1995 Mazda 626 Engine bucking at 2000rpm

RAYSMITH333

MEMBER
1995 MAZDA 626
4 CYL
FWD
MANUAL
125,000 MILES

My '95 mazda 4cyl 5 speed bucks (similar to lugging not missing) when accelerating from 2000 rpm no matter what gear the car is in. Once the rpm has increased to 2200-2300 or so the bucking stops. Otherwise the engine runs fine at both highway and city speeds.

updated by Admin 5/26/09
I disconnected the EGR valve and plugged the vacuum line and test drove the car. Symptoms persist. I checked the function of the EGR valve as instructed

and it checked out OK, the RPM dropped to the point of almost stalling with 6-10 in vacuum.

What is the next thing to suspect?

Saturday, May 2nd, 2009 AT 8:28 PM

2 Replies

RAYSMITH333

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Saturday, May 2nd, 2009 AT 9:04 PM

KHLOW2008

MECHANIC
41,814 POSTS

Hi Raysmith333,

Thank you for the donation and sorry for the delay in answering.

The symptoms seems to describe a malfunction in the EGR ystem

Disconnect the EGR vacumn hose and plug the vacumn end. Test drive vehicle to see if problem reoccurs.

Here are testing procedures for the EGR valve.

EGR VALVE - PISTON ENGINES (W/SINGLE OR DUAL VALVES)
1. Check vacuum lines for correct routing. Disconnect vacuum hose at EGR valve, and plug hose end. Connect vacuum pump to valve. Start engine. Apply 6-10 in. Hg to valve and hold.

2. Engine speed should drop at least 100 RPM or engine should stall. Vacuum should not drop more than one in. Hg in 30 seconds. Reconnect EGR vacuum hose.

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