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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
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Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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91 Toyota pickup 4 cyl runs great, then suddenly starts bogging

Customer Question

91 Toyota pickup 4 cyl runs great, then suddenly starts bogging at around 2500-3000 rpm's seems if I turn the ignition off (while still moving with the clutch engaged) 3 or 4 times in a row it clears and then I can drive for the next 2, 3 weeks or even a month and the same problem will re occurs. the last time 2 days ago and it changed a little this time, the rpm.s at idle would fluctuate from 700 to maybe 11 or 1200 O one more thing may be related or not some times the rpm gauge bounces around randomly
JA: Good to know. The mechanics have tons of experience dealing with this sort of thing. How old is your transmission?
Customer: 1991 new with the truck 125000 miles
JA: Ok. We'll get you to one of the go-to transmission guys. Other than the problems you mentioned, how has the car been running?
Customer: it is not the transmission
JA: Noted. I'll pass this info along to the mechanic so that he can get you a quick fix. Anything else I can tell the Toyota Mechanic before I connect you two?
Customer: I dont think so
JA: Got it. Let's get this figured out. I'm sending you to a secure page on JustAnswer so you can place the $5 fully refundable deposit now. While you're filling out that form, I'll tell the Toyota Mechanic about your situation and connect you two. You'll be on the road in no time.
Submitted: 6 months ago.
Category: Toyota
Expert:  mike switzer replied 6 months ago.
sounds like you have a couple different issue the idle surging issue sounds like the idle control valve they can get gummed up. the rpm bounce is most likely the distributor the tach gets its reading from the distributor and if it is bouncing then your distributor is probably wearing out. i would remove the isle control valve and clean it out and inspect the distributor shaft for play.
Customer: replied 6 months ago.
so do u think that would be the source of the random boggin too
Expert:  mike switzer replied 6 months ago.
yes if the idle control valve sticks it will allow either too much or too little air usually too much air while trying to accelerate. once it gets past a certain point it will run fine.
Customer: replied 6 months ago.
I checked the distributer, the bushings are tighter then some of the new ones i have seen. It runs fine most the time. Other times I will be cruzin down the highway and all of the sudden it looses power if I slow down and keep the rpms below 3000 I can continue with my trip If i turn the ignition off with the clutch engaged 3 or four times in a row while still moving it will clear up. I just ordered a tb gasket and idle control valve gasket till then I cannot clean the control valve. if u can come up with anything else Id be happy to listen Q. do u think it could be the pickup coi,l could it possibly cause all the problems i have described
Customer: replied 6 months ago.
I have ask other question but all I get is a reminder to rate you if in fact your answer helps fix my problem then I will surely let you know
Expert:  Toyota Service replied 6 months ago.
Hello. Different expert here. I may have a different view on this issue if you would like my input. If so, please advise.
Expert:  Toyota Service replied 6 months ago.
Please feel free to ask your other question. I will try to help.
Customer: replied 6 months ago.
Yes please take look and see what u think
Expert:  Toyota Service replied 6 months ago.
Please advise if the check engine light is on.
Customer: replied 6 months ago.
No light is not on
Expert:  Toyota Service replied 6 months ago.
One more question. On the top side of the throttle body (where the tube from the air filter box is connected), is there a slotted screw that one can tighten or loosen this screw?
Customer: replied 6 months ago.
Yes that screw is there
Expert:  Toyota Service replied 6 months ago.
Ok. On this model vehicle, the screw is responsible for the idle, not an idle control valve as described by my colleague; he may be thinking of a different engine. Most often, the idle surging condition is from a worn out throttle position switch (that is the electrical thing on the side of the throttle arm). If it is open or shorted, it will set a code, but, if it is worn, it will not set a code. I would replace the throttle position switch. Also, I would remove the throttle body, take that screw out, and clean the inside of the throttle body/throttle plate area with Gumout carb cleaner. Scrub with an old toothbrush if the carbon buildup is heavy. Spray the cleaner into the hole where the screw goes. The screw (and the air passage it controls) is your idle parameter. Screw it in, less idle. Screw it out, more idle. The setting is roughly 3.5 turns out from all of the way in when reassembling it. Use a new throttle body to intake gasket. Please confirm that you have received my input. If you have any questions, please feel free to ask. Thanks.
Customer: replied 6 months ago.
OK, so I did this job today I did replace the gaskets with new ones now it is the waiting game like I posted a couple times it is one of those things that seem to happen randomly so I never really know if it is fixed. My tach is still erratic at times im not sure these problems aren't related the isle serging only happened one time but almost all day
Expert:  Toyota Service replied 6 months ago.
If you have any other questions, please feel free to reply; I will be very glad to help you further.If you do not have any questions, and are satisfied with my input on your request, thanks for choosing Just Answer. It was a pleasure to assist you today. I trust my input to your request is satisfactory to you and meets your expectations. A positive rating would be greatly appreciated for my assistance on your inquiry. Thanks in advance and thank you again for choosing Just Answer