Notsure if it is a knock sensor or fuel pump issue, or BOTH!!!

[tjrockstar]

Hey Guys, went to T3, who said I had codes on the knock sensor(and a resolved code for the MAF), and quoted a replacement of sensors, harness and plenum gaskets. This is based off my complaints of issues of light to Severe (and I do mean SEVERE, as in giving the GF nausea, does wonders for post dinner romance!! ) bucking, and hesitation. Erratic idling at times, stalling when coming off the gas pedal. Lately there are times, where regardless of how much I press the gas pedal it will simply coast. At times it will buck and then act normal.

All of these issues are intermittant, and sometimes they will happen during a whole drive, or other times these issues will not show at all. And I do have the fuel pump noise on less then 1/2 tank of gas, but lately I somtimes get the noise above 1/2 a tank of gas.

So I am unsure about going with the knock sensor replacement as T3 suggests, or concentrate on a fuel pump replacement. Or do I need to dig deep in the pocket and go for both? Also if they are under the hood swapping knock sensors, shoudl I have them to do plugs, oil, fuel, pcv, etc etc? I am getting a list of items to purchase from Everything Infinit.com and want to get it into the shop.

Thanks,

Tim

[email protected]

[RobertsnewQ]

Knock sensor is unlikely to cause those symptoms.

In the ECU, if it detects that the KS are bad, it simply switches to the "knock" fuel and ignition maps and sets the code. You just get poor performance and gas mileage, but nothing else.

Fuel pump is much, much more likely. A failing pump will take out the controller (ask GQ Jay about that) so make sure to do it if you even suspect that it is close.

On any high-powered EFI car, a fuel pump is a 100,000 mile item. Period. Any usage after that point is on borrowed time. How many miles are on yours?

A bad MAF or connector is another likely suspect. Clean the MAF and connector and see if it helps.

But if you hear the pump, and you have more thn 100,000 miles, do it right away.

[maxnix]

If you do go the KS and harness route, do all the under plenum hoses too.

What's the fuel pressure vs rpm?

[tjrockstar]

If you do go the KS and harness route, do all the under plenum hoses too.

What's the fuel pressure vs rpm?

I have no idea of the fuel pressure vs RPM. not that mechnically minded these days, and don't have the personal facilties to dive in. With limited funding at this point, I want to know what I should do, for repairs in what priority, and what I will need to get for the repairs. Gotta find the least expensive parts, and keep labor costs down for now.

But I do realize that there is a serious issue that needs to be resolved and soon.Thanks for the advice guys

TJ

[Q451990]

I think your bucking issues are far more likely to be from a bad fuel pump, or fuel pump controller. Or from a bad MAF. If I were working with a limited budget, I would address that issue first and then go for the knock sensor/under plenum overhaul when you have the funds to replace everything under there. Bad knock sensors will typically cause the car to just "not feel right" to the average driver... due to the reduced power from the ECU retarding the timing advance. You may notice a very slight bucking (e.g. at 40-45 mph uphill in 4th right before the T/C unlocks) but nothing as severe as you describe.

T3 is the best place to take your first gen. Q so take advantage of Byron's expertise! We've had members drive from KY and beyond to have them work on their Q's.

Heath

[96Qowner]

Do the MAF first. Your symptoms sound exactly like a failing MAF, and you have a code for it ($75-100 used, easy DIY). Then think seriously about replacing that fuel pump before it fries your controller (FPCU).

The knock sensors can wait until you have the funds, but plan on replacing all the under plenum hoses, sparks plugs, Knock sensor harness, and probably the valve cover gaskets, while Byron's in there - over $2000.

(I'm one of the guys who drives all the way to T3 for service on my Q.)