Split Second Hesitation at Specific RPM

[wlmbusiness]

This is a great forum. I have read through a lot searching for an answer to a hesitation problem I am having and would really appreciate some thoughts. PLEASE NOTE: there have been other threads about hesitation that sound like the same or similar issue, but I'd like to provide my details and see if any new light gets shed on the subject. Thanks in advance for reading.

I have a 97 SRS 4WD with 140K miles.

I have been having a hesitation issue for almost two years, but intermittently. It happens when I am just cruizing along, not while excellerating, or going up a hill, etc.

It is a momentary hesitation -- literally about a half a second -- where it's as though the engine is not getting gas for that split second. In fact, the first time this ever happened, I had just filled up in a remote rural area and I thought for sure I got some bad/dirty gas. This theory was supported by the fact that the first time this hesitation happened, it happened a few times in a row, much more than a split second. Yet, over the next 2-3 weeks, the issue subsided and I thought I was free and clear. HOWEVER, every once in a while, I would feel this split second hesitation (like the engine was going to cut out). After the initial event, it would happen sometimes twice a month, sometimes not at all. Finally, it stopped all together for about 6-8 months.

Then, out of what seemed like nowhere, it happened again. Same cycle of events as the first time it all started. Hesitated a number of times during and shortly after initial "event". Then over a couple weeks, it diminished, and now it

 

[Stick Figure]

If it were my truck doing this, i would look to the ignition side. Since there are three coils, a problem in a single coil probably wouldn't be THAT dramatic. I would look into the ignitor for a problem.

Of course i could be off base on this since i don't know what kind of regular service and maintenance your truck gets.

 

[Nuke]

I'm thinking ignition also. But another possibility is fuel delivery.

Intermitent issues like this can be a bear to get your arms around. It's not as if you can, say... change the plugs, go out and drive and know it's fixed.

With that said, I'd begin the "selective modular replacement" routine...

When was your last tune-up? Replace the plugs and test the coils/cables (there's a simple procedure in the Repair Manual which I no longer have, sorry). You might want to replace those, too, but they're a bit pricey I think.

If it continues, replace the fuel filter. It's an often overlooked item and inexpensive. I'll bet it needs to be done anyway. I 'm not versed on fuel injectors but there could be an issue there, also.

When I first began reading your thread, I immediately thought bad MAF. I had a hesitation every time I goosed the pedal. The engine would stumble anytime I'd try any acceleration. But that was 99% of the time.

Good luck and let us know how things go.