Strange reving patterns... please help??

[Guest mitch2jz]

Hi all,

 

I have a 6spd JDM VVTI 98 running in TTC mode. She's all pretty stock with the exception of FMIC, EVC-s boost controller, pod filter and exhaust with 2nd cat delete.

Have never had any issues with the car since purchase however as of recent I'm experiencing these issues and I cannot seem to diagnose the problem..

 

After driving for about 20mins and engine is at normal operating temps the car will do either TWO of the following things..

 

1. Engine revs drop and I have loss of all power. Can roll along in first but cannot get any rpm above 1k. (No engine check lights present) OR

 

2. I will be sitting in neutral and the engine will automatically rev all by itself up to about 5K at which point I turn the car off (check light present). If I try to start it straight away she revs straight up to redline again. After waiting 20 - 30mins to let engine cool it will start and idle normally but then either 1 or 2 happens again within 5mins of driving.

 

 

I've done all the following checks and found no issues.

Fuel pump check

MAF sensor check

Paperclip bridge engine code check

 

 

Some are suggesting a possible leak and that would make sense for the low revs and loss of power but not for the redline revs. Car was boosting fine before all these issues and still seems to boost up until the problems start.

 

Can anyone possibly tell me what could be causing this behavior... Totally lost..

Cheers,

Edited October 26, 2014 by mitch2jz (see edit history)

[rider]

An air leak on the inlet side that could be fluctuating the mixture? I'd check all the coupling are firmly secured and hose in ear listen over for any sucking sounds. Reset on the ECUs by disconnecting the battery.

 

Unless its you on the right foot you'd imagine it has to be mixture or ECU related.

[SupraLEDrears]

My ECU died causing revving problems. They were not similar to yours but worth a test because I spent a whole week on my car tinkering about hours on end for nothing. Reset the ECU first like rider said and go from there.

[Ian C]

That really smells like a problem with the DBW throttle body, they are a bit of a nightmare unfortunately. Have a search on here, some people have sorted strange behaviour with dissembly and cleaning, others had to buy a whole new throttle body in the end

[Chris Wilson]

DBW has gone into limp home mode, the two potentiometers on each end of the system have to

tally exactly, as a safety and sanity check. One will be giving no, or a corrupted signal. Fixable, but not for the feint hearted, and could be costly.