Mindspin311

Ok here is my situation: As of now, my car has no power, whenever I get on the gas, the car will build boost, hold boost perfectly but go nowhere. The hesitation usually occurs between 3000 and 3500 rpm. Also sometimes when first starting off, the car will bog really hard, the randomly kick up and drive off just fine.

Here is a list of things Ive done to the car lately to help everyone figure this out:

1. replaced old and busted TPS with a new one, then proceeded to drive home 425mi to Atlanta from VA.
2. Removed intercooler and adjusted TPS to spec (1k ohm) the morning after driving home. Car idles smoothly between 730-780.
3. Replaced the RB silencer section with a 3" catco cat and 3" piping. Along with this I installed an electric airpump via a relay and ran heater hose from the pump into the air tube on the cat.
4. While attempting to pass emissions, I drove around for about 30 mins fiddling with my SAFC trying to lean out the lower RPMs, in the end I returned the SAFC to +/- 0 across the board, this is how it rests now.

This is where it gets interesting, I went out to get gas and paid in cash. Upon leaving the building I saw that the heater hose had somehow come off the air tube on the cat. I popped the hood to see a small amount of smoke, it seems when the tube came loose it dropped down on to the turbo. I immediately pulled it out, and there was a big melted secition about 5" long.

Once this happened I started to notice the hesitation when boosting. I contined to drive to Home Depot and as I tried to merge I gave it about 50% throttle and proceeded to go nowhere, the car sounded like it was going fast, it just wasnt.

At first I thought it was because I had no hose on the airtube. So this morning I proceeded to put the silencer back in and take the car for a drive, nothing had changed at all, still the same hesitation. At this point I also have noticed that there is a lot of back pressure coming from the exhaust, more than I can remember from the past.

I talked to a friend and he mentioned something about a 3rd port opening in the throttle body that is vacuum activated, im going to pull the IC back off tomorrow to make sure I didnt miss or accidently pull off a hose.

Beyond this hesitation, the car runs fine, idles fine and smoothlty, its just when I try to get on the power that the car falls on its face.


So thats my situation, if anyone has any insight please let me know, I am supposed to drive back to VA for summer classes that start Monday and I really dont want to limp the car all the way back

ilike2eatricers

Maybe you melted your cat and/or it blew up and has pieces logged in other parts of your exhaust and it's blocking exhaust flow?

EDIT: did you check the condition of your cat?

311unity13B

no, his exhaust flow seems fine

Mindspin311

When I took the cat off it appeared to be in one piece and nothing seemed out of place or missing.

Whizbang

how do you know?

Mindspin311

I was just at his house 45 mins ago

Mindspin311

The flow seems fine, maybe even more than I was aware of before.

Whizbang

hmm....could your leaning out attempts be part of it?

Mindspin311

I thought about it at first, but Ive since returned the SAFC to zero, as it was before all of this happened. Unless I inadvertently did something to the SAFC that I didnt realize.

Whizbang

because the ECU might not be compensating for the rise in boost. or it might be and the SAFC is telling it othewise.

Mindspin311

Do you know how to "reset" or properly set up the SAFC for the FC? I really have no knowledge of it other than how to get into there you can adjust fuel and stuff.

Mindspin311

I almost forgot to mention that I also rewired the O2 sensor, I now have it spliced directly into the ECU, right side connectort, top row, 2nd from the right. Although I believe I am still getting an O2 sensor CEL. Could the sensor be totally shot which would cause a mis-delievery of fuel at increased load?

Ocelot

Just cut the O2 sensor line and see if anything changes. The sensor/wiring could still be screwed up causing the CEL, but if you wired it up wrong then the problem should go away.

Mindspin311

up

DMClark

So that's what WTFcar means.

Mindspin311

Alright so I changed the O2 sensor back to the original line, still the same problem

Wankel7

You check compression?

Also, have you checked to see if the ignition is advancing with a timing light?

Whizbang

well seeing a motor needs five things to run; air, fuel, timing, spark and compression. check each system individually. seeing at least your car is running, this is much easier of a process to complete. first do timing. then check fuel pressure. then go through the compression just to check. then comes air flow. ie vac leaks, etc. doesnt sound like this is a ECU related event. seeing the pipe coming off is the turning point for this car, focus around that. why did it fall off. hmm...it is possible that your cats are infact clogged. you will get exhaust flow, but under higher rpm loads, (when boost comes into play) the effects of any clogging will be amplified.

Mindspin311

The cat is no longer on the car, I have put the silencer back in, which is a straight pipe. It doesnt feel like the exhaust is clogged as there is plenty of exhaust gasses coming out. I do no t have access to a timing light or a compression tool. How can I check fuel pressure?

Mindspin311

And I can still get the car past 3500rpm, is timing still a possibility?

Mindspin311

Any possibility that it could be the secondary throttle plates not opening?

Wankel7

Yes, check that!

Mindspin311

Well I took the IC off and found a loose vac hose. It is supposed to be connected to some little device coming off the rear of the TB, it appears to be plastic as the nipple that the vac line connects to is plastic. This plastic nipple has since broke and is leaving the line laying there. With more driving I have found out the car hesitates whenever it us under positive boost, when pulling vac it is fine, the minute the car reaches positive boost, it falls on its face. I dont have a camera handy so I cant get a picture.

Wankel7

So, did you check the throttle plates?

Mindspin311

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/possible-secondary-throttle-plate-malfunction-427508/

Read that