Idles, but stumbles/"bounces" @ 2300 RPM

[kevtar658]

Well, I got it adjusted where it idles pretty happily around 900 rpm. I put in a boost gauge as well and I'm getting a steady 16 in. vac @ idle. The problem is when I try to rev it up either slowly or quickly (more so slowly) it seems to hit a wall around 2300 rpm and bounce right off of it. If I rev slow it will just bounce off of this spot and keep bouncing, if I rev it faster/harder it is able to get past but it still bogs. Is this the lean tip in described in previous post?
I have not done any adjustments to the PC Pro at this point.
Any help is appreciated.
KT

[bogey]

Here are my thoughts...

It could be a BIG vacuum leak. But I doubt it would idle well.

Could be the MAF. Did you check the wiring when you extended the harness? What kind of connections did you use? Solder? Crimp? Twist and tape?

Is the TPS plugged in?

Otherwise, it sounds like its not getting fuel. But it would have to really be low not to rev over 2300rpm. I had an open FPR but it would rev to redline. Have you ever checked fuel pressure?

I assume when you are revving, you are not getting into boost at all. So the PCPro should not be active at all.

Do you get a Check Engine Light? That could point the way...

[bogey]

Well, I got it adjusted where it idles pretty happily around 900 rpm. KT

Realistically, I don't think you should have any real adjustments to get it to idle. If there was significant problems with idle, I would lean towards the MAF as the problem.

[kevtar658]

Bogey, I went out this morning and started it, again started right up and idled. (When I say adjusted the idle I gave it a half turn or so on the idle screw.)
I turned it back off and unhook the MAF (I soldered all my connections by the way) and tried to start it again, much harder to start and I immediatly got a check engine light. Plugged MAF back in and it started back up "normal" the CEL was out and it was idling semi happily.
I'll also note that prior to the install I would occasionally get what I've heard called the idle droop where the engine would idle down real low when coming to a stop but never stall and pick back up.
I revved it a little and when revving slowly I still run into the "bounce" at about 2300 when revved it hard it pulls right to redline with no trouble.
I appreciate all your help so far. I'm going to put the belly pan back on get it on the ground and try to drive it a little today and see what I get.
Thanks.
KT

[kevtar658]

Went out and drove it, holy cow it's fast! I didn't hear any abnormal noises coming from the engine either (ie. detonation). Bu the transition to boost is extremely rough. Your either on boost or your not driving.
The boost gage is giving me 8-9 lbs boost around 5500, I didn't dare go more than that because I didn't have room or no the mixture yet. The A/F ration gage is going on real soon.

Any thoughts on the rough transition to boost?
Thanks,
KT

[Tom @ Fast Forward]

16" vacuum at idle sounds like a vacuum leak. There is no such thing as a small leak when it comes to driveability.

When you drive the car, have someone watch the PC-Pros and tell me what the lights are doing. The blue light comes on bot cards when the card sees boost. The other lights come on the main card to represent RPM. 1 light 0-1000, 2 lights 1000-2000, 3 lights 2000-3000, etc. The E-Cool shows lights at boost. 1 light 0-2 PSI, 2 lights 2-4PSI, 3 lights 4-6 PSI, etc. Does it always happen at 2300RPM? Or always when you tip in the pedal?

[kevtar658]

Ok, watched the cards:

I'm getting Blue lights on both at boost.
I am getting the tach readings on the main unit, but only under load
I am getting a boost reading on the second one but I didn't see it hit more than 3 lights.
I'm not seeing more than 7-8 lbs of boost on the boost gauge.
When idling it reads between 16-17 in. vac, when revved it drops to 0 when the gas pedal is depressed then jumps back to 20 when the pedal is released before settling back into an idle at 16.5ish in.

It is especially bad in the 1800-2500 rpm range when tipping into the throttle.
It's there but less noticeable above that ie. on the gas at 4000, off the gas then back on at 3800 not nearly as bad.

And one other question, would it hurt anything to move the brass pulley on the throttle cable bracket towards the front of the car by drilling a new hole in the bracket, to help increase the throttle cable tension? I can't move the bracket any farther towards the front of the car, it hits the bypass.
Thanks,
KT

[bogey]

Places to look for vacuum leaks...

I found I made a mistake when I installed the flexible throttle tube. I rolled the ends in to make a nice clean edge where it attached to the TB and MAF. It was only leaking slightly, but enough to cause lean conditions.

Check that the boost line has a good seal all the way from the manifold to the boost gauge and PCPros. The hard tubing can leak if it is not installed correctly. I had a slight leak where the hard line went in the manifold.

Did you install the intake manifold gasket off the old manifold?

[kevtar658]

I did use the intake manifold gasket.
Tomorrow I'll go through more of the vacuum lines.
Thanks.
KT

[kevtar658]

Well I went over the intact tube with a fine tooth comb and tightened it all up, as well as the vac line for the pc pros. I also clamped a few other questionable lines, but to no avail.
I'll keep digging but any other ideas are appreciated.

KT

[bogey]

Did you adjust the TPS properly?

If it is set to far off, the throttle plate is partially open, and then the computer dumps too much fuel, causing a jerky transition to boost.

[kevtar658]

Well, I went back over my TPS and that seems to have fixed it. It's very smooth in and out of boost now and seems to be running really well. I've picked up a little bit of vacuum, closer to 18 in. now, and I'm running about 8 lbs boost @ 5500 rpm.
Thans for the help!
KT

[kevtar658]

I did throw a CEL when I went out and drove it though, it reset right away when I got back and shut down/restarted but it concerns me a little bit.
How rich or lean are the original adjustments in the PC-Pros on arrival?
KT

[bogey]

Well, I went back over my TPS and that seems to have fixed it. It's very smooth in and out of boost now and seems to be running really well. I've picked up a little bit of vacuum, closer to 18 in. now, and I'm running about 8 lbs boost @ 5500 rpm.
Thans for the help!
KT

Glad to help.

[bogey]

I did throw a CEL when I went out and drove it though, it reset right away when I got back and shut down/restarted but it concerns me a little bit.
How rich or lean are the original adjustments in the PC-Pros on arrival?
KT

Can you read the CEL code?

[kevtar658]

No, I don't have a code reader. Is this something that I could get on the cheap, or even borrow from an autozone?

I also got the A/F ratio gauge in and drove it again last night. It's only a narrow band but it was showing full rich under boost, and with a passenger to watch the lights I was getting 4 lights of boost on the PC-Pro, with a short peak of 5 lights at full boost.

[Tom @ Fast Forward]

I think you have a vacuum/pressure leak. The lights are showing about 8PSI right at 7000 RPM (5th light just turning on). The 5th light should be on sooner.

[bogey]

I thought the lights were RPM indicators, not boost.

[Tom @ Fast Forward]

RPM on the main card. Boost on the E-Cool. There were a couple sets that got out early on set to show RPM on both but only a few.