help please 88 Fiero

S

stebowden

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I have just resurected my 88 Fiero 2.5l after 6 years laid up. Amazingly everything worked. Drove round the block and handbrake dragging slightly. Service engine soon light on but no codes stored. Fixed handbrake but now an engine problem. Car starts fine and idles beautifully no miss firing whatsoever. Idle speed drops as engine warms up. However open the throttle ever so slightly and the engine cuts instantly like an electrical cut. Blipping the throttle is the only way to keep it running. However once over 3500 rpm it is possibly to hold steady rpm on the throttle. Any attempt to lower the rpm and it instantly cuts.
Standard car apart from cat removed. Just removed EGR and blanked it off. No change. Blown out fuel line and filter. No change and no crap. Not suspecting fuel pump due to the steady high revs. Possible TPS fault that does not give code? Will see if any of my mates has a digital waveform scope. Unfortunately bolt on the TPS damaged so going to need a big strip down to remove it.
Please bear in mind I am over the pond in England so nipping down the road for a spare part to try and if no luck try this is not really an option. I need to know what it is and order in from your part of the world. Reading other posts this seems to be a common problem with slight variations.
Thanking you in anticipation.
 
88 Fiero in England

Jumped A and B on the alcl connector. Got 3 12s followed after a short break by 3 12s. Disconnected battery. Ran engine again and re-read codes.Same result. Regards steve
 
88 Fiero

Forgot to mention if it helps. Car is manual transmission. I do have the Factory service manual and a Haynes manual. I am a bit out of my depth with such a modern computer controlled fuel injected car having never had a car more modern than 1973 before but I am sure I will be able to implement any suggestions.
Regards Steve
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Bad Vacumn leak or dirty IAC motor pintal or clogged injector is my guess since no codes are shown.

Take out the IAC and clean the end with carb cleaner spray and clean the port in the TB it goes into. Disconnect the battery for a half hour and reconnect and it will take a few days to relearn the idle.

Throw some injector cleaner in the fuel tank and check for vacumn leaks. ( all hoses and the brake booster also if it has power brakes)

Doug in P.R.:cool:
 
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88 Fiero

No vac leaks found. IAC was pretty clean now completely cleaned up. Only about 10 thou movement when end is pressed i guess it is therefore a stepper motor. Opened the butterfly slightly as it was jamming slightly. Removed broken TPS screw which turns out to be m4.5 x 0.75 pitch. Never in 45 years of engineering have I ever encountered that size before. Cannot see them on the internet either.
My next thought for tomorrow is to refit the throttle body run the engine with the TPS hanging loose. I will then move the throttle butterfly and see if the engine will run any better between idle and 3500 rpm without moving the TPS. Then move the TPS by hand to see what happens without the throttle. Hopefully that will prove the TPS. Then clean the injector. After that I will be baffled again.
Regards Steve
 
88 Fiero

Fired up car with TPS plugged in but disconnected from throttle body. Engine runs but speed varies between 2000 and 3000 rpm without touching the throttle. However the throttle can now be operated without stalling the car and be driven in and out of the garage. Manually moving the TPS with a screwdriver immediately stalls the engine. The inference therefore is that the throttle operates in a fashion with the TPS at idle position but some faulty signal is being sent once off the idle position which kills the engine. Weather it shuts off fuel or ignition I cannot tell. Therefore the problem is the TPS but the fault codes must only check the low and high end voltages giving the false impression that the TPS is OK when it is anything but. Hope this helps others.
Any other thoughts welcome before I order a TPS.
Regards Steve
 
If you vave a volt meter, back probe the tps and cycle it. The voltage should come up from approx. .5 to 5 volts smoothly, no cut outs.
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I have now solved my problem. It turns out that the short piece of fuel pipe between the pump and the tank outlet pipe had been seriously eaten away internally presumably by the alcohol in the fuel we now have to put up with and then split. Consequently only some of what was being pumped actually got out of the tank. Strange though that it would rev. Amazingly you cannot buy submersible fuel pump hose in Britain.
Despite the pump being original it still gave 13psi and 2.2 litres a minute but I changed it anyway.
Hope this helps somebody else.
Regards Steve
 
thanks for the update
 
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