serving 1 and 4 is suspect.... but it is within the limits of rejectability, and it totally maps what the adjacent coil does. Now I could pull the negative battery lead, allow the fault codes to reset to "zero"; and switch coils around. That MAY show new codes like P0300 (again), and P0302, P0303 - which would then nail it down as a bad coil. But that is a bit of PITA.... I note that all plugs look good. Plus, it'd be double jeopardy to have both plugs 1 and 4 bad, at the exact-same time. Ideas. PLEASE! I am really getting deperate! MAP is good, IAT is good, TPS is good, 4 wire O2 sensor is good, Coolant temp sensor is good. Did not check crankshaft position sensor or camshaft position sensor. PCV is good, and so is the grommet and the hose out of the PCV to the throttle body. All clear, no gunk, replaced PCV and grommet and hose. This model of Corolla does NOT have a hot-wire or other device... for measuring mass flow. Oh, one more thing: this car has neither a conventional fuel filter (only a "sock" on the in-tank fuel pump) nor a schrader valve to determine fuel pressure. However, I should note that it is ONLY at very little throttle opening that "lean surge" occurs. It does seem to be worse in 3rd and 4th gear of the automatic. Less so in first. And it does NOT correlate with how full the fuel tank is. Sometimes if a fuel filter is compromised... a full tank can operate adequately (i.e. sufficient fuel pump NPSHA)... but can fault at low tank conditions. No such correlation here.

Ign Coils - 1998, 1999 Toyota Corolla-B.jpg
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Since it's a 99 I take it you don't want to spend a lot of money on parts or professional diagnosis. That leaves effort. Get on with swapping the coils and see what that tells you.
New NGK coil packs are $40.79 each on RA. You're at the limits of what is "okay" so my vote is new coils. But it could be a crankshaft or camshaft position sensor... my dads Caliber was throwing a code for random misfires above 2,000rpm and that's what it ended up being.
Dunno if this applies, though vacuum leaks in themselves don't cause misfires: I've read somewhere the 1ZZ-FE is prone to having intake leaks. Misfires are more with ignition. Check to see if the cam/crank sensors that generate the CMP(G) and CKP(Ne) signals are creating proper signal and the wiring isn't severed or nicked. If you must replace coils, I recommend OEM Toyota or Denso. Also check the ignition wires for cuts/nicks/cracks and watch the engine run at night for bad wires. You have a waste-spark ignition system, meaning if one plug is fired just before the compression stroke ends, the other plug connected to that coil will fire on the exhaust stroke. You will notice the plugs wearing differently, since one plug is getting voltage through the center electrode and the other plug is getting it through the ground electrode. This might be useful reading:
Thank you - all of you - for your quick responses. Here are some comments: i) according to Haynes, servicing the EGR system only applies to '97 and earlier models (in the 1993 thru 2002 model year range). I take that to mean that there is NO EGR system on my '99. At the least, compared to my '99 Camry, there is no EGR actuator / pot device on my '99 Corolla. ii) quite right, re saving the $ associated with a professional diagnostic session; this car has a knackered ring and pinion.... though it has for the last five or more years... it "sings". In any case, I do want to save $... and so far I have a new MAP sensor (after it tested out badly ... and I tested it several times, applied a vacuum to it, etc...) and I also changed the PCV and the grommet and downstream hose.... and so I really don't want to throw parts at it. iii) I do have the Haynes manual that speaks to testing the Crankshaft position sensor, and likewise for the camshaft. I should do that, too.. Great to know that one of these could cause similar symptoms. I kinda think, though, switching coils around may be good. I can't fathom that BOTH coils have gone bad at the same time... and both appear to be close to teh 16,700 ohm upper limit. One strange thing that happens... and I don't think I'm seeing things - is that both coils, sometimes test out as zero resistance on the secondaries... i.e. 0.000 ohms... and then moments after, test again, and they read 12,300 ohms. BOTH do this! ??? This not about probing in the wrong spot... and it finding a closed circuit (zero resistance). Strange. I will swap coils to see if I can chase the fault codes over to cylinders 2 and 3. Thanks again!
I had thought about putting a closed cell foam cylinder (a retrievable cylinder) up the tailpipe - and fitting a PVC plug / rad clamp / Schraider valve into the intake boot... to see if I can presurize to 2 to 3 psi (assuming no mega exhaust system leaks). And then, to introduce soap sudds with a spritzer bottle. The thing is, that on warmup... i.e. right from cold - no abnormalities are (at least by me) detectable. Now I know it "carburets" rich on open loop / startup, and I know I drive really gently when cold.... but would a leanness caused by unmetered air... also be evident right from the get-go, i.e. right from startup, too?
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IF the fault codes read P0300, P0310, P0304 - i.e. misfires - but TO ME, it feels like a lean surge - well, how can I square that? On a previous vehicle I had ('71 Datsun 510) - it had a manual choke. On my current 1985 Moto Guzzi 850 T5 - which has a starting system (effectively, call it a manual choke) - for both vehicles, if you prematurely pushed in the choke... or pushed-in the choke too much / too soon - there was a characteristic "lack of response" to the throttle, or there were backfires... (or intake system "Pops"). This is exactly how my Corolla is behaving. I know what a stumble / miss feels like... and this, by comparison, feels like a lean surge. The characteristic "improvement" in running occurs, by backing-off the throttle.... not throttling more. This problem seems load dependent. Trying to climb a city hill - can be very challenging... four-ways on, in the right lane, people behind you cursing you, wondering why you are not accelerating. On the flat, generally, I can manage it. I have to solve this issue; it's driving me nuts!
For vacuum leaks, spray carb cleaner around the intake manifold and all the vacuum lines with the engine running. If you hear a difference in the engine's sound you found your leak. On mass-sensing EFI, the PCM/ECU will throw a lean code if the AFS/O2S detects excessive oxygen and the MAF isn't sensing the extra air. Your engine uses a MAP sensor that senses speed density of air coming into the intake. Speed-density systems are slower to respond compared to mass-sensing. It can still throw a lean code if the conditions are right.
I will try the aerosol can of carb cleaner. Oh, I forgot... one more thing. The air cleaner element is really dirty... and I am going to buy one 'real soon. I think I will remove it for a few miles... to see if that has any effect. I would guess not, though... as the engine can rev-up.... and I would think that only at high-rev / high intake airflows - would a condition be evident that is NOT evident at low flows. So I don't think it is the air cleaner element.
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Verify the intake bellows hoses are not cracked. They can crack in the pleats when aged. It's easy to waste money replacing electrical.
Yet another good idea. BITOG is the greatest! Not to denigrate Toyota Nation... but save for one Moderator's comments, and over the course of a number of weeks and added info / bumps from me - do you think that I could get a single comment or practical suggestion from Toyota Nation (in the correct classification for my post)?. NOOOH! So, I mean it when I say BITOG is the Greatest! Thanks!
Usually a "Lean Surge" points towards an ( air : fuel ) ratio problem. Either too much air or not enough fuel. Unmetered air entering an engine is what a vacuum leak is.
Do you have a Incandescent Test Light?, This procedure is a barbaric approach but VERY effective in finding/identifying a weak coil. I don't normally link to Youtube videos....But this guy did a pretty good job of explaining the procedure, I don't have the reservations of hooking my test light to the negative battery terminal like he does. If you keep the tip of the test light near the tower while pulling the wires off.....You will NOT get bit by secondary! Start at the 7 minute mark to avoid all the BS intro stuff.
A weak coil can fire the spark plug/s at idle but break down under acceleration, If you ever watched the coil KV output/demand at idle vs acceleration you would see the difference! The demand placed on the coil jumps dramatically under acceleration!
There has to be a used coil pack/ ignition module you can get for a few bucks for that car. They don't go out too often, but yours sounds suspect. I assume you've pulled your plug boots and looked down the valve cover to make sure it isn't leaking oil in the spark plug tubes. How much oil are you burning? I had a worn out corolla with that motor that would stall after I drove it on the highway and shut it off for gas. 2nd restart always worked. I think it was fouling its own plugs. Harbor Freight (Princess Auto?) sells a fuel pressure gauge that splices inline with the one in your car, doesn't need a tap.
Originally Posted by nthach
"...…..This might be useful reading:"
Lots of good information here.....Thank you! smile
Common 1zz-fe problem is leaky intake manifold gasket. Gets worse in cold weather. The original black rubber gasket eventually fails near 100% of cases. Be sure to get the updated orange silicone version. It's a medium complexity DIY job. Did it way back when on my previous 2006 Matrix. In meantime check fuel trims. Likely way positive.
Check the fuel pressure? If it is low, then check the fuel filter (if any), otherwise, it is the fuel pump. Of course, all the sensors have to be good also.
Originally Posted by clinebarger
A weak coil can fire the spark plug/s at idle but break down under acceleration, If you ever watched the coil KV output/demand at idle vs acceleration you would see the difference! The demand placed on the coil jumps dramatically under acceleration!
That is a great idea. I will view the Youtube video. Many Thx!