I am looking for help with my 1990 Celica GT, with a 2.2 The engine runs extremely rough at idle, and bucks like a wild horse at low speed. It does accelerate ok as long as you are on the throttle, but as soon as you lift it wants to die. I have checked the egr valve, egr vacume modual, map sensor, vsv valve, IACV, 02 sensor, distributor cap & rotor, ignition wires. All check ok according to the specifications available to me. Any help with this engine probluem wouls be greatly appriciated. Thanks, Rattler
At what engine speed does the roughness stop at in terms of increasing the idle speed, or doesn't it? Does the engine sound like it is misfiring constantly on a single cylinder? Does the tachometer jump arround erratically, or does it seem to indicate proper engine speed?
Have you done any work or anything on the engine that led to this? Has this slowly developed over time, or did it just come on suddenly?
The engins settles down at 2000 rpm, but a slight stumble is still noticeable. The same is at 3000 rpm. The engine does not seem to be misfiring on any single cyllinder until you let off the throttle, and it goes back to idle, then is seems to be missing on one to two cyllinders. The tacometer is not jumping around, and seems to be keeping track of actual emgine rpm. There has never been anything done to the engine except normal tune up procedures. This situation has developed over a short period of time.
I have visualy inspected spark plugs, and wires. The wires are in like new condition. The plugs in cyllinder # 3 & 4 were both wet, but otherwise looked, and gapped fine, although all four plugs were darker in color than what I think would be normal. This engin does not have a PCV valve, so I am not sure if this would contribute to a dirty intake / combustion chamber or not. The engine vent hose is routed directly from the valve cover to the throttle body. The trhrottle body was also extremely dirty until I cleaned it up the best I could while cleaning / checking the IACV. Both wires & plugs were replaced less than 10,000 miles ago.
For the wet plugs is cylinders 3 & 4, do you know what the liquid was on them? Gas or oil or coolant?
Has your coolant levels been dropping at all? Coolant looks good, no light brown spots or anything (look in the overflow bottle as well)? Oil looks normal?
If all looks good, but if you can't identify the liquid on plugs 3 & 4, I would suggest at this point you do a compression test on all 4 cylinders and post the measured results.
While I have some ideas because of how suddenly this comes up, we should probably work through the process to try to pinpoint the problem.
I have visualy inspected spark plugs, and wires. The wires are in like new condition. The plugs in cyllinder # 3 & 4 were both wet, but otherwise looked, and gapped fine, although all four plugs were darker in color than what I think would be normal. This engin does not have a PCV valve, so I am not sure if this would contribute to a dirty intake / combustion chamber or not. The engine vent hose is routed directly from the valve cover to the throttle body. The trhrottle body was also extremely dirty until I cleaned it up the best I could while cleaning / checking the IACV. Both wires & plugs were replaced less than 10,000 miles ago.
fyi the 5sfe does have a pcv valve. thats what is on the back right corner of your valve cover (looking from front of car)
The liquid on the plugs in cyllinders 3 & 4 is fuel. The coolent, and oil are both full. No discoloration of the coolent whatsoever. Oil & filter was changed recently. I will not be able to check compression until next week. I was wondering if the issue could be caused by faulty fuel injectors, or fuel pressure regulator? I don't know if there is an acess on the fuel rail to check the pressure?
No access on the fuel rail to check fuel pressure. This would be a good test to conduct. I don't think that you have a fuel pressure issue though, because as your engine speeds up, I got the impression from your responses that it runs a bit better.
It sounds to be the cylinders 3 & 4 just aren't functioning. That could be from lower compression on those cylinders, or ignition problems. The fact you have fuel in them suggests to me that your injectors are at least putting fuel in them (doesn't say if the spray pattern is good, but they are getting fuel).
Visual inspection of spark plug wires rarely tells anything. Resistance measurements is helpful. Each wire needs to be less than 25,000 ohms. And, I've had experiences where spark plug wires were arcing to the metal spark plug tubes, causing no spark to the plugs, yet the wires visualy looked OK. You can do a test, with engine running, pulling the spark plug wire off of cylinder 3 or 4 spark plug and see if the engine idle problem gets worse or not, and if the spark plug is arcing to the metal tube. Even new wires can do this, new parts aren't always defect free anymore.
Might as well replace the plus and wires as they pretty cheap. Make sure to use OEM wires or something like MSD. Use NGK plugs or OEM plugs and make sure to gap them correctly. Even if the toyota parts guy says they are pre gap, check them anyway as they are never pre gap.
I have done some more research. Here are the results.
The ohm resistance for the spark plug wires were measured on the 20K setting.
cyl #1-(1.16), #2-(.88), #3-(.91), #4-(.67)
Compression check,
cyl #1-(145), #2-(131), #3-(124), #4-(127)
The maximum spark plug wire resistance is 25k-ohms. You are pretty close on #1 cylinder, but still within spec. And that doesn't appear to be your problem cylinder either.
The 5S-FE target compression pressure is 178 psi or more. The minimum pressure is 142 psi. The maximum difference between any two cylinders is 14 psi or less.
I would say your compression pressures are too low all the way around, and the lowest cylinders (3 & 4) are the ones giving you problems. I wish there was better news, but I think you found the source of the problem (low compression pressures).
You could try to put a tablespoon or 2 of oil down each cylinder and recheck your compression values. If they go up to normal, then your problem are the piston rings. If they do not change at all, then you have valve seat problems. If they go up halfway, you have a combination of piston ring and valve seat problems.
Thank you for all your help.
I understand what you are saying about the compression, but I have to tell you that I drove the car today, and it has all kinds of power beyond idle. The engine realy runs strong. As long as you keep it at 3-4 thousand rpm it doesn't miss a beat, but as soon as you lift, or try to granny along it acts up, and wants to stall. My compression gauge is old, and I did the test with a cold engine if that makes any differance? The exhaust sounds (puffy) like that of a marine engine exhausting into the water. When I unplug the vacume line to the (throttle opener), from the IACV the rpm increases some 500 rpm, and the engine idles somewhat smooth, but with still a stumble. I also seen a (electric controled vacume switch) of some king located underneath the intake manifold behind the engine mounted between 1 & 2 cyllinders. I am not shure what this is, but it looks like the VSV switch located on the R/H side of the firewall. Could the IACV, or the throttle opener have anything to do with the idle problem?
The VSV under the intake manifold is for the EGR valve.
I guess you could look at a lot more things, but in my opinion, your cylinder compression is too low to maintain any kind of steady idle, and likey it doesn't run to smooth at higher speed either. You said that in an earlier post.
You can take your compression readings to a mechanic and let him know what the target compression values are for the engine, and get an opinion from a mechanica, maybe even two different ones. But I think they will tell you the same thing - your cylinder compression is too low.
PS: The correct way to check cylinder compression is to warm up the engine to normal operating temperature, shut it down, pull the EFI fuse, remove all spark plugs, block open the throttle (or floor it when your turn the engine over inside the car, and go through all 4 cylinders while the engine is warm. You may pick up a little more pressure on a warm engine than what you got cold, but not much, unless you didn't get the compression gauge tightened down sufficiently and it was leaking badly. So if you want to try it again with a warm engine, then let us know what you got, that would be great. Otherwise, unfortunately, I would say you need to do something to get the engine compression values back to normal before worrying about anything else (as I think that is the problem you are having with the roughness of the engine now).
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