J240

1990 zr1 53000 miles car started to run bad 3 weeks ago checked all the vacume and secondary systems everything is good . Both primary and secondary full pumps are on. If i leave the power key in normal or turn it to full power there is no change in the way it runs . As soon as the secondary throlle plates open its just sucking air like the secondary injectors are not even on. Pulled all the plugs they look fine no difference between them. Can the power key system go bad is their a common issue with it. Any way to test it or bypass . Thanks for the input

C6FirstVette

Read this thread...provides some insight>>

http://www.zr1.net/forum/showthread....ighlight=power

Aurora40

On a 1990, it is very simple. If the "Full Engine Power" light comes on when you turn the power key, the key is working. The ECM lights the "Full Engine Power" light.

I don't understand the "sucking air" thing though. You mean like a vacuum leak? You can hear air sucking?

If the secondary fuel injectors aren't working, but the secondaries are opening, you will get code 55 set within 2 seconds. The ECM will pick up on the narrowband O2 sensors reading lean and will disable secondary operation until the code is reset.

J240

Thank you for the info on the power key. the dash light is on Full Engine power. and it does go off when i turn the key so that means that system is working. The sucking is the secondary throttle plates opening, its like a bog ,it runs fine on the small primary throttle plate but as soon as the secondary throttle plates open it bogs all air . There are no trouble codes set which is what's bothering me so i'm stuck for the moment. thank you both for the info any further thought are appreicatied.

jrd1990zr1

I had a problem with my power key not staying on. Was bad contacts, easy fix.

Watch the light to make sure it stays on. It may be pulsing like mine did which caused the secondaries to stay off.

Good luck!

Aurora40

You are talking about the large diameter throttle body butterflies, not the individual butterflies in the cylinder heads?

If so, those open no matter what the key is set on, once you press the pedal far enough. It sounds like your car runs poorly no matter the power key position, is that correct?

J240

Auorura40 yes you are correct it runs poorly with either the power key on or off it makes no differnece. Yes i'm speaking of the throttle plates not the secondary air plates . I let it idle this morning for a while and the ses light finally came on going to pull the codes and see whats up

J240

Ok codes were 44 lt o2 sensor lean and code 54 low voltage primary fuel pump from me testing the fuel pump. Just took it out for a run and it is definitly the secondary system not turning on at all, runs as if your in normal mode, power mode does not come on yet full engine power light is lit. I'm thinking the secondary vacume sensor under the plemtum. I believe it is the brains of the system that turns it on ? Any thoughts

Aurora40

I wouldn't think it is the secondary system, as you said it runs like crap with the power key turned off. Did it idle rough when the code was set?

Do you have a fuel pressure gauge?

J240

Yes it was idling rough but clears up with a little throttle , i do not have a fuel pressure gauage but will borrow one just to check thanks

A26B

If it runs poorly with the power key off, then it's not likely to be in the secondary system. The lean condition of the LH O2 sensor is pointing to the left bank only, not likely to be low fuel pressure, but could be I suppose.

Considering it's a 90 model, most likely it's failed fuel injector(s). It's a very common problem these days for the 90~92 models. You could check the resistance of the injectors, but that's only part of the failure potential. The other facet is the mechanical aspect..... corrosion of the metallic trim. Being lean, points to electronic failure of the injector(s).

I would suggest you ohm out the injectors. Here's a link that contains a great diagram to follow.
http://www.zr1.net/forum/showthread....7299&post17299

BTW, when probing the ECM connectors, be very careful not to force the meter probes into the connector. it can enlarge the connector and create an intermittent failure to connect.

When you trouble shoot DTC's, always start with the lowest numerical code first. In this case, #44, Left O2 Sensor lean condition. Fixing the first code will likely resolve the higher numerical DTC also.

J240

Ok went out and bought a fuel pressure test hooked it up and fuel pressure at idle is about 42-44 . If i hit the gas it jumps up to around 50 or so. This is just sitting at idle not driving. I shut the car off and did notice the pressure slowly start to drop i/m going to leave it hooked up overnight and check in the morning to see what it is. Any thoughts? It should stay up around 40 or right?

A26B

There are 2 fuel pumps, FP1 is the primary and FP2 is the secondary pump. For a cold start, both FP1 & FP2 will run until the engine reaches appx 176F, then FP2 will shut off. For a hot start, above 176F, both FP1 & FP2 will run, but after 2 sec, FP2 will shut off.

To determine the functionality of the pumps, they must be tested separately. There are 2 fuses. FP1 fuse is on the pass side of the dash in the fuse panel. The fuse is labeled FP1. FP2 fuse is under the passenger side dash kick panel. Remove the panel. The fuse is labeled FP2.

The procedure to check fuel pumps is as follows;

Cold Engine
Key off, Engine off
Attach Fuel pressure gauge line to fuel rail. Bleed down any pressure in the rail.

Testing FP1 (Primary Fuel Pump)

1. Remove FP2 fuse.

2. Turn Key on, Engine off.

3. Observe fuel pressure. Should be appx 45 psig

4. Key off, engine off.

5. Bleed down fuel pressure

Testing FP2 (Secondary Fuel Pump)

1. Replace FP2 fuse and remove FP1 fuse

2. Turn Key on, Engine off.

3. Observe fuel pressure. Should be appx 45 psig

4. Key off, engine off.

5. Bleed down fuel pressure

6. Replace FP1 fuse.

Aurora40

Jerry is right on, and also about how to ohm the injectors. However, I would also tape the gauge to the windshield and go for a drive to see what the fuel pressure is when the car is exhibiting a problem. That would let you quickly rule out fuel pressure as the cause (or not if it's the problem), and then move on to things that are more time-consuming to troubleshoot.

J240

Both fuel pumps checked out at 45lbs each on the gauage. So i'm still thinking its something in the secondary system as i'don't drive it ever with the power key on normal and this must be what it feels like in normal mode. I already vacume tested both actuators , the resouvior, and seleniod and all passed but when i close it up and test the vacume at the line for the vacume pump under the pletum it leaks down . But would that be enough to cause the secondary system not to work at all??

A26B

Forget about the secondaries right now. All you have at present is "key-off" power, no matter which position the key is set. Secondaries are not the problem.

Right now, with DTC 44 & 55, the secondaries are disabled by the ECM via DTC 55.


You have a lean indication as per DTC 44, for the left bank. As previously stated, start resolving the lowest numerical DTC first, which is DTC 44. Check the injectors in the left bank. Follow the procedure provided above to check injector solenoid coil resistance.

J240

Jerry i agree with you forget the secondary system i just went though it again everything is good. I started it from cold and it sounded great for the first minute or two then all of a sudden the idle got rough and started to run rough as before. Had the fuel pressure gauage on it it was normal even went for a little ride and fuel pressure stays good but still runs rough. As i sit at idle for a while you can hear it runnig rough then if you hold the gas a little it clears out for a moment then runs rough again. I cleared out all the trouble codes hoping one would set again but has not. Does this sound like bad injectors they are orginal but i just can't wrap my head around that they went bad all of a sudden and that it would run like this all of a sudden. Time to go with jerry and do the reistance test . Still can't believe it injectors