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Discussion Starter #1
I have a 1994 toyota pickup. Runs great, except after you drive it for a while, get out and turn it off for a short time (5-10 minutes), then it has trouble starting. The starter turns and the engine will go but sputter and die right away. If I give it gas it seems to work....Fuel pump? Valve seals?
It's got the 4cyl, 4x4, 22RE engine. No other symptoms, no check engine light, etc. I bought it used last week and replaced the oil pan gasket because of a leak, changed the cap, rotor, pcv valve, new plugs, new fuel filter, new wire set, and oil pressure sending unit. Runs great, and you would never know there was an issue other than if you drive it for a while, shut it down, and within 10 minutes try and start her she'll turn, then sputter and die. I usually have to crank her over a few times and once she catches, rev the engine to keep her running. Once she goes, no problems again. Very weird. A friend who saw me try and it start it once after it did this said a decent amount of exhaust blew out the tail pipe when it caught. But I did pump the gas to keep her going for the first few seconds. She turns over and goes but revs down and dies. Leads me to think it's flooded. Maybe a check valve.
The specs: 220, 000 miles, factory rebuilt engine put in 5 yrs ago when there was 170 k on it. Runs great, no problems, just what I mentioned.
Some thoughts: Engine coolant temp sensor (set too rich for a warm start), Idle air control valve or throttle body need cleaning, Air/fuel ration is off, O2 sensor? Cold start injector?
 

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Your list of things to check is good; but I would add:

When you say "give it gas" - on a fuel injected vehicle, what you are doing is opening the throttle which is actually giving it air, not gas. It's the computer that gives it gas. So, your friend's observation that there's a lot of smoke when it finally starts could mean the computer has been giving it too much gas, not too little. By opening the throttle, you're giving it more air which may help balance the mixture.

A few things could cause too much gas when starting a warm motor:

1. The cold start injector is operating (when it shouldn't)

2. Fuel pressure is too high

3. The TPS or VAFM is mistakenly informing the computer that the throttle is open too much/too much air is going into the motor.

For the cold start injector, test the cold start injector time switch - see instructions in the factory manual (google 1993 toyota pickup service manual if you don't have one)

For fuel pressure, you'll have to have the pressure tested - especially during the conditions when it has trouble. Print out the Fuel Pump section of the fsm and insist that the person who does the test run the test with the fuel pressure regulator vacuum hose attached AND unattached. There should be a difference at idle (the fuel pressure vsv is supposed to reduce fuel pressure at idle by applying vacuum to the pressure regulator - check that pressure at idle reduces to the specified level (33-37 psi) when the vacuum hose is attached.

TPS and VAF meter. Search forum for info on checking both. In addition to making sure all the terminals are in spec in all the sensor positions, you need to make sure the resistance changes smoothly as the throttle (tps) or vane (vafm) are slowly opened and closed, and that there are no spikes in resistance, and no dropouts.

Other things to check:

EGR - it's not supposed to open at idle - if it does, it will cause stumbling and rough running. To test, pull the vacuum hose on top of the egr valve and plug the hose - see if there's a difference in starting.

Clogged injectors - these cause all kinds of havoc with mixture as they get deposits on the end - easiest way to clean is using Red Line SI-1 Complete Fuel System Cleaner (only product left that still has a good amount of polyether amine (PEA), the most effective injector cleaning chemical). Add a bottle to 2/3 to 3/4 tank gas, and run down to 1/8 tank, then add another bottle and fill gas again to 3/4 tank and run again to 1/8 before refilling tank. Sometimes SI-1 won't do the trick. In that case, when you have fuel pressure tested, have the shop feed some of the concentrated injector cleaner right into the fuel rails. That is more effective. Sometimes injectors are so bad they must be removed and ultrasonically cleaned, but if your injectors were that bad you'd be having more trouble than you are.

O2 sensor is hard to check - the computer will give you a code 21 if the heater in the sensor is shot, and it will give you a 25 if sensor volts are below .45 volts for 90 seconds or more (lean condition) and a 26 if above .45 for 90 secs (rich). You can do the diagnostic on VF1 and E1 in the check connector (see factory manual) to make sure the sensor is switching at least 8 times in 10 seconds between 0 and 5 volts (normal operation). A sensor that is not switching between lean and rich almost once a second is considered to be a "lazy sensor" and needs to be replaced.

However - even if the sensor is properly switching back and forth, the computer has no way to know if the O2 reading reported by the sensor is correct: as the sensors get coated with carbon, they start to read leaner than the exhaust really is, causing the computer to add more fuel than is necessary, and making the motor run too rich.

The only way you can know if the O2 reading is correct is to attach an exhaust analyzer. For this reason, if the sensor has over 90k miles, you should just replace it. Denso is the best bet, if you can afford; if $$ is tight you can try an NGK (NTK). sparkplugs.com has good prices.
 

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Discussion Starter #4
I have someone looking at it now, but they've had it for 4 days and still haven't done much of anything to it.
I told them what I wanted them to check since I'm not the greatest mechanic but they are dragging their feet.
I'll pick it up tomorrow if they haven't looked at it by then and do some work on it myself.
I'll let you know what happens. Thanks for all the help...I hope it's an easy fix!
 

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Discussion Starter #5
So my mechanic had the truck for 4 days and could not really find the solution....or the problem. He said everything checks out, but the only thing that helped was to clean the mass air flow sensor. It's better, but it will still start and then die if the engine is warm....but not always. It's not that big of a deal to me at the moment, since it always starts back up, but for a $250 part, I'll live with it for a while. If it gets worse, I'll look into buying the part and seeing if that works.
Thanks for all the help. If anyone knows where to get the part for cheap, I'm all ears. Or send me one that works, and if it solves my problems I'll pay for it. If not, I'll send it back.....not too many vendors would go for that huh!
 

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Dude, don't you read? :hammer: . Sometimes I think all this typing is just a waste of time. You can CHECK the vafm that you have, so you KNOW whether you need a new one. You don't just buy one to see if it works. Search the forum for info. (And as mentioned test the tps, too.)

And if the VAFM IS bad, get a used one off craigslist or ebay or from a junkyard for well under $100. car-part.com is a good portal to a bunch of bone yards.

If your mechanic said he cleaned the mass air flow sensor he doesn't know what the hell he's doing - your truck doesn't HAVE a MAF sensor - which has a heated wire - it has a VAF meter - which uses a trap door. Cleaning a MAF often helps since a dirty wire causes it to read low; cleaning a VAFM is like polishing your pole - it may make you feel good, but it isn't going to accomplish anything much.

Anyway if he said "everything checks out" obviously he's incompetent, since the motor is not running right. If he were honest with himself and with you he would have said: "I couldn't find the problem". I'll bet he was able to write up a bill, though.

:rant:
 

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Discussion Starter #7
Walker, thanks for the info, but you could use a little more tact when typing responses.
The facts: I'm very new to toyota trucks, I am a biologist; not a mechanic, and my experience with mechanics is 90% related to outboard motors.
I'll gladly take your input, and I will do my best to incorporate your suggestions. I have a repair manual, so I'll go through and try and test the VAFM. Reading and understanding are two very different things. I can have you read about how to calculate channel roughness in a stream, but you won't understand it without some further instructions and a few mistakes allong the way.
Again, thanks for taking your time to try and help out, and typing is not a waste of time, but you can leave your ego at home and save some typing by skipping the superiority complex. Just because you know a lot of basic info, does not mean I do. I thought the guy was full of S### since I never saw anything about a MAFS in the repair manual, but assumed he meant the VAFM.
Actually, I was surprised that the mechanic charged me nothing. He admitted he did not find the problem, so I paid nothing.
I'll let you know what I find on my own using these tips. I'm not giving up.
By the way, your wrong: If you polished your pole a little more often, you'd lower your blood pressure....which must be pretty high to get bent out of shape over nothing.

Dude, don't you read? :hammer: . Sometimes I think all this typing is just a waste of time. You can CHECK the vafm that you have, so you KNOW whether you need a new one. You don't just buy one to see if it works. Search the forum for info. (And as mentioned test the tps, too.)

And if the VAFM IS bad, get a used one off craigslist or ebay or from a junkyard for well under $100. car-part.com is a good portal to a bunch of bone yards.

If your mechanic said he cleaned the mass air flow sensor he doesn't know what the hell he's doing - your truck doesn't HAVE a MAF sensor - which has a heated wire - it has a VAF meter - which uses a trap door. Cleaning a MAF often helps since a dirty wire causes it to read low; cleaning a VAFM is like polishing your pole - it may make you feel good, but it isn't going to accomplish anything much.

Anyway if he said "everything checks out" obviously he's incompetent, since the motor is not running right. If he were honest with himself and with you he would have said: "I couldn't find the problem". I'll bet he was able to write up a bill, though.

:rant:
 

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Girlfriend's truck does the same and it is a 1992 V6. Starts great when cold but once warm and off for 5 - 10 minutes it does the same. This vehicle started at -40C (-40.0F) and not plugged in. Her truck started but mine had to be boosted, almost started. I suspect that the cold start injector time switch is at fault. The switch is telling the computer that the motor is cold so inject extra fuel. Her truck takes about one second longer to start when under the same cold condition but tends to stall when warm.

Now that the weather has warmed up I will compare the two when I get home. Her truck has 25,000 miles on it with the head gasket replaced 10,000miles ago. New plugs, timing belt, valves adjusted, cap and rotor replaced, all work done by Toyota.

Could Luck and try all the things people have suggested.
 

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Languishing in Virginia
1994 XtraCab 4x4 P/U
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Your list of things to check is good; but I would add:

When you say "give it gas" - on a fuel injected vehicle, what you are doing is opening the throttle which is actually giving it air, not gas. It's the computer that gives it gas. So, your friend's observation that there's a lot of smoke when it finally starts could mean the computer has been giving it too much gas, not too little. By opening the throttle, you're giving it more air which may help balance the mixture.

A few things could cause too much gas when starting a warm motor:

1. The cold start injector is operating (when it shouldn't)

2. Fuel pressure is too high

3. The TPS or VAFM is mistakenly informing the computer that the throttle is open too much/too much air is going into the motor.

For the cold start injector, test the cold start injector time switch - see instructions in the factory manual (google 1993 toyota pickup service manual if you don't have one)

For fuel pressure, you'll have to have the pressure tested - especially during the conditions when it has trouble. Print out the Fuel Pump section of the fsm and insist that the person who does the test run the test with the fuel pressure regulator vacuum hose attached AND unattached. There should be a difference at idle (the fuel pressure vsv is supposed to reduce fuel pressure at idle by applying vacuum to the pressure regulator - check that pressure at idle reduces to the specified level (33-37 psi) when the vacuum hose is attached.

TPS and VAF meter. Search forum for info on checking both. In addition to making sure all the terminals are in spec in all the sensor positions, you need to make sure the resistance changes smoothly as the throttle (tps) or vane (vafm) are slowly opened and closed, and that there are no spikes in resistance, and no dropouts.

Other things to check:

EGR - it's not supposed to open at idle - if it does, it will cause stumbling and rough running. To test, pull the vacuum hose on top of the egr valve and plug the hose - see if there's a difference in starting.

Clogged injectors - these cause all kinds of havoc with mixture as they get deposits on the end - easiest way to clean is using Red Line SI-1 Complete Fuel System Cleaner (only product left that still has a good amount of polyether amine (PEA), the most effective injector cleaning chemical). Add a bottle to 2/3 to 3/4 tank gas, and run down to 1/8 tank, then add another bottle and fill gas again to 3/4 tank and run again to 1/8 before refilling tank. Sometimes SI-1 won't do the trick. In that case, when you have fuel pressure tested, have the shop feed some of the concentrated injector cleaner right into the fuel rails. That is more effective. Sometimes injectors are so bad they must be removed and ultrasonically cleaned, but if your injectors were that bad you'd be having more trouble than you are.

O2 sensor is hard to check - the computer will give you a code 21 if the heater in the sensor is shot, and it will give you a 25 if sensor volts are below .45 volts for 90 seconds or more (lean condition) and a 26 if above .45 for 90 secs (rich). You can do the diagnostic on VF1 and E1 in the check connector (see factory manual) to make sure the sensor is switching at least 8 times in 10 seconds between 0 and 5 volts (normal operation). A sensor that is not switching between lean and rich almost once a second is considered to be a "lazy sensor" and needs to be replaced.

However - even if the sensor is properly switching back and forth, the computer has no way to know if the O2 reading reported by the sensor is correct: as the sensors get coated with carbon, they start to read leaner than the exhaust really is, causing the computer to add more fuel than is necessary, and making the motor run too rich.

The only way you can know if the O2 reading is correct is to attach an exhaust analyzer. For this reason, if the sensor has over 90k miles, you should just replace it. Denso is the best bet, if you can afford; if $$ is tight you can try an NGK (NTK). sparkplugs.com has good prices.

Holy Crap that is some of the most well-thought-out and complete advice I've ever seen on here!
:thumbsup:
 

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Walker, thanks for the info, but you could use a little more tact when typing responses.
He was being tactful. I'm the tactless one around here. :rolleyes:

We get tired of giving detailed answers to people who ignore them. Happens more than you can imagine.
 

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Thanks guys, appreciate the support.

Truth is, I was feeling a lot of pent-up annoyance and this guy just set me off. Straw that broke the camel's back kind of thing. I normally try to be a LITTLE more tactful. :D

I do get discouraged when I take time to give some thought to a mechanical problem, and then the OP completely ignores it. I mean, why bother to ask?? I suppose I just have to accept it's going to happen from time to time.
 

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^^this guy has the most detailed info i've ever seen. he helps by replying to everyone with full details plus more. that's the kind of help i want. seems to have great knowledge in these trucks.

btw, my truck does this too. i might have to try these to see if it works. i know i had a thread about this a few weeks ago. search for it, it does have a few good tricks that i haven't had the time to try. this weekend will be a very busy one as i try to find the problem. thanks!
 

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Discussion Starter #13
Found the problem, finally!
The cold start sensor was giving it too much fuel. Only tricky problem was it was a minor short and didn't do it all the time so finding it sucked!
Thanks for all the help, I spent a lot of time learning more about the truck and the tips sb5walker gave me were really good leads to figure out the issue.
Like I said, no hard feelings sb5walker, you gave good advice and I was able to check most of the items you listed that could have been faulty.
I think everyone appreciates the advice and time everyone takes to try and help, but for someone like me with less mechanical experience, it is a little tough to just pop the hood and go to town. I'm learning and I'll get there!
 
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