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Ted Ritter
Ted Ritter, Toyota Master Tech
Category: Toyota
Satisfied Customers: 4433
Experience:  Toyota Master Tech, ASE Certified
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1988 toyota: 4x4..v6 3.0 has 110000 miles on it..warms..accelerate

Customer Question

1988 toyota 4x4 v6 3.0 has 110000 miles on it when starts cold runs great when it warms up starts running a little rough like its getting to much fuel no chk engine light when you accelerate it clears up possible causes???
Submitted: 6 years ago.
Category: Toyota
Expert:  Ted Ritter replied 6 years ago.

Hello, there are a few things that could be the cause, a tight valve/ low compression on one or more cylinders, a leaking headgasket, sticking EGR valve, leaking cold start injector.

Does it seem to run rough one one or two cylinders only, have you tried to isolate which cylinder may be the problem by shorting out each cylinder one at a time. If the idle just seems erratic with no particular pattern then it may be an egr valve problem, especially if it clears up after accelerating and then returning to idle normally, at this time I suspect that this may be the case. If the misfire can be isolated to a particular cylinder then it's not an egr problem but may be a loss of compression in that cylinder but in that case it would idle the same all the time after warm up, this may not show up on cold starts because of the fuel enrichment and fast idle associated with a cold engine.


Customer: replied 6 years ago.
If I disconnect the egr and it goes away then thats it true? Have 160 compression on all 6cyl yes I tried the shorting spark test nothing changed and where is the cold start located?
Expert:  Ted Ritter replied 6 years ago.
Disconneting the vacuum line on the egr valve won't do anything, if you have a vacuum pump you can check it's operation, when it's idling rough try tapping on the egr valve top with a small hammer and see if the valve unsticks and the idle goes to normal. the cold start injector is located on the passenger side of the intake chamber, it has a small steel fuel line on it and a banjo type fitting on the valve and an electrical connector. By the way is there any black smoke coming out of the exhaust? Does the engine use any coolant at all?
Customer: replied 6 years ago.
No black smoke or coolant loss whatsoever will chk egr valve in the morning and get back to you
Expert:  Ted Ritter replied 6 years ago.
OK, thanks.
Customer: replied 6 years ago.
All the cylinders are working tapped on egr no change and when I rev it up to 2000rpm it clears out but at idle it still misses after warmed up checked cold start as well no leaks replaced cap and rotor to could the intake hose cause this i noticed a crack in it
Expert:  Ted Ritter replied 6 years ago.
Yes, any intake leak between the throttle body and air filter can cause this, try taping the crack and see if it helps. The reason I didn't bring this up yet is that you mentioned replacing the intake gasket in which case this hose has to be removed.
Customer: replied 6 years ago.
Found a new intake hose and has subsided some but still have a little miss at a idle when driving it has plenty of power just rough idle
Expert:  Ted Ritter replied 6 years ago.

Was this rough idle there before, was it the reason the parts in your original post were replaced or did this happen later. It sounds like there may be a small vacuum leak still, recheck all the hoses and if possible check the PCV hose on the valve cover on the passenger side. As a last resort I would recommend checking the valve clearances even though the compression may not show this, valve clearance will change when the engine warms up so a valve may have just enough clearance when cold but tighten up as the engine heats up and then not seal completely. Another possibility could be a cracked or broken valve spring which will also not show up on a compression test.

Customer: replied 6 years ago.
K will check all lines and hoses and get back to you and yes the rough idle was already there
Expert:  Ted Ritter replied 6 years ago.
The only recommendation i have left if the vacuum hoses are not the problem is to do a valve adjustment check.