Car starts to jerk in lower gears

[Crusin]

Its starting out to be a season from hell. In the last two weeks I have noticed car starts to jerk back and forth while in low gears and giving it gas. On the highway car seems to run okay. I always use Premium High Test Gas so I know that isn't the problem. Wondering if it could be a blocked Gas Line Filter? Any suggestions would be greatly appreciated. Thank You :cheers:

[DaveK]

I had a similar sounding problem a couple of years back after coming out of storage. Would stumble when trying to accelerate in low gears but would cruise more or less okay. Turned out to be the plugs just needed changing. Might be worth trying, it's a cheap 'fix' if it works.

Dave

[VetteMed]

I had a similar issue when my throttle position sensor had failed. Took weeks of driving like that before it actually set a code in the ECM. Of course, I'd want to take a test drive witha fuel pressure gauge attached to the fuel rail, to see what the pressure is doing when this problem occurs. Fuel filter, or fuel pump, could possibly cause this.

[Crusin]

Thank you all for your suggestions. I believe I will pull the plugs tomorrow and check them, if okay I will change the fuel filter. If that fails I will have Fuel Pump checked out.

[tomtom72]

You will have to bleed off the fuel pressure before you loosen the F/F so you might as well do the test for pump psi at the same time...it's connected anyway. You loosen that filter without bleeding off the rail pressure first, fuel goes all over the place. My test gauge has a 'bleed off' valve & hose attached to it.

fwiw, I find that if you pull out the IAC motor it is easier to get my F/P gauge attached. It isn't a biggie and you get a straighter shot at the rail valve and a bit more room to work and it will not affect the KOEO pump test results.

:cheers:
Tom

[Crusin]

Is it possible that the Fuel Pump is going and not getting enough gas at lower speeds?

[VetteMed]

possible, yes, which is why we suggested the use of a fuel pressure gauge to see what the rail pressure is when the problem occurs.

[Crusin]

Unfortunately this problem only occurs at random so hard to do that, since I don't know when this will occur.

[VetteMed]

Well, if you want to just throw money at the problem, start cheap, with the fuel filter, air filter, and spark plugs.

If that all checks out and the problem persists, then change fuel pumps (easy job on these cars).

If the problem still persists, you probably have a plenum pull in your future. Injectors, coils, plug wires, and close inspection of all vacuum components.

Throttle position sensor is also doable and not terribly expensive, if you're taking the shotgun approach .

[Crusin]

What you stated, Vette Med makes a lot of sense to me. Start with the cheap fixes first and work down. I certainly hope a plenum pull and injectors not required for awhile. Unfortunately I am not all that much mechanically inclined ( shop in high school no mechanics way back then). CHEERS!

[VetteMed]

Don't worry -- we're all here to help you through the process. All of us at some point, feared that first plenum pull!

[scottfab]

So far I've heard a lot about shotgunning but not the usual "do you have codes set?"
So, I guess I'll advocate looking.
If you do have codes set, record them then clear them and see if they reset.

By what I've heard such that it's random and hard to predict I'd cast my vote directly to fuel pump(primary) . They can very much become this way just before failing all the way. A lean code would support it.
On the other hand I've not seen a spark plug do random failures nor a fuel filter. They are more consistent when they fail. And throttle position sensor is indeed a rare one.

One other easy to check thing is that all the plug wires are seated on the plugs all the way. I've had intermittent misses that went away when i changed plugs only to find that it was really a loose wire not the plug. On mine #3 pops off now and then.

[Crusin]

Thanks for your suggestions. Your approach makes sense, I will have codes checked first.:cheers:

[Blue Flame Restorations]

My car ran inconsistant for weeks until I replaced the pumps. Sometimes it ran great, other times it did not. This was a daily thing. Never ran the same twice on a given day. Even had an intermittant miss (at times)

Immediate fix.