90 - Running out of breath at 5000 - No Codes

[Kevin]

Originally Posted by scottfab

41psi is not low. It's way low.
Yes fuel filter on GP first if you're not sure how long it's
been but note likely the issue.
You're sitting right on the problem I'd say.
One or both fuel pumps. If you get 41 at about idle
imagine how it may drop off under high demand.
Best investment would be an extension and some tape.
Seems prudent before proceeding.

A note about the pig tail. It's the only one at that
location so unless someone added something you've got it.
It ONLY works as a test when the key is off. It does nothing
with key on because the way it is routed through the relays.
ALSO important to note with key off and applying 12v to the
pig tail you get BOTH pumps running. It's a great static test.
From there you can remove one or the other of the fuel pump
fuses to see what pressure each pump can do. You do not want run
these pumps for long periods of time through the pig tail. Just saying.... do each test, not the pressure and shut it off.

As for a place to work on your car. YOU will be the best influence
on how well they do with the car but you have to study up here
on the forum and show them the results.

i thought 42 psi at idle was normal and 52ish when the secondaries kick in

[scottfab]

Originally Posted by Kevin

i thought 42 psi at idle was normal and 52ish when the secondaries kick in

I always tell people to be suspicious of any idle pressure below 43. It is one of those threshold values that should lead to more investigation. In my case it was a bad fuel pump that could not get higher than 41.
Easy to find out. Pinch the regulator vacuum. A really good pump will hit above 53 a mediocre one will be just above 50. Anything less than 50 is crap especially if it is new.

[RedSled]

My recent lack of power issue turned out to be bad ignition wires. And they only had about 8K miles on them.

[dondon]

So the potential fuel pump problem has been resolved. I installed 2 P240KC fuel pumps (if you are fearful of doing this, don't be it was very very easy - I have no prior experience with this stuff - <2 hours should probably be 45 minutes) and a fuel filter. Immediately after doing the swap I went for the excited test drive... same issue and saw a SES light very soon after start. Went home, hooked it up - Code 65 Rich Exhaust... I reset it and went for another test drive just to hopefully confirm the problem... Code 61 - Secondary Port Throttle.

Anyway, I'm a little confused as to what the problem is and where to find it. I recently replaced much of the whole secondary vacuum deal(solenoid and spider tubes). I hooked up the Tech 1 I recently acquired and noticed the Secondary Vacuum is 0 KPA. It does not move from this number. So I thought maybe I have a bad sensor, hooked up my handheld vacuum pump, and watched the secondary sensor work and show changes in vacuum in accordance with what I was doing.

So I feel at a loss for finding the leak. I've checked the pipe leading from the pump to plenum, and no leak also the vacuum pump does stop shortly after energizing and stay off. I had previously followed the code 61 instructions on this forum and I'm unsure of what I can do differently if I pull the thing apart again. Is there a good restart point or something obvious I may have missed. Any thoughts are welcomed.

Best Regards
Jonathan

[Franke]

I don't know if I can be of much help but looking at the FSM for a 1990 on page 6e3-c1-11and 12, It shows the vacuum and voltage at normal and full power switch settings. Normal mode should be 0.0 kPa and .54 - .62 volts at all times. Full power mode should be 33-66 kPa and 1.3 - 3.1 volts with the Tech1 tool.
You won't have full secondary operation if an engine code is present.
I am also wondering if the ECM is not recognizing full power mode for some reason even though the FP switch is on. Chart C1-F on page 6e3-c1-22.

[scottfab]

Jonathan, here is way to operate the secondaries with the plenum in place. This will allow you to test them and actually see them pull in without rolling down the highway.

I agree with all in this article except the assertion that 1 sec cycle time on the pump is ok. It states that that having a longer cycle time does not affect the engine power. While this is correct, to leave a system with this amount of leakage is just asking for the pump to cycle itself into oblivion. I'd investigate and fix a vacuum system that cycled 10 sec or less. So anyway, try this and actuate the secondaries several times. If they seem to pull in on both sides, clear any codes then go for a drive and see. If it drops out again look to see what codes are set again and we can go from there.


http://www.zr1specialist.com/HAT%20W...0Operation.pdf

[dondon]

Originally Posted by scottfab

Jonathan, here is way to operate the secondaries with the plenum in place. This will allow you to test them and actually see them pull in without rolling down the highway.

I agree with all in this article except the assertion that 1 sec cycle time on the pump is ok. It states that that having a longer cycle time does not affect the engine power. While this is correct, to leave a system with this amount of leakage is just asking for the pump to cycle itself into oblivion. I'd investigate and fix a vacuum system that cycled 10 sec or less. So anyway, try this and actuate the secondaries several times. If they seem to pull in on both sides, clear any codes then go for a drive and see. If it drops out again look to see what codes are set again and we can go from there.


http://www.zr1specialist.com/HAT%20W...0Operation.pdf

Hi Scott

Thanks for the info. FYI - car feels as though it starts quicker with new fuel pumps.

I've already run that test with success and it holds the actuators open as long as I want them to be open (was shorting the circuit on the front suspension arms). Pump runs while actuators are moving then shuts off again immediately and never turns on until the actuators are energized again.

These are the vacuum tests I previously ran:

Passenger side connector to the pump (by the oil filter), if I vacuum test it holds in both directions. If I pull the cylinder 3/5 vacuum pipe, it holds going down, but going into the plenum(metal side), I cannot get vacuum to hold.
Vacuum test Map sensor by the battery / ECM, the pipe does not hold vacuum, but the Map sensor does.
Vacuum test MAP sensor behind plenum, vacuum holds on the sensor, but does not hold going back into the plenum.

Don't think any of the above is a problem but in the interests of full information.

I think I'm going to try something ODD prior to pulling the plenum off again (its on the outer edge of my comfort level). Add vacuum to the sensor under the ECM, and pinch the pipe off when its in the range that Franke Specified, and then block the spider vein that would run to the sensor. My expectation is that and I am probably wrong... the sensor will be within range, the ECM will activate the secondaries and the pump will provide all vacuum necessary. If it runs well then I think the problem is somewhere in the spider vein headed to the sensor, but then again maybe not. This is not my area of expertise.

Thanks for the continued help
Jonathan

[scottfab]

Originally Posted by dondon

Hi Scott

... snip...
I think I'm going to try something ODD prior to pulling the plenum off again (its on the outer edge of my comfort level). Add vacuum to the sensor under the ECM, and pinch the pipe off when its in the range that Franke Specified, and then block the spider vein that would run to the sensor. My expectation is that and I am probably wrong... the sensor will be within range, the ECM will activate the secondaries and the pump will provide all vacuum necessary. If it runs well then I think the problem is somewhere in the spider vein headed to the sensor, but then again maybe not. This is not my area of expertise.

Thanks for the continued help
Jonathan

You will be an expert at the end of it all.
Can you confirm. No codes are set AND the loss of power is always at 5000rpm? (each and every attempt?)

[dondon]

Originally Posted by scottfab

You will be an expert at the end of it all.
Can you confirm. No codes are set AND the loss of power is always at 5000rpm? (each and every attempt?)

I tried the

Add vacuum to the sensor under the ECM, and pinch the pipe off when its in the range that Franke Specified, and then block the spider vein that would run to the sensor. My expectation is that and I am probably wrong... the sensor will be within range, the ECM will activate the secondaries and the pump will provide all vacuum necessary.

Surprise surprise - I was wrong . So it immediately set a HARD Code 61, the ECM clearly is smart enough to know I was messing with it.

Anyway, I reset the code, hooked up the plumbing as it was before and. went for a ride. Car ran as before, with same symptoms. The code 61 is intermittent... meaning the code gets stored, it does not have the hard stop at 3000 rpm as you see when the service engine soon light is on.

So maybe I need to setup a video... the car accellerates, and it feels brisk, probably within a second it feels less brisk but continues accelerating to 4000 with some force from 4000 to 5000 acceleration is slow and at 5000 I run out of patience and shift (usually I'm in 1st and 2nd gear), as I'm in the city.

Easiest way to get the code 61 stored is to get on the the highway in a high gear at low speed and mash the accelerator.

http://www.zr1specialist.com/HAT%20W...0Operation.pdf

- what does this test eliminate any items from the suspect list
- actuators [yes / no]
- solenoid [yes / no]
- reservoir tank [yes / no]
- front portion of vacuum system pipes [yes / no]
- check valve near solenoid [yes / no]

My gut feel says and the secondary vacuum number is the big clue, does anyone know perhaps if it stays at 0 kpa like mine does, and at which point that changes. ie does it change when the secondary pump charges the system or some other time. All I can think is something under the GD plenum is preventing Vac from getting to the Vacuum sensor under the ECM... there may be other issues as I recently replaced the solenoid, reservoir tank and spider hoses... so who knows.

There is so much info on this forum about the code 61, you would swear I was deaf to something or overlooked something.

[dondon]

Originally Posted by Franke

I don't know if I can be of much help but looking at the FSM for a 1990 on page 6e3-c1-11and 12, It shows the vacuum and voltage at normal and full power switch settings. Normal mode should be 0.0 kPa and .54 - .62 volts at all times. Full power mode should be 33-66 kPa and 1.3 - 3.1 volts with the Tech1 tool.
You won't have full secondary operation if an engine code is present.
I am also wondering if the ECM is not recognizing full power mode for some reason even though the FP switch is on. Chart C1-F on page 6e3-c1-22.

Thanks Franke, I went through the manual on these sections, and will go ahead an apply the FP test. If the rich exhaust comes back I'll run the other test. Thanks again for the input, and nice easy to get at locations in the FSM - I have a digital copy bought from WRP - and its a bit of a PITA to look at more than one page at a time.