Over 3500rmp or even when you give it hard acceleration the car bogs down shutters and hesitates.
Back firing and a rreally low grumble sound to it.
Also around 5500rpm (when vtec engages) if it engages which sometimes it wont its really lagish and pretty much well goes no where?
Any ideas as to what can xause this or maybe whrre to start looking

 

what ecu are you running, what car is it in? im assumming your running it as obd1? more details

 

Running a p30 ecu,
Its a b16a2 in a 94 honda civic.
And not sure what you mean obd1?

 

The revs are fluctuating between 3500rpm and 5500rpm.
If you give it easy gas and hit 5500rpm vtec engages but has no power if that makes sense.
But if you give it hard gas it will fluctuate and hesitate and splutter :/

 

It was fine today hittting vtec with power no lag no bogging no back fire then i put fuel in it about half a tank worth and about 20 minutes after that noticed it was running really boggish then started doing as i explained earlier comment. I was thinking contaminated fuel but rang the fuel station i bought from and no other complaints on bad fuel today so not sure weather or not it could be that?

 

And im pretty sure its obd1 it only has 1 02 sensor before the catalactic converter not another one after the catalactic converter.

 

iacv wiring. your welcome

 

Sorry what do you mean?

 

Post all CEL codes.

And, in the future, create thread titles that summarize the tech problem - edited.

 

No codes. Put injector cleaner through this morning but still doing it.