EFI TROUBLE! ED W. All Cooters, Help!!

[Ed Wright]

I would be surprised if it's an EFI problem.
What system do you have?
Using a data logger?

[Bill Bogues]

I'd check the rubber brake line hose at the rear end housing.I've had 2 that all of a sudden would let fluid through under pressure but internally had collapsed and wouldn't let the pressure release. Same symptoms on our car as yours.Hope you get it fixed fast without a lot of trouble.

[Alan Roehrich]

Compare incrementals and see where you are off.

If your A/F ratio and RPM are the same, odds are your timing is as well.

If your RPM is the same, but your MPH is low..................

The humidity is 22% higher on the slower pass.

What change did you make with the oil (and filter)?

[J.R. Haddad]

Incrementals- 60- 1.48-1.53
594-6.75-6.92
660-7.24-7.42
1000-9.55-9.79
1320-11.52-11.82
The 330's were not working either day. Thanks so far guys, J.R.

[J.R. Haddad]

Alan, oil was Mobil 5-30 and stock filter G.M. A.C. Delco before and after,
no changes on either. I try not to introduce any variables unless I'm at
the track while I'm sorting out this new to me combo. J.R. Ed, Datalogger
is an Accel Gen.7. I am able to download it, but cannot get graphs
lately. J.R.

[Pedigo Perf]

Did you measure the amount of oil you drained out? Maybe it is carrying more now,

If it has the same RPM but lost 8 MPH then it about has to be in the converter.

[Mike Pearson]

I would shy away from any AC Delco filters. I had several collapse due to plastic internals. Cost me an engine. Check the filter it could be collapsed. Now I run a System One reusable filter. No more passenger car filters or oil.

[ALMACK]

Originally Posted by Pedigo Perf

Did you measure the amount of oil you drained out? Maybe it is carrying more now,

If it has the same RPM but lost 8 MPH then it about has to be in the converter.

^^ That 8 mph difference is what stood out to me.

[D.Johns]

I've seen where a two-step would intermittently come off and on during a run as the car vibrations made the switch connections. Picked it up on the data logger for the ECU.

Also seen where the O2 sensor has went bad threw the computer into safe mode since when the sensor fails it fails lean.

Check TPS and throttle opening 100% physically.

Could be a valve hanging open at the top of the rev range or ring flutter also.

Lots of possibilities just have to start the process of elimination with any data you have.

[Bobby Fazio]

Originally Posted by J.R. Haddad

Alan, oil was Mobil 5-30 and stock filter G.M. A.C. Delco before and after,
no changes on either. I try not to introduce any variables unless I'm at
the track while I'm sorting out this new to me combo. J.R. Ed, Datalogger
is an Accel Gen.7. I am able to download it, but cannot get graphs
lately. J.R.

Email me your downloaded runs and I can try to graph them for you and also look to see if anything is funky between a good run and bad run. Bobby.fazio@gmail.com Also make sure no tunes were uploaded in between or anything else was changed. Check your timing on the wheel vs what the computer reads to make sure they are on same page.