86 240 wagon auto Spudders in Drive

Kenwood240 · Post by **Kenwood240** » 19 Oct 2015, 19:18

Once up to speed the car will driver normal unless you hit the throttle hard. In idle it will and rev up all day long without issues. I've replaced, Intank pump and sending unit, fuel pressure regulator, plugs, wires and cap along with the fuel filter. The vacuum lines look all good as well. Does anyone have any advise on what to check next?

93Regina · Post by **93Regina** » 19 Oct 2015, 20:38

Kenwood240 wrote:unless you hit the throttle hard

If I translate this correctly, then a lean mixture is the issue.

So, possible solutions:

1. Main Pump weak
2. MAF (AMM) has an issue
3. O2 Sensor would tend to enrich the mixture if bad...what color is inside of you exhaust pipe at rear?

Any Codes? On socket 2 & 6 ?

Kenwood240 · Post by **Kenwood240** » 20 Oct 2015, 18:16

The exhaust is original to the car and is black and sooty. I have ordered a replacement O2 sensor and inline fuel pump as well since those both appear to be original to 1986. Downside is they won't be here until tomorrow. The maf was just replaced two weeks ago since the car wouldn't run before with the old one. This studdering was still present before as well.

Kenwood240 · Post by **Kenwood240** » 21 Oct 2015, 13:23

I've replaced the O2 sensor and also the inline pump today and it still has that stutter. I'm not quite sure what else it would be at this point.

lummert · Post by **lummert** » 21 Oct 2015, 16:41

Fuel pressure regulator?

Kenwood240 · Post by **Kenwood240** » 21 Oct 2015, 21:01

I just replaced that along with the two prong coolant temp sensor. The car now drives very well when cold but once up to operating temp it has the and stutter again. Could a bad ecu cause this?

93Regina · Post by **93Regina** » 21 Oct 2015, 21:30

Kenwood240 wrote:up to operating temp it has the and stutter again. Could a bad ecu cause this?

When running in open loop, extra fuel is dumped into cylinders. In Closed Loop, any vacuum leaks (injectors' o-rings, brake booster, interior power-vents, intake manifold gasket, etc) can cause a lean mixture.

Also, the throttle switch must be set correctly, and the throttle valve needs to be at OEM specs. I'm not familiar with LH 2.2, but on earlier LHs, there was an air-adjustable idle screw.

I would never replace an ECU until OEM spec/adjustments are to OEM standard.

When I buy an EFI vehicle, I replace injector o-rings, intake gasket, and check for vacuum leaks.