20v 4age engine probs.idle lopes at 500rpm and hesitates above 5000rpm burning fuel f

[linton]

Hello Guys,

I’ve had some issues lately with my 89sx corolla with 20 valve conversion.

Started when the car wasn’t driven for a week, went to start but was dead flat. So i pulled out the battery and noticed it was pretty low on water. Topped it up and charged it overnight, wacked her in and started her up. Noticed it started very easily but revved up to almost 3000rpm when cold and settled back down to 1500rpm when at operating temp. Was fine before the battery went. Figured the computer had reset so I drove it in for a few weeks to no avail. Engine running bad, also missing at load and running rich. Scaring neighbours in the morning.

Later engine making shitloads of high pitch noises when revving. Turned out the noise was my pulley tensioner (had suspected this) on the timing belt. So I’ve had the pulley belt and water pump changed along with the relevant seals, old belt fine but changed anyway.

Mechanic said it was running very rich so i made it leaner.

Car came back running a lot better. Still idles too high. cold 1500rpm warm 1100rpm.
Power great until 4500rpm then it hesitates badly but will push on to 7800rpm no probs. So i suspect VVT engage problem, noticed that when cold engine does not hesitate throughout the rev range, so I’m thinking fuel issue instead?

Drove around the other day for a while and the engine is now rough as. Lopes at idle at 450 to 550 rpm almost stalls, sounds like a rotary or a Harley Davidson when idling. Could be running on 3 cylinders so im going to check that this weekend. Cant get above 5000rpm cleanly. But will run well when accelerating moderately up to 5000rpm or when decelerating. But it misses when maintaining the same speed or idling or accelerating very hard. I am using more fuel than a 747!!! Yet the car doesn’t smell like a petrol station or backfire.

Is it out of timing somehow? I am going to check my plugs and leads etc to see if im getting spark.
Only other problem I think it could be is if one of the injectors isn’t working properly? Maybe one cylinder isn’t getting fuel and the others have to burn more to make up for it? Or the FPR leaking? I have very little puffs of black smoke coming out of the exhaust.

I’ve had vacuum problems before on my Celica, but this doesn’t seem like that, although they are fucking hard to find or diagnose.

Has anyone had this problem before? Would really like some suggestions on what to do.

[kassma]

OK...

First off... which 20v is it? BT or ST?

2nd... Check for vacuum leaks... I've just had similar experiences with my 20v BT in that it was idling at 1500RPMs when warm... it ended up being the air line coming of the top for the power steering, which wasn't blocked. As soon as I blocked this off... it was perfect at idle and spot on 850RPMs.

3rd... start with the smaller stuff first... IE: vacuum leaks, ECU error codes, diagnostics steps from the manual, etc.

4th... if #3 hasn't helped, then start fiddling wth Idle up/down, timing, plugs, injector cleaning, etc.

MIKE.

[linton]

Its a silvertop, AFM version. Ive electrically disconected one fuel injector at a time, engine wont run, if any injector is disconected so i assume they all work, but how well, i dont know?

Ive disconnected each spark plug and im getting a spark in each lead. Engine will still run even if 2 cylinders spark is removed. Pulled out each spark plug and there black, and covered in soot, so i assume its running rich? I cleaned them with a cloth and put them back in.

Still running bad. I'll check the vacuum lines again and see if blocking off the p/steer line works.

[linton]

Well i checked a few things.
1. my o2 sensor is open circuit. How much difference will fixing this make? It didnt do much on my old celica 3sge, it was never working. What is the part number for the sensor?
Does the huge black soot stain on the ground from my exhaust means im running very rich?
2. checked my oil control valve resistance, and it was ok.
3. injector resistance all good.
4 ISC valve resitance all good.
what is the little black box that has an air line from the air filter hose, 2 wires and an air line to the vacuum of the IACV? how do i test this?
How do i test my AFM?

[ollie83]

I dont know if this will help linton but this is a video i found when fixing an AFM on a 5mge, and it should be the same process for the 4a, but i doubt this will be the problem, but its worth a look. Its relatively easy to do and may just solve your problem.
Good luck mate
http://www.youtube.com/watch?v=-11J8XawQtc

[linton]

thanks ollie, might just do that. does anyone know what the part number for the o2 sensor is on the 4age 20v silver top? or any othe types of o2 sensor that will fit in? its a 4 pin heated type?

[ollie83]

89465-19685 - AE111
this website will be helpful for you:
http://www.toyodiy.com

[linton]

Hi Ollie thanks again. But the website didnt seem to mention 20v engines? only 16v and SC engines.

[ollie83]

Yeh i just tried it then. thats a bit odd? Owell, i found that part number on http://4age20v.blogsome.com/