i have a 1992 mustang that use to be a 4cyl but is now a v8. i have now made it fuel injected, i got a wiring harness out of a 93 gt along with intake. now i have it running but when it idles it lik surges between 750- 500 rpm and when i drive i if im jus cruising once i get the motor under a little bit of a load and the motors at lik 1500 rpm it starts surging and it just doesnt seem right, now i ran some codes on it and these are what came up 67,81,82,85,84 ive already put a new mass airflow sensor on it along with to new o2 sensors and a throttle position sensor and a idle valve assembly thing ive checked all the vacuum lines and have most capped off and others hooked up if i know they need it. i thought it was the egr so i made a plate to delete it today and it didnt help at all it may have actualy made it a lil worse so i think im going to put it back on. i dont know if theres something i could have forgotten or if a sensor is bad or a injector could be messing up or if it could jus be timing. it starts just fine and runs great if ur on the gas or even jus above 1500 but it seems lik once u get below that it starts surging and staying steady. please help im at my witts end and tired of throwing money at it.

 

Go to Joel 5.0 and follow the test proceedures. Ck fuel press.Do all 3 cyl bal tests. Post results.

 

fuel pressure is fine brand new pump lines and all

 

Doesn't mean you didn't get a defective pump or something. It's free t rule that out before you dump money into it to find out its a factory messed up part. It happens.

 

did youi put a FP gauge on it and check or are you assuming that a new pump=good pressure? I had the small hose from the pick up to the pump body come loose and it was enough to cause your symptoms. The Joel checklist is a fantastic trouble shooting tool as noted in another post.