1992 ZR1 Seems Sluggish

[KJL]

Car was running fine the last time I dove it. It has been about 6 weeks since then. I usually disconnect the battery as well. When I went to start it the battery was about dead, not enough juice to turn it over. I hooked up my remote charger and she fire right up with the usually guide chain rattle for a few seconds but this time she barked out a bit or smoke momentarily but that cleared up. When I drove it, it seemed to lack power, it idles fine but when I give it some gas, it is unresponsive. It feels like i am driving on 4 cylinders. The idle is smooth, there has always been a slight vacuum leak, the pump runs once every 2.5 seconds with engine off and when running maintains a steady 17" of vacuum. There is spark on all 8 cylinders. The car is drivable with no engine codes. The only thing left I can think of is bad or fowled fuel injector....or the fact I have been driving my 700 HP 434 cuin C3 around all week....

Any thoughts?

[BigJohn]

Is that a 454 C3 ?

[KJL]

Yes, it is a 434 small block.

[RussMcB]

A guess (I think I've heard other people mention this) - The small backfire pushed the vacuum tube off the back of the plenum, and the fix is to simply slip it back on.

[BigJohn]

Yes, it is a 434 small block.

That is what I was thinking!
:-D

[KJL]

Hello Russ, I checked all the tubes that can be seen.... my vacuum pump test with the car off runs at the same frequency it always has and my vacuum at idle is steady at 17". I am thinking the vacuum is likely not the culprit here. I guess I will just run the car some more maybe put in a can of injector cleaner and check the plugs before I pull the plenum and have a look around. Also going to pull the plastic intake and take a look at the throttle blades. I guess that is the best way to describe how it feels.... like I am pushing the pedal but the throttle blades are not opening up in a proportional manner.

[efnfast]

The vacuum line Russ is refering to is right at the back of the plenum. It tends to blow off with a backfire. Unrelated to the vacuum pump.

[KJL]

Understood, the line is definitely still connected.

[KJL]

Took it out for another drive yesterday. Ran better but still hesitates at times.

[dredgeguy]

Took it out for another drive yesterday. Ran better but still hesitates at times.

I have a 92 and same except that it starts to stumble badly around 3000 RPM. Think it is the common fuel pump issue. Just purchased a pair from RockAuto and hope to install them this weekend. Will let you know if this is the cure, I hope so.

[KJL]

Please do! A pair? there are two pumps? My plan is to ultimately go through the top end and replace all the fuel rail seals and fix any vacuum issues. May do some top end porting as well. The injectors are original I believe so I may upgrade those too. At the moment trying to finish up my 95 project involving changing the rear gears to 4.10 and swapping over to a light weight RAM dual clutch set up.

How do you like the 4.10 gears? I hear the lightweight flywheel can be noisy buy I added a thicker counter shaft shim as recommended by Bill Boudreau including his C-Beam plates. It has been a fun project but I am ready to get it done. Everything else has been done to it except secondary system removal. I am in the process of registering the car in a county that does not require emissions testing so I am planning on pull all that stuff out as well now.

[dredgeguy]

Yes a pair, primary and secondary. If the injectors are original, that is for sure must be done. When I purchased my car in CT it was fine on the test drive and then driving down to MD it started stumbling on the NJ Turnpike. I was lucky to limp home, 7 out of 16 injectors were dead. Thanks to Wazoo, all worked out.

[RussMcB]

I have a spare ECU you can swap in for a quick test. Send me an email if you'd like to get together to try that.

[KJL]

Thanks for the offer! I am going to check a couple more things first. Figured I would just go ahead and replace the spark plugs while I am checking them. Maybe run some injector cleaner in the tank as well. Interesting thought....I guess there are only a finite number of ECMs available for these cars. Probably wouldn't hurt to track down a couple of spares.

What is a good plug to use?

[dredgeguy]

Just remember that injector cleaner will not fix the issue if it is injectors. Ethanol gas will short out the original injectors, ask me how I know:) The stainless steel ones from FIC are the fix.

[KJL]

Thanks for the info, decided not to mess with gas additives. So far the problem seems to be getting a little better each time I drive her. I changed out the plugs and the old ones, while old, looked very good. All plugs looked the same. A couple of plugs had oily threads but that is about it. I was reading elsewhere that a bad O2 sensor will also cause issues with lack of power. I would think that would throw a code.....

[We Gone]

Check your O2s.

[KJL]

Yes, I need to do that. I am sure there is a procedure somewhere on this forum for doing this.

[dredgeguy]

Well, Wazoo fixed my issue. The dealer had not connected the small hose going to the MAP and also my throttle cable was messed up so the throttle was 59% when the pedal was all the way to the floor. The dealer has no clue.

[Scrrem]

Glad Jim got it sorted out 👍
Rich

[KJL]

Happy to hear it worked out. I realized I have an Autoxray 6000 so I did a scan and the O2 sensors seemed to be reading like they are supposed to and cycle between .1 and .9 volts. The TPS ramps from .54 to 4.6 volts. Still having power issues. Now stumbles a bit upon acceleration. Next I will check the coil pack resistance which seems simple enough at the ECM harness and perform a fuel pressure test on both the primary and secondary pumps. If those turn out to be OK, my guess will be the injectors.

What is Wazoo?

[KJL]

Update:
Engine also seemed very hot tot he touch and running a bit on the hot side. The dip stick was so hot I couldn't even hold it. Both my valve cover emblems also came off although they seemed like they were in the process of doing so regardless. I am traveling this week and look forward to seeing how the fuel pump tests pan out.

[KJL]

I just finished checking some things and found the following:
Cyl 3 Primary Injector: 6.1 ohms
Cyl 5 Primary Injector: 9.9 ohms
Cyl 8 Secondary Injector: 9.9 ohms

All others 12.2 to 12.6 ohms

Coil Packs Secondary with Plenum installed cold:
1/6: 20.5 ohms
2/3: 20.8
4/7: 18.2
5/8: 20.6

FP-1: 40 psig
FP-2: 40 psig

AND, what ever GM engineer thought it was a good idea to put fuse blocks up under the passenger side dash with no access doors need to be fired. If he has already retired, they need to re-hire him so they can fire him.
KJL is offline Reply With Quote

[Paul Workman]

I just finished checking some things and found the following:
Cyl 3 Primary Injector: 6.1 ohms
Cyl 5 Primary Injector: 9.9 ohms
Cyl 8 Secondary Injector: 9.9 ohms

All others 12.2 to 12.6 ohms

Coil Packs Secondary with Plenum installed cold:
1/6: 20.5 ohms
2/3: 20.8
4/7: 18.2
5/8: 20.6

FP-1: 40 psig
FP-2: 40 psig

AND, what ever GM engineer thought it was a good idea to put fuse blocks up under the passenger side dash with no access doors need to be fired. If he has already retired, they need to re-hire him so they can fire him.
KJL is offline Reply With Quote

As suspected, the injectors are NOT alcohol tolerant. Highly recommend you get the new, stainless injectors; the ZR-1 "kit" from Jon at FIC - he knows what you need, AND the kit includes gaskets and O-rings from Jerry's Gaskets.

Do you have an FSM? If NOT, my I suggest you contact WVZR-1 (Dave). He can provide you with a full .pdf file for, IIRC, $26. Ya can't beat that!

[KJL]

Thanks for the info. I def need a manual. I have a BISHKO CD for my 95 that is quite nice as well. Interestingly the car has been running better. I know the bad injectors still function but just not very well. I guess I will need to replace them this fall. The car is mostly stock with the cat-back Flow master system. Was thinking if I remove the plenum, I may as well do some porting and have Marc upgrade the chip. Now that it is exempt from emissions, was also thinking about removing the secondaries. Who does good porting at decent price? I know Marc offers that service and I am sure it is an amazing work of HP increasing art when he is done but I cant afford him at the moment. I just had him upgrade my 95 rear diff to 4.10's.

[Paul Workman]

*...I know the bad injectors still function but just not very well. I guess I will need to replace them this fall. ...*

You might want to re-think that injector replacement schedule, especially if you are going to be driving the car in the interim!

I had a burnt valve in one of my cylinders that also had a bad primary injector.

It would idle a little rough, and die while idling sometimes. And, it too seemed to run best at moderate to WOT.

What do the knock counts look like? IF in fact the injector is not delivering enough fuel, resulting in a lean condition and knocking (and you don't always hear knocks), the ECM could be backing timing off - which would also make it seem sluggish! What is the timing at cruise?

[KJL]

That is a great observation and seems to make perfect sense to me. I guess my obd would tell me what the timing is a cruise. Although I am going to change out the injectors at this point regardless. I will also check the knock count.