Coughing and spluttering 4A-GE 20V - anyone had this issue?

[timbosaurus]

OK, I know I'll probably have to sus out this problem from scratch, but if any of you 20V gurus can suggest some possible causes, i'd really appreciate it!

Background:

I bought a ex-race AE101 levin recently (originally came with a silvertop 20v) that has been converted to a blacktop 20V. Unfortunately a lot of the wiring and vacuum lines are done pretty roughly, which makes troubleshooting a bitch. In addition to this, I know the car raced last year (and it ran well), but I can't be certain whether the old owner has taken any parts (aftermarket ECU, gauges etc) off the engine to return it to stock before he sold it. He was a really nice guy, but just didn't tell me much history of the car.

I've never given it a good run, mainly because it has a straight through exhaust and is way too loud to rev or idle for too long at my house. I'm taking it in to get a muffler fitted soon, and that should make testing a lot easier

Syptoms:

It idled fine, but when you planted the accelerator, it coughed, spluttered, missed and banged at 2000+rpm. Kinda like it was running out of fuel. If you put your foot down slowly, it would rev a bit further, but still turned to crap at around 3000rpm and above. Because of the exhaust noise I didn't hold it there for long enough to see if it could pull through.

So I put a little bit of fuel in, and drove it to the fuel station (~1km return) to fill up with ultimate. I had to keep the throttle and revs very low low to keep the spluttering away, and any attempt to plant my foot made LOTS of noise and jerking/coughing/spluttering/etc. I was hoping that the run would blow some cobwebs out and that it would come good, but by the time I got it back it still didn't rev past 3000rpm, and now it also didn't want to idle (it was now warm). So I left it.

Now it idles again... just VERY low! But it still has the coughing/spluttering problem.

Without a muffler... the coughing is very loud, so I don't want to be annoying neighbours trying to fix it, and can't want to drive it to a shop in the condition it's in.

Things I've checked:

Compression - nearly spot on 170 across all cylinders. Sounds fine to me for a stock raced blacktop.

Plugs - pulled them out in the hope they were gummed up, and they were REALLY heavily sooted. Cleaned them up, ran it for another 30 seconds, and still had the problem. Pulled them out again and they were sooty again. On all accounts (sound, smell, plugs, etc) the car sounds like it is running excessively rich. Moreso than even a factory tune.

Ideas:

Fuel filter - This obviously won't make the car run so rich, but maybe it could be the cause of the spluttering. Unfortunately it looks like a Toyota specific part, not just inline filter, so probably not so easy to replace.

Vacuum leak - Possible, will have another look tonight. Especially if some aftermarket stuff was removed, and hose not reconnected etc. Wouldn't have thought it would lead to these symptoms. Could explain the slight miss in the idle though.

Faulty TPS - Dunno what affect this would have, but when I unplug it, it doesn't seem to make the engine run much differently :S

Faulty VVT solenoid - No idea on how this affects the engine, but I doubt it would have such a dramatic effect.

Wiring fault - Very probable But if there is a quicker suggestion than belling out all the wires in the hope that I find something, i'm up for it!

O2 sensor - possible, but not as likely as the other stuff to have been changed/unplugged/broken in an effort to return to stock. Also a pain to check

Overheated - for some reason the cooling fan wiring was ripped to shreds. Maybe had some after market temp switch fitted, so who knows if it has had temp issues. Comp seems alright though, so can't think of any other checks.

Hasn't got the check engine light working, and haven't looked how to check codes, so unfortunately I cant help with that info.

Any suggestions would be great

Cheers, Timbo!

[Trekka273]

It won't be the VVT solenoid, as even if that isn't working it won't do anything like that to the engine.

The TPS sensor might be a problem, as I would have thought it would make a difference if you had it unplugged while running. Perhaps it isn't working properly and the computer thinks you are on full throttle or something and is pumping in heaps of fuel. I would have thought for plugs to get dirty so quickly after being cleaned that they must be getting a LOT fo fuel in there....

Of course, the sensor might be fine and it might be the poor wiring to it. Perhaps you can test the TPS to determine if it is working correctly, and if it is, work your way back from there as a start.

[wilbo666]

MAP sensor or AFM?

Is the MAP sensor pluged in if it is MAP?

What ECU is it using?

Cheers
Wilbo

[timbosaurus]

Perhaps you can test the TPS to determine if it is working correctly, and if it is, work your way back from there as a start.

You mean, just test to see if voltage changes at the ECM when moving throttle?

I'll try that tonight. Thanks!

But I know that as soon as I start probing/tracing wires, I'll end up getting the shits and rewiring the whole lot... which means I'll probably megasquirt it... which means I'll definately miss the next track day

[timbosaurus]

It's definately a blacktop ECU, it's definately a MAP sensored engine, and it's definately got black cam covers. Didn't check the other B/T unique stuff, will do tonight

Thanks!

Timbo

[JP]

when that car was previously advertised at the higher price it was running a Motec and blueprinted motor

Now it's back with a standard AE111 20V and ECU you could check to see if any codes are being logged in the ECU (hopefully the diags terminal is wired in properly).

Also check the cam timing to make sure it's not a tooth out on one of the cams, have you checked the base timing yet?

[timbosaurus]

when that car was previously advertised at the higher price it was running a Motec and blueprinted motor

Cool, you saw it advertised? mind PMing me any past info/links on the car with it's previous setup?

I did find it hard to believe it was running the lap times it was with standard ECU, engine, suspension etc As I said, the old owner was really nice, so I'm not sure why he didn't tell me the history

Having said that, the engine didn't look swapped, just a lot of peripherals did. I'll have a closer look tonight.

Now it's back with a standard AE111 20V and ECU you could check to see if any codes are being logged in the ECU (hopefully the diags terminal is wired in properly).

This is as easy as making sure throttle is close, acc off, engine warm, and diagnostic pins are shorted... then look at the MIL?

Also check the cam timing to make sure it's not a tooth out on one of the cams, have you checked the base timing yet?

Didn't check base timing value, no, but I can rotate the dizzy from full retard to full advance, without much effect on the idle speed.... which surprised me

[timbosaurus]

Ok, so I had a bit of a play tonight.

It was late, and the car is loud, so I couldn't start and run it, so I just traced a lot of the "new" wiring and tried to work out what has been done and why.

This is the engine, and from all accounts I think it is a genuine blacktop. Haven't pulled much off to confirm though. Anyone notice anything I don't?



OK... 3 questions to see if anyone can help.

1) Can anyone recognise the 2 connectors (i'm holding one, the other is beneath the bright blue/green wires) that come out from the console? They seem to have patched a few wires between there and the ECU. (3x blue wires below) It would help if I knew what they are patched into



2) There is one black wire they have run from the IGN terminal under the steering column, into the engine bay, where is is twisted into three others which go to:
a) Into either the coil/ignitor,
b) Somewhere down near the starter, and
c) around the engine and into the loom that runs along the injectors.



I've no idea what the reason is... I will suss it out tommorow. Anyone think why?

3) Finally, I can't seem to find the Inlet air temp sensor. I'm guessing it was part of the stock inlet, and no longer present. Does anyone know if it's required? At first I thought this was the connector for it, but it doesn't bell out with the ECU pin.



Anyone got any suggestions?

Cheers,
Timbo

[ViPeR_NiPPleX]

Make sure your idle up solenoid is functioning. My dad had the same problem with his and he worked it out he left a wire out, ran it and was like factory.

[timbosaurus]

Idle up solenoid eh?

wherethefuckisthat????

[ap7]

Check your ISC valve is functioning properly. Also check there is nothing clogging the exhaust like a busted Cat converter.

[JP]

is that a single wire plug from the last photo?

Kind of looks like a knock sensor plug.

Your intake air temp sensor's sitting on top of the top transmission mount in the photo with the red highlighting.

One of the two plugs in the cabin is the 22 pin "F" plug the body loom plug from the engine loom usually plugs into. This usually contains stuff like:
-reverse light switch wires,
-water temp sender signal for dash,
-tacho from ignitor to dash,
-engine check light for dash (I think... that could go direct from the orignial 12 pins ECU plug)
-FP trigger to the circuit opening relay from the diags box,
-Vc from alternator to the charge light on dash,
-AC compressor signal,
-AC clutch signal,
-intake manifold ground

and a few others...

[timbosaurus]

Thanks JP, you're a champ!

Well, I had to drive it to get a quieter muffler put on (well, at least put a muffler on it ) and it was about a 10km drive, not through housing. So I gave it a squirt and it absolutely loved it. Came good after about 3-4kms of reving, spluttering, etc, and kept going strong.

So now the only problem is that it idles low, nearly stalling... sometimes it stalls. So I'll try all the things i've now read about idle quality (clean throttle bodies out, check caps in ECU, idle up valve, etc).

It's much easier to do that stuff and check it now that I have a muffler

The front wheel bearing are also rooted... so have to try and find whether or not the are common with any corolla's

Thanks for all your help.

[timbosaurus]

One of the two plugs in the cabin is the 22 pin "F" plug the body loom plug from the engine loom usually plugs into. This usually contains stuff like:
-reverse light switch wires,
-water temp sender signal for dash,
-tacho from ignitor to dash,
-engine check light for dash (I think... that could go direct from the orignial 12 pins ECU plug)
-FP trigger to the circuit opening relay from the diags box,
-Vc from alternator to the charge light on dash,
-AC compressor signal,
-AC clutch signal,
-intake manifold ground

and a few others...

AHUHH!!!!! Bingo!!!! That makes my next job easier!!!!

The tacho, speedo, water temp and engine check light don't work. Now I know where to look

The FP is wired seperately and it has no A/C, so that pretty much covers your list! I love you JP, yet I don't even know if you are male or female

[timbosaurus]

Oh, and all the other wiring is starting to make sense.

I've pulled a lot of crap off that obviously unused (old gauges etc) and most of the modified stuff I can account for.

They ran a single thicker wire from IGN direct to the coil IGN and direct to the injector IGN.... presumably they were worried about voltage drop.

Some wires they have patched in to join the body harness to engine harnes... yet to work out what they are. Probably the wires JP mentioned above.

So all in all, car is coming good!

Thanks guys!