Cold/Delayed Start Issue 2010 2.7L

2010 Tacoma, 2.7L. 4cyl Access Cab, 305000 km, purchased 1 year ago at 270,000 km

Engine turns over well but won't start normally when cold. Ambient temp. -5C or less.
Scanner reports correct ambient temp. Battery 12.8V

Apply heat to engine compartment for 1 hr.
Engine starts, pumping accel. pedal, idles rough for 5 sec. then smooths out at 1200rpm til
warm at 600rpm - no codes set. Drives well. No power or rough idle issues.

Turn engine off at operating temp. and restart within 1 min. - starts normally, no codes set and smooth idle. But if restart after 15 min. with engine temp. not cold - starts with initial rough idle for 5-10 sec. then smoothes out after a noticable noise(click ?) from engine compartment(no accel.pedal use). Code(s) 301 or 300, 301, 302 are issued as 'pending'. No dash engine light yet. Drives well. No power or rough idle issues.
Edit: I believe the noticable noise/click is the secondary air pump clicking off...?

With pending codes set, turn engine off at operating temp. and restart within 1 min. - starts normally, no codes set(still pending) and smooth idle. But if restart after 5 min. with engine temp. not cold - starts with initial rough idle and dash engine light flashes as well as anti-traction light. Engine will continue rough idle and drives with miss. Codes are 300, 301, 302 and are now set. Without clearing codes, subsequent start or driving in this state will issue more pending 300, 301, 302 codes but no other codes are pending or set. If codes are cleared, while engine idling, no difference is observed to rough idle. But if engine is turned off and immediately started, after codes are cleared, it starts normally, idles smooth and drives well. No power or rough idle issues. No codes are set on a subsequent drive/trip.

New spec.'d iridium NGK plugs and new COP coils recently installed, MAF cleaned, new air filter, fuel pump relay tested OK. No throttle body cleaning attemped yet.

Toyota doesn't have a fuel pressure test port on this model so can't test fuel pressure without
dealer, but I am leaning toward a fuel issue, maybe a pressure leak/bleed-down, clogged fuel
filter(with pump in tank) or failing pump.

I understand the traction light 'on' just indicates the ECM detects an engine issue(misfires) and
turns off the traction control (safety precaution) so light indicating 'off' condition gets set.

Any suggestions ?

 

The iridium plug might be the issue. These trucks like the OEM plugs and they aren't iridium.
Or could be a vacuum leak. When cold it shrinks to let more air in and when hot, it expands to close the gap.

 

Clean the throttle body. You mentioned the ambient temp is normal but what about coolant temp?

 

Thanks for your response, Jay. My owners manual says only iridium plugs , either Denso or NGK. The plugs I removed were Denso iriidiums but I'm sure they weren't the originals and gap was .058(wicked too large). Made sure new NGK were .044+/-. Thought at this point I had found my problem but issues described continued. Don't hear any obvious hissing indicating vacuum leaks either while cold or at operating temp. but still could contribute to issue...

 

Thanks for your reply. I am thinking of doing a throttle body clean next just because of the mileage and I have no idea if it was ever done previously. But the old fella at least deserves it at this point. The ambient temp. was read by a scanner hooked up to the DTC port from a sensor dedicated to reporting the outside(air) temp. to the ECM for adjusting the air/fuel ratio richer for 'cold' starting. Is there a scanner reading for current coolant temp. which would modify the air/fuel ratio for warm start on cold ambient(air) temp?

 

Iridiums are OEM for the 4cyl.

Maybe a leaking/sticking fuel injector? Try priming the fuel system first by turning the key to "On" and then wait 10 sec before cranking.

 

Plug your scanner back in and look for coolant temp (ECT). Its a very important sensor at startup. Sometimes when they go bad they show crazy readings like negative 140°. It can cause a flooding condition and long crank times. Any trouble codes stored?

 

Thanks, Pork Chopper. a leaking / sticking injector sounds like a possibility.
Unfortunately these tacos have a fail-safe fuel pump system that will not turn on initially, unless in 'start' key position. It stays on (primes/pumps) for a few seconds but if the ECM doesn't get RPM's from crank sensor, indicating a 'real' run condition, it shuts down the fuel pump for safety. That's why, with these babys, no-one can hear the pump priming when the key is turned to 'on' position or the fuel pump relay( labelled I/OPEN) in fuse box can be tested unless you swap it for a similar relay, say the horn relay, and then test the horn. If the horn works with the fuel pump relay in its spot then the relay itself can be considered functional but that doesn't mean that the fuel pump relay wiring/contacts might not be at fault. If that was the case though, I'd have similar problems, warm engine or cold.

 

Well hell, carry on and disregard what I said lol Thanks for the info though.

 

Thanks for the info on ECT, b_r_o... I will check it out at cold start and at operating temp. It seems that when cold, unless I pump the accel. pedal, there is no fire but if I press the accel. pedal a couple of times while cranking, it will at least fire. This leads me to think it's lack of fuel or low fuel pressure instead of too rich which would cause flooding and no start . When it sets codes, as I described in my original post, they are always p0300, 301 and 302. Since cyl 1 and 2 are the last two served by the fuel rail which feeds into cyl 4 and 3 before 2 then lastly cyl 1, I'm thinking weak, leaking, or plugged injectors and/or low fuel pressure but as I also mentioned in my original post, Toyota has not provided a fuel pressure test port on this model, so this would have to be handled by a pro/dealer tech. As far as I know, fuel pressure cannot be measured/read with a scanner. I am trying to eliminate the options that my limited knowledge/tools can handle first before involving the $80-100 an hour crew. I appreciate your input though and will check the ECT readings.

 

I plugged the scanner back in this morning and once I got it started after warming the engine compartment for an hour, i checked the ECT and it was at about -5C but as the engine warmed up I could watch the ECT rise about 1 degree every 1.5-2 sec. to +21C so the ECT sensor is working as expected. I think I will explore trying to fit a pressure gauge into the fuel delivery system where the metal fuel delivery tube changes to rubber hose at a fitting on its way to the fuel rail. Is there anyone who has tried this on the 2nd gen 2.7L tacomas ?

 

A decent fuel pressure set should have the correct fittings for the connection you're referring to.

 

Thanks, b_r_o... I will shop around and look for some on-line help/videos for my taco 2gen 2.7L setup.

 

I plugged an AutoLink AL419 into the DTC port and read the following values...Do any of them look like they could be indicating a poor cold start in -10 C. degree weather ?
2010 Tacoma 2.7L Scanner read-outs
DTC_CNT - 0
FUELSYS1 - CL
LOAD_PCT - 32.0-32.9@650rpm
- 28.2-28.6@2000rpm
ECT - 86C.
SHRTFT1 -1.6%
LONGFT1 -0.8%
RPM - 650
VSS - 0
SPARKADV - 7.6-9.0 (cyl 1)@650rpm
- 20+ (cyl 1)@2000rpm
IAT - 17C.
MAF - 2.7@650rpm
- 7.5@2000rpm
TP - 16.9%
O2B1S1 - 3.28@650rpm
- 3.26@2000rpm
O2B1S2 - .525@650rpm
- .445@2000rpm
EVAP - 25.95@650rpm
- 63@2000rpm
EQ_RAT11 - .999
CATTEMP11 - 408
CATTEMP12 - 350
TAC_PCT - 16.9@650rpm
- 18.8@2000rpm
EVAP_VPA - 99.7

 

I dont see anything obvious in that data.

Hows the battery? Does it sound like its cranking a little slow?

 

Thanks for looking over the data, b_r_o... Battery is 12.67v while engine not running, 13.62v at idle and cranks really well, even at -18C. ...
I have an appointment tomorrow for a diagnostic check at my garage... I told them the story in my original post and they said the would take about 1 hr. and let me know the results ... 1 hr. labour $100.

 

Update: I read a post about a v-6 owner having similar issue with cyl 6 and respondent suggested it might be coolant leaking into cyl. through bad/old head-gasket, so I thought I would try releasing rad pressure by leaving rad cap at the safety-click position. I left the truck overnight and with outside temp -12C. at 7am, it started right up, no codes...If I continue this practise, does anyone know of any long/short-term harm that can result ? Is there another issue that would interact with rad pressure(but no coolant-cyl. leak) to cause the codes P0300,301,302 to be recurringly set and poor/no cold-start ? There was no white smoke from exhaust that would usually indicate coolant is being burned during combustion but I have noticed coolant level down to where once lately having no heat or gurgling from heater core... Perhaps the leak into cyl. 1 and 2 is so small so far that noticeable white smoke is not there but sufficient enough to cause poor cold-start after overnight layovers while rad pressure squeezes enough coolant into cylinders to dampen plug-firing...?! Any help would be appreciated. Thinking of doing a rad pressure leakdown test and using that blocktester kit to see if exhaust gases are in rad system...

 

Update 2: Got a few(4) pH strips and dipped them in base antifreeze from purchased 50/50 mix, my wife's 2017 hatchback, some of the collected taco's exhaust vapour drippings(pretty clear like water) and my taco's overflow reservoir (coolant level directly from rad was not high enough to access). referring to a chart provided with pH strips the base 50/50 a/f mix colour indicated approx. 7.2, wife's car's a/f 7.8, my taco's reservoir a/f 7.2 and taco's exhaust at 6.8. Monday I will drive 40km's to try the Blocktester test and a buddy has access to a rad pressure leakdown tester. I will then update these results.

 

Update 3: Did the Blocktester test for exhaust gas in coolant and the result was the fluid turned a lighter blue than the bottled fluid. Back at home, I retested by using bubbles from the overflow tube to the overflow reservoir and the fluid changed to a light blue-ish green. So maybe some exhaust gas in coolant passages. Is the existance of some gas(air) bubbles in the overflow/recovery tube(varies from 20-40 per minute) an indicator of a leak in the system or is this an expected occurance ? I also did a pH test of the coolant and the test strips for the coolant before pouring from store-bought jug and coolant from my rad tested virtually the same colour. I tried to do a pressure leakdown test on the rad but buddies tester was acting up(I had to hold the pump handle down to keep/maintain measuring pressure. If I let go of the pump handle, it would rie back up to top of stroke and pressure would drop at the same time). Any help or suggestions would be appreciated...

 

Update 4: Found out that design of rad neck/overflow hose outlet was such that only if rad cap pressure washer was raised from it's seat in the neck would add'l coolant/gas be expelled into overflow tube and on to the reservoir. I cut a 1/4" wide gap in a 1/16" thick rubber washer about the same size as the rad cap pressure washer. This allowed me to use the overflow hose coupled with 5/16" fuel hose fitted with a clamped bicycle tube stem at the other end. This allowed me to use a 12V air pump with digital pressure readout to pump up the cooling system to 14 psi and watch for leakdown. For 10 min., with engine warm and running the leakdown was 2.5 psi. Then I shut the engine off for 5 min. and lost an added 1.5 psi. Does anyone think this is a reasonable leakdown to suspect that a small leak has developed which is allowing coolant to leak into #1 and #2 cylinders while cooling system is pressured and engine is off? Then the next start attempt is delayed and engine sputters and DTC codes 300, 301 & 302 are set ? After 5-10 sec.'s, the engine smoothes out to normal expected idle for engine temp. conditions.