93 rough idle piss poor performance at lower RPM

[Karl Pollock]

Gave the new t-body a good scrub, and checked all the mechanicals out butterfly plate springs cranks ect. Now for the slow soak. I proped it up so the offending vac port is compleatly submerged in mineral spirits but the electronics are high and dry. Leaving it to bathe over night. if there is a better method to unplug this that doesn't involve music wire please let me know.

 

[Karl Pollock]

finished t-body service this morning. All vac ports are clear and there are no aditional features, bench tested electronics all passed. Removed upper intake and fuel rail assembly. Injectors will go to Whitch Hunter for service this week. I'm having the upper cleaned by an engine shop near my job. Although I have the gasket, given the state of everything I've disassembled so far I don't think it's going to be nessesary to pull the lower intake. I plan to get some plugs to stuff in the injector ports then give the thing a good scrub while its exposed. Anyways it's cocktail time.
Cheers!

 

[toyotaspeed90]

You've gone a bit further than I have..... as my 93 with idle issues and low rpm performance issues have resolved.

None of this is 'fact' but more instinct for me.... In my vehicle I replaced:
Plugs, wires, cap, rotor, coil
Swapped AFM
Swapped IACV
Pulled the TB, cleaned it, new gasket

I was still getting a CEL (26) and random/intermittent issues. Others were pointing to the O2's but in my vehicle I knew once I unbolted the first one, the studs would snap and I would need new downpipes (or to find a set of o2's that work with this rig that are bung-style). I found a set of pipes from a 94 relatively locally, at 150k miles, with o2's and had those sent to me (actually in really great shape). These are still sitting on my garage floor.

Curiosity bit me. My 93 has the factory EGR resistor - so I bypassed the EGR by simply looping vacuum lines. The CEL was intermittent, but less so than ever. The more I drive it, so far, the less it happened. I bypassed the EGR about a week/week and a half ago and I haven't seen the light in probably 300 miles with zero intermittent low rpm performance/idle issues. Those miles include back road, stop and go in town, and freeway miles.

What I have a feeling is (or did) happen - is that the o2's are definitely on their way out. There have been some threads regarding the 93 ecu's being problematic, and I have a feeling that the system is set to rely on the o2's way too much. In my vehicle if I put the pedal all the way down, it would kick down and take off and rev just fine (o2's get ignored at WOT). I think the increased exhaust gas temps with EGR were causing problems with the 02's getting too hot and/or misreading - causing a code 26, which causes the system to go into 'limp home mode' and the intermittent issues.

 

[Karl Pollock]

I had a look at the o2s while I was pulling the intake, they look pretty bad I don't think I can remove them without damage unless I pull the assembly there attached to. They're on the list of s*** to replace if what I'm doing now doesn't work. I've read here that Toyota recalled the 93s for o2 replacement, if I'm lucky maybe mr T can do them for me. I forgot to mention the problems I'm having do not trigger a CEL light at all. I know the lamp works because it lights when the rig is turned on but not started. I never did do the paper clip trick to pull codes either, just got a bug up my ass and decided if I'm going to own it I'd better get to know it and best way in my mind to do that is to go through it top to bottom test and replace things As I go. It will also be good to know all the vac lines are new and routed properly and that all ports are clear. The further down I go the more I see this truck was pretty mutch a socker mom car. I think it got regular lube service, but not much else every piece of rubber I touch seems to be vintage. I'm rambling I'll stop now. Thanks for reading, a lot of good info and knowledge here.

 

[Karl Pollock]

Ok, pictures of the harness insulation part II. And other assorted nincompoopery. The stock insulation fell off as soon as I touched it so I think I've got a good fix. Black tape first sticky side out then in. Makes a sleave then tiger patch muffler tape, over that I put aluminum tape to reflect the heat. The collar that clips to the stay on the head is ****ed so I tossed it and used zippy ties to fasten, I'm not crazy about this but it's what I have. Any other ideas would be most welcome.
I got the injectors back from witch hunter a few weeks ago, the data states they were good before service but piece of mind goes a long way and now they are tip top. Bench tested all of the vcf vcv pcp and xyz components that live between the two intake halves and replaced all of the vacuum lines. Swapped out fuel pressure regulator and installed the fuel rail. I've since installed the upper intake half with fresh gaskets. I'm out of light now and it's my birthday so it's time for cake!
Cheers

 

[Mighty690]

My '93 had similar issues. It was my air flow meter: the black plastic cap/lid at the top had lost its seal upon close inspection. I bought a tube of black silicone, cleaned and taped it off neatly and applied the silicone. Problem solved, and that was a while ago!

 

[Karl Pollock]

Got her all back together but I still have the same issues. It low idle and very low power until good and warm. Then everything is good. I put a jumper on the diagnose block to pull codes per the FSM and all the light did was blink steadily for around 30 seconds. Is that normal? Do I need to wait a little longer for it to go into output mode? Also I can't force a cel at all, I pulled #1 plug to force a miss and nothing. Disconnected the tps and nothing. I've got a used ecu in hand, I'm thinking about just installing it and see if that does anything good. Any thoughts?

 

[toyotaspeed90]

The light blinking constantly just means there are no stored codes.

Some have stated that it has to go though a warmup cycle and then multiple starts/moves for the CEL to kick on.... though in my 1993 I've had the ecu unplugged, then 15 min to a drive the CEL would come on. So, I'm unsure if that's a later feature (multiple cycles) or not...

 

[Karl Pollock]

The warm up cycle makes sense. I drove the thing to work in a snow storm last week, that's 83 mi round trip mostly freeway but some city as well. I'll jumper the OBD over the holiday and see if anything pops up.