Looking for a Fix

[BlownAway]

My S/C'd 95 GSR has been running like crap and I just can't find the problem. I have varing amounts of hesitation at partial throttle - between 10 inHg vac to 0. Sometimes feels like the ignition just shut off for a moment. I've just installed pressure gages and A/F ratio gage.
The fuel pressure acts as I would expect as normal: steady 52 psi with full vac to 0, rising to almost 100 at full boost (6psi). Spark plugs don't look too bad, tried a new set last night but no help.
The readings on the Autometer A/F gage are really bizzare. I now see what the previous A/F gage posts were all about.
I was able to induce the hesitation on a long uphill stretch. Holding at about 5 inHg vac. fuel was at 52 psi and then it started. My A/F gauge which had calmed to the 1:00 oclock position during this time, fell to 0 (7 oclock - full lean) for an instant and the hesitation occured. It cycled off and on but the car still pulled up the hill.

Full boost performance seems unaffected - but so does the idle.

Any suggestions? Is this a stuck injector?

[Holden]

From what you wrote, your fuel pressure is staying constant at 52psi from full vacuum to 0 vacuum. If this is true, it's a problem and probably explains your symptoms.

Fuel pressure should increase 10-15psi between full vacuum and 0 vacuum. Most of this increase takes place between 10" vacuum and 0 vacuum. (i.e. 22" vac to 10" vac should see little or no rise in FP).

The OE FPR is mainly responsible for raising FP as vacuum dissapears. Did you remove your OE FPR? Is its' vacuum line blocked? JR told me they have seem cases where the loctite used on the vacuum fitting into the manifold created a "flap" that could block the fitting intermittantly.

To test for that, swap vacuum lines between the OE FPR and the RR FPR (swap which fittings they plug onto). If there's a blockage in one fitting, I'd expect non-boost performance to improve and on-boost performance to degrade. Be carefull boosting like that.

The JR or Cartech or whatever Rising Rate FPR controls FP during boost conditions. Since you say things work well under boost, the RR FPR is probably not the problem. This also rules out the injectors and fuel pump as suspects.

(The RR FPR could still be a problem. Check the FP at idle with the vacuum line to the RR FPR disconnected and plugged up. You should see a 10-15psi jump.)

Good luck,

Greg

[This message has been edited by Holden (edited September 06, 2000).]

[BlownAway]

Thanks for the suggestions. I checked out a few things at lunch. FP is 52 @ idle, ~59 with vac (stock FPReg) disconnected and plugged. Same with JR FPR disconnected and plugged. No change with manifold nipples swapped. I did notice an surge when gently increasing from about 5 vac to 2 boost when the 1 psi relay kicks in. This makes me think maybe the @0 vac/boost pressure is too low. The A/F meter is still bouncing below 2 psi. - hard to make anything of it. It does stabilize above 2 psi though.
You had posted earlier that your're at 65psi @ 0 vac. I'll try increasing to that setting next.

[randomwalk101]

Here is the fuel pressure JRcivic recommended to me..

GSR @ 6 psi (vaccum ON/OFF)

warm idle: 60/48 psi
typical cruise: --/48-50 psi
WOT: --/92-96 psi

[Holden]

I'm a bit higher at idle and cruise than those settings recommended by JRCivic. I can't get the idle pressure that low without lowering the max pressure too much. This is with a Cartech with the bleeder fully closed.

I'm at 51psi idle, 55 cruise, 65 with no vac, 94 max.

BUT... you won't be able to do this with a JR FPR. They behave differently.

With a JR, you want to get 65psi with vacuum to the OE FPR but no vacuum to the JR FPR.

59psi sounds too low to me, but my car has always run lean.

Greg

[JRCivic]

Keep in mind that the numbers (those quoted by me from 101) that you have referred to above are "General" settings to get you well in the ball park... there is still some tuning one way or the other here to be perfect in your particular car/climate/driver. Make small adjustments and drive the car a while. This will help you tune in properly.


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'93 Civic Si H/B with B18C1, JRSC @ 8psi
Best 1320: 12.68 at 110 mph

[BlownAway]

Boy, JRCivics the night owl. Does he ever sleep?
The increase in 0 vac to 65 psi from 59 has helped a lot. I'll try bumping it up a little more to see if the hesitation can completely go away. The butt dyno has noticed an improvement too.
I keep wondering if I can trust my bouncing A/F gage to make any tuning decisions. For now, I guess if the gage bounces to the first green LED, the fuel pressure is high enough.

[Holden]

Don't worry about the A/F when it's bouncing.

What's important is when you're at WOT. It should be 2-3 LED's into the green and not moving.

Greg

[JRCivic]

I am glad to hear that the fuel pressure changes were an improvement. Keep on tuning !!!


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'93 Civic Si H/B with B18C1, JRSC @ 8psi
Best 1320: 12.68 at 110 mph