Hi yotatekkers. I've been having this problem intermittently since buying the car. For a while sometimes it would start up just fine, but recently it has been every time.

Basically what happens is I crank it and it stops one out of 5 times. The rest of the times it barely goes above 700rpm and then down to 400rpm unless I give it some gas the instant after starting. I stopped giving it gas as I started it, because occasionally it would backfire and I don't like that sound one bit!

As well I am getting an 02 sensor CEL holding the throttle steady at any position on the highway. As soon as I let of the gas for an instant and re-throttle it disappears in a few seconds. I have an autozone O2 sensor so that could be the problem I suppose...

I seafoamed everything today and when it started clouding, I noticed that my headers have a leak coming out near the flange before the cat. I feel like this could be causing the O2 CEL, but could it also be part of the startup issue? Doubtful I would assume.

I've checked the Fuel pump relay and Open Circuit Relay before, they both checked out with flying colors. I also suspect it could be leaky injectors or the fuel pump. I have tried jumpering the fuel pump ON in the diagnostic box with no success, so I don't think it's the fuel pump.

Any ideas or shared experiences are greatly appreciated. One the motor is revved it runs "like a top".

 

Noticed a small oil leak pooling up on top of the timing cover, which lead my eye down to the bolts on the timing cover. There were little air bubbles passing from underneath the bolt heads. I threw a 12mm wrench on the bigger one and it was barely tight at all. Stopped the bubbles. I just adjusted valves yesterday so I think that's probably where the oil leak is coming from (didn't change the valve cover gasket at all).

For solidarity checked the rest of the timing cover bolts I could get to, they were all partially not tight. I tightened them a little bit (not overtight) and here's to hoping that stops the leak from the bolts.

Obviously made no difference to the issue at hand, but why on earth would those bolts be not tightened down all the way? Sketchy.

EDIT: here is a pic

 

Hi. It could be...the experience around here is that non-Denso O2 sensors are generally not liked by our Toyota rigs.

Any cracked or loose vacuum hoses?

 

Yeah I think I'll order that Denso 234-1056 asap. $23 from Amazon? That is cheap.

I took the propane torch and flew some propane around all of the vacuum hoses, no change to engine rpms. Most of the hoses are new, except for a lot of the molded ones.

Just picked someone up from the airport, then had dinner and the car sat for about an hour. Starting it up, it nearly stalled out. RPMs down to 350-400 and running rough. Gave it a couple of slow revvs followed by 3 or so faster ones and it was good.

So perplexed. Seems like it's getting worse. Could the seafoam have dislodged something and now something is blocked? I don't get it at all.

Thanks for your time, I am going to pull the throttle body and check the IAC tomorrow- that is my next suspicion unless y'all have any ideas

 

Hmmm. It's kind of to coincedental that the O2 sensor isn't working properly AND you have this idling issue.. I'd assume they are connected to start with. for $23, put the denso on and see if that changes anything.. I'm pretty sure it doesn't as the idling is during open loop operation (if I remember correctly from my own trouble days). I believe the rpm that triggers closed loop is 2500, so that may be why you are getting the CEL on the hwy.

I had a rough idle not to long ago do to my old clamp on the air intake hose being warn and loose, did you check those? When was the last time your injectors were cleaned/serviced?

 

Thanks Gevo

Yeah I just ordered the denso, it'll be here tomorrow.

I usually drive pretty slow on the highway these days, around 2.2krpm. But this was happening even when I was driving it faster, slower, going up a hill or whatever. It happens when I hold the throttle steady for a while...

Hmmm. Maybe I should have another go at my TPS while I'm looking at the IACV. My adjustment method wasnt exactly mathematical- I used 4crawlers suggestion of credit cards and paper to add up to the tolerances (measured with digital caliper). I still hadn't bought feeler gaugest at that point. Perhaps my TPS is bad, too.

Thinking I may go to a boneyard and pick up a TPS+IACV just for craps

 

Also looking into doing away with the cruddy aux air system and swapping in the intake/TB for a later model with integrated idle up if I can find a yard with the parts. Being in LA I don't foresee this as being much of a problem to locate

 

IIRC operation is closed loop except at wide open throttle. It is also open loop until coolant temp is reached, so if this happens hot or cold it is unrelated to fuel/air ratio. At least in terms of what the ECU is handling.

In my experience TPS has generally been "good enough" if idle RPM drops when you jumper the test connector. At least then you know your ECU is reading the idle position. If you get the idle position and the truck ISN'T sluggish off the line (sluggish would mean it's not reading "off-idle" quickly enough) I'd leave the TPS alone.

My feeling is you should clean out that throttle body. Is your rpm at idle rock solid after you drive the thing a bit? Once your truck revved and at normal rpm can you close the throttle by hand and get the rpm to drop?

 

Another thing to check is your afm. That flap can get stuck closed when the truck isn't running, then when you rev it up you free it and the truck runs properly.

 

Good idea Andy! I already spit-shined the TB though, which is what lead to TPS adjustment in the first place.

Yeah once the car is driven for some time, idle is rock solid. Sometimes even just a few revs will do it. It is weird to me that I had to adjust the idle up after seafoaming yesterday. My mind keeps going back to that for some reason because the problem got way worse afterwards. I put half a can of spray seafoam in the brake booster line and a couple of ounces in the near empty gas tank just before I refueled.

The plenum is still crazy gunk, and I have no idea when the injectors were last service, for all I know they might have never been serviced... and the odometer reads 491k.

It was suggested some time ago (when I tried to tackle this the first time here) that it's possibly a leaky injector causing a rich condition when the car sits. Seemed like a viable cause until recently the problem has gotten worse and now the engine idle stays low for longer. Basically just have to rev it more to get it toasty before it starts running .

Another interesting note. Before seafoam, my fuel pressure gauge was reading 40psi continuous (no change applying throttle). Now it is reading 33psi idle and 38psi with throttle.

Thank you for the help guys

 

Just saw post about the AFM. Yeah I cleaned that out not long ago too, took it apart and everything. Seemed to be working a-okay. Maybe I'll double check it. That is a great idea, too: afm flap sticking shut and being more flexible once the surrounding engine bay temps warm it up.

 

So last night I adjusted the idle up because like I said after seafoam my idle seemed to drop. This morning started up just fine arrrgh

Pinched the IACV hose shut and idle dropped, then once warm pinched it again and no drop. So no longer think it's IACV.

Once warm engine off'd and restarted. Low idle present, slowly climbing back up. Same crap.

Noticed something too. If I press the brakes idling it is fine. If I press repeatedly the car nearly dies, rpms severely drop.

 

Started up great 7x in a row after taking for a test drive.

Then letting it sit for 30mins and trying again the problem is back. Rough start and low idle. Exhaust smells like gas. Has to be running rich.

Now I'm thinking it's GOTTA be a leaky injector/CSI. Here's the hypothesis...

After pressurization of the fuel line and then off sitting a while, the fuel leaks out into the manifold making for a rich condition.

After the car sits for a LONG time, the leaked fuel dissipates and evaporates, allowing decent startup. Concurrent startups shortly after are good (no excess fuel).

Waiting 30-60min allows the leaky injector to once again cause the rich condition, but it has not had enough time to evaporate so a rough start and low idle is experienced until the fuel is heated up, evapped, and burned away by revving/engine under load.

What do you think? Plausible?

 

Yum.

 

I think I wrote about this in a previous thread. I had a truck where the cold start switch was effed up and would cause the CSI to fire every time. Similar really low idle thing when truck sat for 30 mins or so. My theory is that right after turning off the truck, the engine is still hot enough that if I restarted it immediately it could deal with the excess gas. After thirty mins or so it's still warm enough to not need the CSI, but could not easily start due to rich condition. With the CSI unplugged I good easy starts up to an hour after turning the truck off. After that the problem was reversed - tough starting while cold. Actually, much tougher - I plugged the CSI back in until I got a new switch.

Anyway though your idea is plausible too. What happens if you unplug the CSI?

 

Viola. Now about that intake........



Thanks andy- I think you must've been the one a few months ago that gave me this idea. I remember the thread. I'm going to do some CSI tests now. Going to see if I can just cover the hole with gorilla tape and start it up completely disconnected first, then reinstall with lead disconnected

 

Just an idea, and maybe a bad one, but what if you leave it connected to the fuel line but keep it out of the intake plenum. Then jumper the fuel pump so the system is pressurized, and look for fuel dripping from the injector?

 

Off topic, but I'm about to go start my truck in 2 degree weather. That picture at the top is making me dislike Colorado.

 

Andy- essentially that is what I tried. Gorillataped the hole closed and left the CSI on. Turned the car on, it ran rough... Must not have taped the hole well enough

Anyway I did check the CSI for leaks and all was well with that.

Reinstalled the CSI and back to the drawing board

 

By "left it on" I meant left it on dangling next to the taped up intake. Thought I should clarify.

My next step is overhauling the whole intake, hot bath status. The amount of sludge in there is heinous. It's like the before pic of the CSI I posted but even thicker. A leaky injector definitely seems plausible to me! I guess I can probably expect a performance increase from doing that... neat!

Oh and Andy- yeah I have always wanted to live here because of the weather... ever since I can remember. I grew up in Ohio. Not quite as extreme as the CO weather but still had California dreamin' going on big time.