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3.4 cold start and idle problem by Atlanta1
Started on: 10-01-2014 09:58 PM
Replies: 11 (260 views)
Last post by: lou_dias on 10-03-2014 12:20 PM
Atlanta1
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Report this Post10-01-2014 09:58 PM Click Here to See the Profile for Atlanta1Send a Private Message to Atlanta1Edit/Delete MessageReply w/QuoteDirect Link to This Post
I have had a 3.4 swapdone and when starting cold my mechanic has to use starter fluid to
start the engine then it idles rough. I have had a 5 speed emc plugged in from an auto ecm would appreciate
17lb injectors . Tach is not wired up so don't know about the tach yet. could this
be a bad cold start injector? too much fuel pressure? 5 speed ecm needs tuning?
fuel pump is new along with most parts new like distributor and plugs.Would appreciate any
ideas .
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phonedawgz
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Report this Post10-01-2014 10:03 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Did the mechanic jumper A-B when setting the timing? Unlike most GM OBD1 ECMs the Fiero does not have a disconnect on the Tan/Black wire to the distributor to disable the advance when setting the timing. Instead on the Fiero you jumper A-B on the ALDL connector. If your mechanic isn't familiar with how it is done on the Fiero he will have the timing set about 10 deg retarded.
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Atlanta1
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Report this Post10-01-2014 10:10 PM Click Here to See the Profile for Atlanta1Send a Private Message to Atlanta1Edit/Delete MessageReply w/QuoteDirect Link to This Post
Thats the first thing I asked him and he said he did jump the AB pin
and adjust the timing to 10 degrees.
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Alex.07.86GT
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Report this Post10-02-2014 03:06 AM Click Here to See the Profile for Alex.07.86GTSend a Private Message to Alex.07.86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
does the engine smooth-out after warm up
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Atlanta1
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Report this Post10-02-2014 08:51 AM Click Here to See the Profile for Atlanta1Send a Private Message to Atlanta1Edit/Delete MessageReply w/QuoteDirect Link to This Post
yes the engine idle does run smooth after the start
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mattman8
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Report this Post10-02-2014 09:06 AM Click Here to See the Profile for mattman8Send a Private Message to mattman8Edit/Delete MessageReply w/QuoteDirect Link to This Post
I had a similar problem on my 3.4, it wouldn't start in when it was cold unless you used starting fluid then run like a champ once started. It turns out one of the wires going to the connector on the coil started to break, I replaced the connector and wire and it's been great since.
Good luck.
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lou_dias
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Report this Post10-02-2014 09:41 AM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
a 3.4 with a Fiero ECM needs 18.2 # injectors to run "right"...
So you need to add some fuel to the tuning or turn up the fuel pressure.

Also, have you taken the car over 35mph since the swap so that the IAC recalibrates?

On one of my 3.4 swaps I was running 16# Tomco injectors with FP of 45 instead of 39 and it ran great.

[This message has been edited by lou_dias (edited 10-02-2014).]

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Atlanta1
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Report this Post10-02-2014 10:10 AM Click Here to See the Profile for Atlanta1Send a Private Message to Atlanta1Edit/Delete MessageReply w/QuoteDirect Link to This Post
we are just finished the swap.it still needs a muffler,just got the front clutch line
repaired after the conversion from an auto to a 5 speed. .The car has not
been out on a test run yet.I belive we have the 17lb bmw injectors at 53psi
with a holly adjustable fuel pressure. maybe we need to bring the fuel pressure back down?
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Alex.07.86GT
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Report this Post10-02-2014 10:52 AM Click Here to See the Profile for Alex.07.86GTSend a Private Message to Alex.07.86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
im not sure what fuel pressure you need but you need to observe the fuel pressure: key on; cold cranking; running while cold.
while cold cranking are the plugs wet with fuel? or Black? lean/ ect???

Vacuum leak through EGR or bad vacuum hoses/ connections need to be checked. plug up all vacuum ports for testing.

Timing might still be an issue. I would make a mark where the timing is then move it in small movements to see if it will start cold in a different spot.

move the coil wire away from the coil 1 inch from the coil wire. does the spark jump or start the engine that way?
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lou_dias
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Report this Post10-02-2014 12:32 PM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Atlanta1:

we are just finished the swap.it still needs a muffler,just got the front clutch line
repaired after the conversion from an auto to a 5 speed. .The car has not
been out on a test run yet.I belive we have the 17lb bmw injectors at 53psi
with a holly adjustable fuel pressure. maybe we need to bring the fuel pressure back down?

You got to find out what voltage and fuel pressure those BMW injectors were rated.

For instance, the Ford 19# injectors act like GM 22# injectors when used on a GM vehicle.

[This message has been edited by lou_dias (edited 10-02-2014).]

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fierofool
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Report this Post10-02-2014 10:50 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm running those same BMW modified pintle injectors if Atlanta1 took my advice on what he purchased. They're rated at 16.6 lb/hr (17#) with the stock Fiero pressure regulator at 43.5 pi. Several of us in the club with 3.4 conversions are running them on stock Fiero ECM's and with all other parts of the engine being stock. We have no problems. There are also others who are running the same setup. If you use any injector rebuilder or manufacturer's chart, you will find that injector flow is based upon the number of cylinders and the horsepower. A 3.4 V6 produces 160 hp and requires 16.6 lb/hr flow at 80% duty cycle and 43.5 psi fuel pressure.

The Rochester injectors used in the 3.4 were also 17# and the fuel pressure regulator was exactly the same as the Fiero. There is no need to use a high volume pump or an adjustable regulator with those injectors.
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lou_dias
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Report this Post10-03-2014 12:20 PM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
Without vacuum to the regulator at idle is should be ~39, no?

Regardless, the IAC won't calibrate until that 'test run' is taken at over 35 mph...hence it won't idle right.
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