Hesitation when Humidity is High

[blazerbrat]

Ok, here is my problem:
99 Blazer - Hesitates during exceleration usually only when its pretty humid outside. Heistation exists more when a load is on the engine, but if its humid enought, idle might be slightly effected. Most commonly felt during 1200 and 2000 RPM in first and sometime second gear; a general weak feeling as speed increases. Happens only when engine is cold, and will usually go away after 10 to 15 minutes of regular driving as engine reaches normal operating temperature. On nice dry mornings, all is well. No codes ever thrown since the misfire code described below.

So that is the problem, here is what i did the first time to solve the problem when a misfire code eventually fired:
first replaced bosch platinum plugs with AC Delco.
replaced fuel filter
replaced cap, rotor and wires
replaced coil
and had shop professionally clean the injectors

After all that, the hesitation vanished for maybe 6 months; i blamed the Bosch plugs and went on. It has now returned.

I have racked my brain thinking what else it could be.

Mileage on truck: 116k

Any suggestions? I was contemplating changing O2's, or anything else that could adversly effect my A/F ratio when engine is cold and burning humid air. My only hesitation is there are no SES codes.

I do have a OBDII code reader, and all is always clear.

Please help; my wife is so bummed on her blazer, she is seriously contemplating a minivan, and i just can't take a minivan hunting like i did this blazer this weekend.

Thanks,
Eric
Dallas TX

[BlazerLT]

Most of the time, hesitation is because of a MAF sensor that needs cleaning.

[blazerbrat]

Is there anything spcifically i should us to clean the fine wires, which i assume is what needs cleaning? Will carb-cleaner work?

[BlazerLT]

Brake cleaner is best seeing it won't leave a residue.

Also if the junk is on there hard, a super soft toothbrush can be used with the brake cleaner to ever-so-gently message the deposits off.

[wolfox]

Check/change spark plug wires. Any fault in the jacketing or the boot seals/end caps will allow moisture infiltration and allows a bypass spark condition. This will cause hesitation at start, and especially at high speeds/engine loads. Also make sure that your plugs are properly gapped and in spec for your model year. Check to make sure that your cap is installed correctly. Any water in there will kill the engine performance. Drying it out with a shot of WD-40 works perfectly. Handle your wires carefully when installing them, and use dilectric grease on all of the boots too. This sounds like a classic "wet wire" problem to me.

[RJ MALIBU]

Im With Wolfox,i Would Check The Plug Wires Had Same Prob On My Cavalier And It Was Wires And Plugs

[blazerbrat]

Ok, i have followed just about all of your advise to no avail. I cleaned the MAF; i pulled all the plugs, checked to make sure gap was .06, and inspected all the boots. I pulled the cap and rotor, cleaned the posts, and cleaned out the dist. cap with wd-40 to displace any moisture present. I also put dielectric grease on all plug shafts to prevent moisture infiltration.

Any more suggestions?

Another side effect i didn't mention before was until the hesitation leaves, or before the engine reaches a nice warm temp., the trans will not lock into overdrive; it continues to stay in it's normal 4th with slipage even after 50 mph. After about 10 minutes of driving; the hesitations are gone, and the tranny will lock up and all is normal. I am thinkin' the hesitation is causing the computer to go into some kinda "limp home" mode and won't lock up the O/D, what do you think of that?

Anyway, if i can't get this fixed on my own; i have to take it to the shop. If that happens, the wife uses it as an excuse to sell the piece.

Thanks guys,
Eric

[DINO55]

Originally Posted by blazerbrat

Ok, i have followed just about all of your advise to no avail. I cleaned the MAF; i pulled all the plugs, checked to make sure gap was .06, and inspected all the boots. I pulled the cap and rotor, cleaned the posts, and cleaned out the dist. cap with wd-40 to displace any moisture present. I also put dielectric grease on all plug shafts to prevent moisture infiltration.

Any more suggestions?

Another side effect i didn't mention before was until the hesitation leaves, or before the engine reaches a nice warm temp., the trans will not lock into overdrive; it continues to stay in it's normal 4th with slipage even after 50 mph. After about 10 minutes of driving; the hesitations are gone, and the tranny will lock up and all is normal. I am thinkin' the hesitation is causing the computer to go into some kinda "limp home" mode and won't lock up the O/D, what do you think of that?

Anyway, if i can't get this fixed on my own; i have to take it to the shop. If that happens, the wife uses it as an excuse to sell the piece.

Thanks guys,
Eric

Hopefully, your plugs are gapped at 0.60...
What Kind of wires did you use? hopefully not EL CHEAPOS, Also the bracket holding the coil, is it a clean ground for the coil itself?
You may have a Possible (intermittent) bad ignition module or a bad coil...
Good luck and let us know what it is when you find it...

[wolfox]

I am with Dino55 on this one:

OEM Wires and plugs are your friends. Same goes for using OEM parts for your distributor and rotor. If and only if, after making sure that you have stock AC/Delco ignition parts, time to start looking at your ignition system/ignition coil. One way to test is to remove a boot with the engine idling from the end of a sparkplug. Draw it away slowly, and you should see a bright blue arc jumping from the end of the boot to the plug. If it's weak and yellow-orangish, you have a weak coil. (Be VERY careful when you do this. Secondary voltages in the ignition system are not a very pleasant exerience if you get "bit" by it.)

[Rmbodie]

Real men don't hunt out of a minivan . I had to do that once in an emergency hunt day . Never again I will just walk to the woods . Rob