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View Full Version : '92 Celica w/ 5SFE/automatic: major repair mystery



red92ragtop
07-05-2013, 05:08 AM
It's been awhile since I've posted on here, but I still have my '92 GT convertible. It sat for several years, but I've been trying to get it going again lately, and it's giving me a huge headache. It's been sitting since '08, but I've run about 2 tanks of gas through it recently. I've run 2 bottles of Gumout injector cleaner and about half a can of Seafoam through it as well. With the vacuum line from the throttle body to the throttle opener (I have no idea if that's the general name for it or not, it's what's listed on the routing chart under the hood) unhooked, it idles fine, but there is a nasty vibration, and when I put it in gear, it starts running rough. With the aforementioned vacuum line hooked it up, it just dies unless I have my foot on the gas. I can get it moving down the road, and it will eventually get up to 55-60MPH, but A) there's no low-end power at all, B) it won't shift into overdrive, and C) once I get up to around 45MPH, there's barely any acceleration. I also noticed that the last time I drove it, the plug wires on cylinders 1 and 4 were popping off, but I ran it yesterday and revved the engine up several times and they didn't pop. Plugged catalytic converter was my first suspicion, but there seems to be plenty of flow through the exhaust. I put new plugs in and checked the coil, distributor and plug wires, and all the resistances are in spec. I replaced the fuel filter as well. I'm not sure what to look for from here, so if anyone has any ideas, I'm all ears.

Galcobar
07-05-2013, 05:18 AM
What is the tach doing as you accelerate, and if you cruise does it smooth out?

red92ragtop
07-05-2013, 05:23 AM
It's rough up until 2000 if I remember right... from there onward it's relatively smooth. Unless I let off the gas it doesn't want to shift until around 5000 though. If my memory serves me right, it ran smoothly in cruise control, it was just wrapping up higher than it should've due to the lack of overdrive. Could it be transmission-related?

If necessary, I can take it for a little drive tomorrow and get back to you on exactly how it behaves when I try to drive it.

red92ragtop
07-14-2013, 06:46 PM
Okay then, plan B.

Can anyone recommend a forum that's active enough that somebody there might be able to actually help me?

Galcobar
07-15-2013, 07:32 AM
You never did report back on the car's behaviour when driven.

red92ragtop
07-16-2013, 12:21 AM
You never did report back on the car's behaviour when driven.

I just got done taking it out, and here's what it does:

Just starting it up, it idles at around 1100RPM. Noticeable vibration but it doesn't act like it's going to die.

As soon as I shift into reverse or drive, it drops down to around 500. Vibration gets worse, if I give it gas it'll backfire, if I'm not giving it gas while it's moving it'll die. I did finally get it out of the driveway, but I had to restart it several times. It runs in neutral the same as it would in park.

On the road, once I get it up above about 1500-2000 RPM the engine revs smoothly. If I stay on the gas it won't shift until around 5000 (no matter whether the ECT is in normal or power) and it shifts hard. Up until 50 MPH it seems to accelerate slower than it used to, but it still gets there in a reasonable amount of time, but getting from 50 to 60 takes forever. I tried setting the cruise at 50 and it ran smoothly at about 2800-2900 RPM. I drove about a 4-mile loop, and when I got back to park it, it was idling rougher than it was when I first started it.

Galcobar
07-16-2013, 01:23 AM
It's actually backfiring -- as in you're getting explosive detonation in the exhaust or intake systems?

If it's in the exhaust system, then you've got fuel getting past the combustion chambers. If it's in the intake, then your valves aren't closing. Have you checked your timing (mechanical and ignition)? Also take a look at your spark plugs, their condition is diagnostically useful. Third, you mentioned the car sat for two years, did you check for any critter-related issues (chewed wires and vacuum hoses, and nests in the intake system are common)? Fourth, is the CHECK ENGINE light on, and have you checked for any diagnostic codes?

red92ragtop
07-16-2013, 02:23 AM
I can't tell where the backfiring is coming from, but I can hear occasional popping sounds that sound like detonation, generally just off-idle when I'm barely moving. Don't notice any popping above about 1500 RPM. I haven't checked the timing yet, that's my next item of business. I just put new plugs in it, if necessary I can pull the plugs and let you know what the insulators look like. I don't see any chewed wires or vac lines, or nests anywhere in the intake. The CEL isn't lighting up.

red92ragtop
07-18-2013, 12:27 AM
Ignition timing reads 10 degrees BTDC. How do I check the mechanical timing?

93celicaconv
07-22-2013, 03:50 PM
Did you read the ignition timing using the jumper in the diagnostic port? If you did, was your check engine light flashing properly when jumpered? Only if your diagnostic port is jumpered with the check engine light flashing can you properly check and set your ignition timing.

But, from a very simple perspective, it sound like you timing belt jumped a tooth or two, or your have a spark plug wire which is either open or is shorting within the cylinder head spark plug tube, or you a a fuel injector not functioning, or you have a compression problem in one cylinder. I would suggest you go through and rule out each one of these possibilities separately to see which situation is your root cause.

red92ragtop
07-25-2013, 05:43 PM
It was jumpered and the CEL was flashing when I checked.

Thanks for the response, I'll look into those things.

andy
07-30-2013, 03:04 PM
pull the case on the ecu and look for black goo spilling from the capacitors (the 2 big ones). I just had a 93 do the exact shit to me and it was the caps. Replaced them and now all is fine again.

red92ragtop
07-30-2013, 10:30 PM
pull the case on the ecu and look for black goo spilling from the capacitors (the 2 big ones). I just had a 93 do the exact shit to me and it was the caps. Replaced them and now all is fine again.

I pulled the ECU and everything is clean. Is there a way to test it?

Compression only read 140, but I got the same reading on all 4 cylinders, and it wasn't warmed up prior to testing. Am I alright there, or is that most likely my problem?

93celicaconv
07-31-2013, 02:09 AM
Compression only read 140, but I got the same reading on all 4 cylinders, and it wasn't warmed up prior to testing. Am I alright there, or is that most likely my problem?

Compression pressure target for the 5S-FE is 178 psi or more, no more than a 14 psi difference from highest reading to lowest reading, with a minimum pressure of 142 psi.

Do you trust the psi readings of your pressure gauge?

Uniform 140 psi pressure values, assuming done with a good battery & starter and the throttle plate being wide open, is quite low, but not something that would prevent the engine from running, just will have poor power. Normally, I would say a uniformily low compression pressure across all 4 cylinders is an indication of a timing belt that jumped a tooth. You negated that possibility because you said your ignition timing was spot on at +10 deg BTDC, and you verified you checked your ignition timing properly. While it is possible to adjust your ignition timing to this setting after the timing belt jumped a tooth, you didn't say the timing was retarded a fair amount at first check and you subsequently reset your ignition timing to +10 deg BTDC. So, based upon what you said, I really don't know what you have going on there.

andy
07-31-2013, 05:18 PM
was it warmed up when you took those comp readings?

red92ragtop
07-31-2013, 10:39 PM
was it warmed up when you took those comp readings?

No. I had the ECU out so I couldn't run it at the time.

Facime
08-01-2013, 07:11 PM
symtomatically it sounds like mechanical timing.

You never mention why it was parked for so long in the first place. What led to its being parked? was there an event that preceeded the poor running condition. For example, was it running fine then you put fresh fuel in it and it started running poor, or did it get driven through alotof water, etc.


We need to get back to the basics here: spark, fuel, compression, timing, air. The first three being critical to run, the last two being important to run well.


Your compression numbers are low but, as mentioned, not so low they would keep the engine from running reasonably. Uniformly low is a bit odd.

Using a spark tester or an old plug, verify good strong spark at the end of all 4 wires.

Jumper the Fp and B+ terminals of the diag block and with the key on listen to the sound of the pump. Is it unusally whiney? Or does it sound labored? Now squeeze one of the rubber fuel lines before the fuel rail and see if you can feel the fluid pulsing. You can use a soft cloth to keep from damaging the hose, but use a vice grips to completely close off the fuel flow at that same hose and relisten to your pump, its tone should change a little, but it shouldnt sound...."chunky".

After that I would be inclined to unhook the exhaust pre-cat and verify your exhaust isnt plugged. Ive actually experienced a melted cat on a supra once. Most frustrating problem to find and it was a last resort in my case. Punched the cat and my car came to life. (this is why vehicle history is nice to know). An engine is a big air pump. If it cant pump air, it no worky.


Also, if it were me, knowing how the 5S likes to jump time later in the life of their belts...I would visually verify physical timing.


Lastly, I would backprobe all the pins on the ECU and related engine control components, and compare the voltage and resistance figures against the BGB (http://bgbonline.celicatech.com/93celica/) starting at page FI-92.



I know its alot but hopefully something will come to light as your work through it.

andy
08-01-2013, 10:28 PM
expect to see those compression number in the green after you warm up the engine. If you don't want to unbolt the cat, you can pull the o2 sensor and see if it acts like its blowing all the air out of there.