Car runs in rain but dies when floored

[89lxsc]

I have an '89 LX 5.0 with T trim supercharger. My car is acting strange. It runs perfect when it's dry out ,but when it is raining the car starts and drives fine until I press the gas too hard. When I do this the engine just shuts off . What could be causing this? I suspect my MAF and possibly my air filter is wet, but I don't know for sure . What do you think?


Other parts FMU, Vortech 80mmMAF, 70mm BBK TB, GT40(Explorer) Intake, Ported lower, GT40p heads, 32lb injectors. I feed the supercharger through the passenger side fender near the front through a 4" Duct currently connected to a paper filter.

 

[Black1987Stang]

Try pulling codes? there might be something as a code or stored in the memory telling u what its about. You could try cleaning the maf, I would just pull the codes n see what u get first

 

[RsStanG1987]

I feed the supercharger through the passenger side fender near the front through a 4" Duct currently connected to a paper filter.

So you pull air from under the fender? That can be your problem right there..

 

[Black1987Stang]

So you pull air from under the fender? That can be your problem right there..

arent most other boosted cars have their filters in the fender too tho along with? mine is too but mines also n/a so theres no crazy sucking from the blower sucking in all that air...I could see maybe if he had no wheel well plastic shield or something so the water from the tires and road would go right up into the filter or something

 

[RsStanG1987]

arent most other boosted cars have their filters in the fender too tho along with? mine is too but mines also n/a so theres no crazy sucking from the blower sucking in all that air...I could see maybe if he had no wheel well plastic shield or something so the water from the tires and road would go right up into the filter or something

There is a guy over in talk who had the same problem on his stock 5.0 with fenderwell intake it was sucking rain water in.

 

[89lxsc]

There is a guy over in talk who had the same problem on his stock 5.0 with fenderwell intake it was sucking rain water in.

Codes are:
67 - Neutral Switch
29 - Vehicle Speed Sensor (do I have one?)
33 - EGR Valve Position
56 - MAF Signal Too High
87 - Fuel pump relay - circuit failure

Worse than I thought!!

My filter looks wet too. It has top and bottom rain access. Any picture of a "good" in fender setup?

 

[jrichker]

Code 29 - Vehicle Speed Sensor (VSS) is an electronic sender mounted on the speedo
pickup gear on the trans. It works the cruse control for both 5 speed and auto trans cars.
The VSS is used to tell the computer to speed up the idle as you slow to a stop. This helps
keep the engine from stalling when you slow down for a stop sign or stop light.
Check to see if the electrical connector is plugged into it. Clean the connector & contacts
with non flammable brake parts cleaner prior to replacing the sensor, as that may fix the
problem. The sensor cost is under $30 and it is easy to replace.

Code 33 - Insufficient EGR flow detected.
Look for vacuum leaks, cracked vacuum lines, failed EGR vacuum regulator. Check to see if
you have 10” of vacuum at the EGR vacuum connection coming from the intake manifold.
Look for electrical signal at the vacuum regulator solenoid valves located on the rear of the
passenger side wheel well. Using a test light across the electrical connector, it should
flicker as the electrical signal flickers. Remember that the computer does not source any
power, but provides the ground necessary to complete the circuit. That means one side of
the circuit will always be hot, and the other side will go to ground or below 1 volt as the
computer switches on that circuit.
Check for resistance between the brown/lt green wire on the EGR sensor and pin 27 on the
computer: you should have less than 1 ohm.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif


EGR test procedure courtesy of cjones

to check the EGR valve:
bring the engine to normal temp.
connect a vacuum pump to the EGR Valve
apply 5in vacuum to the valve.
if engine stumbled or died then EGR Valve and passage(there is a passageway through the
heads and intake) are good.
if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is
blocked.
if engine stumbled, connect vacuum gauge to the hose coming off of the EGR Valve
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 5in vacuum?

if not, check for manifold vacuum at the EGR vacuum valve.
if you have manifold vacuum then connect vacuum gauge to the EGR valve side of the
vacuum valve and snap throttle to 2500 RPM.
should read about 5in vacuum

The operation of the EGR vacuum regulator can be checked by using a test light applied
across the wiring connector. Jumper the computer into self test mode and turn the key on
but do not start the engine. You will hear all the actuators (including the EVR vacuum
regulator) cycle. Watch for the light to flicker: that means the computer has signaled the
EGR vacuum regulator successfully.

Code 56 MAF - output voltage too high. Failed MAF sensor, short between
MAF sensor and heater or short in wiring between pin A (12 volts) and pins C or D.

There are three parts in a MAF: the heater, the sensor element and the amplifier.
The heater heats the MAF sensor element causing the resistance to increase.
The amplifier buffers the MAF output signal and has a resistor that is laser
trimmed to provide an output range compatible with the computer's load tables.

The MAF output varies with RPM which causes the airflow to increase or
decease. The increase of air across the MAF sensor element causes it to cool,
allowing more voltage to pass and telling the computer to increase the fuel flow.
A decrease in airflow causes the MAF sensor element to get warmer, decreasing
the voltage and reducing the fuel flow. Measure the MAF output at pins C & D
on the MAF connector (dark blue/orange and tan/light blue) or at pins 50 & 9
on the computer.

At idle = approximately .6 volt
20 MPH = approximately 1.10 volt
40 MPH = approximately 1.70 volt
60 MPH = approximately 2.10 volt

Disconnect the MAF sensor, battery negative post and computer connector.
The computer connector is located under the passenger side kick panel & is
secured by a single 10 MM bolt. Do not make any resistance checks
without disconnecting the connectors. You will get incorrect readings.
Check the resistance between the MAF signal wiring and power.
Pin D on the MAF (dark blue/orange wire) and Pin A (red wire) should be
1 megohm or higher (meter shows infinite resistance or open circuit.).
Pin C on the MAF (tan/light blue wire) and Pin A (red wire) should be
1 megohm or higher (meter shows infinite resistance or open circuit.).

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Code 67 - clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On
position when codes where dumped. Possible neutral safety switch or wiring problem. This
code may prevent you from running the Key On Engine On tests. You can generally ignore
this code, since it has no effect on engine performance.

Code 87 – fuel pump primary circuit failure. The fuel pump lost power while the engine was
running. Check fuel pump relay, check inertia switch, wiring to/from inertia switch, red wire
going to inertia switch for +12volts. Check the other side of inertia switch for +12 volts.

To help troubleshoot the 87 code, follow this link for a wiring diagram for 89-93 cars
http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp

For 79-88 cars use, http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp

 

[89lxsc]

Thanks for ideas, I'll investigate.

 

[Black1987Stang]

I say check out the maf...take off the top black and clean the wires with brake cleaner or electrical cleaner

 

[89lxsc]

The car only does this in the ran. Is it possible that water is getting on the MAF it is going out of range and the computer is shutting off the fuel pump as a result?

 

[dragnazz5.0]

if the hot wire was getting wet it would cool off really quickly and the computer would see that as a huge load of air, therefore dumping more fuel. that could be your problem. or there is water getting on a wire somewhere and shorting out an ignition circuit in the computer or tfi module.