98 HAS ENGINE MISS AT 60 TO 70 MPH (Full Version)

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98 HAS ENGINE MISS AT 60 TO 70 MPH

  

amxal -> 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/5/2008 6:14:32 PM)

I have a 98 Blazer with 154,000 mi. It has developed a slight miss at 60 to 70 mph, but seems to be a steady miss at about 65 mph. Recently it has started to miss at around 30 but goes away once it reaches operating temp. Yesterday the SES light came on at low speed and it was running rough, once it warmed up the SES went off. I have had it to a local GM mech. and he cleaned the injectors but that hasn't worked, he also said the fuel press. regulator was low but still within factory spec. So far this is what I have done within the last 3 months, new fuel pump (old one was bad and the car stopped running) new fuel filter, new gas cap, wires, cap and plugs have less than 5000 miles, replaced the dist. due to a cracked housing. Hwy fuel mileage has dropped from 24 to 18 / 19 mpg. I am the 2nd owner the 1st was 85 years old so I doubt the vehicle was beat, I have owned for the last 3 years. Any help is greatly appreciated.
AMXAL

  
Chevy Lover -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/5/2008 9:50:48 PM)

Can you get the code read and let us know?
Does it have the miss at 30 if you run it in "D3" instead of "D"?

Jharper -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/5/2008 11:24:40 PM)

my motor blew at that exact mileage, watch your gages.

Mr Blazer LT -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/6/2008 11:15:48 AM)

The highway figures you have are about the average for most, 24 is great mileage on the highway for your truck.  Could be tranny issue.  Maybe have differential fluids and/or tranny fluids checked.  Mine has a miss at that speed too, but my bearings are also being bathed by coolant that isn't supposed to be there[:(].  My engine is also around that 154k mileage range.

amxal -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/6/2008 1:33:14 PM)

Thanks for the info, I'll try the idea of running in"D" and if that does anything, I stopped at the local Auto Zone to have them read the code but they say they can't because it (SES) is currently not on, is that true??

Chevy Lover -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/7/2008 12:02:50 AM)

I don't actually know what Autozone can do as we don't have Autozone in Canada.
I know that the dealer can check for information stored in history, such as codes.


swartlkk -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/7/2008 4:10:33 AM)

The problem with Autozone is their crappy generic scantools that they use can't see stored codes, only active (atleast that's what they say).  If they used the higher feature one that they sell, you could see stored codes as well as freeze frame data.

amxal -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/7/2008 5:10:12 PM)

I was able to get the codes read today, but 1st todays "excitement" here in the Chicago area it has been 50 degrees and very damp, it's raining now, when I started the it was hard starting and when I put it in gear to drive it missed badly until about 30mph then it seemed to straighten out, then at 55 mph it started to miss again up to 65 mph, I did not go faster. It ran this way the 18 miles I travel to work, when I left work this afternoon it did the same thing as in the morning except this time the SES came on, at this point I was able to get the codes read, the scanner showed a 300 and 440, The tech said the 440 idicated a bad or loose fuel cap, I checked that and it was tight ( I purchased it 2 weeks ago) he also said the 300 showed multiple cyl. miss fires. I guess I'm lost, I tried driving in "D" and that made no difference, I have also cheched all the fluids, (trans and coolant) and both are correct and clean. Am I to the point of taking her "out back" and shootin her??

HeyYou -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/7/2008 7:17:14 PM)

Running worse in the rain?? Hhhmmm, try opening the hood, starting the engine, and taking a look, when it is DARK out, and see if you see a light show, if necessary, spray the engine LIGHLY with water, like from a spray bottle used for glass cleaner, and see if you get a light show.

What kind of plugs did you put in? Did you reset the timing? Tried resetting the computer? Does it do the same thing on a cold motor? or, only when up to operating temp?

chevcamls1 -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/7/2008 7:21:40 PM)

how u reset timing?

swartlkk -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/7/2008 8:05:14 PM)

quote:

ORIGINAL: chevcamls1

how u reset timing?

You don't.

sh1520 -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/7/2008 10:18:32 PM)

Hey Amxal--I also live in the chicago area (well more near the Wis. border) and am having the same exact problems you are with the wet weather. However, it was doing the same thing last spring, and I changed the wires, cap and rotor, and it solved the problem. That is until now. My SES light is also on, and they told me the same things about the gas cap, and multiple misfires. I find it hard to believe that I need to change the wires, cap and rotor again though. Maybe I need a new coil?? Anyway, let me know what happens with you. Good luck.

HeyYou -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/8/2008 1:39:12 AM)

quote:

ORIGINAL: swartlkk

quote:

ORIGINAL: chevcamls1

how u reset timing?

You don't.



Is the 98 motor DIS? If not, then BASE timing MUST be set.

swartlkk -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/8/2008 4:01:00 AM)

You cannot set the base timing on the '96+ motors.  The distributor hold down clamp fits onto a square drive on the base of the distributor.  There is no adjustment that can be set, period.  The only thing you can do is make sure you are on the right tooth down at the cam gear.  The rest is handled by the PCM.

And no, it is not DIS (distributorless ignition system). 

amxal -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/8/2008 11:38:46 AM)

I agree, you cannot do anything with the timing for a 98, just drop the dist. into the right tooth. I tried the trick of spraying a fine mist of water on the engine, (wires, cap, plugs) last night and I found nothing....no light show. I have not changed the coil and to the best of my knowledge it is original. The thought of replacing the wires,cap and rotor has passed my mind, except I've done it 2 times in the last 2 years,  I am using AC Platinum Plus plugs, the best Napa wires, cap and rotor (I did not go cheap) I have had to replace the cap 3 times, the last time (before the new dist) I put a bead of silicone where the cap meets the dist. to help seal...can't say I saw any improvement, but I do know you have to be careful when tightening the cap down so you don't crack the dist.

Thanks for all the help and ideas, I'm still open to all.
AMXAL

HeyYou -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/8/2008 11:49:25 AM)

quote:

ORIGINAL: swartlkk

You cannot set the base timing on the '96+ motors.  The distributor hold down clamp fits onto a square drive on the base of the distributor.  There is no adjustment that can be set, period.  The only thing you can do is make sure you are on the right tooth down at the cam gear.  The rest is handled by the PCM.

And no, it is not DIS (distributorless ignition system). 



Ah, this is news to me. Wonder what GM was thinking on that score.... Maybe they got tired of folks tweaking the timing a bit? Upsetting their carefully scheduled emissions stuff?? Curious.

@OP: What are your plugs gapped at?

amxal -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/9/2008 7:01:29 PM)

Well I dropped the Blazer off at the shop today for repairs tomorrow, the mechanic prepped me idea that he may need to change the spyder, said that maybe the pop off valve (s) could be sticking. I would have thought the pressure flush he performed last week would have cured that. In any case he said repairs could be $500 + for the spyder replacement.

sh1520 -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/9/2008 8:20:37 PM)

Sorry for being mechanically DEclined but, what'a a spyder? And pop off valves?  Never heard of them................

Mr Blazer LT -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/9/2008 8:57:11 PM)

I would get rid of those platinum plugs and install what GM recommends before letting that mechanic do anything else.  Platinums are never really needed unless they are specifically recommended by the manufacturer.

swartlkk -> RE: 98 HAS ENGINE MISS AT 60 TO 70 MPH (1/9/2008 9:37:00 PM)

Um, AC Delco Platinum plugs are what is installed from the factory and are what is recommended...  Specifically double platinums.  

  

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