hillsteepler

First post here, been lurking for quite a while (especially during my headgasket job...). Anyway I have a 95 4runner 3vze manual tranny. It's been having a hot starting problem, starts fine cold and runs good for a while but it seems like it loses power after being driven for a while and won't start after sitting for less than 30 min. or so when warm.
Tried replacing the fuel filter, new TPS adjusted to spec, pulled a wire and it does have spark when not starting.
Yesterday it was refusing to start again so I decided to disconnect the coolant temp sensor and it started up after few cranks. Went to parts store and bought a new one, installed it today took it for a drive, came home, and it wouldn't start again. Unplugged the ECT and it started so I shut it off plugged the ECT back in and it started after that too...

Did I get a bad sensor from the store? Is disconnecting it resetting something else? Any thoughts?

hillsteepler

Anyone? Also I should mention that the engine turns over, acts a lot like it's vapor locked but still no check engine light or codes...

Gamefreakgc

Try checking the sensor with a ohm meter (or multimeter, $10 at Harbor Freight) using this diagram:

http://personal.utulsa.edu/~nathan-b...98engineco.pdf

If it's out of spec, it's bad or they sold you the wrong one. If that's the case, try another brand.

If it checks out ok, it may be your Cold Start Injector Switch (right next to your ECT sensor). It does not throw a CEL light when it's broken (neither does the ECT). The CSIS tells the Cold Start injector if the engine is hot or cold and whether to inject extra fuel into the engine when you crank it over. My guess is that the Cold Start Injector Switch is sending a COLD signal when in fact, your engine is HOT. See below for more info:

http://personal.utulsa.edu/~nathan-b...ne/97colds.pdf

If you do decide to put a new one in, go to a junkyard and get one. Bring a ohmeter and test it before you buy it (although the place I got to has a 30 day warranty). They cost $200 from the dealer, I got mine for $7.50 and works great.

hillsteepler

Thanks for the input... The new ECT checked out ok, I unplugged the cold start injector switch and got no resistance when cold, so I left it unplugged and drove the car a while to warm up the engine and still got no resistance when hot so I'll have to start looking for a new one...
Oddly enough the car still wouldn't restart after warming up, even with the switch unplugged, could the cold start injector still be functioning even with the switch disconnected? It looked like the CSI itself was ok a week or two ago when I checked it out.

Gamefreakgc

I've heard from others that the injector will still work without the switch, I think the ECT sensor also sends hot/cold data to the ECU or something like that. Even though it doesn't sound like that's the real issue, you'll notice an improvement in power when the engine is warm when those two are replaced. They were broken for two years in my truck and didn't know (neither throw a CEL), it was just sluggish when warm.

I was just on the phone with my Dad the other day and he had a similar issue with his GMC. Does the engine turn over when you try and start it? If not, you might have a flat spot in your starter. Try tapping the starter when someone is turning the key over. If that gets it running, your starter is going bad.

If the engine does turn over, I've exhausted my knowledge of starting issues. I had my distributor go out once, but that one is obvious. The engine will turn over but will never start. $400 new (ouch). You could try a new cap and rotor though, the rotor might be going bad. That fix is cheap (normally done when you change spark plug wires), only about $20.

hillsteepler

I'll have to post an update once I track down a cold start injector switch... It cranks over fine and has spark so I don't think it's something with the distributor, replaced the cap and rotor pretty recently too... I suppose something with the cold start system would make sense.

pwd

Any update on this? I have similar symptoms on my '92 4Runner 3vze. It is difficult to start once its warmed up.

hillsteepler

No updates yet, none of the junkyards around here were open after I got done working so I haven't been able to try another CSI time switch... I'll have probably try again monday.

hillsteepler

Got another CSI time switch at a junkyard today and put it in, not much difference, feels like there's almost a dead spot in the throttle too. I need to borrow another multimeter and double check some readings, I'm beginning to question the accuracy of mine...

shullkevin

https://www.yotatech.com/forums/f2/1...issues-251560/

hillsteepler

Thanks for the link, the car seemed better today, only "vapor locked" or whatever it is once. So far every time I've unplugged the ECT when not starting it starts up again right afterward, despite replacing the ECT and CSI time switch. I was going to check the fuel pressure but harbor freight's computers were down and they couldn't run credit cards. Have to try again this weekend.

hillsteepler

And the plot thickens...
So I just ignored/dealt with the problem for the last few months and about a month ago when I had some time and money decided to replace the fuel pump as this seemed like the most probable culprit. No change really, still intermittent hot start and power loss issues.
About a week ago I parked it at night and it wouldn't start at all the next morning, I let it sit for a while checked to make sure the distributor was lining up with TDC on the crank and it had spark, everything seemed ok but still no start.
SO... today I try to spray some starting fluid in the intake to verify that it's a fuel delivery issue. it starts up and just keeps running... I turn it off and repeat and after two startups with the fluid it started and ran fine a third time without and kept going for five or so minutes until I shut it off...
I have no clue what to look at now, I just got a new multimeter and will probably begin rechecking electrical sensors related to EFI...

scope103

What is your ignition timing set to ? (Don't guess; a timing light is $20)

hillsteepler

I haven't checked it recently but it was set to factory spec when I did the timing belt a few months ago.

scope103

Did you have the hot-start problem when you did the timing belt? Since you don't know (off-hand) what "factory spec" is, are you sure it was set correctly? (and by correctly, I include with the jumper in the right place)

If your problem is "usually starts okay, except when the engine is hot," you might have vapor lock. Have you checked the FPU VSV? http://personal.utulsa.edu/~nathan-b...ne/41fuelp.pdf

hillsteepler

The problem was present before I replaced the timing belt, the timing was correct (10 degrees BTDC with jumper installed, and rechecked one or twice since then) I'll have to check the FPU VSV after work, although if it didn't start after sitting for a week could it still be vapor lock?

hillsteepler

Alright, so while investigating all of the above I found an exhaust leak before the oxygen sensor and a vacuum leak right by the throttle body. Fixed both and haven't had the problem again. (yet...) Not totally sure but it appears fixed. Thanks for the input everyone.

hillsteepler

Update: (Yeah it's been a while)
So fixing the above mentioned problems seemed to help but not totally fix the hot-start and low power issues, which returned shortly after. I ran out of time and money to work on it and basically just lived with the problems while I went back to school this past year.

So about a month ago I finally had some time/money and decided to start by replacing the oxygen sensor since it had never been done that I knew of. The truck ran terrible afterward and stalled so much it was basically un-driveable. I checked out everything I could think of (and double checked things I had previously fixed) and eventually ran across another thread here that mentioned a loose ground wire on the passenger side cylinder head. Sure enough, mine was loose. Tightened it back up and it immediately started and has been running and driving great since. Even has more power like it used to.

It's been about a month and everything's been fine with the exception of the engine throwing codes 25 and 26 which I believe to be unrelated...

joel1952

ANY UPDATE???

Loose ground wire on the cylinder head fixed the poor running and hard starting?

You said it was good for a month, but now it's been 4 months. Just wondering, as I have a similar problem. Those intermittent gremlins are tricky....

hillsteepler

Hey Joel, sorry, don't know how I missed your question for 3+ years. Or if you even care any more. But the ground wire did seem to be the long-term issue, hasn't happened again since.