99 Winny Still bucking/jerking!

[SRamsey625]

Some of you may have seen my previous post about my 99 bucking and jerking when cold. I set off on a quest to resolve the problem. I bought a Haynes manual and began checking things. I checked the dpfe, it checked good. I checked the egr vacuum regulator: good. I even borrowed a new dpfe from a friend at the ford dealer and it bucked with it. I got a constant 2 volts of signal voltage at the dpfe and I was sure that my egr valve was stuck. I replaced it. One ford mechanic I spoke with said it sounded like my egr ports were plugged except one causing a misfire. I pulled my upper manifold off and cleaned the runners and egr ports. I even put a little seafoam down each port. It runs much better, but still bucks at me on the way to op temp. (mainly when I get on the highway) If I isolate the egr system, the whole problem goes away. As soon as I hook it back up, it returns. you get the idea. everything checks good but the problem is still there. It's doing this to me . Surely someone else is having the same problem. Give me some ideas..

[SonOfDolomite]

I had a problem with my 95 surging when idling and driving at low rpms. It ended up being a dirty MAF sensor, picked up some electrical contact cleaner sprayed it off really good and *poof* problem solved. I dont know if this has any relation with the bucking and jerking, but might as well give it a try, you never know!

[lewisnc100]

Sounds like you've done a good job of isolating the problem to the EGR system. Just to confirm, you are getting no error codes right, check engine light is off?

You've already replaced the EGR valve but have you checked the following EGR components (I would think you would have a check engine light if these were bad):

Differential pressure feedback EGR sensor - The differential pressure feedback EGR sensor is a ceramic, capacitive-type pressure transducer that monitors the differential pressure across a metering orifice located in the orifice tube assembly. The differential pressure feedback sensor receives this signal through two hoses referred to as the downstream pressure hose (REF SIGNAL) and upstream pressure hose (HI SIGNAL). The HI and REF hose connections are marked on the aluminum differential pressure feedback EGR sensor housing for identification (note that the HI signal uses a larger diameter hose). The differential pressure feedback EGR sensor outputs a voltage proportional to the pressure drop across the metering orifice and supplies it to the PCM as EGR flow rate feedback. Approximately $85 list.

EGR vacuum regulator solenoid - The EGR vacuum regulator solenoid is an electromagnetic device which is used to regulate the vacuum supply to the EGR valve. The solenoid contains a coil which magnetically controls the position of a disc to regulate the vacuum. As the duty cycle to the coil increases, the vacuum signal passed through the solenoid to the EGR valve also increases. Vacuum not directed to the EGR valve is vented through the solenoid vent to atmosphere. Note that at 0% duty cycle (no electrical signal applied), the EGR vacuum regulator solenoid allows some vacuum to pass, but not enough to open the EGR valve. Approximately $25 list.

[DRW1000]

It sounds like the EGR is good, and the DPFE is good (as you replaced both) and your EGR ports are clear.

The Vacuum Solenoid as Lewis suggests controls the EGR valve and when to open and close. If it is always closed (due to the vacuum solenoid) I would suspect the DPFE to give a code as it "reads" the flow and the PCM has commanded the valve to open but it has not. I would also expect a code if it constantly open for the same (yet reversed logic).

A partially working solenoid may be on the threshold of working correctly and thus no code. If the EGR is not openeing all of the way I would expect an increase in NO emissions but perhaps no driveability issues but if it opened more than required I would expect a cold or idle or both driveability issues. Similar to what you see.

If your CEL light is on you might want to read the codes (if you can at Autozone) or you may just wish to buy a new solenoid. The other thought is perhaps a blocked vacuum line to the solenoid or from the solenoid to the EGR. You may also wish to check the feedback lines from the manifold to the DPFE to ensure they are clear and/or not broken.

Good luck............Keep us posted