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Throttle response (urgent!) by notaguru
Started on: 12-27-2013 08:40 PM
Replies: 16 (338 views)
Last post by: notaguru on 01-02-2014 01:05 PM
notaguru
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Report this Post12-27-2013 08:40 PM Click Here to See the Profile for notaguruClick Here to visit notaguru's HomePageClick Here to Email notaguruSend a Private Message to notaguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
This '88 has 40k miles on it - and was rotting in the sun for at least six years. I'm trying to recover it.

The first time I drove the car, the throttle response was terrible - even scary. After about 3/4 throttle, the car began to move. At no time did it have the responsiveness I expected. Think about a 36hp VW... uphill.

Today I installed a new TPS, cap, and rotor. Plugs and cables looked fine. Voltage on the low side of the TPS is about 0.5. Compression is about 100psi on the three accessible cylinders (I didn't go the extra mile). Idle cold is about 1100, less when warm.

I know the ECU takes time to "learn" new parts, but when I drove the car after the install there was no difference whatsoever. I warmed it up and tried it again. Same. The throttle problem persists. I inspected the linkage and see no obvious fault.

In its current state, the car cannot be safely driven to a shop for a smog check!

Probabilities?
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phonedawgz
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Report this Post12-27-2013 08:46 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
The fuse box has latches on the two sides. Squeeze the latches push up slightly and it will pivot down to vertical. There are two injector fuses. Each controls 3 injectors. Pull one and put it back and then try the other. You will need to give it some extra throttle to keep it running. If both fuses cause a signifigant loss in power/rpm than you know that each bank of injectors are working. If one does nothing and the other one kills it then look to see why one bank is not working (bad fuse most likely).

I put this test first since it is easiest.

Check the fuel pressure and make sure it is in spec.

Finally since the car sat for a long time, what I think is most likely is the fuel injector tips are plugged. You can soak them in injector cleaner and re-install them and that will most likely clean them.
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Bloozberry
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Report this Post12-27-2013 08:49 PM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
Did you try to see if there were any ECM codes? It also could be low fuel pressure, or a clogged cat or muffler.
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lateFormula
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Report this Post12-27-2013 08:57 PM Click Here to See the Profile for lateFormulaSend a Private Message to lateFormulaEdit/Delete MessageReply w/QuoteDirect Link to This Post
My first guess would be ignition. You could eliminate the obvious and the least expensive by replacing the plugs and plug wires. If that doesn't improve it the next item to replace would be the ignition control module, which is fastened to the base plate on the distributor. ICMs cost more than plugs+wires, but they are the source of a lot of performance issues on the V6 Fieros.

If you replace the ICM, it would be strongly recommended to only use an AC Delco model ICM (AC Delco D1943A), and make sure you apply the entire packet of thermal grease to the underside of the ICM before you install it. Any new ICM should come with a small packet of thermal grease in the package.
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cmechmann
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Report this Post12-27-2013 09:58 PM Click Here to See the Profile for cmechmannClick Here to Email cmechmannSend a Private Message to cmechmannEdit/Delete MessageReply w/QuoteDirect Link to This Post
Is the crap fuel still in it?
Changing the fuel filter after sitting a long time is a must. Any old filters that has a chance to dry out has a chance of the filter element coming apart and sending crap through everything up stream.
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notaguru
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Report this Post12-27-2013 10:00 PM Click Here to See the Profile for notaguruClick Here to visit notaguru's HomePageClick Here to Email notaguruSend a Private Message to notaguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
No Service Engine codes evident, though I do not have an OBD1 scan tool.

Idles on either bank of injectors. If an injector or two were bad, wouldn't the O2 sensor show a lean code?

Just pulled the cap off the air filter can, and found a really ugly/dirty K&N. I'll pick up a 3902 tomorrow and see if it makes a difference.

Scoped the throttle body. No mouse nest, clean - especially considering the condition of the air filter. I guess it did its job...

Fuel and filter tomorrow.

[This message has been edited by notaguru (edited 12-27-2013).]

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Jake_Dragon
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Report this Post12-28-2013 12:34 AM Click Here to See the Profile for Jake_DragonSend a Private Message to Jake_DragonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Plugged exhaust could also cause poor throttle response.
Look at the exhaust in low light and see if its glowing.
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tebailey
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Report this Post12-28-2013 10:24 AM Click Here to See the Profile for tebaileyClick Here to Email tebaileySend a Private Message to tebaileyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Could be little critters nesting in the exhaust.
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notaguru
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Report this Post12-28-2013 10:45 AM Click Here to See the Profile for notaguruClick Here to visit notaguru's HomePageClick Here to Email notaguruSend a Private Message to notaguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by tebailey:

Could be little critters nesting in the exhaust.


I used a fiber optic scope to look up the rear end of the car, and didn't find anything.

I have not yet checked to see if the exhaust system runs hot, but will do so if cleaning the fuel system doesn't help. I'm about to pump out the old gas (yeah, I forgot to do that in the beginning) and change the filter. Hopefully the injectors are ok...
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fiero5150
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Report this Post12-28-2013 03:28 PM Click Here to See the Profile for fiero5150Send a Private Message to fiero5150Edit/Delete MessageReply w/QuoteDirect Link to This Post
Had a similar problem after recovering a GT that had been sitting over 2 years. Car drove sluggish and lacked any pep. Changed plugs, new fuel pump and filters, new gas, etc. Still no improvement. Took to shop and mechanic believed engine was not "getting enough air" (whatever that means). He suggested installing a new catalytic converter. Put in a new converter and immediately the car ran like a stripped "___" ape. Super fun to drive now.
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Patrick
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Report this Post12-28-2013 04:03 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fiero5150:

Took to shop and mechanic believed engine was not "getting enough air" (whatever that means). He suggested installing a new catalytic converter. Put in a new converter and immediately the car ran like a stripped "___" ape.


Engine has to breathe in order to run, which includes being able to "exhale".

This is a picture of the plugged cat from my '86 GT (from This thread.)

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notaguru
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Report this Post12-28-2013 05:36 PM Click Here to See the Profile for notaguruClick Here to visit notaguru's HomePageClick Here to Email notaguruSend a Private Message to notaguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
The car is in my garage, at home. The tank is now empty, and the 6-year old gas doesn't look too bad. HOPEFULLY, replacing the fuel filter will get it functionalk BUT:

I haven't found a safe way to get it into the air with enough clearance to provide access to the fuel filter. My small floor jack is insufficient..A friend is coming over with a much larger floor jack than mine - hopefully that plus jackstands will do the job. Is there a safe central jack point that will support the entire rear end of the car?

The way it is right now, it really cannot be driven. Once the car is running, I can drive to a local resource and put it on the ramp. At that time I'll drop the tank, blow out lines, drop some of fthe exhaust, etc.
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Jake_Dragon
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Report this Post12-28-2013 07:17 PM Click Here to See the Profile for Jake_DragonSend a Private Message to Jake_DragonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Unscrew the O2 sensor and see if it drives better. If the cat is plugged then by opening the O2 sensor port it should make a big difference.
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phonedawgz
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Report this Post12-28-2013 07:41 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
A restricted exhaust tends to fall off at higher RPMs. From what you are describing the power is off right off of idle????

Does it idle smoothly?

When you have the loss of power is it missing or just a loss of power? The power loss is across the rpm band? It seems to go away at a higher RPM?

Timing set way too retarded can cause significant reduction of power. If you set the timing incorrectly by not jumpering A-B the timing will be retarded by about 10 deg.



[This message has been edited by phonedawgz (edited 12-28-2013).]

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notaguru
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Report this Post12-28-2013 09:49 PM Click Here to See the Profile for notaguruClick Here to visit notaguru's HomePageClick Here to Email notaguruSend a Private Message to notaguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
Idles smoothly, though a bit high. Never misses, always feels smooth at any RPM.

But when the accelerator is depressed, nothing happens until it hits the 3/4 area, and even then it's sluggish right up to its maximum RPM - perhaps 2,000.

It's never gotten really hot since I first picked it up.

The next step is to get under the car, hopefully in the morning when Jackzilla gets here. I like the idea of pulling the TPS - I should have remembered that!! And, I'll be able to reach the tank and fuel filter. I have a very bad feeling about the pump, especially if there's a sock on it. It's been more than SIX YEARS without running.
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notaguru
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Report this Post12-29-2013 07:57 PM Click Here to See the Profile for notaguruClick Here to visit notaguru's HomePageClick Here to Email notaguruSend a Private Message to notaguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
No jack+helper until next week, so did some minor tasks on the car. Drove it around the block with the O2 sensor removed, and it's the same. Max rpm under load on level ground is under 2000. I still think it's fuel. I hate to think about a rotted tank - it's not an item easily found.
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notaguru
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Report this Post01-02-2014 01:05 PM Click Here to See the Profile for notaguruClick Here to visit notaguru's HomePageClick Here to Email notaguruSend a Private Message to notaguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
The (primary) culprit was ROTTEN FUEL.
After draining the tank, flushing, and replacing the fuel filter, the car runs well. The exhaust is clear.
This drive was the first to go over 30mph, and I'm happy to report that shifting and general drivability seems fine.

Thanks to the gurus here - and now, BACK TO THE PUNCH LIST

[This message has been edited by notaguru (edited 01-02-2014).]

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