hey guys, i was wondering if you could help me with something. i have a 94 yota 4 cyl 5 speed 4x4. when i start it up, whether the engine is cold or warm, it will miss really badly for a minute or so, only at idle. after about a minute, it will instantly kick back in, and it idles fine until i turn it off and restart it. then it happens again. i just replaced the spark plugs and wires. the previous owner got a check engine light diagnosed a while back and it came back as a sticking egr valve. it never got replaced, but its never done this before. it runs at other rpms without missing while it will miss at idle. im a little hesitant about buying a 170 dollar part if theres a chance that it isnt causing my problem. what do you think?

 

I would check to see if the check engine light is still flashing any codes first. If you dont know how to check it, click here. The codes are at the bottom of the page.

If there are no codes showing the next thing I would do is pull the vacuum line that goes to the EGR and plug it. See if the engine still starts abnormal. But if the EGR is clogged and always opened, it might be the same...

 

alright, i have some more info now. i bought the truck from my friend, and he said it has happened to him only a couple times where the truck doesnt want to idle smoothly. it happened to me for the first time wednesday, it worked fine for a while and now its getting worse. even earlier today i could get it to smooth out after a minute like i posted earlier, but now it will go back to idling badly even after ive been driving for a while. it still runs fine at all other rpms except for idle. hope this clears things up a little.

 

Are you sure it is just missing at idle? Try revving up the motor in neutral to about 2500 rpms and listen for a miss. It might be kinda hard to hear, so listen closely. Also you can watch your shifter and see if it moves at all. My truck is missing right now at idle because of a burnt or tuliped valve (i think). When your truck is idleing rough, what rpm is the motor at? Are the rpms the same when the truck is idleing ok, as opposed to when it is runnig rough?

 

im pretty sure its not missing any other time. one of my valves is tapping, but it doesnt sound like just one cylinder when its missing, its more rough and irregular. im not sure about the rpm cause my truck doesnt have a tach, but it sounds low. when it smooths out the rpms increase a little. my reasoning was that if the egr valve was never closing all the way, it would affect it a lot more at lower rpms than higher. i got the statement from the garage my friend took it to and it said the diaphram in the valve was sticking, im guessing open.

 

does it smoke when its running rough?

 

no not at all. today it actually ran pretty well, i didnt have any problems with it and it felt like it had more power.

 

it doesn't sound like an egr to me but i could be wrong. I just rebuilt my 22re and instead of putting the egr back on i made block off plates and put them on instead. I havent had any problems yet. dumb question but have you tried adjusting the idle?raising it a little. If that doesnt help, it sounds like something electrical in the ignition or timing.

 

What is the idle like when its rough. Rythmic, sparatic (sp?), etc? What is your timing set at?

 

could easily be vacuume leak, mine did that and i sprayed contact cleaner around the vaccume lines and intake untill i heard the motor idle up and then i located the leak. and determined that it was the intake manifold gasket. runs great now.

 

Try tapping on the EGR valve when it starts idling funny. If it clears up then it could be the EGR sticking open (it should close at idle). If so, clean or replace it. Also check the TPS, if the idle adjustment is not right (or the throttle is being held slightly off idle, you'll have the engine "running really slow" instead of a smooth idle:

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

 

That sounds just like the problem I am having..Mine misses sporadically with no rhythm during idle..but also has a miss when higher rpms just harder to detect. I have tried for over a year to fix mine..have taken it to 2 diff garages..and they look at it for about 10 min then say ..change the plug wires..well after 3 sets of plugs and wires and coils and new exhaust and replacement of questionable air lines...etc..no luck..still a miss. I had the Valves checked and all read a perfect compression. I would lovee to lose the miss on mine..im gonna get the fuel filter and pump checked next...dunno where else to go from there.

 

Pull the EGR off, get hour hands on a gun cleaning kit (small round wire brushes and gun cleaning solvent) and go to it, or pop for $100+ and get a new EGR valve. A buddy just replaced the EGR in his '94 p/u, says it runs as good as new now.

 

Does you motor have a tapping/ticking noise? Try holding a piece of paper up to the tailpipe. Does it get sucked up against the tailpipe?

 

Im gonna try that..I need to clean my guns too anyway..Thanks for the suggestion..Ill let ya know how it turns out.

 

One of the first things I tried and no sucking..i was worried about the Valves at first..but I really think its something else.

 

i decided to block off the egr instead of buying a new one, i took it off at the intake manifold and the pipe from the valve to the manifold was completely unscrewed at the valve. i blocked it off anyways and it runs a lot smoother overall for sure, but it still runs rough at idle once in a while. its weird cause it will run perfectly for a few days and then act up all of a sudden. mine has a tapping sound that i think is coming from the rocker arm area. its usually worse when its running rough.

 

i feel like driving my truck into a pole. its running like crap still. it idles roughly and a new symptom is that it doesnt have any power when the throttle is anywhere between idle and wot. once i put the pedal all the way down its like flipping a switch, all of a suddent it will pull strong. it seems like the more throttle i give it the more it bogs until it reaches wide open throttle. it only does this it seems when the engine is already warm. ive replaced the plugs, wires, cap, rotor, and blocked off the egr system. i need help!

 

hmmm...my old acura did this once...turned out to be the O2 sensor had gone bad...the reason it ran OK at WOT was because the ECU was programmed to ignore input from the O2 sensor at WOT...

i dunno if yota ECUs do the same or not (anybody know?)...prolly not your problem, but maybe something worth looking at if ya can't figure anything else out.

 

i was thinking the throttle position sensor was dirty or messed up maybe. that would explain why it doesnt work at throttle positions other than wot. i did the test on it and it checked out alright. it is an intermittent problem, so maybe it is still bad. i think im going to take it off tomorrow and replace it with one from the junkyard to see if it makes a difference. another clue is when the engine is cold it will go into warmup idle and work fine but once the rpms drop to normal idle it goes bad.