90 wont pass smog

[TonyTZR1]

Well, the dreaded SMOG issue. The car passes everything but the idle test. The idle fluctuates up and down, even more so when the secondary injectors are on. Is this a result of an injector/injectors leaking down?

Thanks;

Tony

[Jeffvette]

Need to check fuel air and spark.

More than likely you have a couple of injectors petering out.

[TonyTZR1]

Thanks for the feedback, I have just acquired the car and in the process of trying to get it to pass SMOG, here is what I have done so far:

Removed the injectors and had them flow tested.
Replace plugs, and found some bad smog hoses. Replaced. Also found the hose to the map sensor off.
Fresh tank of fuel and added Teckron.

Tony

[tccrab]

Check for vacuum leaks.
I had a funky idle similar to what you describe after I changed my injectors last year. Turns out I had a small vacuum leak at the funky one piece two pipe PCV connector just behind the throttle body on the drivers side of the plenum. If it's not exactly in place it will leak and cause you all kinds of grief. GM realized it was a problem because they changed it to a different connector in the following years.
Use a portable propane bottle (the one the plumber uses to solder pipes), don't light it but crack the valve and spray around the hoses while the car is idling. Where's a vacuum leak the propane will be sucked in and the idle will increase a little. The bigger the change, the bigger the leak.
What you are looking for is a small leak that will temporarily seal when the engine gets warm or if the RPM's are up and the engine vacuum is greater.
Also check the PCV hose that runs behind the plenum, it's a common fault, it degrades from engine heat and cracks.

Good luck!!!

[TonyTZR1]

Tom;

Thanks for the reply. When I had the plenum off, I did find three hoses that were bad. The manifold hose that holds the two pcv valves and the small "F" hose that goes on top of the pcv valves. Also found the MAP hos off and cracked. Replaced those and installed clamps on the MAP hose.
But, I will check for leaks again and see what I find.

One other question, I noticed some guys are using Accell injectors as a replacemnt. Is their any modification for the secondary side?

Thanks again;

Tony

[tomtom72]

Tony, I think this maybe a shot in the dark. There is a TSB over at the netreg site about idle fluctuation in closed loop. GM issued a updated PROM as a remedy for the 90 ECM's. I don't think this is your issue but it maybe worth a look if ya run out of things that are obviously n/g.

:cheers:
Tom

[TonyTZR1]

Tom;

Thanks for the information. The ECM was replaced by the previous owner in 2005. I don't know if the prom was a part of the replacement or not. I will check out the TSB.

Thanks again

[tomtom72]

Tony, you're welcome. I still don't think the PROM is a good bet because the TSB was not a recall. It was a remedy to customer complaints about hot idle surging & fluctuation. If the ECM was replaced by a dealer they proly talked the customer into an updated PROM if they were looking to pad the job/bill at a low cost-hi profit margin....I bought the updated one for my 90 and it only cost like $35 from GM. The ECM's don't come with PROM's, so you have to do the transplant if you swap ECM's, but you proly know that, I'm just covering all the bases. I didn't know beans about EEC systems when I bought my Z, boy o boy am I getting edjamacated...:o I come from the holley carb generation!

When your state does the idle test did they give you the print out of the results? If so then tell us what they were & it would help the guys analyze the issue.

Does she smell rich or lean? What was beyond the limits?

If I can do this correctly, someone posted this awhile back vis a vie smog testing so I put it in my favs because I'm so behing the curve with this stuff.
http://www.aircare.ca/index.php?repinfo-ere-causes-hc.php

I'm just not good with this stuff yet!
:cheers:
Tom

[Aurora40]

The idle fluctuates up and down, even more so when the secondary injectors are on.
That seems odd that the secondary switch position would affect the idle?

[TonyTZR1]

Me too, from the Holley generation and yup, I am getting an education. I will have to go back tot he dealer and get the print out. Unfortunately the guy I am getting the car from brought it to the dealer for the smog test. Found three bad injectors, replaced and flow checked the rest.
I checked the idle myself, brought it up to the 2500rpm required for the smog test and after a couple of seconds, engine at normal operating temp, the idle drops down by 400 to 500 rpm then immediately goes back up to the 2500rpm.
The dealer said that one or more of the injectors could beleaking down, so I asked a folish question, actually two, if the injectors were a suapect to begin with why didn't you run a leak down on them before putting the car back together? And, did anyone pull a spark plug and check it? I didn't get an answer.
I think another thing I can check is the air control solenoid valve and the canister purge solenoid valve. I know the dealer didn't do that.
Now that I have the car in my posession, I am going to have it scanned and see what it says.

Really appreciate everyones help, what the hell is a computer? Man what a cluster.

Thanks again and I will try to get the print out.

Tony

[tccrab]

I checked the idle myself, brought it up to the 2500rpm required for the smog test and after a couple of seconds, engine at normal operating temp, the idle drops down by 400 to 500 rpm then immediately goes back up to the 2500rpm.

Really appreciate everyones help, what the hell is a computer? Man what a cluster.
Tony

Tony:

If I read this correctly, your idle is up around 2500 rpms?!!:confused:

If your idle is this high, then your problem sounds a little like what my buddy Joey Gibson had about a year ago. I will attempt to dig up his posts and his answer, but in the end I think it turned out to be a bad ECM.
I'll go digging around...
The posting is over on the CF and I'm no longer a member there, but if one of you guys will go searching for user name JoeyGibson you will hopefully find his thread on solving his high idle.

My idle was running around 1000-1200rpms at most and was variable. No where near the 2500rpm you mention.

Tom

[tomtom72]

This was the thread I found...it was the coolant temp sensor...is this the one ya mean TC??

http://forums.*************.com/showthread.php?t=1729591&highlight=high+idle

:o
Tom

ps this link will not work. don't know why I musta did it wrong, sorry. Let me know & I'll try to search over "there" again.

[tomtom72]

Jez ya think that a dealer would know to do a leak down test. If the injectors are OEM there is a chance that they could be falling victum to the ethanol in the gas. The early 90 - 92 or 91 were not intended for use with ethanol.

I also hope the dealer did not try to clean the OEM injectors....that usually makes them worse.

I'm with you...look over the plugs & ohm out the wires + coils...you can do a set at a time. 4 coils, one coil drives two plugs. So if ya ohm a wire you are reading the ohms from that plug ya start at , thru that coil, to the other plug wire in that pair. I believe there is a thread about that here plus a thread about checking the injector resistance over at ZR1specialist.com....Mr. Haibeck's site...

I really think that maybe the CTS could be n/g or a better bet maybe that the injectors are fubared.....they should have done a leak down test with the plenum off:mad:

Can you smell her...is she rich? When my injector coils went, man did mine smell lean, make your eyes water she was soooo baaad!:cry:

:cheers:
Tom

[tccrab]

This was the thread I found...it was the coolant temp sensor...is this the one ya mean TC??

http://forums.*************.com/showthread.php?t=1729591&highlight=high+idle

:o
Tom

ps this link will not work. don't know why I musta did it wrong, sorry. Let me know & I'll try to search over "there" again.

Tom:

Nope, that's not the posting, the right guy, but not the right post. It was in one of his last few posts as he sold his ZR1 late last year and had finally fixed the high idle after messing with it for months and months and months.
A search based on just "JoeyGibson" and sorted by ascending date should dig it up fairly quickly.

As far as the link not working, I'm beginning to see a pattern...
And I'm totally in agreement with the obvious new policy.

Tom

[tccrab]

Found it!!
Don't ask what I had to do in order to use the search function at that other forum. I'm so ashamed, I feel so dirty...

I had an extremely high idle from first startup for about 20 - 30 minutes or so every morning. Turned out to be a bad ECM. Also found the ECM ground was bad, and a new one was run.
<snip>
..He ran a new ground for the ECM, and then diagnosed it as an ECM problem. I bought one from White Racing Products, put it in.......and the entire car acts differently. My gas mileage went up, secondaries seem to kick in harder, seems to have more power.

[TonyTZR1]

Tom;

The smog test requires bringing the idle up to 2500rpm and holding it for a short period of time. What is taking place is, at the 2500rpm the idle will drop down by 400 to 500 rpm and then will go back up to the 2500rpm. If just sitting in a normal idle condition, it is around 950rpm but will increase to 100 to 1200rpm then drop back to the 950.
Here is some information I got from the dealer. I don't have an actual read out because they didn't want the car going into the system and be labled a gross polluter. But they gave me the are of failure which is co reading. The left bank is fine, it's the right side that the reading fluctuates, from 65co to 450co.
Sorry if my original post on the rpm was vague.

Everyone, your help is really appreciated.

Tony

[tomtom72]

Tony,

That was nice of them. I'm just not sure what's wrong with that bank. It would appear that it gets too much fuel or not enough spark to burn the fuel(? that don't make sense) at 2500 but why just at 2500... I'm not getting this...I'm sorry man, my only input is useless.

I'll pull a guess outta my arse...that O2 sensor is n/g? but that would show up big time on the scan's cross count numbers.

I think if I have time at lunch I'll look in my helm FSM in section 6E, emissions. If I learn anything I'll post up.

hang in there man, somebody knows this answer & they'll post up.:thumbsup:

[TonyTZR1]

Hey, thanks again. I am going to a friends shop this morning and put on a scan. I know the dealer didn't do that. They don't do anything unless given direction to do so. By the way, I went to pull a pluk on it and found every plug finger tight. Pull all the plugs, they looked good all the same color, none wet, checked the gap and reinstalled them. The plugs have about 300 miles on them. I took the car car for a drive, and the idle is still the same.

Frustrating.
Thanks again

[TonyTZR1]

Forgot to mention, one idea was a crappy ECM tune, but with one bank being affected I am inclined to say that is not the problem? But then what do I know?

[tccrab]

Tony:

Which local dealer did you take it to? The Lithia Chevy shop in Redding has a guy there that knows ZR1's, he used to take care of mine when it lived up there. I'll have to ask the previous owner what the guy's name is.

There are at least two ZR1's in Redding, a Yellow '94 owned by Steve (IttlFly) on that "Other Forum Who Shall Remain Nameless" and another one but I don't know much about it.


Tom

[TonyTZR1]

Tom;

The previous owner brought the car to Taylor Motors for the SMOG. That's when theproblems started. Yup, I think I know the guy from Lithia, Mike Brooks. He did a lot of work for me on my Z06, knows his stuff. He is now an airline pilot. Quit about three years ago.
But here is the latest news. The good first, I took the car over to a friends shop, put it on the scanner and as you mentioned, the 02 sensor on thre right bank bad. The dealer did not run a scan, but was sure anxious to remove the intake again claiming a leaky injector. I pulled the plugs and they all looked great.
Also, and the dealer had the intake off to replace three injectors, their is a small rubber manifold, 4- holes, two in two out, that is located just under the throttle body area. When the tech put this back on it was on backwards, two holes on one side are smaller than the opposite side so a massive vacum leak. New 02 sensor and vacum leak fixed and wala, idle is normal and at 2500rpm it holds without variation.
Now thw bad, When the dealer removed the vacum tube, left side and two torx bolts hol it in place and it crosses or lays under the small 90 degree intake collant purge tube, they cracked that purge tube where it press into the intake. Found this when I went to move the rubber hose up a little, just touch it and collant leak. So I had to jury rig a fix to get it home. Now I am on the hunt for the 90 deg. tube.

I am taking it in to a friend tomorrow for a SMOG, so I hope this is the final chapter in the story.

Again, thank you all for the help and I hope this site does not change, it is great.

[tomtom72]

Hey Tony:thumbsup:
That is way cool that you solved this issue.....now go enjoy your toy!

I hate to say this but with these cars unless you get lucky and find the rare Tech that is into their job.....we're better off working on our cars ourselves. We own rare birds indeed.

:cheers:
Tom

[TonyTZR1]

Tom, thanks and yup, you are correct. I think the guy that owns the yellow one bought it from his father. If it's the same guy, I used to work with him, he is really a nice guy but not a wrench.

Thanks again

[Jeffvette]

When the dealer removed the vacum tube, left side and two torx bolts hol it in place and it crosses or lays under the small 90 degree intake collant purge tube, they cracked that purge tube where it press into the intake. Found this when I went to move the rubber hose up a little, just touch it and collant leak. So I had to jury rig a fix to get it home. Now I am on the hunt for the 90 deg. tube.


You had better tell the dealer to be on the hunt for it. It has been discontinued for a loooooooooong time.

[TonyTZR1]

Yup, I have had some words with them. I do a lot of business with this dealer, mostly in parts. I have a 427 ZL1 motor on order and told them I can cancell or buy it, how they treat this situation is up to them but I need the part by next week.

More good news, the car passed smog this morning, no issues at all.

[Jeffvette]

Yup, I have had some words with them. I do a lot of business with this dealer, mostly in parts. I have a 427 ZL1 motor on order and told them I can cancel or buy it, how they treat this situation is up to them but I need the part by next week.

More good news, the car passed smog this morning, no issues at all.

Good job on smog.

I'm willing to wager that they will not find the 90 degree elbow. New or used.

[TonyTZR1]

I am with you. But I do have a solution, their is a shop here that deals with special lines/fittlings etc. They can make one up and I will give the dealer the bill.
I am not sure, but I think this tube is metric, as it's between a 5/16 and 3/8 in size.

[TonyTZR1]

Well I lucked out on the 90deg fitting. I got a fitting from a shopt that makes up A/C lines. The piece I got did have two fittings on it but I used a die grinder and removed them. Looks just like the original all for $4.00.
I ran the car for about a hundred miles, runs great all injectors working fine.
I have a guy that wants to buy it so it looks like it may be sold.
Just waiting on the new one.

Thanks again for all the help.

Tony

[1FST ZR-1]

Glad you got it fixed, I think I am the other guy that has a yellow Z in Redding, The guy that has the 94 did buy it from his father, man what a nice Z, and the third yellow Z is owned by Steve(ittlfly) they are both 94s. Hope to meet up sometime, if you need any help with issues that may show let me know.:cheers: