Help!!!
87 Camaro 305 Tpi.
Daily driver, no other car :-(

Problem started several months ago when stuck in a traffic jam, idled fine, but on pulling forward in traffic it started to stumble, which went away when I opened throttle more. This disappeared when I got out of the traffic. Car ran fine for several weeks after.

Stuck in a 2 hour jam then, problem the same but worse due to severity of the jam, but was fine later in day on return journey, and no problems for several weeks since.

Recently it started to play up more in shorter jams, same thing. Then it progressed to ‘stumbling’ at small throttle openings on the motorway (after a big jam), and then started to ‘stumble’ as I went over big bumps in the road.

This then developed to the car stalling over smaller bumps in road (or running very poorly – 400rpm & picking up again) or stalling when pulling away from standstill.

It has now got so bad that it dies over almost any bump or when selecting drive. It will only be a problem when the engine is warm, from cold (mornings) it will run fine for the first 10 mins, then play up. Less if later in the day.

It will usually re-start immediately with no problems??
No trouble codes are being stored.
It will idle absolutely fine, and rev fine, but die under load/bumps.

It now does not always re-start (but usually does), battery seems to drain fast (too fast?) under continued cranking but has good voltage.

I have checked all that I know/can as listed below.

New dizzy cap & rotor & coil.
Checked fuel pressure – 38Psi at cranking, 45 Psi at idle, jumps to 60 Psi after it stalls.
Checked all connections on loom (that I can see).
Wiggled all wires that I can see.
Checked charging system, 12.5v at rest, 14.7v at idle, 13.6v with heated rear window & headlamps on at idle.
Checked for 12v at coil when stumbling or cutting out, it has voltage.
Checked magnetic pickups in dizzy, all seem strong.
Checked resistance in pickup coil, all in spec.
Checked all voltages on dizzy/coil loom connections, all in spec.
Checked for 12v on injectors while cranking (would not start) and it had a steady LED lit up.
Checked for sparks from coil HT lead (with induction strobe lamp) under cranking (but wouldn’t start) conditions, and it was getting a stream of pulses.
Checked for spark on No1 while driving (with induction strobe lamp) when it was stumbling, and it was still getting a pulse.
Checked ECM connections, all seemed ok.
IAC unit is functioning correctly, raised rpm & drops off again after 10 secs or so running.
EGR valve is (I think) operating ok, as it does not function below 900rpm, and it stalls at less than that when selecting drive.
Tried tapping block by knock sensor, does not cause problems.

When it stumbles on M/way, it rocks the car against the rear diff gears, so is quite harsh, so I don’t think it is a fuel fault?? As this is usually a ‘softer’ stumble.

My gut feeling is its ignition, but it all appears to be working fine in tests, it will idle all day no problem, and will rev fine no problem, just dies over bumps or when selecting drive (but not always reverse?????)

Heeeeeeelp!!!!!!

 

check fuel pressure and volumn

 

Pressure is fine, less sure on volume, but when it dies it often floods upon restart, so im guessing its not a fuel fault.
Its got to be a bad connection somewhere, but everywhere I tap or pull does not affect it??
Soon as I try to drive it though it obliges straight away. Grrrr.......

Just added,
Had it up on stands and played around underneath with wiring, all to no avail.
It stalled again when put into drive and refused to restart.
Had a plug out and it still sparked when cranking - might be a weak spark? - no way to tell?
Had an led in the injectors, pulsed while cranking, so injectors working too.
Fuel vapour was pouring from exhaust at this point, so it was flooded (even though I had foot to floor, which should cut off injectors).
So it has fuel (too much) and a spark, so why wont it run?

 

Well it seems to be the fuel pump, finally got it to stall on demand by gently bouncing the rear of the car about 3/4".
Stripped the tank out tonight, but the pump circuits all appear ok???
Very odd.
I've been told that pump failure, even for an instant will kill the engine dead, is this correct?
I'll try running the pump in a tray of fuel tomorrow, see if there is a running fault on it.

 

if all else fails, try a new computer. i had the same problem, only mine ran a little worse. i didnt have the stalling on bumps, but i did going into gear and i also had the flooding problem. everything i checked out good, and i didnt have any codes either. put a new computer in and it has been running perfect ever since

 

Tried running the pump in a bucket of warm water tonight, left it 20 minutes, all seemed ok???
Tapped it, wiggled wires etc, no problems???
It was running full tilt, very high pressure & volume, but I guess it does not run like this in the car though?
Got a new pump on order, but very worried its not the problem.
How come such a tiny movement on the back of the car kills the engine if its not the pump???

 

Maybe you have a short or a worn wire?

 

I guess it must be, as its so intermittent, cant be a fault on a unit as it would either fail or work I guess.
I think its a poor connection somewhere, but the big question is where?????

 

could it be your ecm? just a thought i had to have mine replaced today . . car ran fine cut off once in a wile and over speed bumps at the gym. next thing you know i dead in the water. it would turn over but not stay running i thought fuel pump but it was ecm.

 

Well its not the pump, put a new one in today and soldered all connections to make sure. I tried pulling the power plug to the pump while it was running, it still ran for about 4 seconds before it started to complain, so that rules that out.

It might be the ECM, I just dont know.
It also might be the Ign module as it does seem worse when warm.

 

Finally found it (after fitting new ignition module) its a wiring loom fault behind the coil area, in the big fat section of loom.
So far (only had quick look) I have found a 1" section of exposed copper wire that links the 3/4 injectors on the right hand bank, so I'm guessing it is grounding the injectors, either shutting them down or causing the ECM to kill the motor to save a short?

 

Well, If the injectors were truly shorting, they would blow the injector fuse (10 amp) unless it was shorting after the injectors... in which case it would just flood the crap out of the motor.


You probably got it though. An exposed section of wire is no good for anybody

 

Not repaired yet (been away for weekend) but its the ground wire loom for the injectors, from the ECU so I guess its grounding them all full time, instead of when the ECU is 'pulsing' them.

Re-taped all the loom today, and its all running fine again, yeah!!!

 

i happy you got it fixed