Help! 1st Time Removing Plenum....now rough idle

[2ljd]

Thanks for the checklist. While some of the items would be nice to do, they'll have to wait a bit.

The purpose of my plenum pull was to change out the injectors and trace a secondary vacuum leak. While I was in there, I changed out the plugs, wires and coils for good measure. I traced the vacuum leak to the solenoid and replaced it. The secondaries worked perfectly after that.

Everything went back together smoothly enough, but upon startup, it felt as though it was running on only half the cylinders. That was last night...tonight, I pulled the plugs to inspect them and only one of them looked slightly discolored (probably didn't run them long enough to affect them).

Then I started the engine again and began to pull each plug wire one by one to see if the idle changed at all. Well, it appears that cylinders 2, 5 and 8 didn't change the idle when I pulled the wires. I know they were all getting spark because it was jumping to the heads.

So I need to pull the plenum and check each injector for resistance as well as for spray, and make sure I pushed the connectors on all the way. If they check out, I'm dreading having to trace back from there...

[Hib Halverson]

Originally Posted by jon_d4

94 ZR-1

I just removed the plenum to fix an oil leak from the crankcase vent and tubes. Got everything back together, and I'm getting a really rough idle and the car won't rev above 3k. It runs fairly smooth up to 3k, then it just pulses and shakes violently refusing to go any further.

I've already pulled the plenum back off once to check all of my vacuum lines and that I have a good connection on all of the plug wires. It's still possible that I've missed something, but I've rechecked as much as I can.

It's also throwing a code, but since it's a 94, I can't get the ECM codes by just jumping wires on the connector for the ALDL. (snip)

Oh...but you can indeed!
For your future reference, because partial OBD2 capability was only on 94 base cars, you can get codes from the LT5 ECM two ways.

1) Ground pin 6 of the 16-pin "OBD2" DLC connector, then key-on/engine-off and the MIL will flash codes.
2) Ground pin 12 of the 16-pin "OBD2" DLC connector, then key-on/engine off– and observe the IP Display. When the sequence gets to module 4, any codes there will be ECM codes.

You can find more detailed descriptions of these procedures in the 94 Factory Service manual. Section 6E for flash code diagnostics and Section 8D for CCM diagnostics.

Glad you got the engine running. Mixing up those plug wires does it every time, be it an LT5 or otherwise.

[max76]

Hi dynomite, what are Air Bag Accelerometer?
Are the two little box on the frame?
I remove them and check the ground, clean the frame and put dielectric grease, reset the error
But I always have the error "inflt rest" and the "man with safety belt"...what I can do???
Thanks in advance!!!

[max76]

Dynomite i deleted the codes, flashing code 12...but if i start engine the error and the light come again...can i check other?

[mgbrv8]

Hey Jon

Here are pics of my plenum pull I hope they are helpful and if there is anything I can do I will be happy to help

https://www.facebook.com/media/set/?...1&l=8f46fa4533

Dave

[Paul Workman]

Originally Posted by jon_d4

So, just wanted to wrap up this post and fill you guys in on the results. Sorry for the delay. I was traveling for work this last week and wasn't able to work on the car until yesterday.

Car is now running great! I think my issue was actually the vacuum lines going to the MAP sensor....I pulled the plenum and checked the connector going to the ignition module like was suggested; everything looked good. Well, when I got it all back together the car wouldn't run at all... I was out of time to work on it, so that's where it sat until yesterday.

I pulled the plenum again to recheck everything and discovered that I had two of the ignition coils swapped on the drivers side of the car. When I pulled the plenum the last time to check the connector for the ignition module, I also pulled the ignition coils and the plate above the starter out to retrieve a dropped bolt and must have got them mixed up then.

I got it all back together and double checked my vacuum line going to the map sensor....fired right up and didn't throw a code! Thanks for your help, guys!

Nothing like a digital camera and some "before" pictures to sort things out "after", I find. Especially when working on something new!

[max76]

Dynomite, i have error code 26...suggestions???
Thanks guys

[Dynomite]

Originally Posted by max76

Dynomite, i have error code 26...suggestions???
Thanks guys

Yes......your RH INFL REST Sensor is not grounded or otherwise not functioning. There is a yellow connector under the Floor mat on passenger side that needs to be checked.

For 90-93 Cars jumper A to K on the ALDL and the INFL REST light will flash
1990 SIR Codes
14 Front Sensor #1 (LH); Short to Ground
15 Front Sensor #1 (LH); Open Circuit
16 Front Sensor #1 (LH); Sensor Fault
24 Front Sensor #1 (RH); Short to Ground
25 Front Sensor #1 (RH); Open Circuit
26 Front Sensor #1 (RH); Sensor Fault

[max76]

Ok dynomite, in the next weekend ill check the connector and ill let you know.
Thanks in advance.
Max

[max76]

Hi dynomite, i check the connector on the passenger side, it Was loose!!!
I close it and reset the error, the infl rest light and the man with safety belt are disapears!!
Thanks a lot!!!