Hey all,

Minor annoyance here and I cant figure it out. The engine appears to "hold back" at 2000 rpm and above. Anything below 2000 and its fine, but when you get to 2000 or above, it doesnt want to accelerate for a second or so, but then picks up, then "holds back", then picks up again. The tachometer shows this as a slight drop in rpm, and then goes back up again. Anyone have any ideas on this. Chevy Blazer 2 dr 4wd

TinW

 

Hey bud, I know this thread is a million years old and you may not even have access to the email that is associated with it anymore but after a couple days of looking this is the first thing I have found that is the same as My issue. Only, mine does what yours is PLUS at idle it will RANDOMLY stumble and shake but never in rhythm and doesn't throw a cel unless the idle drops too low then it will actually misfire and throw the cel. and like you said, under heavier acceleration, it like, surges, takes off with lots of power, then feels like it lost power then finds it again then loses it again. and if you are going down the road up a hill or something and holding the throttle steady in the same position it will stumble and shale like the ignition is randomly cutting out but again, never in rhythm or like a dead misfire. it has been driving me insane and I cant figure it out. best I can tell i track down and fixed any and all vacuum lines that were suspect.

 

Do you have any codes?

Can you read live data?

George

 

I believe, just wouldn't know what to look at or for. I'm a old fart carburetor guy and spider injection is even different than all the other fuel injection stuff I've had to deal with when I did. I just can't figure it out, it's getting to where it stumbles pretty good even when starting to accelerate away from a stop normal. when it's in gear it stumbles a lot harder and maybe more, than when in park, in park it just stumbles intermittently every few seconds but like I said not rhythmically like a dead miss, it did just turn the cel on this morning and I'll read that later at lunch. When you try to accelerate hard enough to either drop into passing gear or if you lay in to it a little heavy from a stop you can literally feel it surging like its in and out of power the entire time, like, pull, lay over, pull, lay over and it will do it the entire time youre down in it hard. what live data should I try to run?

 

Well, I’m 71 years old and started fixing cars in the 60s if that makes you feel better. Lol. I’ll be more than glad to walk you through this if you’d like, first step is see if you have any codes.

George

 

OK, Thank You for your time and willingness to help! so here are the codes,
P0102 - Mass Air Flow A circuit low input (intermittent)
P0147 - Oxygen Heater Circuit Bank 1 Sensor 2 (intermittent)
P0171 - Bank 1 System Too Lean (intermittent)
P0174 - Bank 2 System Too Lean (Intermittent)
P0300 - Random Multiple Misfire Detected (History) this one I want to say threw the one time the idle dropped really low while sitting in park.
P0440 - Evaporative Emission System (intermittent) I think this is because the purge valve is bad, well, it constantly clicks but I've tried it with it plugged in and unplugged and it still has these problems.
P0442 - Evaporative Emission System Leak Detected (Small Leak) (History MIL) (this is really always there and common with every GM I've ever seen.
P0302 - Cylinder 2 Misfire Detected (Confirmed) Again, I feel like this only happens because the idle will drop super low when it is stumbling and carrying on.
Now sometimes it will run like its ok but I can't say it's when the engine is cold it runs fine, I can't say once it's up to operating temp its fine, it seems to just run nice when it wants to and usually only does it for a minute maybe, at most.

 

You are in good hands with George!

P.S. I wanted to ask George about a possible cause of these symptoms but then I realized this would hijack the thread. So jnstead I'll just sit back, follow along, and wait to ask later. LOL

 

Lol, well, the way I was raised, no one is entitled to free help and no one owes you any help so I am happy as a pig in **** that he is even taking his time to help me, so as long as I (if it can be figured out) can figure out my problem still at the end, feel free to jump in and ask him whatever you'd like.

 

What are the misfire counts for each cylinder?

what are your fuel trims at idle and again at 2500 rpm. Need stft and ltft for each bank

we need a fuel pressure test with a ten min leak down (see the sticky)

George

 

If I understand what you're asking, my scanner only says, random multiple and cylinder 2. but it only out right labels cylinder as far as what all cylinders. i will get those readings shortly, assuming my scanner supports it, I know it can read live data, I just don't know HOW MUCH of the data it can read live. I don't have a fuel pressure tester, I could order oner but don't have one on hand, I just put another new pump in it about 5-6 months ago though. (I know that doesn't mean it can't have bad fuel pressure and so on, just volunteering the info.)