June 29, 2013

Close Up: Isuzu 4Z Idle Air Control Valves

This is an IAC valve for the 4Z family of Isuzu motors.  I just changed back to the new one from the old on on the Impulse so I thought I would snap a few photos of the old one and the new one together.  The differences are subtle; they are essentially identical. This is also one helluva part to change out on the car. You pretty much need to have baby arms with octopus tentacles instead of fingers. This is the devices that regulates the airflow after a cold start.  It allows air into the throttle body when the engine is cold, and it slowly changes the flow as the engine warms up to maintain a steady idle. If your Isuzu isn't idling well after a cold start, this part might be the culprit.
Old on the left, new on the right.

June 26, 2013

At long last...

In December of 2010, I parked the Impulse and began tearing it apart.  Even though it only had a hair over 60,000 original miles, the car needed a complete mechanical refresh.  So the motor came out and in April of 2012 I finished assembling everything.  Then things came to a halt as I worked to sort out a problem with the car not idling.  I worked on it on and off over the following months, taking several months off here and there to concentrate on other projects and to ease some of the frustration I was feeling about the Impulse.

The problem was simple.  The car would turn over and immediate stall out.  At first, I thought the problem was with the timing.  But once I was certain that was not it, I thought the problem was related to fuel pressure. After I figured that was not it, it was obvious that it was an air/fuel mixture issue or some sort of electrical problem.

Fast forward to last weekend.  My good friend Tom was in town and we started working on the problem.  He is much more mechanically experienced than I am, which was a great help. We methodically started plugging every vacuum line from the MAF back in an attempt to isolate the vacuum leak that was causing the issue.  For a while we thought it was a vacuum leak at the throttle body, but ultimately, while squirting carb cleaner into every nook and cranny, Tom heard the engine bog down when he sprayed around the injectors where they mate to the intake manifold.

So basically, a tiny gap around all four injectors was allowing a vacuum leak big enough to cause the car to fail to idle, but run smooth if you could get it to turn over and stay running around 3000 RPMs.

So I dug through my bin of parts, and I don't know if it was blind luck or a subconscious memory, but I pulled out the original box that contained the Beck/Arnley injector o-ring kit and I found a little pack of smaller o-rings still in the box.  Voila!

Now, mind you, the original OEM Isuzu injectors had only one o-ring on them.  This being the larger one.  So when I replaced the OEM injectors with a new set, I only installed the large square-shouldered o-ring from the Beck/Arnley kit, assuming the smaller ones must be for a different vehicle with similar injectors.  Bad decision.  Here is a photo:

June 24, 2013

Strange sign at the car wash...

So I was at the DIY car wash last weekend, and a sign on the stall wall caught my eye.  I snapped a photo with my phone to see if I was right. Sure enough...

This sign is on the wall of each of the 4 stalls at the car wash.
And here is the original photo...the Isuzu 4200R concept!!!  How odd to see this on the wall at my local car wash!

June 1, 2013

Keeping with the depressing theme...

...ran across these pics of a 1985 gen1 Trooper...rusted to hell.