GT Won't go over 3000rpm While Driving (Page 2/2)
Patrick JUN 08, 02:45 PM

quote
Originally posted by reinhart:

I changed the original GM pump about 30,000 miles ago... I don't believe there are any rubber lines inside the tank.



Ummm...




Another possibility is that your muffler is partially blocked with broken up innards from the removed cat.
zkhennings JUN 08, 03:13 PM
As someone who has had the hose inside the tank split (reused the 4cyl submersible hose in a V6 swap), it will not develop full fuel pressure during priming, idling, or driving, so while a possible point of failure for the fuel system, I would be surprised if it is the culprit here.
reinhart JUN 08, 04:44 PM

quote
Originally posted by zkhennings:

Fuel and air are you factors that will differ when parked vs when driving. The car will consume much more fuel and air under load, spark however is the same. If it can rev out at idle then spark is almost certainly not the issue.

I would agree that it is probably a restriction to the fuel. You really need to record the fuel pressure while driving to be certain it is not a fuel issue. You can have good pressure when parked and the engine is not asking for a lot of fuel, but poor pressure when the fuel demand goes up when driving. Could you mount the gauge and have a go pro record it?

It could also be air, if you have a massive restriction in your air intake system. Pushing air out could also be a restriction, you make a lot more exhaust under load than when parked.



Interesting idea. I was trying to rack my brain as to how I could be able to see the guage while driving when I was testing it in the driveway. I don't have a go pro but it gives me the idea to use a cell phone video recorder. I could tape both the gauge and phone in place. and just have it record for a couple minutes while I drive around. I'll have some time to work on this later in the week. Thanks for the ideas guys.
reinhart JUN 08, 04:47 PM

quote
Originally posted by Patrick:

Ummm...




Another possibility is that your muffler is partially blocked with broken up innards from the removed cat.



Ah there is one rubber connector. I reused that.

Regarding the cat, It was removed about 25 years ago lol.

[This message has been edited by reinhart (edited 06-08-2021).]

Dennis LaGrua JUN 08, 05:34 PM

quote
Originally posted by reinhart:


Ah there is one rubber connector. I reused that.





I would guess that there is a small leak in that old connector hose limiting the supply at high engine demand. You can buy or borrow (many auto stores loan them out) a fuel pressure gauge with a 3' hose. Attach the gauge to the schrader valve on the fuel rail , remove the passenger side vent grill and tape the gauge to the rear window. Accelerate to the 3000 rpm limit and have an assistant record the readings. If you do not get about a 43 psi reading then it is the hose connection, the fuel pump or possibly a bad connection at the connector near the firewall.

------------------
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reinhart JUN 09, 05:35 PM
I own a gauge like that which is what I used to test it. I'll likely get a chance to test it on the road tomorrow. I'll report back.
reinhart JUN 11, 12:45 AM
I hooked up the fuel pressure gauge and taped my cell phone nearby and went out for a drive. The car was back to its old self. No issues revving and power was great. LOL So the only thing I messed with since my previous last test drive was some of the wires that go from the distributor to the ignition coil I had repositioned and reinsulated a few days ago but never took it out for a test driv. I mentioned one wire had a fray previously although I had taped it up and my test drive after that didn't make a difference.

So either the problem is intermitant or it was the wires from the distributor to the ignition coil. Regardless fuel supply block/leak ideas were incorrect. It could also be some other intermittant spark issue.

Thanks for the ideas. I'll update if the gremlin comes back.
zkhennings JUN 11, 12:43 PM
I very much doubt it was an issue with driving vs parked then, and more of an intermittency that got triggered when you were driving by luck (or unluck). Those cables that go to the ignition coils and distributer are suspect and should be replaced IMO, they are right above the exhaust and I have seen them become an issue on my Fiero and others. Though usually they cause the car to intermittently die and not have a rev limiting effect. You can construct new ones yourself from connectors with pigtails that you can buy from RockAuto. I soldered and heatshrinked mine together but crimps would work fine too.