The Car:

1988 Firebird Formula 350, auto. High output fuel pump. AFPR. (48lbs.) TBAF. MSD 6A smart box, MSD Blaster 2 coil. K&N air filter. New dist. cap, wires, plugs, fuel filter, egr valve and solenoid, replaced distributor with used part. also used MAF sensor.

The problem.....

Occasionally, after the car warms up, the car will hesitate off idle, be low on power, and generally very sluggish. Stepping on the gas has NO effect whatsoever. This will also occur at cruise, when trying to accelerate to pass, for instance. The engine will just bog out, and not quite die. This is not as noticeable with a full tank of gas.......

also, the car is occasionally VERY hard to start.....

What I have done......

Well, the tune-up helped some, the distributor helped some more, cleaning the grounds for the ECM at the back of the drivers side head helped alot. but the problem still persists. I am not getting any codes, fixed the vacuum leaks when I replaced the egr valve, all connectors are tight, all sensors appear to be working. (i do have a scan tool available to me) At this point, I am at a loss as to what to look for next. Any help would be greatly appreciated.

Thanks in advance

Brian

 

It could possibly be the isolator(pulsator) connecton on the in tank fuel pump. Reason I say this is because of the statement you made about a full tank of gas. The way that the pumps mounts in the tank w/o any type of clamps or compression fittings is crap. I just replaced a burnt out pump and I have no FP. All I can think is that it is the connection in the tank or a bunk pump.

I would wait to see if anyone else has a similar problem since it's such a PITA to get to the tank.

Or maybe just a clogged fuel filter?

I would get a hold of a fuel pressure gauge to see if the pressure is falling off when this is happening.

I also have heard hard starts are caused by bad FP relays. Cheap thing to try first. Also, you could check to make sure that you are getting 12V to the pump. Pull up the carpet at the back seat and test the voltage over the tan and black wires.

Just my .02 Hope it helps.
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Michael Graeber

My Garage

1)83 Z-28 T-Top: Full cage, 9" w/ lad.bars, Midwest Engine Tech 406sbc,Strip Dominator, Demon Carb, Phase VI Chevy Bowtie heads, .630" Crower roller set-up, 1 3/4 coated Hookers 3" true dual exhaust th400, fuel cell & still not running

2)89 Formula WS-6 305 TPI Auto For the road: minor motor, more suspension stuff. MODS

[This message has been edited by graebz28 (edited September 26, 2000).]

[This message has been edited by graebz28 (edited September 26, 2000).]

 

I think you have to much fuel pressure!
Try turning down on the AFPR to 40-42 psi.
I had similar problems and that worked for me. Mike

 

Is that fuel pressure (48lbs) checked with the vacuum connected or disconnected? And if that is disconnected, did you plug the vacuum line? Makes a big difference....

And the best bet for fuel pressure is to have a gauge with enough hose so you can tape it to the window. (yes, it looks silly driving down the road, but it is better than not knowing)

Drive the car while your friend checks on the the fuel pressure at part-throttle and Wide Open Throttle...

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Sportsman II 72 CC heads, Pete Jackson gear drive, Performance Resources chip, Edelbrock 1 5/8" headers and Edelbrock cat back exhaust, hi-flow cats, Trans-go stage 3 shift kit, Vigilante 9.5" 2800 stall convertor, SLP cold air induction, SLP roller camshaft, 24lb ADS injectors, AFPR, 3.45 rear end gears, and other goodies...

http://members.aol.com/jwnolte/raven.htm

 

I was having similiar problems; the car was driving me nucking futs!

I tested, checked, reconditioned, replaced ignition pieces, with only minor improvements.

I acquired a snap on scan tool from a friend and discovered I was lean at WOT (about 700mv) about 150mv below the ideal norm for WOT. I used propane to check for intake leaks, there were none. Fuel pressure was weak, past 3500 RPMS.

Since the original fuel pump was extremely noisy and millions of miles old I decided to replaced it with a walbro 255lph pump.

the pump cured the ills, and resolved the dilemma, the car felt like it picked up 100hp literally. You should check your pump regardless if it is new to make sure it is functioning properly.

Make sure your TPS refernce voltage is in range, that will also create those symptoms.

[This message has been edited by blak92! (edited September 27, 2000).]

 

that described my car to a t. i replaced the magnetic pickup coil, ignition control mod.. to a slight help. i checked the timeing and it was dancing in rythem with the rattle of my timing chain. i replaced that have a base of 8 deg BTDC and a new fuel pump relay and it cured about 60% of the problem, the past week o so it fires right up acaisionaly it has a long start i did this w/ 117k on it

-Stell

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1988 IROC 305TPI MINT!!
Mods= Accell SuperCoil, MSD 6A, Ported Plenum, No MAF Screans , K & N, 160 Thermostat+ Temp Switch
And Always Trying To Go Faster

 

Thanks for the help, I will have to get my pressure gauge out, and see what is happening. (something I have been meaning to do, just did not have the time.....) The FP relay has already been replaced, did not help, bummer, Fuel pressure was set with vacuum line disconnected from regulator, and plugged (the line). I REALLY do not look forward to dropping the tank again...... whatta nightmare......

 

That is my car also, didn't 1LE have a different fuel pumps though? I am getting a AFPR soon, that may help some. How do you set/check your TPS?

 

Could be a bad ignition coil. They tend to act up after they get hot. They show a good spark at idle and low rpms, but at higher rpms and/or under load they short the voltage internally to ground and engine dies, you let off the gas pedal and it continues to run. It could also be the MSD unit itself. Just plug a stock coil into the factory harness to bypass the MSD and blaster coil.