grindy

90 4runner with 176000 miles. Everything was fine but then started having problems with hot starts. It starts fine when cold and idles at 1k. Smooth.
- when hot it will die on start-up unless I give it gas.
- may belch a little black smoke.
- really chugs along and runs rough until I hold rpms at 2k. After 5 seconds I can release the gas and it will idle at 1k. Smell of gas. Inside of exhaust pipe is black. It is almost like it is flooded.
- changed distributor cap and rotor - no change
- mechanic said it was a bad distributor. Replaced - no change.
- replaced spark plugs (evidence of burned oil on one). No change. Spark plugs were in pretty bad shape (burned electrode) which could have been caused by faulty distributor. Gaps were from .037 - .040 instead of .031 spec.
- seems to be using more gas than normal.
- could not identify any vacuum leaks.
- compression a little low ( expected) but no too bad.

I have some ideas but I don't to pollute the feedback. Any ideas?
Any ideas?

grindy

Been thinking about this (actually wake up thinking about it). The mechanic said it was an ignition issue. I disagree. I think it is a fuel issue. After researching the web I think a possible source is the Cold Start Injector leaking or the Cold Start Injector Timer Switch (stuck on). This would cause the engine to flood and the rough start when hot and ease of starting when cold. One post said a 25 year Toyota mechanic told him they replace 20 of the switches for every one injector. I can't get to the mechanic for a couple of days but as a first shot I will run some fuel injector cleaner through the system. That may help the CSI if it needs cleaning.

kiyobrown

We have different years, but next time it's hot, turn the key with your foot OFF the clutch. (assuming you are 5 speed of course). Do it for 3-4 seconds, then try to start. A service bulletin came out in 89 for the CSI time switch and well as another sensor. Both caused hard starts when warm. What I described above bypassed the symptoms so I didn't buy the $200 of sensors to fix the problem. It starts everytime within 2 cranks now, so I run it as is.

Like I said. Service bulletin in 89, yours is a 90. Probably not your problem, but worth a shot. If it helps you start it easier, it's worth trying.

Keep us posted.

SoCal4Running

Simply unplugging the CS wire will let you know if its stuck on. If its leaking unplugging it will not stop this.

Hows the vacuum hose that goes to the Fuel Pressure Regulator and the vacuum switch for it also?

BTW ditch the mechanic. I sick of so called mechanics that throw parts at problems till they get lucky and change the bad part because they have ZERO diagnostic skills.

grindy

I'll give the foot off approach. Good for getting it started but that is not really an issue. I start it up and keep rpms at about 2k for 5 seconds to burn off excessive fuel. Interesting the same thing happens with my lawn mower when I am cleaning the carburetor. I spray the carb with cleaner when it is running. RPMs decline (like the truck) it runs rough until the fuel is burned off (like the truck) and them it runs fine (like the truck).

I agree with unplugging the CSI timer switch will identify the source of the problem. AND I agree with the issue about the mechanic and am not looking forward to the confrontation an Tuesday. He said it was an ignition problem. Replaced the distributor $400 (labor $118 +$263 parts). B.S. If it smells like it is flooded. If it runs like it is flooded. It is flooded. I think the problem is they have turn over customers to make a profit. Easiest way to do that is to replace willy-nilly and hope for the best. Unfortunately for him I was teaching high school auto mech 35 years ago (but cars have changed dramatically since then).

SoCal4Running

I cant believe its not throwing a CEL!
Or is it?

Hows the air filter look?

I would buy a few feet of vacuum hose and change them ALL. Do one at a time and none will be mis connected.

Service/Clean the EGR too.

grindy

EGR is a possibility but I still look the highest probability being the CSI timer switch, then the CSI. Air filter is new. Vacuum lines have been checked twice. What do you mean by CEL?

BTW, I failed to mention the problem did not come on gradually. One day - no problem with hot starts. They next day - a problem. Leads me to believe it was a failure of a component (again the CSI timer switch).

SoCal4Running

CEL= Check Engine Light. Orange light on instrument panel

The CSI switch is easily check with a multimeter and a bowl of boiling hot water. Basically it gives different Ohm reading as it warm up from room temperature to around 200 degrees. At a certain Ohm reading the computer then turns off the CSI.

I would still change the vacuum hoses. For less than $10.00 and 20 minutes with a pair of wire cutters its time and money well spent.
I change mine every 3 years regardless of their condition.

grindy

Thanks. The CEL does not turn on. I will unplug the CSI timer switch and see if that cures the problem.

Mr.Utah

Im having a similar problem. I have also been thinking about this, could it possibly be the line to or from the charcoal canister?

grindy

Tried the "turn key without depressing clutch for 4 seconds" approach. No change. Sticking with a faulty CSI timer switch as first option, leaking CSI the second. Starts great when cold. Floods when hot.

grindy

Latest and Greatest. Replaced the spark plugs and put a can of injector cleaner into it two days with no change. Yesterday no change. I am convinced it is either the CSI temp switch or a leaking CSI. Two days ago it was still dying or trying to die when hot started. Today I drive down to the shop and drag the mechanic out. First I ask him to show me the "loose" distributor. He said it did have some laterial play when it was installed and showed me where some wear had occurred. He asked about the spark plugs. I told him two were burned hot and the other two had a indication of unburned fuel residue. He said the two burned hot were because of the distributor. I told him I thought the problem was with either the CSI temp. switch or a leaking CSI. I got in to start it for a "before" condition before we unplug the switch from the CSI. It starts right up and idles at 950. I shut it down and start-up again. Ditto. Great. First time in two weeks it has not died. I discuss it with the mechanic and tell him maybe the fuel injector cleaner I put in there 2 days ago is doing its magic. He tells me he put a can in three days ago before I picked it up (didn't tell me). It is back to running/starting great. What a relief. I went to look at Prerunners over the weekend thinking I was going to sell it. Don't have to be looking at a car payment for while. BTW, he said the CSI will also fire a burst after a hot soak. What is a hot soak?

grindy

Disconnected the CSI timer switch. No change in symptoms. Still floods at hot soak. I need to keep rpms at 2k until the excess fuel is burned off - about 5 seconds. Then it runs fine. May just punt and buy a new truck but there isn't much out there.

grindy

Finally problem solved. Could not isolate the problem myself and the first mechanic I took to said it was a bad distributor. No change in symptoms. Disconnected the CSI timer switch with no change in symptoms. Thought maybe it was the bad cat or a plugged muffler. Replaced the muffler (it had a broken baffle) and checked the cat. No change. Finally I went back to the dealer thinking I may have to buy a Prerunner. They must be under new management because they were helpful and knocked 15 off my bill. Had them run a diagnostic. It was the temp. coolant sensor. It was faulty causing the engine to think it was cold when it was hot thus flooding the engine. Problem solved and it only took a few hours of my time and a grand.

Mr.Utah

Did you go with a Toyota sensor?

grindy

Dealer installed. I assume so.