91 celica wont throw trouble codes?

[ckusse]

hi guys...new here. i didnt find anything in the search on this so hopefully some one can help.
my car was driving fine then, very suddenly started to have acceleration issues. around 2300 4500 rpm..the car would buck and try to die. if i let of the gas the car would return to normal manner. if i eased into the throttle it would accelerate better. as soon as i punched it, it would bog again. as this is happening, the check engine light would flutter. once of the gas...light dissapears. at idle it would do the same thing. under load and without load it acted the same way. i checked timing and it was at 10 deg. wires good from what i can see. so i changed fuel filter and air filter. same problem. i checked compression and it was 150 to 154 across all four cylinders. i took it to the toyota dealership...and they have had the car for close to two weeks now. they dont know what the problem is. they tried checking the codes and its not showing any
is what they said. they have gone through all vac lines and electrical sensors. every thing is in place where it should be. they did compression check and came up with same #'s. theres currently two techs looking at it right now in between there other projects. i dont get it...a toyota dealership with toyota certified technicians and toyota scan tools and they cant figure out the problem?..or read the codes? is this possible. how can my car act like crap and not throw a diagnostics code? please help me if some out there has had a problem like this.

[93celicaconv]

What model 91 Celica do you have (ST, GT, GT-S, All-Trac)? What engine (1.6L 4A-FE, 2.0L 3S-GTE, 2.2L 5S-FE)? Manual or automatic transmission?

All this would help us a lot to narrow down some options.

You have an OBD-I system on this car, not OBD-II, which is far more comprehensive. So it is possible the ECU isn't generating a trouble code because it is not set up to do so on your early Celica.

Does your engine run this way only when cold, only when warmed up, or it doesn't matter? Did you check your timing with the procedure shown on the sticker under the hood?

[ckusse]

gt convertable. 2.2 5sfe manual.....runs this way cold and hot.....timing was checked by me and toyota techs. both read same way...used by haynes manual(me)..and however they do it there.

[93celicaconv]

The 91 5S-FE cylinder compression pressures should be 178 psi or more to be considered acceptable, with no more than 14 psi difference between the highest and lowest pressures recorded. The engine should still run as low as 142 psi, but with diminished power and throttle response. Anything below 142 psi would not be considered safe to use.

Your cylinder compression values should be considered low, meaning there is something wrong causing your low compression values. But not so low that the engine should be acting the way it is.

If your ignition timing is at 10 deg BTDC, and hasn't been recently adjusted to get to that setting, then one would have to assume your mechanical timing is good. Mechanical timing being off would cause these symptoms. But your ignition timing, if never adjusted to compensate, would also be off when measured. So let's assume your mechanical timing is OK.

When your check engine light flickered a bit, a code should have been set in memory that is retrievable (unless the battery terminals were removed in between, or the EFI fuse was pulled out). Too bad, it would have been great to have obtained the code that was there when your check engine light flickered.

I would be checking ignition coil primary & secondary resistance values, distributor position and speed pick-up coil resistance values, oil in the distributor housing, igniter health, MAP sensor output values, fuel pressure values at idle and under acceleration, spark quality (hot bluish color spark or weak yellow/white spark), etc.

This kind of condition is hard to help with from a distance. Sounds like it is even hard to help with when the dealership service techs are right there with it.

[ckusse]

thats just it ......the light flickers for them too......they try to read it after and no code stored.?... yeah the engine has 185k on it so im sure rings are worn, but there still in spec . ill tak to them about checking those sensors youve mentioned. and other items as well. the tech said his next step was to measure the fuel pressure...but that was 5 days ago. i havnt recieved a call back yet on those results. so i assume it measured fine. i just want this to end. im so looking forward to hearing that they actually found something wrong instead of ' it checks out alright'. they told me i gave them a real challenge.wtf!!!