Pre-Ignition
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From: TX
Pre-Ignition
My Bone stock '91 knocks a couple of times whan I get on it. Some History: I had a bad oil leak coming from the back of the motor. I convinced myself it was coming from the back of the lower manifoid gasket. So I pulled off the intake and changed out the gaskets, it turned out to be one of the sensors on the back of the block was cracked. Anyway, I allways wanted to pull the TPI off to check it out 
Now it runs good and idles nice but pre-ignites when I get on it, I think the knock sensor is woking becouse is stops after a couple knocks. Any ideas? Also, as a side note it does it worse if the gas cap is on tight
And when the cap is tight and I remove it it lets lots of air in the tank, like a vaccume. I drive with the cap loose now. I was wondering if my fuel pressure was on the low side? Getting a gauge soon to check.
THX
Now it runs good and idles nice but pre-ignites when I get on it, I think the knock sensor is woking becouse is stops after a couple knocks. Any ideas? Also, as a side note it does it worse if the gas cap is on tight
And when the cap is tight and I remove it it lets lots of air in the tank, like a vaccume. I drive with the cap loose now. I was wondering if my fuel pressure was on the low side? Getting a gauge soon to check. THX
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From: Lubbock for now, headed for Oklahoma
My Bone stock '91 knocks a couple of times whan I get on it. Some History: I had a bad oil leak coming from the back of the motor. I convinced myself it was coming from the back of the lower manifoid gasket. So I pulled off the intake and changed out the gaskets, it turned out to be one of the sensors on the back of the block was cracked. Anyway, I allways wanted to pull the TPI off to check it out
Now it runs good and idles nice but pre-ignites when I get on it, I think the knock sensor is woking becouse is stops after a couple knocks. Any ideas? Also, as a side note it does it worse if the gas cap is on tight And when the cap is tight and I remove it it lets lots of air in the tank, like a vaccume. I drive with the cap loose now. I was wondering if my fuel pressure was on the low side? Getting a gauge soon to check.
THX
Now it runs good and idles nice but pre-ignites when I get on it, I think the knock sensor is woking becouse is stops after a couple knocks. Any ideas? Also, as a side note it does it worse if the gas cap is on tight
And when the cap is tight and I remove it it lets lots of air in the tank, like a vaccume. I drive with the cap loose now. I was wondering if my fuel pressure was on the low side? Getting a gauge soon to check. THX
The vacuum in the tank is supposed to be there. It's part of the emissions system(EVAP). Leaving the cap loose can cause A/F mixture issues(although slight). I don't remember what year it went from HEI to opti but if your car still has a distributor you need to adjust your timing. You would hae had to do this when you had the TPI off. If you reset the timing with a light be sure that you have or had the EST connector disconnected.
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From: TX
I have a distributor. I thought the timing was set buy the ECU. I just stuck it back in and aligned a set of marks I made. Could I have gotting that luckey. It runs well. I will put a light on it and adjust. So I guess it must be a little advanced to cause the knocking. It seams a little slugish, my guess would have been in was retarded. Unless the ECU over compsensates when it hears the knocks? Thanks for the info. So I guess I need to tighten the fuel tank cap? Are there any gains to fuel presure increases?
THX
THX
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From: Lubbock for now, headed for Oklahoma
Here is the procedure for setting the timing. It is controlled by the ECM, but it has to have the correct starting point. It only knows how far it is adjusting it one way or the other, not what the actual timing is. Everything is based off of the initial timing of 6 deg. advanced. The EST connector will break out of the loom behind the distributor. It has to be disconnected to set the timing otherwise you are not seeing the true timing you are seeing what the computer is adjusting it to
http://www.autozone.com/shopping/rep...00c1528008f848
As for fuel pressure I don't see any big gains from it. Disconnecting the pressure regulator will cause the ECM to adjust the injector pulse width down to compensate. This is all the time except during WOT, when you would have the full fuel pressure anyway.
http://www.autozone.com/shopping/rep...00c1528008f848
As for fuel pressure I don't see any big gains from it. Disconnecting the pressure regulator will cause the ECM to adjust the injector pulse width down to compensate. This is all the time except during WOT, when you would have the full fuel pressure anyway.
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From: TX
Thx - I will give it a go tonight and leave the fuel pressure alone. I did disconect and plug the vaccume line to the regulator and all I got was a rough idle, still slight knock under load. I must have stabed the dis. within a couple of deg of 6 deg. It will be interesting to see.
THX again.
THX again.
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From: TX
I disconnected the 4 pin connector from the dis. and the engine would not start. So i moved the dis both clockwise and counter and no go. So I reconnected and it started. I assume that was right thing to unplug? I could see when it was cranking that is was getting spark, i hook up a spark checker so i can connect my old style light. Any ideas?
Drifting
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From: brookville pa.
timing
you unhooked the wrong plug, the est plug is just a one wire connector it is just to the left[facing car] of brake booster, i think it is a brown wire not sure it kinda hard to find it is loomed into the wiring harness
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From: TX
So much for my GM shop manual, it says to 'disconnect ECM harness connector at distributor'. I saw a single wire connector taped to the outside of the harness by the booster. That might be it. It looks like it was set outside the harness so it would easer to get to. I will try that one. THX
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Joined: Dec 2008
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From: TX
ok the timing was off a little more then I thought. It was off the marker. It is at 6 deg BTDC now. I set it with the the car kinda cold. I didn't have much time to play. Shoud I recheck later and let the engine warms up to opt temp? BTW my engine runs way too cool in the winter. I drop a 180 deg stat in it and changed out the TCU. I was wondering how to tell when it goes into closed loop? I cruse at about 160 deg in the winter. In summer (i am in Houston so most of the year) it runs around 180 right were I like it.
Thx
Thx
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From: Lubbock for now, headed for Oklahoma
Time and temp. are the main factors for closed loop. It will go but to be sure you need to see it on the scanner unless it will set and warm up. Once the fan cycles on you know it's in closed loop.
The timing should be fine being set cold as long as the EST was disconnected. I get other than that the car runs much better now?
The timing should be fine being set cold as long as the EST was disconnected. I get other than that the car runs much better now?
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Joined: Dec 2008
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From: TX
yes it does run alot better. I didn't have a chance to get on it on the test drive but it feels better at normal driving . Thxs for your help - this Forum is great!
I removed the frisbee on the front as well, any other easy mods? I am thinking about getting another air cleaner lid that I can open up, keep the old in stock just in case I want to go back stock. Does that help any?
I removed the frisbee on the front as well, any other easy mods? I am thinking about getting another air cleaner lid that I can open up, keep the old in stock just in case I want to go back stock. Does that help any?