Hesitation from 2nd turbo on auto kickdown

I think this question has been asked before, but here goes.

When I'm accelerating through normal L, 2, D and overdrive, there is no problem, and it's as incredibly quick as always, but when I'm at speed and the auto box kicks down to get the revs ready for boosting, turbo 2 seems to hesitate a little before giving me full power.

It's slowly getting worse over time, and has done it for about a year now, and I've had the plugs changed for iridiums within this time too.

It sounds like a boost leak, almost a rumbling breathy stutter, almost farty!

Anyone got any ideas?

Anyone?

I had similar issues on mine, It turned out that it was the wastegate actuator had a slight leak so it was delaying it and causing the boost leak.

I would check for boost leaks. I cant see there being damage to the turbo itself as the number 1 turbos are normally the ones that take most of the abuse and tend to fail.

Thanks for that. It definitely happens in the transition from one to both turbos (4-5k revs).

Can the wastegate actuator be cleaned, or are they just replaced?

I had something similar, turned out to be a split hose, one of the ones near the bulkhead, think it went to the EGV actuator but not exactly sure... Anyway check the hoses that connect the pipework behind the head to the valves/actuators

Fixed.

It was a small amount of oil leaking from the top engine gaskets into the 6th cylinder plug 'hole', and was causing a slight misfire.

I now need some new gaskets.

Does anyone know what they are called exactly, or a part number, and where I can get them from? For a 1993 J-spec TT.

I've had my rocker gasket leaking for a while right into the 6th plug. while I was changing to iridiums over the weekend, checked the rocker cover nuts and they were 'all' finger tight torqued em up and all sorted . possibly worth a look

As for part numbers, not sure, there were some for sale in this thread

http://www.mkivsupra.net/vbb/showthread.php?t=228930

but as usual the for sale ad gets edited to completely remove the part number and pics/price. Now that gets my goat . not that the for sale ad would help but poss pm 'little num' for the part number

I will certainly do that too. Thanks

Nope, that didn't fix it, only temporarily shielded the problem. I've since had the rocker gaskets replaced, and now think it's a boost leak somewhere around the operation of the second turbo.

I may just get the garage to replace all the vacuum hoses, and see form there.

Unless anyone can think of another solution?

This may be something similar to the issue I have had previously. I'll describe my symptoms and you can decide...

Pootling along in 6th and someone fancies a play behind me. I drop it into 3rd and floor it, revs instantly jump to 5k and I'm holding on expecting the rush of boost and I get nothing. I let off the accelerator and mash it down again only to be greeted with the rush of full boost.

This would happen more often than not when doing the above. It turned out to be a faulty VSV. It was the one at the bulk head that points upwards to the bonnet. I think it's the IACV VSV? Anyway, replaced that and the vac lines roundabout it.... not had an issue since

It's not like that, as if I keep my foot down it goes back to normal after a few burps and farts, but it's always around 4-5k revs, so within the transition area.

It's unnerving, as when you may need that extra boost, I don't know if it's going to fail completely, or not.

Revving the engine freely doesn't have any issues, so must be a boost issue.

Obvious one but are your coil pack clips all in good order? Did you give your plugs a clean when you had the oil issue?

I assume the garage checked the coil packs, and I do know they cleaned the whole area after sorting the gaskets, etc.

I'll ask when I speak to them. Could it be a voltage thing then, as it feels boost-like, not from normal engine behaviour.

I assume the garage checked the coil packs, and I do know they cleaned the whole area after sorting the gaskets, etc.

 

I'll ask when I speak to them. Could it be a voltage thing then, as it feels boost-like, not from normal engine behaviour.

It sounds like a misfire to be honest. Without actually experiencing it, it is hard to judge though. The coil pack clips go VERY brittle with age. Removing them from the coilpack can kill them off very easily. They are notorious for causing misfires in the Supras.

What you're saying is sounding more and more likely the issue, as I originally thought it was a misfire, but I'll ask at the garage when I go there this afternoon.

They weren't sure, as when they revved the engine, there was no apparent problem, pointing to boost, etc.

Revving the engine will only diagnose a clear cut misfire. I've heard of people having issues above xbar of boost, but having no issues under that levels. It's generally caused by a weak spark, when the coil pack clip has degraded the spark will either not be there (easy to diagnose) or be weak (not so easy). With the weak spark I'm guessing it doesn't ignite the high concentrated mix under load... hence why you get a misfire under load but not under none.

They generally dont missfire when not underload. And just incase check the vac hoses at the back of the engine, I had a similar thing, 2nd turbo slow to come online, turned out to be cracked vac hose.

Revving the engine will only diagnose a clear cut misfire. I've heard of people having issues above xbar of boost, but having no issues under that levels. It's generally caused by a weak spark, when the coil pack clip has degraded the spark will either not be there (easy to diagnose) or be weak (not so easy). With the weak spark I'm guessing it doesn't ignite the high concentrated mix under load... hence why you get a misfire under load but not under none.

Indeed. Another thing to check.

They generally dont missfire when not underload. And just incase check the vac hoses at the back of the engine, I had a similar thing, 2nd turbo slow to come online, turned out to be cracked vac hose.

Ok. Will do.

Do you know what heat range the plugs are? The wrong plugs can also cause misfire/hesitation at higher boost levels.

Problem solved - Fuel.

Because of financial constraints I decided to start using 95 RON fuel around 10 months ago, and not long after that time I started getting the hesitation. I've now been through two tanks of Tesco 99, and it's driving brilliantly again as before.

The moral of this story is, if you have a JSpec TT, then don't scrimp on lesser fuels. It's more economical now too.

Problem solved - Fuel.

 

Because of financial constraints I decided to start using 95 RON fuel around 10 months ago, and not long after that time I started getting the hesitation. I've now been through two tanks of Tesco 99, and it's driving brilliantly again as before.

 

The moral of this story is, if you have a JSpec TT, then don't scrimp on lesser fuels. It's more economical now too.

Slap yourself.... hard

Funnily enough, I still had a slight problem ongoing since that last update.

I've already mentioned in the definitive battery thread that the live terminal didn't fit properly, and since I've had that sorted, I get no hesitation or anything anymore. Could it've been a voltage issue, ie. not being able to draw more power from the battery, or am I imagining things?!

Funnily enough, I still had a slight problem ongoing since that last update.

 

I've already mentioned in the definitive battery thread that the live terminal didn't fit properly, and since I've had that sorted, I get no hesitation or anything anymore. Could it've been a voltage issue, ie. not being able to draw more power from the battery, or am I imagining things?!

It's very possible that the intermittent contact was causing the ignition issues.

Was the terminal the wrong size

Possibly, but I put a little strip of metal in the clamp against the terminal, so now it pinches it perfectly, and is very tight.

I've booted it a few times from various revs and gears, and it's not hesitating at all now. It came as a pleasant surprise, as I was only trying to fix the terminal issue.

so what was the problem in the end