Hesitation when cold

TR4 3rd Gen has 346k miles and has had no major issues.

Just recently when starting her when cold, the idle is a bit rough. After warm up she runs better but not smooth. After 10-15 warmup the rough idle is gone however returns on acceleration.

I do have the CEL on, which has been on for a few years. Has something to do with the EVAP system.

Appreciate any experience and advice.

 

Could be a number of things, off the top of my head

Spark plugs, wires
Clean the MAF
IAC
Clean the throttle body
vacuum line leak
Replace fuel filter

When was the last time you messed with any of the above? When was the last time you pulled codes, you make be getting a new code related to a misfire now

 

Post the current codes.

 

Current code pulled this morning is the P0300.....The EVAP codes have been there for years...P0400 & P0446 EVAP System Vent Control Circuit/EVAP Sys

 

Thx Roboturner, I will start with the easy stuff...Code pulled this morning was a P0300...Thx

 

P0300 is a random misfire. Which makes it seem like your problem is general in nature.

When were your plugs and plug wires changed? I would look at that first.

Next would be fuel. So fuel filter replacement and fuel pressure test which may point you to a bad fuel pump or bad fuel regulator.

Other than that, not sure what to look at.

I agree, the evap stuff shouldn't be related. I, personally would fix it so I would know that the next time the CEL lit up, it would need to be looked at.

 

On a whim, I did a search: Both were head gasket issues and sound similar to your symptoms.

I for one would not do an additive as they tend to clog other stuff up. I would pull plugs and look for coolant fouling the tips.

Edit: use a combustion gas detector for the coolant. That should tell you 100% if you have a HG leak.

 

Definitely agree on starting with new Spark plugs and wires

 

Its been about 5 years for the plug wires and plugs were changed about 2 years ago. Fuel filter has been about 7 years ago. so, I will start there. Roger that on the fuel pump, I have never tested it, given she has high mileage (345K) it would not surprise me if it were bad.

EVAP system is another ball game..I will have to look at that closer...Thank you for your help.

 

I just watched a video on the head gasket issues...with 345K miles I would not be surprised. I had no white smoke at the TP and I do have low coolant but I have not checked it in a while, so not sure if it leaking into a cylinder or the head. I will pull the plugs first and check there first. Thanks for your help..

 

After checking my records ( I have CRS) I had the plugs changed last year. I went ahead and inspected them anyway. All look good.

 

My coolant was not that low...I added about 2 its and marked its level, I will keep an I on it, but not convinced its the head casket. I had checked all the vacuum hoses and removed the throttle body intake hose and air box to clean the throttle body.
the connection into the throttle body was cracked (dry rot). Ordered a new one and replaced it yesterday. Then I cleaned the MAF. and checked the all the wires (I live in the desert and desert rats have already chewed up my spark plug wires) and I noticed I had a loose ground cable going to the battery. The battery hold down bracket is constantly getting corroded. I think I will replace or repair the negative battery cable. After deleted all the codes (P0300, P0440,P0446) and driving for 30 miles, no codes have come back. Now I know the P0440 & P0446 will come back for the EVAP System. Time will tell on the P0300. Currently after these fixes she started up smooth and throttling at higher speeds was smooth (60-80).

Just curious, is the coil on the # 4 cyl a common issue. They were replaced 2 years ago. (Denso) Then the plugs last year.

I will keep an eye on the coolant ( I replaced the radiator cap last year). If it starts to get low, it would be time for more serious action i.e. compression test, leak down test etc.

Appreciate all your help guys.

 

Thx Roboturner...Checked the wires and plugs (the plugs were changed last year). Cleaned the MAF and throttle body. When I took the intake hose off the throttle body, it was really cracked bad (dry rot), Orderd a new one and replaced it yesterday. Found that my battery ground cable was loose. Tightened that sucker again. Yup, This has happened before, along with my hold down bracket constantly corroding..It needs to be replaced or repaired ( I don't like splicing heavy gage wire)

Bottom line: She started without the rough idle. I did a test drive and it was fine up to 60 mph....I felt a little hesitation and just kept driving and accelerating up to 70 mph. Pushed her up to 80 mph....and she did good. Then back to some casual driving and she was smooth. I expect the EVAP System codes to come back, but hoping the P0300 random misfire does not. I will keep an eye on it. Thx for your input..appreciated.

 

I don't know why. Bigger cable, up to a point, the easier they are to splice. Takes a little more "oomph!", but heck, it's a good work-out for your arms. If it were me, I'd at the least get new battery terminals. If necessary, get new ring terminals for the cables, clamp them on, and then attach them to the new battery terminals. That'll keep the terminals from coming loose. Make sure the battery posts are good n clean. Nice and shiney. Don't over-tighten the battery terminals, either.
Check BOTH ends of all the various ground cables. They can look great on one end, and the other is corroded to all heck. Both ends matter.
Clean the hold-down real well with a thick paste of baking soda. That'll get rid of the battery acid, and slow the corrosion. Once it's good and clean, buff it with a wire brush, until the metal is nice and shiney, then paint it. A good base layer of a quality metal primer, let that dry totally, then a couple very light layers of the paint. Much better several light paint layers than a thick, heavy layer. That will really slow the corrosion. Batteries tend to out-gas acid mist, especially during a hard charge, like right after a start, and so forth. That's what causes the corrosion. If you can keep it from getting a foothold, you can stop it's damage. At least up to a point.
The acid mist tends to get under, or inside, the cable's insulation, too. It can destroy the metal with no obvious visible indication. A good piece of heat shrink, especially the meltwall type, covering the connection to the ring terminal will help prevent that.

Remember that the Toyota ECU's need a two-trip logic before they set a code. Try to take two, separate, similar, drives to see what codes will be set. That means a drive, then a stop and shut down totally, letting it cool down and settle out then fire it up again and do your best to drive the second trip the same as the first one. Same distances, same acceleration rates, same braking distance, etc, etc. You may not be able to get everything identical, but try to get it as close as possible.

Best of luck to you!
Pat☺

 

And just after I gave all my crimping tools away for heavy gauge wire. Yup, been there before. Thank you for the information and I agree - having good ground connections is very important on both ends.
I have another year on my battery- then I may just go with an AGM sealed battery. I have done the prep and paint on the holder 4 x and getting tired of the hassle.
I appreciate the help. Take care. Pat

 

I have never heard of a Toyota coil actually going bad. I suppose it happens. People swap them out and it's never the issue.

 

I changed the MAF sensor.
Cleaned the throttle body.
Inspected all vacuum lines.
Inspected all spark plugs.
Swapped could 1&3

Hard to start, rough idle, new codes P0300, P0303, P0306
Any suggestions?

 

You may be due for a fuel injector.

 

Ok, you have misfires in cyl 3 and 6 which are controlled by the same coil pack.



Check the wiring to the middle coil pack. I recommend only Toyota coil packs. Junkyard ones are probably better than the trash Chinese ones you can get cheap.

You can also move that middle coil pack to another location to see if the misfire moves. If it does it's the coil pack. If it stays on 3 and 6 it's something else. Maybe the ECU or wiring.

 

thank you- my bad , went with some dang package on Amazon. Plugs were wrong also. I will try that with Denso coil packs. Thx

 

Yup. I feel I have to beat the drum and sound like a broken record.

You MUST buy sensors and electronics from TOYOTA or their suppliers. NO EXCEPTIONS.

Do not buy from Amazon or Ebay. Those are fakes. Get from a known good seller.

TOYOTAS are picky on the plugs. I advise to only get what is listed by the dealer.