Opti & fuel pressure
Thread Starter
Racer
Joined: Jul 2002
Posts: 437
Likes: 0
From: Rancho Santa Margarita Ca
Opti & fuel pressure
I am still trying to diagnos the drivability problem. I am scared to throw an Opti at it for 300.00 and find out it is not the problem. The problem is at high rpm 4500-5500 it will die out like the key has been turned off. It will then pick back up at about 4000 and do it all over again. It is also intermittant. What has everyones opti done when it failed. Does it sound like this ?
Also where do you hook up the fuel presuure gauge on a 92 ?
Also where do you hook up the fuel presuure gauge on a 92 ?
Le Mans Master
Joined: Apr 2001
Posts: 7,411
Likes: 253
From: Little Elm TX
Re: Opti & fuel pressure (keekster)
I am still trying to diagnos the drivability problem. I am scared to throw an Opti at it for 300.00 and find out it is not the problem. The problem is at high rpm 4500-5500 it will die out like the key has been turned off. It will then pick back up at about 4000 and do it all over again. It is also intermittant. What has everyones opti done when it failed. Does it sound like this ?
Also where do you hook up the fuel presuure gauge on a 92 ?
Also where do you hook up the fuel presuure gauge on a 92 ?
On your opti. Before I changed the opti, I'd replace the plugs and check your wires. I had a similar problem on my car and found that I had a bad coil and a REALLY bad coil wire.
I've had a few opti's go out and they always seemed to be heat sensitive. They'd work fine when they were cold and once the car started to warm up they'd get progressively worse till it got to the point it wouldn't run at all.
Thread Starter
Racer
Joined: Jul 2002
Posts: 437
Likes: 0
From: Rancho Santa Margarita Ca
Re: Opti & fuel pressure (R94 LT 1)
I'm not sure on your fuel pressure hook up. On my '94 it's in between the firewall and the backside of the motor on the fuel rail. If you pull your fuel rail covers and follow them, you should be able to locate it.
On your opti. Before I changed the opti, I'd replace the plugs and check your wires. I had a similar problem on my car and found that I had a bad coil and a REALLY bad coil wire.
I've had a few opti's go out and they always seemed to be heat sensitive. They'd work fine when they were cold and once the car started to warm up they'd get progressively worse till it got to the point it wouldn't run at all.
On your opti. Before I changed the opti, I'd replace the plugs and check your wires. I had a similar problem on my car and found that I had a bad coil and a REALLY bad coil wire.
I've had a few opti's go out and they always seemed to be heat sensitive. They'd work fine when they were cold and once the car started to warm up they'd get progressively worse till it got to the point it wouldn't run at all.
BTW
Is there a proper diagnostic procedure for testing an OPTI ?
Le Mans Master
Joined: Apr 2001
Posts: 7,411
Likes: 253
From: Little Elm TX
Re: Opti & fuel pressure (keekster)
Thank you very much for the post . It does seem to be temperature dependant. It gets much worse when hot. I have done the plugs but the coil and coil wire may be a culprate. I will check then tonight.
BTW
Is there a proper diagnostic procedure for testing an OPTI ?
BTW
Is there a proper diagnostic procedure for testing an OPTI ?
Melting Slicks
Joined: May 2001
Posts: 2,143
Likes: 7
From: San Diego CA
Re: Opti & fuel pressure (keekster)
On an early model opti several things can go bad. There are 2 optical sensors, a low resolution (8 signals per revolution) and hi-res (360 per revolution). Usually, this is caused by anti-freeze creeping in from a leaking water pump seal. The distributor contacts and rotor can corrode caused by water or other liquids creeping in. The bearings can go out caused by mileage.
Except for the bearings fluids can get in through the 3 vent holes on the lower edge of the opti and most likely (IMHO) around the seals on the opti that have been cooked, hardened and shrunk.
If you decide to replace the opti, you should take the new one apart and put a nice layer of hi-temp RTV on all the mating surfaces. To do this you will need a small reverse TORX (E10 I think) and a small TORX (T5 I think). I found them at Kragen's and Autozone in small kits.
There is an good article on the OPTI in either the Oct or Nov, 2002 VETT FEVER Magazine.
Except for the bearings fluids can get in through the 3 vent holes on the lower edge of the opti and most likely (IMHO) around the seals on the opti that have been cooked, hardened and shrunk.
If you decide to replace the opti, you should take the new one apart and put a nice layer of hi-temp RTV on all the mating surfaces. To do this you will need a small reverse TORX (E10 I think) and a small TORX (T5 I think). I found them at Kragen's and Autozone in small kits.
There is an good article on the OPTI in either the Oct or Nov, 2002 VETT FEVER Magazine.
Thread Starter
Racer
Joined: Jul 2002
Posts: 437
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From: Rancho Santa Margarita Ca
Re: Opti & fuel pressure (keekster)
I spoke to a Chevy Tech ( It is nice to still have friends in the bussiness)today he feels that it may be a coil wire. I guess they have a tendancy to go bad. Gonna try that first wish me luck.
Thread Starter
Racer
Joined: Jul 2002
Posts: 437
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From: Rancho Santa Margarita Ca
Re: Opti & fuel pressure (keekster)
Coil wire didn't work OPTI here I come. Any good ideas where to get one? If i plan to do the Hot CAm is this the best time ? Should I do the heads and headers also ? It is gonna have to be shorties cause i live in CA :(
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Thread Starter
Racer
Joined: Jul 2002
Posts: 437
Likes: 0
From: Rancho Santa Margarita Ca
Re: Opti & fuel pressure (keekster)
Any good ideas where to get an OPTI? If i plan to do the Hot CAm is this the best time ? Should I do the heads and headers also ? It is gonna have to be shorties cause i live in CA
Burning Brakes
Joined: Feb 2000
Posts: 824
Likes: 2
From: Camden SC
Re: Opti & fuel pressure (STL94LT1)
A failing opti may throw a low and/or high resolution code. Before the dead presidents start flying out of your wallet, I'd check for codes. Sure sounds like secondary spark issue. Coil wires gotta be cheap. Compare resistance between old and new wire just for grins. Check wire ends. I've seen coil wires with deep pitted ends and big problems. Primary or secondary coil windings can get weak. A good coil tester might nail that. Sounds like you're in the right area. Keep the faith.
dlmeyers 90 coupe zf6 3 speed shocks
dlmeyers 90 coupe zf6 3 speed shocks
Melting Slicks
Joined: May 2001
Posts: 2,143
Likes: 7
From: San Diego CA
Re: Opti & fuel pressure (keekster)
Best price I found on a Opti was Sam Smith at Fairway Chevy in Las Vegas. ~$270. I can't find the phone number at the moment, but you can probably 411 it.
You don't need to dismantle the whole front end to replace the opti, so it's not a good excuse to do the cam, heads & headers unless you really need one. :D
You don't need to dismantle the whole front end to replace the opti, so it's not a good excuse to do the cam, heads & headers unless you really need one. :D
Race Director
Joined: Jan 2002
Posts: 12,263
Likes: 86
From: O'Fallon Missouri
Re: Opti & fuel pressure (John Row)
Best price I found on a Opti was Sam Smith at Fairway Chevy in Las Vegas. ~$270.
Pro
Joined: Jan 2002
Posts: 603
Likes: 0
From: LUFKIN TX
Re: Opti & fuel pressure (keekster)
I just went through this myself. I changed the opti, and it still did not fix my high rpm miss.(around 6,500RPM's) I first noticed mine on the dyno. While the car was cool, it would not miss , but after the first pull, it would start missing, but only at high rpms. I finally tried a new set of MSD wires, and that fixed my problem. The coil wire measured 16,000 ohms that was on my car, and the new MSD coil wire measured .6 ohms. If you haven't replaced all of your wires, then change all of them first, and make sure that plug wire 5&7 are not touching. :yesnod:
Thread Starter
Racer
Joined: Jul 2002
Posts: 437
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From: Rancho Santa Margarita Ca
Re: Opti & fuel pressure (DRAGRACR)
I did the coil wire just not the others. Think It could be a sparkplug wire ? It does not just miss, It falls on its face.
[Modified by keekster, 8:17 PM 9/25/2002]
[Modified by keekster, 8:17 PM 9/25/2002]
Pro
Joined: Jan 2002
Posts: 603
Likes: 0
From: LUFKIN TX
Re: Opti & fuel pressure (keekster)
I just looked at my dyno graphs again, and when it would miss, I was loosing from 75- 100 RWHP. It would pull strong up until that point, and it was like I let off the gas, and nailed it again. Wires are a lot cheaper than an opti...... :eek:
Melting Slicks
Joined: Jul 1999
Posts: 2,875
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From: Olive Branch (Memphis suburb) MS
Cruise-In II Veteran
Re: Opti & fuel pressure (keekster)
Chris, here's the CorvetteFever articule http://www.corvettefever.com/editori...=text&id=16758 If you haven't replace the plug wires, go ahead and do them. :cheers: