I've got the W version with the Central Port Injector (spider). When you spray fuel into the manifold it starts and runs fine as long as you keep spraying fuel inside. Thought it was a bad fuel pump so I replaced the fuel pump/sender. Still wouldn't start. Thought maybe the fuel filter was clogged, but I disconnected the fuel line on the engine side of the filter, turn the key on and fuel shoots out the filter like it was a garden hose.

Don't have a fuel pressure gauge, so i haven't checked the fuel pressure where it comes into the plenum (I know it needs to be about 61 psi key on, engine off).


When I removed the upper plenum, there was about 3 tablesoons of dirty fuel puddled on both sides of the plenum. The Fuel Pressure Regulator side was slightly cleaner, so I replaced the FPR. Checked for cracks around the nut kit and spider, they seem ok.

Still won't start.

When I run the On Board Diagnostic, it flashes codes 22 and 34: Throttle position sensor voltage low, and MAP sensor voltage low.

If the spider or nut kit are leaking a bit, will that throw codes 22 and 34? And will that cause it to not start? I had to replace the FPR 2 years ago when the engine ran roughly, but it still started and ran...

Will a bad MAP sensor cause it not to start without pouring fuel into the air intake? Or perhaps the TPS sensor?

Any help is appreciated. I'm trying to avoid replacing the spider ($550) just to find out it still won't start.

 

deffinately sounds like one of those two sensors. the computer measures the amount of airflow through those, so if it thinks the motor has no airflow, it wont give the motor any fuel. by spraying "fuel" through the intake you are replacing the computer system. it could still be the spider, but i would deffinately start with the sensors. i beleive the tps being bad would through off the map and throw that code too. ive got the same exact motor, no problems yet though.

 

Alright based upon that response, start with the TPS first then, as it may be throwing off the MAP sensor code.

If it still doesn't work, then I'll replace the MAP.

If it still doesn't start, the swearing begins.

I've got the Hanes manual, but it doesn't show the TPS or the MAP. I'm sorta hoping that I buy the parts and can just figure out where they go by locating their identical twin somewhere on that plenum. The problem is that sometimes aftermarket parts don;t resemble the originals. Anyone got a picture of this engine with the MAP and TPS pointed out?

 

TPS is bolted to the driver side of the upper plenum air intake - round tube thing molded into the plenum where your throttle cable mounts (only on opposite side). MAP sensor is right above it in between the runners in the front. Too late to scan. Sorry man. Does your manual tell you how to check the TPS at least?

 

So do I have it right by this picture then?

And no, the manual doesn't explain how to test the TPS or the MAP first before replacing them. Most of the other threads I read about TPS/Map problems talk about running poorly, not causing a crank without a start, but I'm more eager to try replacing them anyway because they're a cheaper first option and I am getting the codes for them.

I did have one further thought - I'm guessing my heater core is cracked because it spilled antifreeze on the passenger side carpet through the heating vents. Another poster mentioned that the ECM is located right below the heater core, I wonder if it got shorted out. Would that throw codes 22 or 34? Or stop it from starting maybe?

 

TEST before you replace! The TPS sensor should transition from ~0.5V at closed throttle smoothly up to ~4.5V at wide open throttle.

If you do not get these values when probing the sensor return wire, the next order of business would be to check the +5V reference wire and the ground to the sensor. Both the MAP & TPS use the +5V reference supply from the ECU. If there is a problem on this circuit, it could cause both of these codes to set along with other issues like a no-start.

 

Antfreeze on the carpet is most likely a heater core (which I would definately get stopped leaking before you throw some more volts to the ECM) even iff you have to bypass it. And yes your picture is right.

 

The grey wire to the TPS is giving me 4.9volts, key on, engine off, with the throttle closed. Makes no difference when I open it.

Just for fun I replaced the fuel filter and the MAP sensor. Still no start. Also wiggled those wires red and blue wires below the TPS going through the plenum to the spider.

How do I track down this TPS oddity before a replacement?

And if I follow you right, probing one of the other wires ought to give me 5 volts, yes? That's the refernece wire? I get no voltage on both of the other 2 wires going into the sensor

 

Update!

Bought a Fuel Pressure Gauge and tested at the schreader valve - reads 18 psi. Far below the 51 psi required for ignition and 60-ish psi it should read.

The fuel filter is brand new today. So I either have the wrong pump meant for the TBI not the CMFI, or the pump is faulty, yes?

Still puzzled by the codes 22 and 34 for Throttle Position Sensor and MAP sensor low voltages. Could be more than one problem perhaps. But replace the pump first, right?

 

Next update.

Guess what - despite being told by TWO different parts guys that I definetely had the right pump, I didn't. Yep, they sold me the TBI version which pumps 20psi not the 60psi CFMI version.

Off to next nearest location with a 60psi version in stock...

For anyone else following in my footsteps, I can't recommend enough just springing for the $50 fuel pressure gauge tool. It would have saved me money, aggravation and in the end is the only thing that diagnosed the problem as a wrong pump. It will save you from removing the plenum unnecesarrily, buying parts you don't need, etc.

Buy the tool.